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Synthesis and properties of fluoro-alkylated end-capped acrylamide oligomers
European Polymer Journal 36 (2000) 231±240
Synthesis and properties of ¯uoro-alkylated end-capped acrylamide oligomers Hideo Sawada a,b,*, Yoshiko Yoshino b, Yuka Ikematsu b, Tokuzo Kawase c a Department of Chemistry, Nara National College of Technology, Yata, Yamatokoriyama, Nara 639-1080, Japan Department of Chemistry, Faculty of Advanced Engineering, Nara National College of Technology, Yata, Yamatokoriyama, Nara 630-1080, Japan c Faculty of Human Life Science, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
b
Received 22 December 1998; accepted 5 March 1999
Abstract New ¯uoro-alkylated end-capped acryloylmorpholine (ACMO), N,N-dimethylacrylamide (DMAA) and Nisopropylacrylamide (NIPAM) homo-oligomers were prepared by the reactions of the corresponding monomers with ¯uoro-alkanoyl peroxides under very mild conditions. Furthermore, ¯uoro-alkylated end-capped acryloylmorpholine co-oligomers were prepared by the co-oligomerizations with comonomers such as DMAA and NIPAM under similar conditions. It was found that these ¯uorinated oligomers, thus, obtained are soluble not only in water but also in common organic solvents such as methanol, ethanol, tetrahydrofuran, ethyl acetate, benzene, toluene, xylene, chloroform, tetrachloromethane, dichloromethane and acetone, although ¯uoro-alkylated NIPAM homo-oligomers are insoluble in water. Interestingly, these ¯uorinated acrylamide oligomers were able to reduce the surface tension of water and m-xylene quite eectively with a clear breakpoint resembling a critical micelle (or reverse micelle) concentration around 15 and 10 mN/m levels, respectively, which are almost the same levels as that achieved by the usual low molecular weight ¯uorinated surfactants. This suggests that these ¯uoro-alkylated end-capped acrylamide oligomers could form the intra- or inter-molecular aggregates with the aggregations of end-capped ¯uoro-alkyl segments in aqueous and m-xylene solutions. More interestingly, ¯uoro-alkylated end-capped acryloylmorpholine homo- and co-oligomers were found to have an extremely high calcium ion binding power, compared to traditional organic chelating agents and the corresponding non-¯uorinated oligomers. These ¯uorinated oligomers were also able to transfer alkali metal and heavy metal ions from aqueous solutions into organic media. Therefore, these acrylamide oligomers are suggested to have high potential for new ¯uorinated materials through their surfactant and metal ion binding properties. # 1999 Elsevier Science Ltd. All rights reserved.
1. Introduction Recently, there has been a great attractive interest in partially ¯uorinated macromolecules due to exhibiting various unique properties which cannot be achieved by
* Corresponding author. Fax: +81-743-55-6169. E-mail address: [email protected] (H. Sawada).
the per¯uorinated macromolecules [1±10]. From such a point of view, we have already reported on the synthesis of partially ¯uorinated macromolecules such as acrylic acid oligomers containing two ¯uoro-alkylated end-groups [11,12]. Interestingly, these partially ¯uorinated acrylic acid oligomers were easily soluble in water and polar organic solvents such as methanol, ethanol and tetrahydrofuran. In addition, it was suggested that these ¯uorinated oligomers can form
0014-3057/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S 0 0 1 4 - 3 0 5 7 ( 9 9 ) 0 0 0 8 6 - 5
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the intra- or inter-molecular aggregates, which are constructed by the aggregations of the end-capped ¯uoroalkyl segments in aqueous solutions to exhibit antiHIV-1 activity in vitro [12±14]. Therefore, it is very interesting to synthesize novel highly soluble ¯uorinated macromolecules in order to open a new route to the development of the ®eld of new functional ¯uorinated materials. In preliminary accounts, we reported novel ¯uoro-alkylated end-capped acryloylmorpholine (ACMO) oligomers, which exhibit a high solubility in various solvents and have a calcium ion binding power [15,16]. Using ¯uoro-alkanoyl peroxides as key intermediates, we would like to report a new synthetic approach to ¯uoro-alkylated end-capped acrylamide homo- and co-oligomers which are highly soluble in various solvents and, in particular, an application of ¯uoro-alkylated oligomers as a new class of partially ¯uorinated functional materials possessing a metal ion binding power.
2. Results and discussion The reactions of ¯uoro-alkanoyl peroxides with some acrylamide monomers such as acryloylmorpholine (ACMO), N,N-dimethylacrylamide (DMAA) and N-isopropylacrylamide (NIPAM) in 1 : 1 mixed solvents (AK-225) of 1,1-dichloro-2,2,3,3,3-penta¯uoropropane and 1,3-dichloro-1,2,2,3,3-penta¯uoropropane were carried out at 458C for 5 h under nitrogen. These acrylamide monomers were found to react smoothly with the peroxides under very mild conditions to give
a series of ¯uoro-alkylated end-capped acrylamide homo-oligomers and acryloylmorpholine co-oligomers. These results are shown in Schemes 1 and 2 and Table 1. As shown in Schemes 1, 2 and Table 1, per¯uoropropylated and some per¯uoro-oxaalkylated endcapped acrylamide homo- and co-oligomers were obtained in excellent to moderate isolated yields under very mild conditions, and each molecular weight of the oligomers and the co-oligomerization ratios of the cooligomers were determined by GPC (calibrated with standard polystyrenes) and 1 H NMR analyses, respectively. The concentration of ¯uoro-alkanoyl peroxides used were higher than that of acrylamides (molar ratio of acrylamide/peroxide = 4.7±6.5), in contrast to the usual case for radical polymerization. Under these conditions, mainly acrylamide homo- and co-oligomers with two ¯uoro-alkylated end-groups would be obtained via primary radical termination or radical chain transfer to the peroxide, as well as by our previously reported method for the synthesis of acrylic acid oligomers having two ¯uoro-alkylated end-groups in one oligomeric molecule [RF±(CH2CHCO2H)n±RF] [12,13]. Hitherto, it is well known that polysoaps in which ¯uoro-alkyl segments have been introduced randomly into polymeric molecules possess a low solubility in various solvents and are not eective for reducing the surface tension of water [17]. Therefore, it is of particular interest to apply our present ¯uoro-alkylated end-capped acrylamide oligomers to new ¯uorinated polymeric surfactants.
Scheme 1.
H. Sawada et al. / European Polymer Journal 36 (2000) 231±240
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Scheme 2.
The ¯uoro-alkylated end-capped acrylamide oligomers except for the NIPAM homo-oligomers listed in Table 1 showed a good solubility in water. It is well known that non-¯uorinated poly(N-isopropylacrylamide) exhibits thermo-reversible phase separation at a temperature of 318C, its cloud point or lower critical solution temperature (LCST) [18]. However, RF± (NIPAM)n±RF was insoluble in water even when it was heated to around 608C. This ®nding would depend
upon the strong hydrophobicity of both ¯uoro-alkyl and N-isopropyl groups in ¯uorinated NIPAM oligomers. Interestingly, the ¯uoro-alkylated acrylamide homo- and co-oligomers listed in Table 1 were found to be readily soluble in not only polar organic solvents such as methanol, ethanol, tetrahydrofuran, dimethyl sulfoxide, N,N- dimethylformamide, chloroform, ethyl acetate, acetone and dichloromethane, but also in nonpolar aromatic solvents such as benzene, toluene and
Table 1 Homo- and co-oligomerizations of acrylamides with ¯uoro-alkanoyl peroxides RF in peroxide (mmol)
Acrylamide (mmol)
Product Yield (%)a
C3F7 (5) CF(CF3)OC3F7 (5) CF(CF3)OCF2CF(CF3)OC3F7 (7) CF(CF3)OCF2CF(CF3)OCF2CF(CF3)OC3F7 (5) CF(CF3)OC3F7 (3) CF(CF3)OCF2CF(CF3)OC3F7 (3) C3F7 (9) CF(CF3)OC3F7 (3) CF(CF3)OCF2CF(CF3)OC3F7 (3) C3F7 (3) CF(CF3)OC3F7 (4) CF(CF3)OCF2CF(CF3)OC3F7 (3) CF(CF3)OC3F7 (5) CF(CF3)OCF2CF(CF3)OC3F7 (3) a
ACMO 24 24 37 24 DMAA 16 15 NIPAM 42 16 15 ACMO 8 13 8 13 8
83 73 57 60 72 44
C±AA (mmol) DMAA (8) DMAA (13) DMAA (8) NIPAM (13) NIPAM (8)
67 17 71 73 76 80 74 23
Mn (Mw/Mn)b
[x : y ]c
RF±(ACMO)n±RF 1700 (1.59) 1860 (1.41) 4730 (1.50) 7290 (2.42) RF±(DMAA)n±RF 1020 (1.28) 2020 (1.05) RF±(NIPAM)n±RF 930 (1.48) 1210 (1.17) 2330 (1.11) RF±(ACMO)x±(C±AA)y±RF 900 (1.26) [66 1290 (1.22) [41 2230 (1.09) [53 1150 (1.25) [37 1430 (1.22) [53
: : : : :
The yields are based on the starting materials (ACMO, DMAA or NIPAM) and the decarboxylated peroxide unit (RF±RF). Co-oligomerization ratio was determined by 1 H NMR. c Molecular weights were determined by GPC.
b
34] 59] 47] 63] 47]
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Fig. 1. Surface tension of aqueous solutions of RF± at 308C. *: RF = CF (ACMO)n±RF (CF3)OCF2CF(CF3)OCF2CF(CF3)OC3F7; w: RF = CF(CF3)OCF2CF(CF3)OC3F7; q: RF = CF(CF3)OC3F7 r:RF=C3F7; T: ±(ACMO)n± (Mn 3750).
xylene as well as in tetrachloromethane. However, these homo- and co-oligomers showed poor solubility in aliphatic solvents such as hexane. From the viewpoint of the development of the ®eld of new functional ¯uorinated materials, it is very interesting to apply our present ¯uoro-alkylated end-capped acrylamide oligomers possessing such higher solubility to novel ¯uorinated polymeric surfactants. Thus, the surface properties of our ¯uoro-alkylated end-capped acrylamide oligomers were evaluated by measuring the reduction in surface tension of aqueous solutions by these oligomers using the Wilhelmy plate method at 308C. These results are shown in Figs. 1±4. As Figs. 1±4 show a signi®cant decrease in the surface tension of water to around 15 mN/m was found for all ¯uoro-alkylated end-capped acrylamide homoand co-oligomers compared with the corresponding non-¯uorinated acrylamide ones. The degree of reduction in surface tension of water depends on the
Fig. 2. Surface tension of aqueous solutions of RF± (DMAA)n ±RF at 308C. q: RF = CF(CF3)OC3F7; *: RF = CF(CF3)OCF2CF(CF3)OC3F7; r: RF±(ACMO)n± RF; RF = CF(CF3)OC3F7.
