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Intercalation of protonated polyoxyalkylene monoamines into a synthetic Li-fluorotaeniolite
Applied Clay Science 52 (2011) 133–139
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Applied Clay Science j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / c l a y
Research Paper
Intercalation of protonated polyoxyalkylene monoamines into a synthetic Li-fluorotaeniolite Zenon Kłapyta a,⁎, Adam Gaweł a, Taketoshi Fujita b, Nobuo Iyi b a b
Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków, Poland National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
a r t i c l e
i n f o
Article history: Received 8 October 2010 Received in revised form 11 February 2011 Accepted 15 February 2011 Available online 21 February 2011 Keywords: Synthetic fluorotaeniolite Polyoxyalkylene monoamines Intercalation
a b s t r a c t A series of intercalates was obtained by adsorption of protonated polyoxyalkylene monoamines (Jeffamines M-600, M-1000 and M-2005) on a synthetic Li-fluorotaeniolite (Li-TN). The amounts of Jeffamines varied in the range of 0.25–10.0 CEC of the Li-TN. The samples obtained were investigated by elemental analysis, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The maximum amounts of the organic cations bound to the Li-TN exchange sites, calculated from the C and N contents, were 23.8–76.2% CEC of LiTN. The SEM images testified that the surface morphology of the starting mica markedly changed after its treatment with the Jeffamines. The XRD patterns of the organo-TNs washed with water and unwashed indicated that the protonated amines were adsorbed on the TN surface as a result of both cation exchange and non-ionic interactions. The basal spacings of the intercalates were between ~ 13 and ~ 130 Å. The Li-TN was also easily intercalated with the unprotonated Jeffamines in a water–ethanol solution. These results revealed that adsorption of both the cationic and the non-ionic forms of the amines was controlled mainly by oxyalkylene segments of their chains. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Adsorption of long-chain organic cations on the exchange positions of clay minerals changes the surfaces from hydrophilic to hydrophobic. The most effective chemical agents imposing this change are quaternary alkylammonium, alkylpyridinium and alkylphosphonium surfactants. The exchange reaction products show, as a rule, ability to swell and disperse in organic solvents. Because of their organophilic character, such organic derivatives of clay minerals and synthetic micas were extensively studied as rheological modifiers and additives (Grim, 1968; Jones, 1983; Jordan, 1949), adsorbents for environmental organic contaminants (Churchman et al., 2006; Stockmeyer, 1991; Street and White, 1963; Theng, 1974) and inorganic toxic anions (Bors, 1990; Krishna et al., 2001; Lagaly, 1995; Li and Bowman, 1998), catalysts (Adams and McCabe, 2006; Breen et al., 1997; Lin and Pinnavaia, 1991), active components of clay mineral-polymer nanocomposites (LeBaron et al., 1999; Ruiz-Hitzky and Van Meerbeek, 2006; Zheng et al., 2005), advanced materials with optical, photomechanical and electronic functions (Fendler, 2001; Fitch, 1990; Fujita et al., 2003; Lagaly et al., 2006; Ogawa and Kuroda, 1995; Ogawa et al., 1999), etc. Modification of the surfactants by incorporating of oxygen atoms in their alkyl chains converts the hydrophobic character of these compounds to more hydrophilic. The organic derivatives of clay
⁎ Corresponding author. Tel.: +48 12 617 3433; fax: +48 12 633 4330. E-mail address: [email protected] (Z. Kłapyta). 0169-1317/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.clay.2011.02.010
minerals prepared using such nonionic, anionic and cationic ethylene oxide polymers were widely studied and show promising electrical, rheological, colloidal and adsorption properties (Aranda and RuizHitzky, 1992; Breen et al., 1999; Bujdák et al., 2000; Deng et al., 2006; Lagaly and Ziesmer, 2005, 2006, 2007; Sonon and Thompson, 2005; Theng, 1979; Vaia et al., 1997; Ziesmer and Lagaly, 2007). Recently, a new type of organic derivatives of natural and synthetic clay minerals, potentially well suited for preparing some clay mineralpolymer nanocomposites, was developed by intercalation of polyoxyalkylene amines into the interlayer spaces of these silicates (Triantafillidis et al., 2002a,b). Such amines are commercially available from Huntsman Chemicals as Jeffamines. They contain primary amino groups attached to the end of polyether backbone based either on ethylene oxide (EO), propylene oxide (PO), or mixed EO/PO segments. The hydrophilic/hydrophobic balance may be controlled by the EO/PO ratio, because PO groups are more hydrophobic than hydrophilic EO groups. Nanocomposites containing Jeffamines were prepared using montmorillonites (Chiu et al., 2008; Lin and Chen, 2004; Lin et al., 2003, 2008; Salahuddin, 2004; Salahuddin et al., 2007; Triantafillidis et al., 2002a,b, 2008; Yoon et al., 2007) as well as synthetic fluorohectorites (Triantafillidis et al., 2002a,b), fluorinated mica (Chiu et al., 2008; Lin et al., 2008), silicas (Wang and Pinnavaia, 2003) and α-zirconium phosphate (Bestaoui et al., 2006; Zhang et al., 2007). In these studies, mainly di- and triamines were applied as the surface modifiers and curing agents. The present authors obtained a series of intercalates with synthetic taeniolite and polyoxyalkylene
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monoamines. The aim of research was to investigate the effects of oxygen atoms in the Jeffamine chains and of the amine molar masses on the intercalation mechanism. 2. Materials and methods 2.1. Materials A synthetic swelling mica, Li-fluorotaeniolite (denoted as Li-TN), with the stoichiometric formula LiMg2LiSi4O10F2 (Topy Industries) was the starting material. The cation exchange capacity (CEC) expected from this formula is 268.2 meq/100 g. However, the value determined by the ammonium acetate method as well as using alkylammonium ions (according to Bergaya et al., 2006; Kłapyta et al., 2001) was 105 meq/100 g. It means that under the determination conditions a large part of Li+ ions balancing the negative layer charge of the mica were non-exchangeable. XRD analysis showed that the Li-TN used had an admixture of ~15 mass% of cristobalite. Three polyoxyalkylene monoamines served as organic modifiers in this study were the commercial Jeffamines M-600, M-1000 and M-2005 (Huntsman Chemicals) of different molar masses (~600, ~ 1000 and ~ 2000, respectively). 2.2. Preparation of organo-taeniolites The organo-taeniolites (organo-TNs) were prepared by a cation exchange reaction. The Jeffamine was mixed with 0.1 M HCl aqueous solution to obtain the organic ammonium salt, well soluble in water. The stoichiometric amount of the acid was calculated from the total amine content declared by the producer. The pH of the solution was adjusted to 3–4 using a small excess of HCl. The protonated Jeffamine solution was added to the aqueous dispersion of Li-TN. The amount of the organic salt, expressed as a multiple or a submultiple of the CEC of Li-TN, varied from 0.25 to 10.0 CEC. The mixture was stirred for 2 h at 60 °C and then left for 24 h. The procedure was repeated once, and the final product was divided into two portions. One of them remained unwashed, and the other was washed several times with hot deionized water by centrifugation at 12,000 rpm for 30–60 min until the washing water was free of chloride anions. Some of the washed samples were dried at 60 °C and ground in an agate mortar. In the case of a 1.5 CEC loading of M-2005 ions, it was not possible to wash out the excess of the Jeffamine and dry the reaction product completely due to its gelatinous nature. Part of this sample was additionally washed with hot ethanol. However, the washing solution was turbid testifying that centrifugation was not fully effective. A series of organo-TNs was also prepared using free (unprotonated) amines. Water–ethanol (1:1) solutions of the Jeffamines were added to the aqueous dispersion of Li-TN in an amount of 10.5 mmol/g, equivalent to 10.0 CEC, stirred for 2 h at 60 °C and then left for 24 h. The samples obtained were analyzed without washing.
3. Results and discussion 3.1. Elemental analysis Large alkylammonium cations replace almost stoichiometrically inorganic exchangeable ions in smectites. The same results were obtained for synthetic swelling micas (Kłapyta et al., 2001, 2003; Ogawa et al., 1999). In contrast, the total amounts of the protonated Jeffamines bound to the Li-TN by ion exchange were significantly lower (Fig. 1). They were calculated from the carbon and nitrogen contents of the samples washed with water and dried at 60 °C, in relation to the silicate framework (according to Favre and Lagaly, 1991). When amounts of the Jeffamine ions were in the range of 0.25– 1.5 CEC (0.26–1.58 meq/g), their adsorption systematically increased but the shape of the adsorption curves was different. In the case of M-600, the amount of the organic ions bound varied from 0.10 to 0.44 meq/g, corresponding to 9.5 and 41.9% CEC of Li-TN. The adsorption of M-1000 was much smaller (from 0.07 to 0.25 meq/g, i.e., from 6.7 to 23.8% CEC) while that obtained for M-2005 increased from 0.13 to 0.80 meq/g, i.e., from 12.4 to 76.2% CEC. The amount of M-2005 ions adsorbed by TN at a loading of 1.5 CEC (point E in Fig. 1) may be overestimated due to the problems with washing of this sample. In our study, there was no clear-cut molar mass effect on the Jeffamines adsorption, which is known for alkylammonium ions. The results suggested that the amount of the amine bound to the TN depended rather on its chemical (hydrophilic or hydrophobic) character. Taking into consideration the EO/PO ratios given by the producer for M-600, M-1000 and M-2005 Jeffamines (1/9, 19/3 and 6/29, respectively), it is evident that the most hydrophilic M-1000 was adsorbed in much smaller amounts than the more hydrophobic M-600 and M-2005 amines. 3.2. SEM observations The starting Li-TN (Fig. 2a) formed the characteristic spherical aggregates of platelets. Some of them showed a cabbage-like morphology. Intercalation of the Jeffamine cations into the well organized lamellar structure of the mica disturbed its original arrangement of
2.3. Sample characterization To determine the amounts of organic matter bound by Li-TN, the C and N contents of the organo-TNs were measured using Euro EA and Sumigraph NCH 21 elemental analyzers. The surface morphology of selected samples was examined with a FEI Quanta 200 FEG scanning electron microscope (SEM). The XRD patterns were recorded using Philips APD X'Pert and Rigaku RINT 2000 diffractometers (CuKα radiation). The specimens were obtained as a thin film formed on glass slides by slow evaporation in air of the solvent (water or water–ethanol mixture) from the organo-TN dispersions as well as from both the protonated and unprotonated Jeffamine solutions.