Fig. 3. Surface tension of aqueous solutions of RF± (ACMO)x±(DMAA)y±RF at 308C. w: RF = CF (CF3) OCF2CF(CF3)OCF3F7; Q: RF = CF(CF3)OC3F7; r: RF = C3F7; T: ±(ACMO)x±(DMAA)y± (Mn 33700, x : y = 42 : 58).
length of ¯uoro-alkyl groups as well as the usual ¯uorinated surfactants [19]; per¯uoro-oxaalkylated acrylamide homo- and co-oligomers were more eective for reducing the surface tension of water than per¯uoropropylated ones. Fluoro-alkylated end-capped DMAA oligomers are able to reduce the surface tension of water eectively, as well as the corresponding ACMO oligomers as shown in Fig. 2. In ¯uoroalkylated end-capped ACMO homo-oligomers, shorter per¯uoro-oxaalkylated (per¯uoro-1-methyl-2-oxapentylated) oligomer was more eective in reducing the surface tension of water to around 20 mN/m than longer chains. This unique result suggests that the longer per¯uoro-oxaalkyl chains in these oligomers are unlikely
Fig. 4. Surface tension of aqueous solution of RF±(ACMO)x± (NIPAM)y±RF. w: RF = CF(CF3)OCF2CF(CF3)OC3F7; T: ±(ACMO)x±(NIPAM)y ± (Mn 37900, x:y 41:59).
H. Sawada et al. / European Polymer Journal 36 (2000) 231±240
to be arranged more closely above the water surface owing to the steric hindrance of ¯uoro-alkyl group. Previously, we reported that low-molecular ¯uorinated surfactants such as sodium m-per¯uoro-octylbenzene sulfonates are able to reduce the surface tension of water to 15 mN/m levels [20]. Thus, our present ¯uoro-alkylated end-capped acrylamide oligomers are novel high-molecular mass surfactants, which can reduce the surface tension of water as eectively as the low-molecular ones. This interesting feature could be attributed to their unique structure, i.e., the ¯uoroalkyl groups in these oligomers are an end-capped structure and are likely to be arranged more regularly above the water surface, similar to the ¯uoro-alkyl groups of usual low-molecular weight ¯uorinated surfactants. Furthermore, we have measured the surface tension of m-xylene solutions of ¯uoro-alkylated end-capped acrylamide homo- and co-oligomers using the Wilhelmy plate method at 308C. These results are shown in Figs. 5±8. As shown in Figs. 5 and 6, per¯uoro-oxaalkylated end-capped ACMO, DMAA and NIPAM homo-oligomers were able to reduce the surface tension of mxylene eectively. This ®nding should result from the strong action of the oleophobic per¯uoro-oxaalkyl groups aligned on the surface, the alkyl moiety in acrylamide segments being, in general, oleophilic so that such moiety would not lie on the m-xylene surface. Similarly, ¯uoro-alkylated ACMO co-oligomers were able to reduce the surface tension of m-xylene
Fig. 5. Surface tension of m-xylene solutions of RF± (ACMO)n±RF at 308C. w: RF = CF(CF3)OCF2CF(CF3)OC3F7; r: RF =CF(CF3)OCF2CF(CF3)OCF2CF(CF3)OC3F7.
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Fig. 6. Surface tension of m-xylene solutions of RF± (DMAA)n±RF and RF±(NIPAM)n±RF at 308C. q: RF± (DMAA)n±RF; RF = CF(CF3)OC3F7; *: RF±(NIPAM)n± RF; RF = CF(CF3)OC3F7; r: RF±(DMAA)n±RF; RF = CF(CF3)OCF2CF(CF3)OC3F7.
eectively as in Figs. 7 and 8. Especially, ¯uoro-alkylated ACMO±DMAA co-oligomers were more eective in reducing the surface tension of m-xylene than the ACMO±NIPAM co-oligomers. This probably depends in part upon the highly oleophilic NIPAM segments. In this way, it was veri®ed that ¯uoro-alkylated endcapped acrylamide homo- and co-oligomers exhibit good solubility in various solvents and are able to reduce the surface tension of water and m-xylene. Interestingly, these ¯uoro-alkylated oligomers in Figs. 1±4 exhibited quite similar curves (plots of surface ten-
Fig. 7. Surface tension of m-xylene solutions of RF± (ACMO)x±(DMAA)y±RF at 308C. w: RF = CF(CF3)OCF2CF(CF3)OC3F7; Q: RF = CF(CF3)OC3F7; r: RF = C3F7.
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Fig. 8. Surface tension of m-xylene solution of RF± (ACMO)x±(NIPAM)y ±RF at 308C. w: RF = CF(CF3)OCF2CF(CF3)OC3F7; *: RF = CF(CF3)OC3F7.
sions versus log[C ]: [C ] is the concentration of the oligomers) typical of monomeric surfactant, and had a clear breakpoint resembling a CMC (critical micelle concentration) for each oligomer. Therefore, our ¯uoro-alkylated end-capped acrylamide oligomers should form the intra- or inter-molecular aggregates in aqueous solutions, although it has been recently reported that hydrocarbon polysoap and randomly ¯uoro-alkylated polysoap solutions have no CMC or breakpoint resembling a CMC [17,21]. Fluoro-alkyl segments in our present ¯uoro-alkylated end-capped acrylamide oligomers are solvophobic in aqueous solutions, and enhance the aggregation due to the strong interaction between end-capped ¯uoro-alkyl segments. Therefore, the synergistical interactions (one is the aggregations of ¯uoro-alkyl segments and other is the hydrogen bonding between amide segments including water) could provide strong aggregates in aqueous solutions. In fact, we have recently reported that molecular assemblies formed in aqueous solution of the ¯uoro-alkylated end-capped acrylic acid±trimethylvinylsilane co-oligomers have an ellipsoidal shape with the aggregations of terminal ¯uoro-alkyl segments [22,23]. Furthermore, ¯uoro-alkylated end-capped oligomers containing triol segments were found to cause a gelation, where the strong aggregations of ¯uoroalkyl segments and the hydrogen-bonding interaction between triol segments are involved in establishing a physical gel network [24]. Per¯uoro-oxaalkylated end-capped oligomers in Fig. 5 showed a break at a speci®c surfactant concentration (Fig. 5: 5 g/dm3; Figs. 6 and 7: 2 or 5 g/dm3), above which the surface tension remains nearly constant. This ®nding indicates that these ¯uorinated oligomers could form intra- or inter-molecular aggregates in m-
Fig. 9. Ca2+ binding isotherms of RF±(ACMO)n±RF.q: RF = CF(CF3)OCF2CF(CF3)OCF2CF(CF3)OC3F7; *: RF = CF(CF3)OCF2CF(CF3)OC3F7; R: RF = CF(CF3)OC3F7; r: RF = C3F7; w: ±(ACMO)n±; Mn 3750.
xylene solution resembling a reverse micelle of low molecular-mass surfactants. From these results, various metal ions are expected to act as guest molecules for these ¯uorinated aggregates. Thus, we tried to develop ¯uoro-alkylated endcapped ACMO homo-oligomers and ACMO±DMMA co-oligomers as a new ¯uorinated oligomeric chelating surfactant. The equilibrium calcium ion concentrations in aqueous solutions, in the presence of RF± (ACMO)n±RF and RF ±(ACMO)x±(DMAA)y±RF (concentration of each oligomer is 0.5 g/dm3) were measured by using a calcium ion electrode. These results were shown in Figs. 9 and 10.
Fig. 10. Ca2+ binding isotherms of RF±(ACMO)x± (DMAA)y±RF. *: RF = CF(CF3)OCF2CF(CF3)OC3F7; q: RF = CF(CF3)OC3F7; r: RF = C3F7; T: ±(ACMO)x± (DMAA)y± (x:y 42:58).
H. Sawada et al. / European Polymer Journal 36 (2000) 231±240
As shown in Figs. 9 and 10, ¯uoro-alkylated endcapped ACMO homo- and co-oligomers were found to have an extraordinarily high calcium ion binding power compared to those of the corresponding non¯uorinated acrylamide oligomers. In the case of ± (ACMO)x±(DMAA)y±, this polymer did not bind calcium ions. Calcium binding ratio (Ca/A) indicates the average number of bound calcium ions per two acrylamide monomer units in each oligomer. Hitherto, it was reported that poly(acrylic acid) is eective in removing calcium ions from solution; however, the binding ratio of poly(acrylic acid) is almost the same as the theoretical binding ratio [25]. In addition, the calcium chelating ability of surfactants such as sodium lauroyl ethylenediaminotriacetate is, in general, not so high [26]. However, for example, Ca/As of RF± (ACMO)n±RF and RF±(ACMO)x±(DMAA)y±RF [RF = CF(CF3)OCF2CF(CF3)OC3F7] in Figs. 9 and 10 are at maximum ca. 30 and 40, respectively. Furthermore, Ca/As of the corresponding per¯uoropropylated oligomers are at maximum ca. 15 and 24, respectively. On the other hand, it was found that Ca/A values of poly(acrylic acid) and ¯uoro-alkylated end-capped acrylic acid oligomer [RF±(CH2CHCO2H)n±RF; RF = CF(CF3)OC3F7; Mn 6700] are similar to the theoretical binding ratio under the above mentioned analytical conditions. Hydrophobically modi®ed polysoaps have been already reported to exhibit no CMC or a breakpoint resembling a CMC [27]. In fact, as shown in Figs. 1 and 3, non-¯uorinated ACMO homo-oligomer and non-¯uorinated ACMO-dimethylacrylamide copolymer exhibit no CMC or a breakpoint in aqueous solutions. In contrast, ¯uoro-alkylated end-capped ACMO homo- and co-oligomers are able to form the intra- or inter-molecular aggregates in aqueous solutions, and calcium ions should act as guest molecules for these aggregates. Especially, acrylamide segments in aqueous solutions should act as suitable host moieties in these aggregates, and interact strongly with calcium ions. Thus, we could have an obvious correlation between the Ca/A values quoted in Figs. 9 and 10 and the reduction of surface tension of water in Figs. 1 and 3; that is, as the oligomers have a higher Ca/A value, the oligomers can reduce the surface tensions of water more eectively. Previously, Guven and Eltan reported that acrylamide polymers such as poly(N-vinyl-2-pyrrolidone) provide a very good site for hydrogen bonding, which is one of the major type of forces causing association in polymer, and water is attached to poly(Nvinyl-2-pyrrolidone) chains through hydrogen bonding interactions [27]. Therefore, it is also suggested that water could act as a guest molecule for the molecular aggregates formed by ¯uoro-alkylated end-capped acrylamide oligomers. The presence of water in these aggregates could provide suitable host moieties to
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interact strongly with calcium ions as guest molecules, and this eect should derive the extraordinarily high calcium binding power of ¯uoro-alkylated end-capped acrylamide oligomers. In contrast, ¯uoro-alkylated end-capped acrylic acid oligomer was clari®ed to exhibit the theoretical binding ratio. This ®nding would depend on the fact that the aggregates which are constructed by the aggregations of end-capped ¯uoro-alkyl segments in this oligomer are not so stable as compared to the aggregates formed by ¯uoro-alkylated end-capped acrylamide oligomers, because this ¯uorinated acrylic acid oligomer is not likely to have the strong inter-molecular hydrogen bonding interactions between the carboxy segments owing to these carboxy segments being directly introduced into oligomer main chains. It is of particular interest to estimate anity of ¯uoro-alkylated end-capped acrylamide oligomers toward not only calcium ion but also the other metal ions. Thus, we examined the liquid±liquid extraction behavior of ¯uoro-alkylated end-capped ACMO± DMAA co-oligomer [RF±(ACMO)x±(DMAA)n±RF; RF = CF(CF3)OC3F7] for various metal ions. Dichloroethane solutions of the ¯uorinated co-oligomer (2.0 g/dm3) and the corresponding non-¯uorinated ACMO±DMAA copolymer (Mn 33700; x : y =42 : 58) were employed as the organic layer. The aqueous phase was a mixture of 9 10ÿ4 mol/dm3 picric acid and 0.01 mol/dm3 metal ion. Extractability was determined spectrophotometrically by monitoring decrease of absorbance of picrate (356 nm) in the aqueous phase. These result are shown in Table 2. As shown in Table 2, it was clari®ed that ¯uoro-alkylated end-capped ACMO±DMAA co-oligomer has an extraction ability toward various metal cations. However, there is in general no metal cation selectivity for this ¯uorinated co-oligomer. This would result from the conformational ¯exibility of this ¯uorinated aggregate. The alkylamide segments in this ¯uorinated co-oligomer would act as suitable host moieties in the aggregates formed by this co-oligomer, and interact strongly with metal cations. On the other hand, it was shown that the corresponding non-¯uorinated copolymer do not have an extraction ability toward various metal cations at all. This ®nding would depend on it that this copolymer is not likely to form the inter- or intra-molecular aggregates. More interestingly, this ¯uorinated co-oligomer showed the anity toward picric acid. Thus, picric acid should act as a guest molecule for the ¯uorinated aggregates. In conclusion, ¯uoro-alkanoyl peroxide was demonstrated to be a key intermediate for the preparation of various ¯uoro-alkylated end-capped acrylamide oligomers. These obtained ¯uoro-alkylated end-capped acrylamide homo- and co-oligomers were readily soluble not only in water but also in common organic sol-
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H. Sawada et al. / European Polymer Journal 36 (2000) 231±240 Table 2 Solvent extraction of alkali metal and heavy metal ions
a PicH: Picric acid. Organic layer: [oligomer] = 2.0 g/dm3. Aqueous layer (Metal): [MCl], [Metal nitrate] = 0.01 mol/dm3, [PicH] = 9 10ÿ4 mol/dm3. Extractability = ([Picÿ]0 ÿ [Picÿ]aq)/[Picÿ]0 100. [Picÿ]0 = initial concentration of picrate in the aqueous layer. [Picÿ]aq = concentration of picrate in the aqueous layer as equilibrium.
vents including non-polar aromatic solvents such as benzene, toluene and xylene. Furthermore, these ¯uorinated oligomers were able to reduce the surface tensions of water and m-xylene quite eectively, and to form resembling normal and reverse micelles in water and organic solvents, respectively, although these ¯uorinated oligomers possess only end-capped ¯uoroalkyl segments. Thus, it was clari®ed that these ¯uorinated oligomers are applicable to new ¯uorinated oligosurfactants which could behave almost the same eectiveness as low molecular-weight ¯uorinated surfactants. Interestingly, the intra- or inter-molecular aggregates formed by ¯uoro-alkylated end-capped acrylamide oligomers were shown to have a high calcium ion binding power, and were able to transfer not only metal cations but also a polar hydrophilic molecule such as picric acid from aqueous solution into organic media. Therefore, these ¯uoro-alkylated endcapped acrylamide oligomers are expected to develop as new ¯uorinated self-assembled aggregates into various ®elds.
3. Experimental NMR spectra were measured using a Varian Unityplus 500 (500 MHz) spectrometer, while IR spectra were recorded on a HORIBA FT-300 FT-IR spectrophotometer. Molecular weights were calculated by
using a JASCO-PU-980-Shodex-SE-11 gel permeation chromatography calibrated with standard polystyrene by using tetrahydrofuran as the eluent. Absorption spectra were recorded on a Shimadzu UV-1600 spectrophotometer.
4. Materials A series of ¯uoro-alkanoyl peroxides [(RFCOO)2 ] were prepared by the method described in the literature [28,29]. ACMO, DMAA and NIPAM were used as received from Kohjin. 4.1. General procedure for the synthesis of ¯uoroalkylated end-capped ACMO homo-oligomers Per¯uoro-2-methyl-3-oxahexanoyl peroxide (5 mmol) in 1 : 1 mixed solvents (AK-225) of 1,1-dichloro2,2,3,3,3-penta¯uoropropane and 1,3-dichloro1,2,2,3,3-penta¯uoropropane (35 g) was added to a mixture of ACMO (24 mmol) and AK-225 (50 g). The solutions was stirred at 458C for 5 h under nitrogen. After evaporating the solvent, the obtained crude products were reprecipitaed from the AK-225± hexane system to give bis(per¯uoro-1-methyl-2-oxapentylated) ACMO oligomers (4.55 g). This oligomer showed the following spectral data: IR n/cmÿ1 1633 (C1O), 1320 (CF3), 1238 (CF2), 1115 (±O±); 1 H NMR (CDCl3) d