Fig. 1. Adsorption of protonated Jeffamines on Li-TN versus their amount added. E — sample washed with water and additionally with ethanol.
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Fig. 3. XRD patterns of organo-TNs obtained at various amounts of protonated Jeffamine M-600 expressed as the CEC of Li-TN (samples washed with water).
Fig. 2. SEM images of (a) Li-TN and (b) organo-TN obtained at an amount of protonated Jeffamine M-2005 equal to 0.25 CEC of Li-TN (sample washed with water).
particles. For example, in the organo-TN obtained at an amount of M-2005 ions equal to 0.25 CEC (sample washed) (Fig. 2b), the spherical aggregates of Li-TN were destroyed and disappeared. Their components reorganized into larger, compact aggregates of platelets, densely covered with the organic substance.
chains contained gauche conformations. The relatively high intensity of this reflection proved that most of the organo-TN interlayer spaces had similar basal spacings and formed particles with a well organized structure. As resulted from the C and N determinations, the M-1000 and M-2005 ions exchanged samples also contained large amounts of Li+ ions on the exchange positions. In spite of that the reflection at 12.3 Å practically disappeared in the XRD patterns (Figs. 4, 5). Thus, a separated Li-TN phase was not detectable by XRD, suggesting that most of the TN interlayer spaces were presumably filled with both Li+ and organic ions in various ratios with the spacings controlled by the organic ions. Nevertheless, a small number of Li-TN layers statistically distributed between organo-TN layers may also be present. The basal spacings of these organo-TNs changed from ~ 15 Å to ~17 Å, indicating random interstratification of the TN units containing the Jeffamine cations with monolayer and bilayer arrangements. The corresponding low-angle reflections were not as broad as those in Fig. 3, testifying that the structure of the samples obtained using M-1000 and M-2005 ions was more regular in the c-axis direction than that of the samples containing M-600 ions.
3.3. X-ray diffraction 3.3.1. Washed samples The XRD pattern of the organo-TN prepared at an amount of M-600 cations equal to 0.25 CEC and washed with water (Fig. 3) showed the broad and diffuse basal reflection with the maximum at 12.4 Å. Its intensity was much lower than that of the sharp reflection of Li-TN (0 CEC in Fig. 3) with the same d001 value. Such an XRD pattern indicated that the organic ions were inhomogeneously distributed within the lithium-saturated interlayer spaces. With increasing amount of M-600 ions, the intensity of the 12.3 Å reflection systematically decreased. However, this reflection was present even in the XRD pattern of the sample prepared at the highest Jeffamine amount added (1.5 CEC). As indicated by the C and N contents, in this sample 58.1% of the exchange positions were still occupied by Li+ ions. The broad reflections with basal spacings of ~14 Å (0.5 CEC) and ~ 16 Å (1.5 CEC) presumably corresponded to interstratifications of organo-TN layers containing different amounts of M-600 cations adopting monolayer and bilayer arrangements. The strong reflection at 14.8 Å (1.0 CEC) may be ascribed to the monolayer structure of these ions, although the basal spacing was higher than that expected for the fully extended conformation (13.6 Å), suggesting that the alkyl
Fig. 4. XRD patterns of organo-TNs obtained at various amounts of protonated Jeffamine M-1000 expressed as the CEC of Li-TN (samples washed with water).
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Fig. 5. XRD patterns of organo-TNs obtained at various amounts of protonated Jeffamine M-1000 expressed as the CEC of Li-TN (samples washed with water).
In the XRD pattern of the organo-TN prepared at a 1.5 CEC loading of M-2005 cations, the additional reflection at 39 Å indicated that the amount of the protonated amine in the TN interlayer spaces was significantly larger in comparison with the remaining intercalates. Considering problems with washing of this sample (see Section 2.2 and Fig. 1) it confirmed that not all of the M-2005 cations bound to the TN surface in excess of exchange positions were removed during washing. From the XRD point of view, the well washed organo-TNs containing M-600, M-1000 and M-2005 ions bound only to the exchange sites of TN, represented monophasic systems with basal spacings in the range of ~ 13–17 Å. 3.3.2. Samples not washed The XRD patterns of the organo-TNs, obtained without washing and analyzed after evaporation of water from the reaction dispersions, were presented in Figs. 6–8. The diffractogram of the sample prepared at a 0.25 CEC loading of M-600 cations was markedly different from that registered after washing. The very small reflection corresponding to the basal spacing 12.3 Å (seen also in the pattern of the sample prepared at a 0.5 CEC loading) was associated with the Li-TN phase. The strong and sharp reflection at 13.8 Å testified that a large part of the organic ions, adopting a fully extended conformation, formed monolayers in the TN interlayer spaces. The second intense reflection at 15.8 Å may be attributed to the mixed-layer structure consisting of M-600 cations in mono- and bilayer arrangements. The barely visible maximum at 43 Å suggested that a small portion of the Jeffamine ions adopted coiled conformations between the TN layers. This XRD pattern was typical of polyphasic systems composed of the mica particles differing in the amount and arrangement of the organic ions adsorbed. The intensity of the reflections at 13.8 and 15.8 Å gradually decreased with increasing amount of M-600 cations whereas the reflection at ~43 Å became dominant. Small and medium reflections in the range of ~17–22 Å probably corresponded to some amounts of interlayer spaces with bilayer and pseudotrilayer arrangements of these cations as well as their random interstratifications. The polyphase character of the organo-TNs was retained up to the sample obtained at the amount of M-600 ions equal to 1.5 CEC. In contrast, further increasing of the amount of organic ions caused their distribution in the TN interlayer spaces to become more homogeneous. Such a structure showed the sample obtained at a 10.0 CEC loading of M-600 ions. In its XRD pattern, a rational series of
Fig. 6. XRD patterns of organo-TNs obtained at various amounts of protonated Jeffamine M-600 expressed as the CEC of Li-TN (samples not washed).
reflections with the basal spacing of 42 Å was observed, indicating a monophase character of this organo-TN. It is worth noting that the increase of the amount of M-600 ions during preparation of the organo-TNs was initially accompanied by an expansion of the basal spacing from 43 Å to 44 Å, and then by its contraction to 42 Å. Similar changes in the XRD patterns were recorded for the samples prepared with M-1000 and M-2005 ions. A significant influence of the molar mass of Jeffamines on their packing and arrangements in the TN interlayer spaces was also evident. The distinct reflection at 13.8 Å (Fig. 6) characteristic of the monolayer structure of the M-600 ions practically disappeared when the M-1000 ions were used, and a new strong reflection at 17.8 Å
Fig. 7. XRD patterns of organo-TNs obtained at various amounts of protonated Jeffamine M-1000 expressed as the CEC of Li-TN (samples not washed).
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Fig. 9. Experimental and calculated XRD patterns of organo-TN obtained at an amount of protonated Jeffamine M-2005 equal to 10.0 CEC of Li-TN (sample not washed).