H. Sawada et al. / European Polymer Journal 36 (2000) 231±240
1.46±1.92 (CH2), 2.34±2.76 (CH), 3.18±3.93 (CH2); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ6.81±(ÿ9.30) (16F), ÿ51.37 (6F); average molar mass (Mn) = 1860, Mw =Mn 1:41 (determined by gel permeation chromatography (GPC) calibrated with standard polystyrenes by using tetrahydrofuran as the eluent). The other products obtained exhibited the following spectral characteristics: C3F7±(ACMO)n±C3F7: IR n/cmÿ1 1639 (C1O), 1310 (CF3), 1230 (CF2), 1117 (±O±); 1 H NMR (CDCl3) d 1.18±2.03 (CH2), 2.20±2.82 (CH), 3.18± 3.98 (CH2); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ5.04 (6F), ÿ44.08 (4F), ÿ51.43 (4F); C3F7OCF(CF3)CF2OCF(CF3)±(ACMO)n± CF(CF3)OCF2CF(CF3)OC3F7: IR n/cmÿ1 1641 (C1O), 1302 (CF3), 1240 (CF2), 1115 (±O±); 1 H NMR (CDCl3) d 1.10±1.99 (CH2), 2.24±3.01 (CH), 3.18±3.96 (CH2); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ4.21±(ÿ6.62) (26F), ÿ54.00 (6F), ÿ69.67 (2F); C3F7O[CF(CF3)CF2O]2CF(CF3)±(ACMO)n± CF(CF3)[OCF2CF(CF3)]2OC3F7: IR n/cmÿ1 1637 (C1O), 1304 (CF3), 1242 (CF2), 1117 (±O±); 1 H NMR (CDCl3) d 1.13±2.01 (CH2), 2.28±2.96 (CH), 3.17±4.01 (CH2); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ4.45±(ÿ6.84) (36F), ÿ54.00±(ÿ55.81) (6F), ÿ69.42±(ÿ69.89) (4F); Similarly, a series of ¯uoro-alkylated end-capped DMAA, NIPAM homo-oligomers and ACMO co-oligomers were prepared by homo- and co-oligomerizations with ¯uoro-alkanoyl peroxides. These exhibited the following spectral characteristics: C3F7OCF(CF3)±(DMAA)n±CF(CF3)OC3F7: IR n/ cmÿ1 1637 (C1O), 1338 (CF3), 1240 (CF2); 1 H NMR (CDCl3) d 1.18±1.95 (CH2), 2.28±3.28 (CH, CH3); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ4.75± (ÿ7.50) (16F), ÿ54.29 (6F); C3F7OCF(CF3)CF2OCF(CF3)ÿ(DMAA)n± CF(CF3)OCF2CF(CF3)OC3F7: IR n/cmÿ1 1612 (C1O), 1340 (CF3), 1238 (CF2); 1 H NMR (CDCl3) d 1.12±1.98 (CH2), 2.28±3.22 (CH, CH3); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ4.29±(ÿ6.88) (26F), ÿ54.08 (6F), ÿ69.81 (2F); C3F7±(NIPAM)n±C3F7: IR n/cmÿ1 1649, 1548 (C1O), 1367 (CF3), 1228 (CF2); 1 H NMR (CDCl3) d 0.98±1.35 (CH3), 1.42±2.64 (CH2, CH), 3.83±4.14 (CH); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ5.27 (6F), ÿ44.03 (4F), ÿ51.46 (4F); C3F7OCF(CF3)±(NIPAM)n±CF(CF3)OC3F7: IR n/ cmÿ1 1649, 1545 (C1O), 1333 (CF3), 1203 (CF2); 1 H NMR (CDCl3) d 0.95±1.30 (CH3), 1.30±2.50 (CH2, CH), 2.78±3.31 (CH); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ4.41±(ÿ7.76) (16F), ÿ54.23 (6F); C3F7OCF(CF3)CF2OCF(CF3)±(NIPAM)n± CF(CF3)OCF2CF(CF3)OC3F7: IR n/cmÿ1 1651,
239
1549 (C1O), 1335 (CF3), 1250 (CF2); 1 H NMR (CDCl3) d 0.90±1.20 (CH3), 1.46±2.35 (CH2, CH), 3.60±4.33 (CH); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ4.29±(ÿ6.86) (26F), ÿ54.18 (6F), ÿ69.92 (2F); C3F7±(ACMO)x±(DMAA)y±C3F7: IR n/cmÿ1 1631 (C1O), 1357 (CF3), 1228 (CF2); 1 H NMR (CDCl3) d 1.19±2.05 (CH2, CH), 2.25±4.02 (CH, CH3, CH2); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ5.19 (6F), ÿ44.16 (4F), ÿ51.53 (4F); C3F7OCF(CF3)±(ACMO)x±(DMAA)y± CF(CF3)OC3F7: IR n/cmÿ1 1633 (C1O), 1344 (CF3), 1238 (CF2); 1 H NMR (D2O) d 1.09±1.98 (CH2), 2.31±2.75 (CH), 2.78±3.18 (CH3), 3.20±3.90 (CH2); 19 F NMR (D2O, ext. CF3CO2H) d ÿ5.79± (ÿ7.71) (16F), ÿ54.08 (6F); C3F7OCF(CF3)CF2OCF(CF3)±(ACMO)x± (DMAA)y±CF(CF3)OCF2CF(CF3)OC3F7: IR n/ cmÿ1 1637 (C1O), 1333 (CF3), 1254 (CF2); 1 H NMR (D2O) d 1.08±1.83 (CH2), 2.19±3.09 (CH, CH3), 3.13±4.04 (CH2); 19 F NMR (D2O, ext. CF3CO2H) d ÿ5.61±(ÿ8.02) (26F), ÿ56.00 (6F), ÿ71.20 (2F); C3F7OCF(CF3)±(ACMO)x±(NIPAM)y± CF(CF3)OC3F7: IR n/cmÿ1 1641, 1547 (C1O), 1363 (CF3), 1238 (CF2); 1 H NMR (CDCl3) d 0.91± 2.92 (CH3, CH2, CH), 3.08±4.22 (CH2); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ4.75±(ÿ7.32) (16F), ÿ54.18 (6F); C3F7OCF(CF3)CF2OCF(CF3)±(ACMO)x± (DMAA)y±CF(CF3)OCF2CF(CF3)OC3F7: IR n/ cmÿ1 1641, 1547 (C1O), 1334 (CF3), 1250 (CF2); 1 H NMR (D2O) d 0.68±2.76 (CH3, CH2, CH), 2.84±4.20 (CH2); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ5.59±(ÿ7.79) (26F), ÿ55.84 (6F), ÿ70.74 (2F).
5. Surface tension measurements The surface tensions of aqueous and m-xylene solutions of the ¯uoro-alkylated end-capped acrylamide oligomers were measured at 308C using a Wilhelmytype surface tensiometer (ST-1, Shimadzu) with a glass plate.
6. Measurements of the equilibrium calcium ion concentration A calcium ion electrode and a digital pH/ion meter (HORIBA F-23) were used to measure the equilibrium calcium ion concentrations. All of the titration procedures were carried out in a KCl solution for the Ca2+ ion binding study. Each oligomer sample was added to a 0.1 mol/dm3 KCl solution. After 30 min of
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stirring, the mixture solution was titrated with a CaCl2 solution. 7. Solvent extraction In a 30 ml vial, 5 ml of an aqueous solution of metal ion containing picric acid and 5 ml of an 1,2dichloroethane solution of an oligomer were mixed vigorously for 30 min at 258C. Concentrations of oligomer and metal ion employed here and de®nition of extractability are shown in Table 2. After standing for 24 h at 258C, the aqueous phase was separated, and then the concentration of picrate ion in the aqueous phase was determined by UV±Vis spectroscopy monitoring absorption at 356 nm to give the extractability. Acknowledgements This work was partially supported by a grant-in-aid for Scienti®c Research No. 09650945 from the Ministry of Education, Science, Sports and Culture, Japan, for which the authors are grateful. Thanks are due to Kohjin for supply of ACMO, NIPAM and DMAA. References [1] Hunt Jr. MO, Belu AM, Linton RW, Desimone JM. Macromolecules 1993;26:4854. [2] Wang J, Mao G, Ober CK, Kramer EJ. Polym Prepr (Am Chem Soc, Div Polym Chem) 1997;38:953. [3] Su Z, Wu D, Hsu SL, McCarthy TJ. Polym Prepr (Am Chem Soc, Div Polym Chem) 1997;38:951. [4] Cooper AI, Londono JD, Wignall G, McClain JN, Samuiski ET, Lin JS, Dobrynin A, Rubinstein M, Burke ALC, Frechet JMJ, DeSimone JM. Nature 1997;389:368. [5] Elman JF, Johs BD, Long TE, Koberstein JT. Macromolecules 1994;27:5341. [6] Arossman S, Bertrand P, Hartshorne M, Ki T, Leonard D, Pethrick RA, Richards RW. Macromolecules 1996;29:5432.
[7] Arossman S, Hartshorne M, Ki T, Pethrick RA, Richards RW. Macromolecules 1994;27:1588. [8] Xu B, Li L, Yekta A, Masoumi Z, Kanagalingam S, Winnik MA, Zhang K, Macdonald PM. Langmuir 1997;13:2447. [9] Zhang H, Hogen-Esch T, Boschet F, Margaillian A. Polym Prepr (Am Chem Soc, Div Polym Chem) 1996;37:731. [10] Zhang H, Pan J, Hogen-Esch TE. Macromolecules 1998;31:2815. [11] Sawada H. Chem Rev 1996;96:1779. [12] Sawada H, Gong YF, Minoshima Y, Matsumoto T, Nakayama M, Kosugi M, Migita T. J Chem Soc Chem Commun 1992:537. [13] Sawada H, Minoshima Y, Nakajima H. J Fluorine Chem 1992;65:169. [14] Baba M, Kira T, Shigeta S, Matsumoto T, Sawada H. J Aquir Immun De®c Syndr 1994;7:24. [15] Sawada H, Kawase T, Ikematsu Y, Ishii Y, Oue M, Hayakawa Y. J Chem Soc Chem Commun 1996:179. [16] Sawada H, Yoshino Y, Itoh M, Kawase T, Hayakawa Y. J Fluorine Chem 1997;83:183. [17] Anton P, Koberle P, Laschewsky A. Makromol Chem 1993;194:1. [18] Heskins M, Guillet JE. Macromol Sci 1968;A2:1441. [19] Abe M, Morikawa K, Ogino K, Sawada H, Matsumoto T, Nakayama M. Langmuir 1992;8:763. [20] Ogino K, Abe M, Morikawa K, Mitani M, Sawada H, Matsumoto T. J Jpn Soc Colour Mater 1994;67:88. [21] Cochin D, Hendlinger P, Laschewsky A. Colloid Polym Sci 1995;273:1138. [22] Nakagawa J, Kamogawa K, Sakai H, Kawase T, Sawada H, Manosroi J, Manosroi A, Abe M. Langmuir 1998;14:2055. [23] Nakagawa J, Kamogawa K, Momozawa N, Sakai H, Kawase T, Sawada H, Sano Y, Abe M. Langmuir 1998;14:2061. [24] Sawada H, Nakamura Y, Katayama S, Kawase T. Bull Chem Soc Jpn 1997;70:2839. [25] Chang DM. J Am Oil Chem Soc 1983;60:618. [26] Crudden BA, Parker BA. Inform 1995;6:1132. [27] Guven O, Eltan E. Makromol Chem 1981;182:3129. [28] Sawada H, Nakayama M. J Fluorine Chem 1990;51:117. [29] Sawada H, Yoshida M, Hagii H, Aoshima K, Kobayashi M. Bull Chem Soc Jpn 1986;59:215.
Synthesis and properties of ¯uoro-alkylated end-capped acrylamide oligomers Hideo Sawada a,b,*, Yoshiko Yoshino b, Yuka Ikematsu b, Tokuzo Kawase c a Department of Chemistry, Nara National College of Technology, Yata, Yamatokoriyama, Nara 639-1080, Japan Department of Chemistry, Faculty of Advanced Engineering, Nara National College of Technology, Yata, Yamatokoriyama, Nara 630-1080, Japan c Faculty of Human Life Science, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
b
Received 22 December 1998; accepted 5 March 1999
Abstract New ¯uoro-alkylated end-capped acryloylmorpholine (ACMO), N,N-dimethylacrylamide (DMAA) and Nisopropylacrylamide (NIPAM) homo-oligomers were prepared by the reactions of the corresponding monomers with ¯uoro-alkanoyl peroxides under very mild conditions. Furthermore, ¯uoro-alkylated end-capped acryloylmorpholine co-oligomers were prepared by the co-oligomerizations with comonomers such as DMAA and NIPAM under similar conditions. It was found that these ¯uorinated oligomers, thus, obtained are soluble not only in water but also in common organic solvents such as methanol, ethanol, tetrahydrofuran, ethyl acetate, benzene, toluene, xylene, chloroform, tetrachloromethane, dichloromethane and acetone, although ¯uoro-alkylated NIPAM homo-oligomers are insoluble in water. Interestingly, these ¯uorinated acrylamide oligomers were able to reduce the surface tension of water and m-xylene quite eectively with a clear breakpoint resembling a critical micelle (or reverse micelle) concentration around 15 and 10 mN/m levels, respectively, which are almost the same levels as that achieved by the usual low molecular weight ¯uorinated surfactants. This suggests that these ¯uoro-alkylated end-capped acrylamide oligomers could form the intra- or inter-molecular aggregates with the aggregations of end-capped ¯uoro-alkyl segments in aqueous and m-xylene solutions. More interestingly, ¯uoro-alkylated end-capped acryloylmorpholine homo- and co-oligomers were found to have an extremely high calcium ion binding power, compared to traditional organic chelating agents and the corresponding non-¯uorinated oligomers. These ¯uorinated oligomers were also able to transfer alkali metal and heavy metal ions from aqueous solutions into organic media. Therefore, these acrylamide oligomers are suggested to have high potential for new ¯uorinated materials through their surfactant and metal ion binding properties. # 1999 Elsevier Science Ltd. All rights reserved.
1. Introduction Recently, there has been a great attractive interest in partially ¯uorinated macromolecules due to exhibiting various unique properties which cannot be achieved by
* Corresponding author. Fax: +81-743-55-6169. E-mail address: [email protected] (H. Sawada).
the per¯uorinated macromolecules [1±10]. From such a point of view, we have already reported on the synthesis of partially ¯uorinated macromolecules such as acrylic acid oligomers containing two ¯uoro-alkylated end-groups [11,12]. Interestingly, these partially ¯uorinated acrylic acid oligomers were easily soluble in water and polar organic solvents such as methanol, ethanol and tetrahydrofuran. In addition, it was suggested that these ¯uorinated oligomers can form
0014-3057/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S 0 0 1 4 - 3 0 5 7 ( 9 9 ) 0 0 0 8 6 - 5
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the intra- or inter-molecular aggregates, which are constructed by the aggregations of the end-capped ¯uoroalkyl segments in aqueous solutions to exhibit antiHIV-1 activity in vitro [12±14]. Therefore, it is very interesting to synthesize novel highly soluble ¯uorinated macromolecules in order to open a new route to the development of the ®eld of new functional ¯uorinated materials. In preliminary accounts, we reported novel ¯uoro-alkylated end-capped acryloylmorpholine (ACMO) oligomers, which exhibit a high solubility in various solvents and have a calcium ion binding power [15,16]. Using ¯uoro-alkanoyl peroxides as key intermediates, we would like to report a new synthetic approach to ¯uoro-alkylated end-capped acrylamide homo- and co-oligomers which are highly soluble in various solvents and, in particular, an application of ¯uoro-alkylated oligomers as a new class of partially ¯uorinated functional materials possessing a metal ion binding power.
2. Results and discussion The reactions of ¯uoro-alkanoyl peroxides with some acrylamide monomers such as acryloylmorpholine (ACMO), N,N-dimethylacrylamide (DMAA) and N-isopropylacrylamide (NIPAM) in 1 : 1 mixed solvents (AK-225) of 1,1-dichloro-2,2,3,3,3-penta¯uoropropane and 1,3-dichloro-1,2,2,3,3-penta¯uoropropane were carried out at 458C for 5 h under nitrogen. These acrylamide monomers were found to react smoothly with the peroxides under very mild conditions to give
a series of ¯uoro-alkylated end-capped acrylamide homo-oligomers and acryloylmorpholine co-oligomers. These results are shown in Schemes 1 and 2 and Table 1. As shown in Schemes 1, 2 and Table 1, per¯uoropropylated and some per¯uoro-oxaalkylated endcapped acrylamide homo- and co-oligomers were obtained in excellent to moderate isolated yields under very mild conditions, and each molecular weight of the oligomers and the co-oligomerization ratios of the cooligomers were determined by GPC (calibrated with standard polystyrenes) and 1 H NMR analyses, respectively. The concentration of ¯uoro-alkanoyl peroxides used were higher than that of acrylamides (molar ratio of acrylamide/peroxide = 4.7±6.5), in contrast to the usual case for radical polymerization. Under these conditions, mainly acrylamide homo- and co-oligomers with two ¯uoro-alkylated end-groups would be obtained via primary radical termination or radical chain transfer to the peroxide, as well as by our previously reported method for the synthesis of acrylic acid oligomers having two ¯uoro-alkylated end-groups in one oligomeric molecule [RF±(CH2CHCO2H)n±RF] [12,13]. Hitherto, it is well known that polysoaps in which ¯uoro-alkyl segments have been introduced randomly into polymeric molecules possess a low solubility in various solvents and are not eective for reducing the surface tension of water [17]. Therefore, it is of particular interest to apply our present ¯uoro-alkylated end-capped acrylamide oligomers to new ¯uorinated polymeric surfactants.
Scheme 1.
H. Sawada et al. / European Polymer Journal 36 (2000) 231±240
233
Scheme 2.
The ¯uoro-alkylated end-capped acrylamide oligomers except for the NIPAM homo-oligomers listed in Table 1 showed a good solubility in water. It is well known that non-¯uorinated poly(N-isopropylacrylamide) exhibits thermo-reversible phase separation at a temperature of 318C, its cloud point or lower critical solution temperature (LCST) [18]. However, RF± (NIPAM)n±RF was insoluble in water even when it was heated to around 608C. This ®nding would depend
upon the strong hydrophobicity of both ¯uoro-alkyl and N-isopropyl groups in ¯uorinated NIPAM oligomers. Interestingly, the ¯uoro-alkylated acrylamide homo- and co-oligomers listed in Table 1 were found to be readily soluble in not only polar organic solvents such as methanol, ethanol, tetrahydrofuran, dimethyl sulfoxide, N,N- dimethylformamide, chloroform, ethyl acetate, acetone and dichloromethane, but also in nonpolar aromatic solvents such as benzene, toluene and
Table 1 Homo- and co-oligomerizations of acrylamides with ¯uoro-alkanoyl peroxides RF in peroxide (mmol)
Acrylamide (mmol)
Product Yield (%)a
C3F7 (5) CF(CF3)OC3F7 (5) CF(CF3)OCF2CF(CF3)OC3F7 (7) CF(CF3)OCF2CF(CF3)OCF2CF(CF3)OC3F7 (5) CF(CF3)OC3F7 (3) CF(CF3)OCF2CF(CF3)OC3F7 (3) C3F7 (9) CF(CF3)OC3F7 (3) CF(CF3)OCF2CF(CF3)OC3F7 (3) C3F7 (3) CF(CF3)OC3F7 (4) CF(CF3)OCF2CF(CF3)OC3F7 (3) CF(CF3)OC3F7 (5) CF(CF3)OCF2CF(CF3)OC3F7 (3) a
ACMO 24 24 37 24 DMAA 16 15 NIPAM 42 16 15 ACMO 8 13 8 13 8
83 73 57 60 72 44
C±AA (mmol) DMAA (8) DMAA (13) DMAA (8) NIPAM (13) NIPAM (8)
67 17 71 73 76 80 74 23
Mn (Mw/Mn)b
[x : y ]c
RF±(ACMO)n±RF 1700 (1.59) 1860 (1.41) 4730 (1.50) 7290 (2.42) RF±(DMAA)n±RF 1020 (1.28) 2020 (1.05) RF±(NIPAM)n±RF 930 (1.48) 1210 (1.17) 2330 (1.11) RF±(ACMO)x±(C±AA)y±RF 900 (1.26) [66 1290 (1.22) [41 2230 (1.09) [53 1150 (1.25) [37 1430 (1.22) [53
: : : : :
The yields are based on the starting materials (ACMO, DMAA or NIPAM) and the decarboxylated peroxide unit (RF±RF). Co-oligomerization ratio was determined by 1 H NMR. c Molecular weights were determined by GPC.
b
34] 59] 47] 63] 47]
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Fig. 1. Surface tension of aqueous solutions of RF± at 308C. *: RF = CF (ACMO)n±RF (CF3)OCF2CF(CF3)OCF2CF(CF3)OC3F7; w: RF = CF(CF3)OCF2CF(CF3)OC3F7; q: RF = CF(CF3)OC3F7 r:RF=C3F7; T: ±(ACMO)n± (Mn 3750).
xylene as well as in tetrachloromethane. However, these homo- and co-oligomers showed poor solubility in aliphatic solvents such as hexane. From the viewpoint of the development of the ®eld of new functional ¯uorinated materials, it is very interesting to apply our present ¯uoro-alkylated end-capped acrylamide oligomers possessing such higher solubility to novel ¯uorinated polymeric surfactants. Thus, the surface properties of our ¯uoro-alkylated end-capped acrylamide oligomers were evaluated by measuring the reduction in surface tension of aqueous solutions by these oligomers using the Wilhelmy plate method at 308C. These results are shown in Figs. 1±4. As Figs. 1±4 show a signi®cant decrease in the surface tension of water to around 15 mN/m was found for all ¯uoro-alkylated end-capped acrylamide homoand co-oligomers compared with the corresponding non-¯uorinated acrylamide ones. The degree of reduction in surface tension of water depends on the
Fig. 2. Surface tension of aqueous solutions of RF± (DMAA)n ±RF at 308C. q: RF = CF(CF3)OC3F7; *: RF = CF(CF3)OCF2CF(CF3)OC3F7; r: RF±(ACMO)n± RF; RF = CF(CF3)OC3F7.