Fig. 8. XRD patterns of organo-TNs obtained at various amounts of protonated Jeffamine M-2005 expressed as the CEC of Li-TN (samples not washed).
corresponding to the bilayer arrangement appeared (Fig. 7). The basal spacings of the phase containing coiled conformations of M-1000 ions were significantly higher than those of the M-600 ions, and changed from 49 to 53 and then to 50 Å. At the same amount of the M-1000 and M-2005 ions, the intensity of the low-angle reflections with basal spacings in the ranges 49–53 Å and 39–47 Å increased with increasing molar mass of the amine ions. Comparison of the XRD patterns proved that the unwashed samples contained considerably higher amounts of the protonated Jeffamine ions in the TN interlayer spaces than the washed samples. If some of these ions had been adsorbed on the TN surface, and then washed out with water, they could not have been bound on the exchange sites of the mica. This indicates that a substantial amount was adsorbed by non-ionic interactions, in addition to the ammonium ions introduced into the TN interlayer spaces via ion exchange. The XRD patterns of the samples prepared at 1.0 CEC and higher amounts of M-2005 ions showed an oscillating character, i.e., in a lowangle range a wavy variation of the intensity without a flat region between the reflections. This indicated that particles of the organoTNs consisted of a very small number of layers (Fujii et al., 2003; Sasaki et al., 1996). The interlayer spacing calculated from the nonrational series of basal reflections of the sample obtained at an amount of the organic ions equal to 10.0 CEC was ~130 Å. For a more accurate estimation, the XRD pattern of this sample was tentatively simulated using the Reynold's NEWMOD program. The profile calculated for the basal spacing of 130 Å and 1–3 stacked layers was in good accordance with the experimental XRD pattern (Fig. 9). Tamura et al. (1999) found that Li-TN in dilute aqueous dispersions formed colloidal particles with the basal spacing of ~ 120 Å, consisting of two silicate layers and a water layer between them. Our study revealed that particles with a similar structure formed when Li-TN was dispersed in solutions of protonated M-2005 Jeffamine. Further investigations were carried out using free, unprotonated Jeffamines. Surprisingly, the XRD patterns of the samples obtained by evaporation of the solvents (water and ethanol) from the dispersions prepared at a 10.5 mmol/g loading of the amine molecules (Fig. 10) showed that large amounts of these compounds were intercalated into the Li-TN interlayer spaces. The basal spacings of the organo-TNs
with M-600, M-1000 and M-2005 Jeffamine molecules were 47, 81 and 97 Å, respectively. The series of four (M-600) or seven (M-1000 and M-2005) 00l reflections with rational or almost rational d00l values testified that the structure of these intercalates was quite regular. The basal spacing values calculated from 001 reflections of the samples with M-1000 and M-2005 amines were lower than those obtained for the remaining reflections. The XRD patterns of these two samples showed also the oscillating character as in the samples with M-2005 ions, testifying that particles of the organo-TNs consisted of only a few layers. In the organo-TNs obtained using highest amounts of Jeffamines (10.0 CEC, equivalent to 10.5 mmol/g), an excess of the amines might remain not adsorbed forming an additional phase, detectable by XRD. However, there were no reflections in the XRD patterns of both protonated (not shown) and unprotonated M-600 and M-2005 Jeffamines (Fig. 10), registered under the same experimental conditions as those used in the case of organo-TN specimens. It means that these four amine species, liquid at room temperature, were X-ray amorphous. In contrast, the reflections at 69 and 35.3 Å occurred in the almost identical XRD patterns of the both protonated (not shown) and unprotonated Jeffamines M-1000 (waxy solids at room temperature) (Fig. 10). These reflections
Fig. 10. XRD patterns of organo-TNs obtained at 10.5 mmol of unprotonated Jeffamines per 1 g of Li-TN (samples not washed) (black curves). The grey lines show the XRD patterns of respective pure Jeffamines.
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did not appear in the XRD patterns of the organo-TNs obtained at 10.0 CEC loadings of the amine (Figs. 7 and 10), suggesting that most of amine species were bound within the intercalates. 3.4. Adsorption mechanism The basal spacings of smectites intercalated with protonated Jeffamines were reported to be mainly 13–21 Å, although larger values (38–92 Å) were also observed (Chiu et al., 2008; Lin and Chen, 2004; Lin et al., 2003, 2008; Salahuddin, 2004; Salahuddin et al., 2007; Triantafillidis et al., 2002a,b, 2008; Yoon et al., 2007). A high degree of intercrystalline expansion (60–97 Å), comparable with some of our results, was found for synthetic micas (Chiu et al., 2008; Lin et al., 2008) as well as for α-zirconium phosphate (Bestaoui et al., 2006; Zhang et al., 2007) and layered silicas (Wang and Pinnavaia, 2003) reacted with the protonated and unprotonated amines. This difference in basal spacings might be associated with the lateral dimensions of the dispersed particles (Sasaki et al., 1996; Tamura et al., 1999) which are much smaller in the case of typical clay minerals in comparison with those of the synthetic compounds. In the cited papers, ion exchange was postulated as the adsorption mechanism of protonated Jeffamines. Van der Waals interactions between the amine chains might cause their self-aggregation in the interlayer spaces (Chiu et al., 2008; Lin et al., 2003). For the non-ionic amines, binding by hydrogen bonds between NH2 groups and active centers on the surface of the solid was proposed (Bestaoui et al., 2006; Wang and Pinnavaia, 2003; Zhang et al., 2007). Our results revealed that the adsorption of protonated Jeffamines on Li-TN was controlled mainly by the non-ionic interactions of their oxyalkylene segments with the mica surface. However, the positivelycharged head groups were attached by ion exchange. Most probably, at the beginning of the process ion exchange must have dominated, but later some of the ammonium groups could not easily reach the exchange sites in the TN interlayer spaces because of steric hindrance. Thus, adsorption of the Jeffamine cations on the mica was much lower than expected and known for alkylammonium and other large organic ions. Van der Waals interactions between the amine backbones were certainly also involved in the adsorption of both the protonated and unprotonated amines, however, it was difficult to estimate their contribution to this process. Intercalation of unprotonated Jeffamines into the interlayer spaces of Li-TN confirmed the interactions between the oxygen-containing groups in the amine chains and active centers on the TN surface (exchangeable cations, water molecules in their hydration shells and oxygen atoms in the silicate tetrahedral sheets), postulated by Aranda and Ruiz-Hitzky (1992), Breen et al. (1999), Deng et al. (2006), Lagaly and Ziesmer (2006), Lu et al. (2008), Sonon and Thompson (2005) and Su and Shen (2009) for the smectite-poly(ethylene oxide) systems. The remaining segments of the chains probably dangled out of the interlayer spaces into the solution. Participation of the NH2 groups in the adsorption process was possible, however, their amount as well as the ability to interact with the TN surface were much lower than those of oxyalkylene groups. Our results were consistent with the data obtained by Breen et al. (1999), Bujdák et al. (2000), Deng et al. (2006) and Ziesmer and Lagaly (2007) for adsorption of non-ionic as well as cationic and anionic poly(ethylene oxide)-based surfactants on smectites. All these forms of the surfactants were easily intercalated into the mineral interlayer spaces, testifying that there was no distinct influence of positive or negative molar charges on the amount of the species adsorbed. 4. Conclusions In spite of the high molar masses of the protonated Jeffamines, they were adsorbed on the exchange positions of Li-TN in amounts
much lower than the CEC of the mica, even if an excess of Jeffamines was used. The Li+ contents of the organo-TNs pointed to a Li-TN phase which, however, was not detected by XRD in most organo-TNs. This suggested that both lithium and Jeffamine ions were distributed in interlayer spaces disturbing their basal spacings. In addition to the ammonium ions bound by cation exchange, considerable amounts of Jeffamines were also adsorbed by non-ionic interactions, being removable with water. Intercalation of protonated as well as unprotonated Jeffamines into Li-TN indicated that oxygen atoms in the amine chains had a stronger influence on the adsorption process than their positively charged ammonium groups. The organo-TN with a basal spacing of ~130 Å, obtained using a large excess of M-2005 ions, may be useful for some applications of nanomaterials prepared from synthetic taeniolite. Acknowledgement This work was supported in part by the AGH University of Science and Technology (Kraków, Poland), the research project 11.11.140.158. References Adams, J.M., McCabe, R.W., 2006. Clay minerals as catalysts. In: Bergaya, F., Theng, B.K.G., Lagaly, G. (Eds.), Handbook of Clay Science. Elsevier, Amsterdam, pp. 541–582. Aranda, P., Ruiz-Hitzky, E., 1992. Poly(ethylene oxide)-silicate intercalation materials. Chemistry of Materials 4, 1395–1403. Bergaya, F., Lagaly, G., Vaier, M., 2006. Cation and anion exchange. In: Bergaya, F., Theng, B. K.G., Lagaly, G. (Eds.), Handbook of Clay Science. Elsevier, Amsterdam, pp. 979–1001. Bestaoui, N., Spurr, N.A., Clearfield, A., 2006. Intercalation of polyether amines into α-zirconium phosphate. Journal of Materials Chemistry 16, 759–764. Bors, J., 1990. Sorption of radioiodine in organo-clays and soils. Radiochimica Acta 51, 139–143. Breen, C., Watson, R., Madejová, J., Komadel, P., Klapyta, Z., 1997. Acid-activated organoclays: preparation, characterization and catalytic activity of acid-treated tetraalkylammonium-exchanged smectites. Langmuir 13, 6473–6479. Breen, C., Thompson, G., Webb, M., 1999. Preparation, thermal stability and decomposition routes of clay/Triton-X100 composites. Journal of Materials Chemistry 9, 3159–3165. Bujdák, J., Hackett, E., Giannelis, E.P., 2000. Effect of layer charge on the intercalation of poly(ethylene oxide) in layered silicates: implications on nanocomposite polymer electrolytes. Chemistry of Materials 12, 2168–2174. Chiu, C.W., Chu, C.C., Cheng, W.T., Lin, J.J., 2008. Exfoliation of smectite clays by branched polyamines consisting of multiple ionic sites. European Polymer Journal 44, 628–636. Churchman, G.J., Gates, W.P., Theng, B.K.G., Yuan, G., 2006. Clays and clay minerals for pollution control. In: Bergaya, F., Theng, B.K.G., Lagaly, G. (Eds.), Handbook of Clay Science. Elsevier, Amsterdam, pp. 625–675. Deng, Y., Dixon, J.B., White, G.N., 2006. Bonding mechanisms and conformation of poly (ethylene oxide)-based surfactants in interlayer of smectites. Colloid and Polymer Science 284, 347–356. Favre, H., Lagaly, G., 1991. Organo-bentonites with quaternary alkylammonium ions. Clay Minerals 26, 19–32. Fendler, J.H., 2001. Chemical self-assembly for electronic applications. Chemistry of Materials 13, 3196–3210. Fitch, A., 1990. Clay-modified electrode: a review. Clays and Clay Minerals 38, 391–400. Fujii, K., Hayashi, S., Kodama, H., 2003. Synthesis of an alkylammonium/magnesium phyllosilicate hybrid nanocomposite consisting of a smectite-like layer and organosiloxane layers. Chemistry of Materials 15, 1189–1197. Fujita, T., Iyi, N., Klapyta, Z., Fujii, K., Kaneko, Y., Kitamura, K., 2003. Photomechanical response of azobenzene/organophilic mica complexes. Materials Research Bulletin 38, 2009–2017. Grim, R.E., 1968. Clay Mineralogy. McGraw-Hill, New York. Jones, T.R., 1983. The properties and uses of clays which swell in organic solvents. Clay Minerals 18, 399–410. Jordan, J.W., 1949. Organophilic bentonites. I. Swelling in organic liquids. The Journal of Physical and Colloid Chemistry 53, 294–306. Kłapyta, Z., Fujita, T., Iyi, N., 2001. Adsorption of dodecyl- and octadecyltrimethylammonium ions on a smectite and synthetic micas. Applied Clay Science 19, 5–10. Kłapyta, Z., Gaweł, A., Fujita, T., Iyi, N., 2003. Structural heterogeneity of alkylammoniumexchanged, synthetic fluorotetrasilicic mica. Clay Minerals 38, 151–160. Krishna, B.S., Murty, D.S.R., Jai Prakash, B.S., 2001. Surfactant-modified clay as adsorbent for chromate. Applied Clay Science 20, 65–71. Lagaly, G., 1995. Surface and interlayer reactions: bentonites as adsorbents. Proceedings of the 10th International Clay Conference, pp. 137–144. Adelaide 1993. Lagaly, G., Ziesmer, S., 2005. Surface modification of bentonites. III. Sol–gel transitions of Na-montmorillonite in the presence of trimethylammonium-end-caped poly (ethylene oxides). Clay Minerals 40, 523–536.