Fig. 3. Surface tension of aqueous solutions of RF± (ACMO)x±(DMAA)y±RF at 308C. w: RF = CF (CF3) OCF2CF(CF3)OCF3F7; Q: RF = CF(CF3)OC3F7; r: RF = C3F7; T: ±(ACMO)x±(DMAA)y± (Mn 33700, x : y = 42 : 58).
length of ¯uoro-alkyl groups as well as the usual ¯uorinated surfactants [19]; per¯uoro-oxaalkylated acrylamide homo- and co-oligomers were more eective for reducing the surface tension of water than per¯uoropropylated ones. Fluoro-alkylated end-capped DMAA oligomers are able to reduce the surface tension of water eectively, as well as the corresponding ACMO oligomers as shown in Fig. 2. In ¯uoroalkylated end-capped ACMO homo-oligomers, shorter per¯uoro-oxaalkylated (per¯uoro-1-methyl-2-oxapentylated) oligomer was more eective in reducing the surface tension of water to around 20 mN/m than longer chains. This unique result suggests that the longer per¯uoro-oxaalkyl chains in these oligomers are unlikely
Fig. 4. Surface tension of aqueous solution of RF±(ACMO)x± (NIPAM)y±RF. w: RF = CF(CF3)OCF2CF(CF3)OC3F7; T: ±(ACMO)x±(NIPAM)y ± (Mn 37900, x:y 41:59).
H. Sawada et al. / European Polymer Journal 36 (2000) 231±240
to be arranged more closely above the water surface owing to the steric hindrance of ¯uoro-alkyl group. Previously, we reported that low-molecular ¯uorinated surfactants such as sodium m-per¯uoro-octylbenzene sulfonates are able to reduce the surface tension of water to 15 mN/m levels [20]. Thus, our present ¯uoro-alkylated end-capped acrylamide oligomers are novel high-molecular mass surfactants, which can reduce the surface tension of water as eectively as the low-molecular ones. This interesting feature could be attributed to their unique structure, i.e., the ¯uoroalkyl groups in these oligomers are an end-capped structure and are likely to be arranged more regularly above the water surface, similar to the ¯uoro-alkyl groups of usual low-molecular weight ¯uorinated surfactants. Furthermore, we have measured the surface tension of m-xylene solutions of ¯uoro-alkylated end-capped acrylamide homo- and co-oligomers using the Wilhelmy plate method at 308C. These results are shown in Figs. 5±8. As shown in Figs. 5 and 6, per¯uoro-oxaalkylated end-capped ACMO, DMAA and NIPAM homo-oligomers were able to reduce the surface tension of mxylene eectively. This ®nding should result from the strong action of the oleophobic per¯uoro-oxaalkyl groups aligned on the surface, the alkyl moiety in acrylamide segments being, in general, oleophilic so that such moiety would not lie on the m-xylene surface. Similarly, ¯uoro-alkylated ACMO co-oligomers were able to reduce the surface tension of m-xylene
Fig. 5. Surface tension of m-xylene solutions of RF± (ACMO)n±RF at 308C. w: RF = CF(CF3)OCF2CF(CF3)OC3F7; r: RF =CF(CF3)OCF2CF(CF3)OCF2CF(CF3)OC3F7.
235
Fig. 6. Surface tension of m-xylene solutions of RF± (DMAA)n±RF and RF±(NIPAM)n±RF at 308C. q: RF± (DMAA)n±RF; RF = CF(CF3)OC3F7; *: RF±(NIPAM)n± RF; RF = CF(CF3)OC3F7; r: RF±(DMAA)n±RF; RF = CF(CF3)OCF2CF(CF3)OC3F7.
eectively as in Figs. 7 and 8. Especially, ¯uoro-alkylated ACMO±DMAA co-oligomers were more eective in reducing the surface tension of m-xylene than the ACMO±NIPAM co-oligomers. This probably depends in part upon the highly oleophilic NIPAM segments. In this way, it was veri®ed that ¯uoro-alkylated endcapped acrylamide homo- and co-oligomers exhibit good solubility in various solvents and are able to reduce the surface tension of water and m-xylene. Interestingly, these ¯uoro-alkylated oligomers in Figs. 1±4 exhibited quite similar curves (plots of surface ten-
Fig. 7. Surface tension of m-xylene solutions of RF± (ACMO)x±(DMAA)y±RF at 308C. w: RF = CF(CF3)OCF2CF(CF3)OC3F7; Q: RF = CF(CF3)OC3F7; r: RF = C3F7.
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Fig. 8. Surface tension of m-xylene solution of RF± (ACMO)x±(NIPAM)y ±RF at 308C. w: RF = CF(CF3)OCF2CF(CF3)OC3F7; *: RF = CF(CF3)OC3F7.
sions versus log[C ]: [C ] is the concentration of the oligomers) typical of monomeric surfactant, and had a clear breakpoint resembling a CMC (critical micelle concentration) for each oligomer. Therefore, our ¯uoro-alkylated end-capped acrylamide oligomers should form the intra- or inter-molecular aggregates in aqueous solutions, although it has been recently reported that hydrocarbon polysoap and randomly ¯uoro-alkylated polysoap solutions have no CMC or breakpoint resembling a CMC [17,21]. Fluoro-alkyl segments in our present ¯uoro-alkylated end-capped acrylamide oligomers are solvophobic in aqueous solutions, and enhance the aggregation due to the strong interaction between end-capped ¯uoro-alkyl segments. Therefore, the synergistical interactions (one is the aggregations of ¯uoro-alkyl segments and other is the hydrogen bonding between amide segments including water) could provide strong aggregates in aqueous solutions. In fact, we have recently reported that molecular assemblies formed in aqueous solution of the ¯uoro-alkylated end-capped acrylic acid±trimethylvinylsilane co-oligomers have an ellipsoidal shape with the aggregations of terminal ¯uoro-alkyl segments [22,23]. Furthermore, ¯uoro-alkylated end-capped oligomers containing triol segments were found to cause a gelation, where the strong aggregations of ¯uoroalkyl segments and the hydrogen-bonding interaction between triol segments are involved in establishing a physical gel network [24]. Per¯uoro-oxaalkylated end-capped oligomers in Fig. 5 showed a break at a speci®c surfactant concentration (Fig. 5: 5 g/dm3; Figs. 6 and 7: 2 or 5 g/dm3), above which the surface tension remains nearly constant. This ®nding indicates that these ¯uorinated oligomers could form intra- or inter-molecular aggregates in m-
Fig. 9. Ca2+ binding isotherms of RF±(ACMO)n±RF.q: RF = CF(CF3)OCF2CF(CF3)OCF2CF(CF3)OC3F7; *: RF = CF(CF3)OCF2CF(CF3)OC3F7; R: RF = CF(CF3)OC3F7; r: RF = C3F7; w: ±(ACMO)n±; Mn 3750.
xylene solution resembling a reverse micelle of low molecular-mass surfactants. From these results, various metal ions are expected to act as guest molecules for these ¯uorinated aggregates. Thus, we tried to develop ¯uoro-alkylated endcapped ACMO homo-oligomers and ACMO±DMMA co-oligomers as a new ¯uorinated oligomeric chelating surfactant. The equilibrium calcium ion concentrations in aqueous solutions, in the presence of RF± (ACMO)n±RF and RF ±(ACMO)x±(DMAA)y±RF (concentration of each oligomer is 0.5 g/dm3) were measured by using a calcium ion electrode. These results were shown in Figs. 9 and 10.
Fig. 10. Ca2+ binding isotherms of RF±(ACMO)x± (DMAA)y±RF. *: RF = CF(CF3)OCF2CF(CF3)OC3F7; q: RF = CF(CF3)OC3F7; r: RF = C3F7; T: ±(ACMO)x± (DMAA)y± (x:y 42:58).