Z. Kłapyta et al. / Applied Clay Science 52 (2011) 133–139 Lagaly, G., Ziesmer, S., 2006. Sol–gel transitions of sodium montmorillonite dispersions by cationic end-caped poly(ethylene oxides) (surface modification of bentonites, IV). Colloid and Polymer Science 284, 947–956. Lagaly, G., Ziesmer, S., 2007. Surface modification of bentonites. V. Sol–gel transitions of Ca-montmorillonite in the presence of cationic end-caped poly(ethylene oxides). Clay Minerals 42, 255–269. Lagaly, G., Ogawa, M., Dékány, I., 2006. Clay mineral organic interactions. In: Bergaya, F., Theng, B.K.G., Lagaly, G. (Eds.), Handbook of Clay Science, Amsterdam, pp. 309–378. LeBaron, P.C., Wang, Z., Pinnavaia, T.J., 1999. Polymer-layered silicate nanocomposites: an overview. Applied Clay Science 15, 11–29. Li, Z., Bowman, R.S., 1998. Sorption of chromate and PCE by surfactant-modified clay minerals. Environmental Engineering Science 15, 237–245. Lin, J.J., Chen, Y.M., 2004. Amphiphilic properties of poly(oxyalkylene)amineintercalated smectite aluminosilicates. Langmuir 20, 4261–4264. Lin, C.L., Pinnavaia, T.J., 1991. Organo clay assemblies for triphase catalysis. Chemistry of Materials 3, 213–215. Lin, J.J., Chen, I.J., Chou, C.C., 2003. Critical conformational change of poly(oxypropylene) diamines in layered aluminosilicate confinement. Macromolecular Rapid Communications 24, 492–495. Lin, J.J., Chen, Y.M., Tsai, W.C., Chiu, C.W., 2008. Self-assembly of lamellar clays to hierarchical microarrays. Journal of Physical Chemistry C 112, 9637–9643. Lu, Y., Kong, S.T., Deiseroth, H.J., Mormann, W., 2008. Structural requirements for the intercalation of polyether polyols into sodium-montmorillonite: the role of oxyethylene sequences. Macromolecular Materials and Engineering 293, 900–906. Ogawa, M., Kuroda, K., 1995. Photofunctions of intercalation compounds. Chemical Reviews 95, 399–438. Ogawa, M., Hama, M., Kuroda, K., 1999. Photochromism of azobenzene in the hydrophobic interlayer spaces of dialkyldimethylammonium-fluor-tetrasilicic mica films. Clay Minerals 34, 213–220. Ruiz-Hitzky, E., Van Meerbeek, A., 2006. Clay mineral- and organo-clay-polymer nanocomposite. In: Bergaya, F., Theng, B.K.G., Lagaly, G. (Eds.), Handbook of Clay Science, Amsterdam, pp. 583–621. Salahuddin, N.A., 2004. Layered silicate/epoxy nanocomposites: synthesis, characterization and properties. Polymers for Advanced Technologies 15, 251–259. Salahuddin, N.A., Ayad, M.M., Ali, M., 2007. Preparation, morphology and electrical conductivity of polyaniline/polyoxyalkylene-montmorillonite exfoliated nanocomposites. Polymers for Advanced Technologies 19, 171–180. Sasaki, T., Watanabe, M., Hashizume, H., Yamada, H., Nakazawa, H., 1996. Macromoleculelike aspects for a colloidal suspension o fan exfoliated titanate. Pairwise association of nanosheets and dynamic reassembling process initiated from it. Journal of the American Chemical Society 118, 8329–8335.
139
Sonon, L.S., Thompson, M.L., 2005. Sorption of a nonionic polyoxyethylene lauryl ether surfactant by 2:1 layer silicates. Clays and Clay Minerals 53, 45–54. Stockmeyer, M.R., 1991. Adsorption of organic compounds on organophilic bentonites. Applied Clay Science 6, 39–57. Street, G.B., White, D., 1963. Adsorption by organo-clay derivatives. Journal of Applied Chemistry 13, 288–291. Su, C.C., Shen, Y.H., 2009. Adsorption of poly(ethylene oxide) on smectite: effect of layer charge. Journal of Colloid and Interface Science 332, 11–15. Tamura, K., Sasaki, T., Hamada, H., Nakazawa, H., 1999. Laue function analysis of colloidal lithium taeniolite. Langmuir 15, 5509–5512. Theng, B.K.G., 1974. The Chemistry of Clay-Organic Reactions. Adam Hilger, London. Theng, B.K.G., 1979. Formation and Properties of Clay-Polymer Complexes. Elsevier, New York. Triantafillidis, C.S., LeBaron, P.C., Pinnavaia, T.J., 2002a. Homostructured mixed inorganic– organic ion clays: a new approach to epoxy polymer-exfoliated clay nanocomposites with reduced organic modifier content. Chemistry of Materials 14, 4088–4095. Triantafillidis, C.S., LeBaron, P.C., Pinnavaia, T.J., 2002b. Thermoset epoxy-clay nanocomposites: the dual role of α, ω-diamines as clay surface modifiers and polymer curing agents. Journal of Solid State Chemistry 167, 354–362. Triantafillidis, K.S., Panagiotis, I., Pinnavaia, T.J., 2008. Alternative synthetic routes to epoxy polymer-clay nanocomposites using organic or mixed-ion clays modified by protonated di/triamines (Jeffamines). Macromolecular Symposia 267, 41–46. Vaia, R.A., Sauer, B.B., Tse, O.K., Gianneli, E.P., 1997. Relaxations of confined chains in polymer nanocomposites: glass transition properties of poly(ethylene oxide) intercalated in montmorillonite. Journal of Polymer Science. Part B: Polymer Physics 35, 59–67. Wang, Z., Pinnavaia, T.J., 2003. Intercalation of poly(propyleneoxide) amines (Jeffamines) in synthetic layered silicas derived from ilerite, magadiite, and kenyaite. Journal of Materials Chemistry 13, 2127–2131. Yoon, K., Sung, H., Hwang, Y., Noh, S.K., Lee, D., 2007. Modification of montmorillonite with oligomeric amine derivatives for polymer nanocomposite preparation. Applied Clay Science 38, 1–8. Zhang, R., Hu, Y., Li, B., Chen, Z., Fan, W., 2007. Studies on the preparation and structure of polyacrylamide/α-zirconium phosphate nanocomposites. Journal of Materials Science 42, 5641–5646. Zheng, Q.H., Yu, A.B., Lu, G.Q., Paul, D.R., 2005. Clay-based polymer nanocomposites: research and commercial development. Journal of Nanoscience and Nanotechnology 5, 1574–1592. Ziesmer, S., Lagaly, G., 2007. Surface modification of bentonites. VI. Sol–gel transitions of sodium and calcium montmorillonite dispersions in the presence of anionic endcaped poly(ethylene oxides). Clay Minerals 42, 563–573.
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Applied Clay Science j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / c l a y
Research Paper
Intercalation of protonated polyoxyalkylene monoamines into a synthetic Li-fluorotaeniolite Zenon Kłapyta a,⁎, Adam Gaweł a, Taketoshi Fujita b, Nobuo Iyi b a b
Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków, Poland National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
a r t i c l e
i n f o
Article history: Received 8 October 2010 Received in revised form 11 February 2011 Accepted 15 February 2011 Available online 21 February 2011 Keywords: Synthetic fluorotaeniolite Polyoxyalkylene monoamines Intercalation
a b s t r a c t A series of intercalates was obtained by adsorption of protonated polyoxyalkylene monoamines (Jeffamines M-600, M-1000 and M-2005) on a synthetic Li-fluorotaeniolite (Li-TN). The amounts of Jeffamines varied in the range of 0.25–10.0 CEC of the Li-TN. The samples obtained were investigated by elemental analysis, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The maximum amounts of the organic cations bound to the Li-TN exchange sites, calculated from the C and N contents, were 23.8–76.2% CEC of LiTN. The SEM images testified that the surface morphology of the starting mica markedly changed after its treatment with the Jeffamines. The XRD patterns of the organo-TNs washed with water and unwashed indicated that the protonated amines were adsorbed on the TN surface as a result of both cation exchange and non-ionic interactions. The basal spacings of the intercalates were between ~ 13 and ~ 130 Å. The Li-TN was also easily intercalated with the unprotonated Jeffamines in a water–ethanol solution. These results revealed that adsorption of both the cationic and the non-ionic forms of the amines was controlled mainly by oxyalkylene segments of their chains. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Adsorption of long-chain organic cations on the exchange positions of clay minerals changes the surfaces from hydrophilic to hydrophobic. The most effective chemical agents imposing this change are quaternary alkylammonium, alkylpyridinium and alkylphosphonium surfactants. The exchange reaction products show, as a rule, ability to swell and disperse in organic solvents. Because of their organophilic character, such organic derivatives of clay minerals and synthetic micas were extensively studied as rheological modifiers and additives (Grim, 1968; Jones, 1983; Jordan, 1949), adsorbents for environmental organic contaminants (Churchman et al., 2006; Stockmeyer, 1991; Street and White, 1963; Theng, 1974) and inorganic toxic anions (Bors, 1990; Krishna et al., 2001; Lagaly, 1995; Li and Bowman, 1998), catalysts (Adams and McCabe, 2006; Breen et al., 1997; Lin and Pinnavaia, 1991), active components of clay mineral-polymer nanocomposites (LeBaron et al., 1999; Ruiz-Hitzky and Van Meerbeek, 2006; Zheng et al., 2005), advanced materials with optical, photomechanical and electronic functions (Fendler, 2001; Fitch, 1990; Fujita et al., 2003; Lagaly et al., 2006; Ogawa and Kuroda, 1995; Ogawa et al., 1999), etc. Modification of the surfactants by incorporating of oxygen atoms in their alkyl chains converts the hydrophobic character of these compounds to more hydrophilic. The organic derivatives of clay
⁎ Corresponding author. Tel.: +48 12 617 3433; fax: +48 12 633 4330. E-mail address: [email protected] (Z. Kłapyta). 0169-1317/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.clay.2011.02.010
minerals prepared using such nonionic, anionic and cationic ethylene oxide polymers were widely studied and show promising electrical, rheological, colloidal and adsorption properties (Aranda and RuizHitzky, 1992; Breen et al., 1999; Bujdák et al., 2000; Deng et al., 2006; Lagaly and Ziesmer, 2005, 2006, 2007; Sonon and Thompson, 2005; Theng, 1979; Vaia et al., 1997; Ziesmer and Lagaly, 2007). Recently, a new type of organic derivatives of natural and synthetic clay minerals, potentially well suited for preparing some clay mineralpolymer nanocomposites, was developed by intercalation of polyoxyalkylene amines into the interlayer spaces of these silicates (Triantafillidis et al., 2002a,b). Such amines are commercially available from Huntsman Chemicals as Jeffamines. They contain primary amino groups attached to the end of polyether backbone based either on ethylene oxide (EO), propylene oxide (PO), or mixed EO/PO segments. The hydrophilic/hydrophobic balance may be controlled by the EO/PO ratio, because PO groups are more hydrophobic than hydrophilic EO groups. Nanocomposites containing Jeffamines were prepared using montmorillonites (Chiu et al., 2008; Lin and Chen, 2004; Lin et al., 2003, 2008; Salahuddin, 2004; Salahuddin et al., 2007; Triantafillidis et al., 2002a,b, 2008; Yoon et al., 2007) as well as synthetic fluorohectorites (Triantafillidis et al., 2002a,b), fluorinated mica (Chiu et al., 2008; Lin et al., 2008), silicas (Wang and Pinnavaia, 2003) and α-zirconium phosphate (Bestaoui et al., 2006; Zhang et al., 2007). In these studies, mainly di- and triamines were applied as the surface modifiers and curing agents. The present authors obtained a series of intercalates with synthetic taeniolite and polyoxyalkylene
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monoamines. The aim of research was to investigate the effects of oxygen atoms in the Jeffamine chains and of the amine molar masses on the intercalation mechanism. 2. Materials and methods 2.1. Materials A synthetic swelling mica, Li-fluorotaeniolite (denoted as Li-TN), with the stoichiometric formula LiMg2LiSi4O10F2 (Topy Industries) was the starting material. The cation exchange capacity (CEC) expected from this formula is 268.2 meq/100 g. However, the value determined by the ammonium acetate method as well as using alkylammonium ions (according to Bergaya et al., 2006; Kłapyta et al., 2001) was 105 meq/100 g. It means that under the determination conditions a large part of Li+ ions balancing the negative layer charge of the mica were non-exchangeable. XRD analysis showed that the Li-TN used had an admixture of ~15 mass% of cristobalite. Three polyoxyalkylene monoamines served as organic modifiers in this study were the commercial Jeffamines M-600, M-1000 and M-2005 (Huntsman Chemicals) of different molar masses (~600, ~ 1000 and ~ 2000, respectively). 2.2. Preparation of organo-taeniolites The organo-taeniolites (organo-TNs) were prepared by a cation exchange reaction. The Jeffamine was mixed with 0.1 M HCl aqueous solution to obtain the organic ammonium salt, well soluble in water. The stoichiometric amount of the acid was calculated from the total amine content declared by the producer. The pH of the solution was adjusted to 3–4 using a small excess of HCl. The protonated Jeffamine solution was added to the aqueous dispersion of Li-TN. The amount of the organic salt, expressed as a multiple or a submultiple of the CEC of Li-TN, varied from 0.25 to 10.0 CEC. The mixture was stirred for 2 h at 60 °C and then left for 24 h. The procedure was repeated once, and the final product was divided into two portions. One of them remained unwashed, and the other was washed several times with hot deionized water by centrifugation at 12,000 rpm for 30–60 min until the washing water was free of chloride anions. Some of the washed samples were dried at 60 °C and ground in an agate mortar. In the case of a 1.5 CEC loading of M-2005 ions, it was not possible to wash out the excess of the Jeffamine and dry the reaction product completely due to its gelatinous nature. Part of this sample was additionally washed with hot ethanol. However, the washing solution was turbid testifying that centrifugation was not fully effective. A series of organo-TNs was also prepared using free (unprotonated) amines. Water–ethanol (1:1) solutions of the Jeffamines were added to the aqueous dispersion of Li-TN in an amount of 10.5 mmol/g, equivalent to 10.0 CEC, stirred for 2 h at 60 °C and then left for 24 h. The samples obtained were analyzed without washing.
3. Results and discussion 3.1. Elemental analysis Large alkylammonium cations replace almost stoichiometrically inorganic exchangeable ions in smectites. The same results were obtained for synthetic swelling micas (Kłapyta et al., 2001, 2003; Ogawa et al., 1999). In contrast, the total amounts of the protonated Jeffamines bound to the Li-TN by ion exchange were significantly lower (Fig. 1). They were calculated from the carbon and nitrogen contents of the samples washed with water and dried at 60 °C, in relation to the silicate framework (according to Favre and Lagaly, 1991). When amounts of the Jeffamine ions were in the range of 0.25– 1.5 CEC (0.26–1.58 meq/g), their adsorption systematically increased but the shape of the adsorption curves was different. In the case of M-600, the amount of the organic ions bound varied from 0.10 to 0.44 meq/g, corresponding to 9.5 and 41.9% CEC of Li-TN. The adsorption of M-1000 was much smaller (from 0.07 to 0.25 meq/g, i.e., from 6.7 to 23.8% CEC) while that obtained for M-2005 increased from 0.13 to 0.80 meq/g, i.e., from 12.4 to 76.2% CEC. The amount of M-2005 ions adsorbed by TN at a loading of 1.5 CEC (point E in Fig. 1) may be overestimated due to the problems with washing of this sample. In our study, there was no clear-cut molar mass effect on the Jeffamines adsorption, which is known for alkylammonium ions. The results suggested that the amount of the amine bound to the TN depended rather on its chemical (hydrophilic or hydrophobic) character. Taking into consideration the EO/PO ratios given by the producer for M-600, M-1000 and M-2005 Jeffamines (1/9, 19/3 and 6/29, respectively), it is evident that the most hydrophilic M-1000 was adsorbed in much smaller amounts than the more hydrophobic M-600 and M-2005 amines. 3.2. SEM observations The starting Li-TN (Fig. 2a) formed the characteristic spherical aggregates of platelets. Some of them showed a cabbage-like morphology. Intercalation of the Jeffamine cations into the well organized lamellar structure of the mica disturbed its original arrangement of
2.3. Sample characterization To determine the amounts of organic matter bound by Li-TN, the C and N contents of the organo-TNs were measured using Euro EA and Sumigraph NCH 21 elemental analyzers. The surface morphology of selected samples was examined with a FEI Quanta 200 FEG scanning electron microscope (SEM). The XRD patterns were recorded using Philips APD X'Pert and Rigaku RINT 2000 diffractometers (CuKα radiation). The specimens were obtained as a thin film formed on glass slides by slow evaporation in air of the solvent (water or water–ethanol mixture) from the organo-TN dispersions as well as from both the protonated and unprotonated Jeffamine solutions.