H. Sawada et al. / European Polymer Journal 36 (2000) 231±240
As shown in Figs. 9 and 10, ¯uoro-alkylated endcapped ACMO homo- and co-oligomers were found to have an extraordinarily high calcium ion binding power compared to those of the corresponding non¯uorinated acrylamide oligomers. In the case of ± (ACMO)x±(DMAA)y±, this polymer did not bind calcium ions. Calcium binding ratio (Ca/A) indicates the average number of bound calcium ions per two acrylamide monomer units in each oligomer. Hitherto, it was reported that poly(acrylic acid) is eective in removing calcium ions from solution; however, the binding ratio of poly(acrylic acid) is almost the same as the theoretical binding ratio [25]. In addition, the calcium chelating ability of surfactants such as sodium lauroyl ethylenediaminotriacetate is, in general, not so high [26]. However, for example, Ca/As of RF± (ACMO)n±RF and RF±(ACMO)x±(DMAA)y±RF [RF = CF(CF3)OCF2CF(CF3)OC3F7] in Figs. 9 and 10 are at maximum ca. 30 and 40, respectively. Furthermore, Ca/As of the corresponding per¯uoropropylated oligomers are at maximum ca. 15 and 24, respectively. On the other hand, it was found that Ca/A values of poly(acrylic acid) and ¯uoro-alkylated end-capped acrylic acid oligomer [RF±(CH2CHCO2H)n±RF; RF = CF(CF3)OC3F7; Mn 6700] are similar to the theoretical binding ratio under the above mentioned analytical conditions. Hydrophobically modi®ed polysoaps have been already reported to exhibit no CMC or a breakpoint resembling a CMC [27]. In fact, as shown in Figs. 1 and 3, non-¯uorinated ACMO homo-oligomer and non-¯uorinated ACMO-dimethylacrylamide copolymer exhibit no CMC or a breakpoint in aqueous solutions. In contrast, ¯uoro-alkylated end-capped ACMO homo- and co-oligomers are able to form the intra- or inter-molecular aggregates in aqueous solutions, and calcium ions should act as guest molecules for these aggregates. Especially, acrylamide segments in aqueous solutions should act as suitable host moieties in these aggregates, and interact strongly with calcium ions. Thus, we could have an obvious correlation between the Ca/A values quoted in Figs. 9 and 10 and the reduction of surface tension of water in Figs. 1 and 3; that is, as the oligomers have a higher Ca/A value, the oligomers can reduce the surface tensions of water more eectively. Previously, Guven and Eltan reported that acrylamide polymers such as poly(N-vinyl-2-pyrrolidone) provide a very good site for hydrogen bonding, which is one of the major type of forces causing association in polymer, and water is attached to poly(Nvinyl-2-pyrrolidone) chains through hydrogen bonding interactions [27]. Therefore, it is also suggested that water could act as a guest molecule for the molecular aggregates formed by ¯uoro-alkylated end-capped acrylamide oligomers. The presence of water in these aggregates could provide suitable host moieties to
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interact strongly with calcium ions as guest molecules, and this eect should derive the extraordinarily high calcium binding power of ¯uoro-alkylated end-capped acrylamide oligomers. In contrast, ¯uoro-alkylated end-capped acrylic acid oligomer was clari®ed to exhibit the theoretical binding ratio. This ®nding would depend on the fact that the aggregates which are constructed by the aggregations of end-capped ¯uoro-alkyl segments in this oligomer are not so stable as compared to the aggregates formed by ¯uoro-alkylated end-capped acrylamide oligomers, because this ¯uorinated acrylic acid oligomer is not likely to have the strong inter-molecular hydrogen bonding interactions between the carboxy segments owing to these carboxy segments being directly introduced into oligomer main chains. It is of particular interest to estimate anity of ¯uoro-alkylated end-capped acrylamide oligomers toward not only calcium ion but also the other metal ions. Thus, we examined the liquid±liquid extraction behavior of ¯uoro-alkylated end-capped ACMO± DMAA co-oligomer [RF±(ACMO)x±(DMAA)n±RF; RF = CF(CF3)OC3F7] for various metal ions. Dichloroethane solutions of the ¯uorinated co-oligomer (2.0 g/dm3) and the corresponding non-¯uorinated ACMO±DMAA copolymer (Mn 33700; x : y =42 : 58) were employed as the organic layer. The aqueous phase was a mixture of 9 10ÿ4 mol/dm3 picric acid and 0.01 mol/dm3 metal ion. Extractability was determined spectrophotometrically by monitoring decrease of absorbance of picrate (356 nm) in the aqueous phase. These result are shown in Table 2. As shown in Table 2, it was clari®ed that ¯uoro-alkylated end-capped ACMO±DMAA co-oligomer has an extraction ability toward various metal cations. However, there is in general no metal cation selectivity for this ¯uorinated co-oligomer. This would result from the conformational ¯exibility of this ¯uorinated aggregate. The alkylamide segments in this ¯uorinated co-oligomer would act as suitable host moieties in the aggregates formed by this co-oligomer, and interact strongly with metal cations. On the other hand, it was shown that the corresponding non-¯uorinated copolymer do not have an extraction ability toward various metal cations at all. This ®nding would depend on it that this copolymer is not likely to form the inter- or intra-molecular aggregates. More interestingly, this ¯uorinated co-oligomer showed the anity toward picric acid. Thus, picric acid should act as a guest molecule for the ¯uorinated aggregates. In conclusion, ¯uoro-alkanoyl peroxide was demonstrated to be a key intermediate for the preparation of various ¯uoro-alkylated end-capped acrylamide oligomers. These obtained ¯uoro-alkylated end-capped acrylamide homo- and co-oligomers were readily soluble not only in water but also in common organic sol-
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H. Sawada et al. / European Polymer Journal 36 (2000) 231±240 Table 2 Solvent extraction of alkali metal and heavy metal ions
a PicH: Picric acid. Organic layer: [oligomer] = 2.0 g/dm3. Aqueous layer (Metal): [MCl], [Metal nitrate] = 0.01 mol/dm3, [PicH] = 9 10ÿ4 mol/dm3. Extractability = ([Picÿ]0 ÿ [Picÿ]aq)/[Picÿ]0 100. [Picÿ]0 = initial concentration of picrate in the aqueous layer. [Picÿ]aq = concentration of picrate in the aqueous layer as equilibrium.
vents including non-polar aromatic solvents such as benzene, toluene and xylene. Furthermore, these ¯uorinated oligomers were able to reduce the surface tensions of water and m-xylene quite eectively, and to form resembling normal and reverse micelles in water and organic solvents, respectively, although these ¯uorinated oligomers possess only end-capped ¯uoroalkyl segments. Thus, it was clari®ed that these ¯uorinated oligomers are applicable to new ¯uorinated oligosurfactants which could behave almost the same eectiveness as low molecular-weight ¯uorinated surfactants. Interestingly, the intra- or inter-molecular aggregates formed by ¯uoro-alkylated end-capped acrylamide oligomers were shown to have a high calcium ion binding power, and were able to transfer not only metal cations but also a polar hydrophilic molecule such as picric acid from aqueous solution into organic media. Therefore, these ¯uoro-alkylated endcapped acrylamide oligomers are expected to develop as new ¯uorinated self-assembled aggregates into various ®elds.
3. Experimental NMR spectra were measured using a Varian Unityplus 500 (500 MHz) spectrometer, while IR spectra were recorded on a HORIBA FT-300 FT-IR spectrophotometer. Molecular weights were calculated by
using a JASCO-PU-980-Shodex-SE-11 gel permeation chromatography calibrated with standard polystyrene by using tetrahydrofuran as the eluent. Absorption spectra were recorded on a Shimadzu UV-1600 spectrophotometer.
4. Materials A series of ¯uoro-alkanoyl peroxides [(RFCOO)2 ] were prepared by the method described in the literature [28,29]. ACMO, DMAA and NIPAM were used as received from Kohjin. 4.1. General procedure for the synthesis of ¯uoroalkylated end-capped ACMO homo-oligomers Per¯uoro-2-methyl-3-oxahexanoyl peroxide (5 mmol) in 1 : 1 mixed solvents (AK-225) of 1,1-dichloro2,2,3,3,3-penta¯uoropropane and 1,3-dichloro1,2,2,3,3-penta¯uoropropane (35 g) was added to a mixture of ACMO (24 mmol) and AK-225 (50 g). The solutions was stirred at 458C for 5 h under nitrogen. After evaporating the solvent, the obtained crude products were reprecipitaed from the AK-225± hexane system to give bis(per¯uoro-1-methyl-2-oxapentylated) ACMO oligomers (4.55 g). This oligomer showed the following spectral data: IR n/cmÿ1 1633 (C1O), 1320 (CF3), 1238 (CF2), 1115 (±O±); 1 H NMR (CDCl3) d