Fig. 1. Adsorption of protonated Jeffamines on Li-TN versus their amount added. E — sample washed with water and additionally with ethanol.
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Fig. 3. XRD patterns of organo-TNs obtained at various amounts of protonated Jeffamine M-600 expressed as the CEC of Li-TN (samples washed with water).
Fig. 2. SEM images of (a) Li-TN and (b) organo-TN obtained at an amount of protonated Jeffamine M-2005 equal to 0.25 CEC of Li-TN (sample washed with water).
particles. For example, in the organo-TN obtained at an amount of M-2005 ions equal to 0.25 CEC (sample washed) (Fig. 2b), the spherical aggregates of Li-TN were destroyed and disappeared. Their components reorganized into larger, compact aggregates of platelets, densely covered with the organic substance.
chains contained gauche conformations. The relatively high intensity of this reflection proved that most of the organo-TN interlayer spaces had similar basal spacings and formed particles with a well organized structure. As resulted from the C and N determinations, the M-1000 and M-2005 ions exchanged samples also contained large amounts of Li+ ions on the exchange positions. In spite of that the reflection at 12.3 Å practically disappeared in the XRD patterns (Figs. 4, 5). Thus, a separated Li-TN phase was not detectable by XRD, suggesting that most of the TN interlayer spaces were presumably filled with both Li+ and organic ions in various ratios with the spacings controlled by the organic ions. Nevertheless, a small number of Li-TN layers statistically distributed between organo-TN layers may also be present. The basal spacings of these organo-TNs changed from ~ 15 Å to ~17 Å, indicating random interstratification of the TN units containing the Jeffamine cations with monolayer and bilayer arrangements. The corresponding low-angle reflections were not as broad as those in Fig. 3, testifying that the structure of the samples obtained using M-1000 and M-2005 ions was more regular in the c-axis direction than that of the samples containing M-600 ions.
3.3. X-ray diffraction 3.3.1. Washed samples The XRD pattern of the organo-TN prepared at an amount of M-600 cations equal to 0.25 CEC and washed with water (Fig. 3) showed the broad and diffuse basal reflection with the maximum at 12.4 Å. Its intensity was much lower than that of the sharp reflection of Li-TN (0 CEC in Fig. 3) with the same d001 value. Such an XRD pattern indicated that the organic ions were inhomogeneously distributed within the lithium-saturated interlayer spaces. With increasing amount of M-600 ions, the intensity of the 12.3 Å reflection systematically decreased. However, this reflection was present even in the XRD pattern of the sample prepared at the highest Jeffamine amount added (1.5 CEC). As indicated by the C and N contents, in this sample 58.1% of the exchange positions were still occupied by Li+ ions. The broad reflections with basal spacings of ~14 Å (0.5 CEC) and ~ 16 Å (1.5 CEC) presumably corresponded to interstratifications of organo-TN layers containing different amounts of M-600 cations adopting monolayer and bilayer arrangements. The strong reflection at 14.8 Å (1.0 CEC) may be ascribed to the monolayer structure of these ions, although the basal spacing was higher than that expected for the fully extended conformation (13.6 Å), suggesting that the alkyl
Fig. 4. XRD patterns of organo-TNs obtained at various amounts of protonated Jeffamine M-1000 expressed as the CEC of Li-TN (samples washed with water).
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Fig. 5. XRD patterns of organo-TNs obtained at various amounts of protonated Jeffamine M-1000 expressed as the CEC of Li-TN (samples washed with water).
In the XRD pattern of the organo-TN prepared at a 1.5 CEC loading of M-2005 cations, the additional reflection at 39 Å indicated that the amount of the protonated amine in the TN interlayer spaces was significantly larger in comparison with the remaining intercalates. Considering problems with washing of this sample (see Section 2.2 and Fig. 1) it confirmed that not all of the M-2005 cations bound to the TN surface in excess of exchange positions were removed during washing. From the XRD point of view, the well washed organo-TNs containing M-600, M-1000 and M-2005 ions bound only to the exchange sites of TN, represented monophasic systems with basal spacings in the range of ~ 13–17 Å. 3.3.2. Samples not washed The XRD patterns of the organo-TNs, obtained without washing and analyzed after evaporation of water from the reaction dispersions, were presented in Figs. 6–8. The diffractogram of the sample prepared at a 0.25 CEC loading of M-600 cations was markedly different from that registered after washing. The very small reflection corresponding to the basal spacing 12.3 Å (seen also in the pattern of the sample prepared at a 0.5 CEC loading) was associated with the Li-TN phase. The strong and sharp reflection at 13.8 Å testified that a large part of the organic ions, adopting a fully extended conformation, formed monolayers in the TN interlayer spaces. The second intense reflection at 15.8 Å may be attributed to the mixed-layer structure consisting of M-600 cations in mono- and bilayer arrangements. The barely visible maximum at 43 Å suggested that a small portion of the Jeffamine ions adopted coiled conformations between the TN layers. This XRD pattern was typical of polyphasic systems composed of the mica particles differing in the amount and arrangement of the organic ions adsorbed. The intensity of the reflections at 13.8 and 15.8 Å gradually decreased with increasing amount of M-600 cations whereas the reflection at ~43 Å became dominant. Small and medium reflections in the range of ~17–22 Å probably corresponded to some amounts of interlayer spaces with bilayer and pseudotrilayer arrangements of these cations as well as their random interstratifications. The polyphase character of the organo-TNs was retained up to the sample obtained at the amount of M-600 ions equal to 1.5 CEC. In contrast, further increasing of the amount of organic ions caused their distribution in the TN interlayer spaces to become more homogeneous. Such a structure showed the sample obtained at a 10.0 CEC loading of M-600 ions. In its XRD pattern, a rational series of
Fig. 6. XRD patterns of organo-TNs obtained at various amounts of protonated Jeffamine M-600 expressed as the CEC of Li-TN (samples not washed).
reflections with the basal spacing of 42 Å was observed, indicating a monophase character of this organo-TN. It is worth noting that the increase of the amount of M-600 ions during preparation of the organo-TNs was initially accompanied by an expansion of the basal spacing from 43 Å to 44 Å, and then by its contraction to 42 Å. Similar changes in the XRD patterns were recorded for the samples prepared with M-1000 and M-2005 ions. A significant influence of the molar mass of Jeffamines on their packing and arrangements in the TN interlayer spaces was also evident. The distinct reflection at 13.8 Å (Fig. 6) characteristic of the monolayer structure of the M-600 ions practically disappeared when the M-1000 ions were used, and a new strong reflection at 17.8 Å
Fig. 7. XRD patterns of organo-TNs obtained at various amounts of protonated Jeffamine M-1000 expressed as the CEC of Li-TN (samples not washed).
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Fig. 9. Experimental and calculated XRD patterns of organo-TN obtained at an amount of protonated Jeffamine M-2005 equal to 10.0 CEC of Li-TN (sample not washed).
Fig. 8. XRD patterns of organo-TNs obtained at various amounts of protonated Jeffamine M-2005 expressed as the CEC of Li-TN (samples not washed).
corresponding to the bilayer arrangement appeared (Fig. 7). The basal spacings of the phase containing coiled conformations of M-1000 ions were significantly higher than those of the M-600 ions, and changed from 49 to 53 and then to 50 Å. At the same amount of the M-1000 and M-2005 ions, the intensity of the low-angle reflections with basal spacings in the ranges 49–53 Å and 39–47 Å increased with increasing molar mass of the amine ions. Comparison of the XRD patterns proved that the unwashed samples contained considerably higher amounts of the protonated Jeffamine ions in the TN interlayer spaces than the washed samples. If some of these ions had been adsorbed on the TN surface, and then washed out with water, they could not have been bound on the exchange sites of the mica. This indicates that a substantial amount was adsorbed by non-ionic interactions, in addition to the ammonium ions introduced into the TN interlayer spaces via ion exchange. The XRD patterns of the samples prepared at 1.0 CEC and higher amounts of M-2005 ions showed an oscillating character, i.e., in a lowangle range a wavy variation of the intensity without a flat region between the reflections. This indicated that particles of the organoTNs consisted of a very small number of layers (Fujii et al., 2003; Sasaki et al., 1996). The interlayer spacing calculated from the nonrational series of basal reflections of the sample obtained at an amount of the organic ions equal to 10.0 CEC was ~130 Å. For a more accurate estimation, the XRD pattern of this sample was tentatively simulated using the Reynold's NEWMOD program. The profile calculated for the basal spacing of 130 Å and 1–3 stacked layers was in good accordance with the experimental XRD pattern (Fig. 9). Tamura et al. (1999) found that Li-TN in dilute aqueous dispersions formed colloidal particles with the basal spacing of ~ 120 Å, consisting of two silicate layers and a water layer between them. Our study revealed that particles with a similar structure formed when Li-TN was dispersed in solutions of protonated M-2005 Jeffamine. Further investigations were carried out using free, unprotonated Jeffamines. Surprisingly, the XRD patterns of the samples obtained by evaporation of the solvents (water and ethanol) from the dispersions prepared at a 10.5 mmol/g loading of the amine molecules (Fig. 10) showed that large amounts of these compounds were intercalated into the Li-TN interlayer spaces. The basal spacings of the organo-TNs
with M-600, M-1000 and M-2005 Jeffamine molecules were 47, 81 and 97 Å, respectively. The series of four (M-600) or seven (M-1000 and M-2005) 00l reflections with rational or almost rational d00l values testified that the structure of these intercalates was quite regular. The basal spacing values calculated from 001 reflections of the samples with M-1000 and M-2005 amines were lower than those obtained for the remaining reflections. The XRD patterns of these two samples showed also the oscillating character as in the samples with M-2005 ions, testifying that particles of the organo-TNs consisted of only a few layers. In the organo-TNs obtained using highest amounts of Jeffamines (10.0 CEC, equivalent to 10.5 mmol/g), an excess of the amines might remain not adsorbed forming an additional phase, detectable by XRD. However, there were no reflections in the XRD patterns of both protonated (not shown) and unprotonated M-600 and M-2005 Jeffamines (Fig. 10), registered under the same experimental conditions as those used in the case of organo-TN specimens. It means that these four amine species, liquid at room temperature, were X-ray amorphous. In contrast, the reflections at 69 and 35.3 Å occurred in the almost identical XRD patterns of the both protonated (not shown) and unprotonated Jeffamines M-1000 (waxy solids at room temperature) (Fig. 10). These reflections
Fig. 10. XRD patterns of organo-TNs obtained at 10.5 mmol of unprotonated Jeffamines per 1 g of Li-TN (samples not washed) (black curves). The grey lines show the XRD patterns of respective pure Jeffamines.
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did not appear in the XRD patterns of the organo-TNs obtained at 10.0 CEC loadings of the amine (Figs. 7 and 10), suggesting that most of amine species were bound within the intercalates. 3.4. Adsorption mechanism The basal spacings of smectites intercalated with protonated Jeffamines were reported to be mainly 13–21 Å, although larger values (38–92 Å) were also observed (Chiu et al., 2008; Lin and Chen, 2004; Lin et al., 2003, 2008; Salahuddin, 2004; Salahuddin et al., 2007; Triantafillidis et al., 2002a,b, 2008; Yoon et al., 2007). A high degree of intercrystalline expansion (60–97 Å), comparable with some of our results, was found for synthetic micas (Chiu et al., 2008; Lin et al., 2008) as well as for α-zirconium phosphate (Bestaoui et al., 2006; Zhang et al., 2007) and layered silicas (Wang and Pinnavaia, 2003) reacted with the protonated and unprotonated amines. This difference in basal spacings might be associated with the lateral dimensions of the dispersed particles (Sasaki et al., 1996; Tamura et al., 1999) which are much smaller in the case of typical clay minerals in comparison with those of the synthetic compounds. In the cited papers, ion exchange was postulated as the adsorption mechanism of protonated Jeffamines. Van der Waals interactions between the amine chains might cause their self-aggregation in the interlayer spaces (Chiu et al., 2008; Lin et al., 2003). For the non-ionic amines, binding by hydrogen bonds between NH2 groups and active centers on the surface of the solid was proposed (Bestaoui et al., 2006; Wang and Pinnavaia, 2003; Zhang et al., 2007). Our results revealed that the adsorption of protonated Jeffamines on Li-TN was controlled mainly by the non-ionic interactions of their oxyalkylene segments with the mica surface. However, the positivelycharged head groups were attached by ion exchange. Most probably, at the beginning of the process ion exchange must have dominated, but later some of the ammonium groups could not easily reach the exchange sites in the TN interlayer spaces because of steric hindrance. Thus, adsorption of the Jeffamine cations on the mica was much lower than expected and known for alkylammonium and other large organic ions. Van der Waals interactions between the amine backbones were certainly also involved in the adsorption of both the protonated and unprotonated amines, however, it was difficult to estimate their contribution to this process. Intercalation of unprotonated Jeffamines into the interlayer spaces of Li-TN confirmed the interactions between the oxygen-containing groups in the amine chains and active centers on the TN surface (exchangeable cations, water molecules in their hydration shells and oxygen atoms in the silicate tetrahedral sheets), postulated by Aranda and Ruiz-Hitzky (1992), Breen et al. (1999), Deng et al. (2006), Lagaly and Ziesmer (2006), Lu et al. (2008), Sonon and Thompson (2005) and Su and Shen (2009) for the smectite-poly(ethylene oxide) systems. The remaining segments of the chains probably dangled out of the interlayer spaces into the solution. Participation of the NH2 groups in the adsorption process was possible, however, their amount as well as the ability to interact with the TN surface were much lower than those of oxyalkylene groups. Our results were consistent with the data obtained by Breen et al. (1999), Bujdák et al. (2000), Deng et al. (2006) and Ziesmer and Lagaly (2007) for adsorption of non-ionic as well as cationic and anionic poly(ethylene oxide)-based surfactants on smectites. All these forms of the surfactants were easily intercalated into the mineral interlayer spaces, testifying that there was no distinct influence of positive or negative molar charges on the amount of the species adsorbed. 4. Conclusions In spite of the high molar masses of the protonated Jeffamines, they were adsorbed on the exchange positions of Li-TN in amounts
much lower than the CEC of the mica, even if an excess of Jeffamines was used. The Li+ contents of the organo-TNs pointed to a Li-TN phase which, however, was not detected by XRD in most organo-TNs. This suggested that both lithium and Jeffamine ions were distributed in interlayer spaces disturbing their basal spacings. In addition to the ammonium ions bound by cation exchange, considerable amounts of Jeffamines were also adsorbed by non-ionic interactions, being removable with water. Intercalation of protonated as well as unprotonated Jeffamines into Li-TN indicated that oxygen atoms in the amine chains had a stronger influence on the adsorption process than their positively charged ammonium groups. The organo-TN with a basal spacing of ~130 Å, obtained using a large excess of M-2005 ions, may be useful for some applications of nanomaterials prepared from synthetic taeniolite. Acknowledgement This work was supported in part by the AGH University of Science and Technology (Kraków, Poland), the research project 11.11.140.158. References Adams, J.M., McCabe, R.W., 2006. Clay minerals as catalysts. In: Bergaya, F., Theng, B.K.G., Lagaly, G. (Eds.), Handbook of Clay Science. Elsevier, Amsterdam, pp. 541–582. Aranda, P., Ruiz-Hitzky, E., 1992. Poly(ethylene oxide)-silicate intercalation materials. Chemistry of Materials 4, 1395–1403. Bergaya, F., Lagaly, G., Vaier, M., 2006. Cation and anion exchange. In: Bergaya, F., Theng, B. K.G., Lagaly, G. (Eds.), Handbook of Clay Science. Elsevier, Amsterdam, pp. 979–1001. Bestaoui, N., Spurr, N.A., Clearfield, A., 2006. Intercalation of polyether amines into α-zirconium phosphate. Journal of Materials Chemistry 16, 759–764. Bors, J., 1990. Sorption of radioiodine in organo-clays and soils. Radiochimica Acta 51, 139–143. Breen, C., Watson, R., Madejová, J., Komadel, P., Klapyta, Z., 1997. Acid-activated organoclays: preparation, characterization and catalytic activity of acid-treated tetraalkylammonium-exchanged smectites. Langmuir 13, 6473–6479. Breen, C., Thompson, G., Webb, M., 1999. Preparation, thermal stability and decomposition routes of clay/Triton-X100 composites. Journal of Materials Chemistry 9, 3159–3165. Bujdák, J., Hackett, E., Giannelis, E.P., 2000. Effect of layer charge on the intercalation of poly(ethylene oxide) in layered silicates: implications on nanocomposite polymer electrolytes. Chemistry of Materials 12, 2168–2174. Chiu, C.W., Chu, C.C., Cheng, W.T., Lin, J.J., 2008. Exfoliation of smectite clays by branched polyamines consisting of multiple ionic sites. European Polymer Journal 44, 628–636. Churchman, G.J., Gates, W.P., Theng, B.K.G., Yuan, G., 2006. Clays and clay minerals for pollution control. In: Bergaya, F., Theng, B.K.G., Lagaly, G. (Eds.), Handbook of Clay Science. Elsevier, Amsterdam, pp. 625–675. Deng, Y., Dixon, J.B., White, G.N., 2006. Bonding mechanisms and conformation of poly (ethylene oxide)-based surfactants in interlayer of smectites. Colloid and Polymer Science 284, 347–356. Favre, H., Lagaly, G., 1991. Organo-bentonites with quaternary alkylammonium ions. Clay Minerals 26, 19–32. Fendler, J.H., 2001. Chemical self-assembly for electronic applications. Chemistry of Materials 13, 3196–3210. Fitch, A., 1990. Clay-modified electrode: a review. Clays and Clay Minerals 38, 391–400. Fujii, K., Hayashi, S., Kodama, H., 2003. Synthesis of an alkylammonium/magnesium phyllosilicate hybrid nanocomposite consisting of a smectite-like layer and organosiloxane layers. Chemistry of Materials 15, 1189–1197. Fujita, T., Iyi, N., Klapyta, Z., Fujii, K., Kaneko, Y., Kitamura, K., 2003. Photomechanical response of azobenzene/organophilic mica complexes. Materials Research Bulletin 38, 2009–2017. Grim, R.E., 1968. Clay Mineralogy. McGraw-Hill, New York. Jones, T.R., 1983. The properties and uses of clays which swell in organic solvents. Clay Minerals 18, 399–410. Jordan, J.W., 1949. Organophilic bentonites. I. Swelling in organic liquids. The Journal of Physical and Colloid Chemistry 53, 294–306. Kłapyta, Z., Fujita, T., Iyi, N., 2001. Adsorption of dodecyl- and octadecyltrimethylammonium ions on a smectite and synthetic micas. Applied Clay Science 19, 5–10. Kłapyta, Z., Gaweł, A., Fujita, T., Iyi, N., 2003. Structural heterogeneity of alkylammoniumexchanged, synthetic fluorotetrasilicic mica. Clay Minerals 38, 151–160. Krishna, B.S., Murty, D.S.R., Jai Prakash, B.S., 2001. Surfactant-modified clay as adsorbent for chromate. Applied Clay Science 20, 65–71. Lagaly, G., 1995. Surface and interlayer reactions: bentonites as adsorbents. Proceedings of the 10th International Clay Conference, pp. 137–144. Adelaide 1993. Lagaly, G., Ziesmer, S., 2005. Surface modification of bentonites. III. Sol–gel transitions of Na-montmorillonite in the presence of trimethylammonium-end-caped poly (ethylene oxides). Clay Minerals 40, 523–536.