H. Sawada et al. / European Polymer Journal 36 (2000) 231±240
1.46±1.92 (CH2), 2.34±2.76 (CH), 3.18±3.93 (CH2); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ6.81±(ÿ9.30) (16F), ÿ51.37 (6F); average molar mass (Mn) = 1860, Mw =Mn 1:41 (determined by gel permeation chromatography (GPC) calibrated with standard polystyrenes by using tetrahydrofuran as the eluent). The other products obtained exhibited the following spectral characteristics: C3F7±(ACMO)n±C3F7: IR n/cmÿ1 1639 (C1O), 1310 (CF3), 1230 (CF2), 1117 (±O±); 1 H NMR (CDCl3) d 1.18±2.03 (CH2), 2.20±2.82 (CH), 3.18± 3.98 (CH2); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ5.04 (6F), ÿ44.08 (4F), ÿ51.43 (4F); C3F7OCF(CF3)CF2OCF(CF3)±(ACMO)n± CF(CF3)OCF2CF(CF3)OC3F7: IR n/cmÿ1 1641 (C1O), 1302 (CF3), 1240 (CF2), 1115 (±O±); 1 H NMR (CDCl3) d 1.10±1.99 (CH2), 2.24±3.01 (CH), 3.18±3.96 (CH2); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ4.21±(ÿ6.62) (26F), ÿ54.00 (6F), ÿ69.67 (2F); C3F7O[CF(CF3)CF2O]2CF(CF3)±(ACMO)n± CF(CF3)[OCF2CF(CF3)]2OC3F7: IR n/cmÿ1 1637 (C1O), 1304 (CF3), 1242 (CF2), 1117 (±O±); 1 H NMR (CDCl3) d 1.13±2.01 (CH2), 2.28±2.96 (CH), 3.17±4.01 (CH2); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ4.45±(ÿ6.84) (36F), ÿ54.00±(ÿ55.81) (6F), ÿ69.42±(ÿ69.89) (4F); Similarly, a series of ¯uoro-alkylated end-capped DMAA, NIPAM homo-oligomers and ACMO co-oligomers were prepared by homo- and co-oligomerizations with ¯uoro-alkanoyl peroxides. These exhibited the following spectral characteristics: C3F7OCF(CF3)±(DMAA)n±CF(CF3)OC3F7: IR n/ cmÿ1 1637 (C1O), 1338 (CF3), 1240 (CF2); 1 H NMR (CDCl3) d 1.18±1.95 (CH2), 2.28±3.28 (CH, CH3); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ4.75± (ÿ7.50) (16F), ÿ54.29 (6F); C3F7OCF(CF3)CF2OCF(CF3)ÿ(DMAA)n± CF(CF3)OCF2CF(CF3)OC3F7: IR n/cmÿ1 1612 (C1O), 1340 (CF3), 1238 (CF2); 1 H NMR (CDCl3) d 1.12±1.98 (CH2), 2.28±3.22 (CH, CH3); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ4.29±(ÿ6.88) (26F), ÿ54.08 (6F), ÿ69.81 (2F); C3F7±(NIPAM)n±C3F7: IR n/cmÿ1 1649, 1548 (C1O), 1367 (CF3), 1228 (CF2); 1 H NMR (CDCl3) d 0.98±1.35 (CH3), 1.42±2.64 (CH2, CH), 3.83±4.14 (CH); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ5.27 (6F), ÿ44.03 (4F), ÿ51.46 (4F); C3F7OCF(CF3)±(NIPAM)n±CF(CF3)OC3F7: IR n/ cmÿ1 1649, 1545 (C1O), 1333 (CF3), 1203 (CF2); 1 H NMR (CDCl3) d 0.95±1.30 (CH3), 1.30±2.50 (CH2, CH), 2.78±3.31 (CH); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ4.41±(ÿ7.76) (16F), ÿ54.23 (6F); C3F7OCF(CF3)CF2OCF(CF3)±(NIPAM)n± CF(CF3)OCF2CF(CF3)OC3F7: IR n/cmÿ1 1651,
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1549 (C1O), 1335 (CF3), 1250 (CF2); 1 H NMR (CDCl3) d 0.90±1.20 (CH3), 1.46±2.35 (CH2, CH), 3.60±4.33 (CH); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ4.29±(ÿ6.86) (26F), ÿ54.18 (6F), ÿ69.92 (2F); C3F7±(ACMO)x±(DMAA)y±C3F7: IR n/cmÿ1 1631 (C1O), 1357 (CF3), 1228 (CF2); 1 H NMR (CDCl3) d 1.19±2.05 (CH2, CH), 2.25±4.02 (CH, CH3, CH2); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ5.19 (6F), ÿ44.16 (4F), ÿ51.53 (4F); C3F7OCF(CF3)±(ACMO)x±(DMAA)y± CF(CF3)OC3F7: IR n/cmÿ1 1633 (C1O), 1344 (CF3), 1238 (CF2); 1 H NMR (D2O) d 1.09±1.98 (CH2), 2.31±2.75 (CH), 2.78±3.18 (CH3), 3.20±3.90 (CH2); 19 F NMR (D2O, ext. CF3CO2H) d ÿ5.79± (ÿ7.71) (16F), ÿ54.08 (6F); C3F7OCF(CF3)CF2OCF(CF3)±(ACMO)x± (DMAA)y±CF(CF3)OCF2CF(CF3)OC3F7: IR n/ cmÿ1 1637 (C1O), 1333 (CF3), 1254 (CF2); 1 H NMR (D2O) d 1.08±1.83 (CH2), 2.19±3.09 (CH, CH3), 3.13±4.04 (CH2); 19 F NMR (D2O, ext. CF3CO2H) d ÿ5.61±(ÿ8.02) (26F), ÿ56.00 (6F), ÿ71.20 (2F); C3F7OCF(CF3)±(ACMO)x±(NIPAM)y± CF(CF3)OC3F7: IR n/cmÿ1 1641, 1547 (C1O), 1363 (CF3), 1238 (CF2); 1 H NMR (CDCl3) d 0.91± 2.92 (CH3, CH2, CH), 3.08±4.22 (CH2); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ4.75±(ÿ7.32) (16F), ÿ54.18 (6F); C3F7OCF(CF3)CF2OCF(CF3)±(ACMO)x± (DMAA)y±CF(CF3)OCF2CF(CF3)OC3F7: IR n/ cmÿ1 1641, 1547 (C1O), 1334 (CF3), 1250 (CF2); 1 H NMR (D2O) d 0.68±2.76 (CH3, CH2, CH), 2.84±4.20 (CH2); 19 F NMR (CDCl3, ext. CF3CO2H) d ÿ5.59±(ÿ7.79) (26F), ÿ55.84 (6F), ÿ70.74 (2F).
5. Surface tension measurements The surface tensions of aqueous and m-xylene solutions of the ¯uoro-alkylated end-capped acrylamide oligomers were measured at 308C using a Wilhelmytype surface tensiometer (ST-1, Shimadzu) with a glass plate.
6. Measurements of the equilibrium calcium ion concentration A calcium ion electrode and a digital pH/ion meter (HORIBA F-23) were used to measure the equilibrium calcium ion concentrations. All of the titration procedures were carried out in a KCl solution for the Ca2+ ion binding study. Each oligomer sample was added to a 0.1 mol/dm3 KCl solution. After 30 min of
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stirring, the mixture solution was titrated with a CaCl2 solution. 7. Solvent extraction In a 30 ml vial, 5 ml of an aqueous solution of metal ion containing picric acid and 5 ml of an 1,2dichloroethane solution of an oligomer were mixed vigorously for 30 min at 258C. Concentrations of oligomer and metal ion employed here and de®nition of extractability are shown in Table 2. After standing for 24 h at 258C, the aqueous phase was separated, and then the concentration of picrate ion in the aqueous phase was determined by UV±Vis spectroscopy monitoring absorption at 356 nm to give the extractability. Acknowledgements This work was partially supported by a grant-in-aid for Scienti®c Research No. 09650945 from the Ministry of Education, Science, Sports and Culture, Japan, for which the authors are grateful. Thanks are due to Kohjin for supply of ACMO, NIPAM and DMAA. References [1] Hunt Jr. MO, Belu AM, Linton RW, Desimone JM. Macromolecules 1993;26:4854. [2] Wang J, Mao G, Ober CK, Kramer EJ. Polym Prepr (Am Chem Soc, Div Polym Chem) 1997;38:953. [3] Su Z, Wu D, Hsu SL, McCarthy TJ. Polym Prepr (Am Chem Soc, Div Polym Chem) 1997;38:951. [4] Cooper AI, Londono JD, Wignall G, McClain JN, Samuiski ET, Lin JS, Dobrynin A, Rubinstein M, Burke ALC, Frechet JMJ, DeSimone JM. Nature 1997;389:368. [5] Elman JF, Johs BD, Long TE, Koberstein JT. Macromolecules 1994;27:5341. [6] Arossman S, Bertrand P, Hartshorne M, Ki T, Leonard D, Pethrick RA, Richards RW. Macromolecules 1996;29:5432.
[7] Arossman S, Hartshorne M, Ki T, Pethrick RA, Richards RW. Macromolecules 1994;27:1588. [8] Xu B, Li L, Yekta A, Masoumi Z, Kanagalingam S, Winnik MA, Zhang K, Macdonald PM. Langmuir 1997;13:2447. [9] Zhang H, Hogen-Esch T, Boschet F, Margaillian A. Polym Prepr (Am Chem Soc, Div Polym Chem) 1996;37:731. [10] Zhang H, Pan J, Hogen-Esch TE. Macromolecules 1998;31:2815. [11] Sawada H. Chem Rev 1996;96:1779. [12] Sawada H, Gong YF, Minoshima Y, Matsumoto T, Nakayama M, Kosugi M, Migita T. J Chem Soc Chem Commun 1992:537. [13] Sawada H, Minoshima Y, Nakajima H. J Fluorine Chem 1992;65:169. [14] Baba M, Kira T, Shigeta S, Matsumoto T, Sawada H. J Aquir Immun De®c Syndr 1994;7:24. [15] Sawada H, Kawase T, Ikematsu Y, Ishii Y, Oue M, Hayakawa Y. J Chem Soc Chem Commun 1996:179. [16] Sawada H, Yoshino Y, Itoh M, Kawase T, Hayakawa Y. J Fluorine Chem 1997;83:183. [17] Anton P, Koberle P, Laschewsky A. Makromol Chem 1993;194:1. [18] Heskins M, Guillet JE. Macromol Sci 1968;A2:1441. [19] Abe M, Morikawa K, Ogino K, Sawada H, Matsumoto T, Nakayama M. Langmuir 1992;8:763. [20] Ogino K, Abe M, Morikawa K, Mitani M, Sawada H, Matsumoto T. J Jpn Soc Colour Mater 1994;67:88. [21] Cochin D, Hendlinger P, Laschewsky A. Colloid Polym Sci 1995;273:1138. [22] Nakagawa J, Kamogawa K, Sakai H, Kawase T, Sawada H, Manosroi J, Manosroi A, Abe M. Langmuir 1998;14:2055. [23] Nakagawa J, Kamogawa K, Momozawa N, Sakai H, Kawase T, Sawada H, Sano Y, Abe M. Langmuir 1998;14:2061. [24] Sawada H, Nakamura Y, Katayama S, Kawase T. Bull Chem Soc Jpn 1997;70:2839. [25] Chang DM. J Am Oil Chem Soc 1983;60:618. [26] Crudden BA, Parker BA. Inform 1995;6:1132. [27] Guven O, Eltan E. Makromol Chem 1981;182:3129. [28] Sawada H, Nakayama M. J Fluorine Chem 1990;51:117. [29] Sawada H, Yoshida M, Hagii H, Aoshima K, Kobayashi M. Bull Chem Soc Jpn 1986;59:215.