Z. Kłapyta et al. / Applied Clay Science 52 (2011) 133–139 Lagaly, G., Ziesmer, S., 2006. Sol–gel transitions of sodium montmorillonite dispersions by cationic end-caped poly(ethylene oxides) (surface modification of bentonites, IV). Colloid and Polymer Science 284, 947–956. Lagaly, G., Ziesmer, S., 2007. Surface modification of bentonites. V. Sol–gel transitions of Ca-montmorillonite in the presence of cationic end-caped poly(ethylene oxides). Clay Minerals 42, 255–269. Lagaly, G., Ogawa, M., Dékány, I., 2006. Clay mineral organic interactions. In: Bergaya, F., Theng, B.K.G., Lagaly, G. (Eds.), Handbook of Clay Science, Amsterdam, pp. 309–378. LeBaron, P.C., Wang, Z., Pinnavaia, T.J., 1999. Polymer-layered silicate nanocomposites: an overview. Applied Clay Science 15, 11–29. Li, Z., Bowman, R.S., 1998. Sorption of chromate and PCE by surfactant-modified clay minerals. Environmental Engineering Science 15, 237–245. Lin, J.J., Chen, Y.M., 2004. Amphiphilic properties of poly(oxyalkylene)amineintercalated smectite aluminosilicates. Langmuir 20, 4261–4264. Lin, C.L., Pinnavaia, T.J., 1991. Organo clay assemblies for triphase catalysis. Chemistry of Materials 3, 213–215. Lin, J.J., Chen, I.J., Chou, C.C., 2003. Critical conformational change of poly(oxypropylene) diamines in layered aluminosilicate confinement. Macromolecular Rapid Communications 24, 492–495. Lin, J.J., Chen, Y.M., Tsai, W.C., Chiu, C.W., 2008. Self-assembly of lamellar clays to hierarchical microarrays. Journal of Physical Chemistry C 112, 9637–9643. Lu, Y., Kong, S.T., Deiseroth, H.J., Mormann, W., 2008. Structural requirements for the intercalation of polyether polyols into sodium-montmorillonite: the role of oxyethylene sequences. Macromolecular Materials and Engineering 293, 900–906. Ogawa, M., Kuroda, K., 1995. Photofunctions of intercalation compounds. Chemical Reviews 95, 399–438. Ogawa, M., Hama, M., Kuroda, K., 1999. Photochromism of azobenzene in the hydrophobic interlayer spaces of dialkyldimethylammonium-fluor-tetrasilicic mica films. Clay Minerals 34, 213–220. Ruiz-Hitzky, E., Van Meerbeek, A., 2006. Clay mineral- and organo-clay-polymer nanocomposite. In: Bergaya, F., Theng, B.K.G., Lagaly, G. (Eds.), Handbook of Clay Science, Amsterdam, pp. 583–621. Salahuddin, N.A., 2004. Layered silicate/epoxy nanocomposites: synthesis, characterization and properties. Polymers for Advanced Technologies 15, 251–259. Salahuddin, N.A., Ayad, M.M., Ali, M., 2007. Preparation, morphology and electrical conductivity of polyaniline/polyoxyalkylene-montmorillonite exfoliated nanocomposites. Polymers for Advanced Technologies 19, 171–180. Sasaki, T., Watanabe, M., Hashizume, H., Yamada, H., Nakazawa, H., 1996. Macromoleculelike aspects for a colloidal suspension o fan exfoliated titanate. Pairwise association of nanosheets and dynamic reassembling process initiated from it. Journal of the American Chemical Society 118, 8329–8335.
139
Sonon, L.S., Thompson, M.L., 2005. Sorption of a nonionic polyoxyethylene lauryl ether surfactant by 2:1 layer silicates. Clays and Clay Minerals 53, 45–54. Stockmeyer, M.R., 1991. Adsorption of organic compounds on organophilic bentonites. Applied Clay Science 6, 39–57. Street, G.B., White, D., 1963. Adsorption by organo-clay derivatives. Journal of Applied Chemistry 13, 288–291. Su, C.C., Shen, Y.H., 2009. Adsorption of poly(ethylene oxide) on smectite: effect of layer charge. Journal of Colloid and Interface Science 332, 11–15. Tamura, K., Sasaki, T., Hamada, H., Nakazawa, H., 1999. Laue function analysis of colloidal lithium taeniolite. Langmuir 15, 5509–5512. Theng, B.K.G., 1974. The Chemistry of Clay-Organic Reactions. Adam Hilger, London. Theng, B.K.G., 1979. Formation and Properties of Clay-Polymer Complexes. Elsevier, New York. Triantafillidis, C.S., LeBaron, P.C., Pinnavaia, T.J., 2002a. Homostructured mixed inorganic– organic ion clays: a new approach to epoxy polymer-exfoliated clay nanocomposites with reduced organic modifier content. Chemistry of Materials 14, 4088–4095. Triantafillidis, C.S., LeBaron, P.C., Pinnavaia, T.J., 2002b. Thermoset epoxy-clay nanocomposites: the dual role of α, ω-diamines as clay surface modifiers and polymer curing agents. Journal of Solid State Chemistry 167, 354–362. Triantafillidis, K.S., Panagiotis, I., Pinnavaia, T.J., 2008. Alternative synthetic routes to epoxy polymer-clay nanocomposites using organic or mixed-ion clays modified by protonated di/triamines (Jeffamines). Macromolecular Symposia 267, 41–46. Vaia, R.A., Sauer, B.B., Tse, O.K., Gianneli, E.P., 1997. Relaxations of confined chains in polymer nanocomposites: glass transition properties of poly(ethylene oxide) intercalated in montmorillonite. Journal of Polymer Science. Part B: Polymer Physics 35, 59–67. Wang, Z., Pinnavaia, T.J., 2003. Intercalation of poly(propyleneoxide) amines (Jeffamines) in synthetic layered silicas derived from ilerite, magadiite, and kenyaite. Journal of Materials Chemistry 13, 2127–2131. Yoon, K., Sung, H., Hwang, Y., Noh, S.K., Lee, D., 2007. Modification of montmorillonite with oligomeric amine derivatives for polymer nanocomposite preparation. Applied Clay Science 38, 1–8. Zhang, R., Hu, Y., Li, B., Chen, Z., Fan, W., 2007. Studies on the preparation and structure of polyacrylamide/α-zirconium phosphate nanocomposites. Journal of Materials Science 42, 5641–5646. Zheng, Q.H., Yu, A.B., Lu, G.Q., Paul, D.R., 2005. Clay-based polymer nanocomposites: research and commercial development. Journal of Nanoscience and Nanotechnology 5, 1574–1592. Ziesmer, S., Lagaly, G., 2007. Surface modification of bentonites. VI. Sol–gel transitions of sodium and calcium montmorillonite dispersions in the presence of anionic endcaped poly(ethylene oxides). Clay Minerals 42, 563–573.