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Synthesis and characterization of metal-containing polyurethanes and polyurethane-ureas
European Polymer Journal 35 (1999) 1939±1948
Synthesis and characterization of metal-containing polyurethanes and polyurethane-ureas R. Arun Prasath, S. Nanjundan* Department of Chemistry, College of Engineering, Anna University, Guindy, Madras 600 025, India Received 29 September 1998; accepted 25 November 1998
Abstract Metal-containing polyurethanes containing ionic linkages in the main chain were synthesized by the polyaddition reaction of hexamethylene diisocyanate (HMDI) or toluylene 2,4-diisocyanate (TDI) with 1:1 mixtures of divalent metal salts of mono(hydroxybutyl)phthalate [M(HBP)2] and digol [DG]. Similarly polyurethane-ureas were synthesized by reacting the diisocyanates with 1:1 mixtures of hexamethylene bis(o,N-hydroxyethyl-urea) (HBHEU) and M(HBP)2. The polymers were characterized by elemental analysis, thermogravimetric analysis, solubility, visocity and spectral studies. # 1999 Elsevier Science Ltd. All rights reserved.
1. Introduction Ionic polymers have emerged in large extent that possess a wide range of properties leading to variety of applications as aqueous thickeners, impregnants, textile sizers, adhesives [1,2], additives [3], resins [4,5], catalysts [6] and in the ®eld of medicine [7,8]. Diols containing ionic linkages between COOÿ and M++ are of interest and useful as difunctional ionic monomers which are used as starting materials for the synthesis of ionic polymers in which the metal is ®rmly incorporated in the backbone of the polymer chain [9±24]. Metallo-polymers containing metal in the backbone of the polymer chain have been studied [25±28]. The previous report [29] from this laboratory was synthesis and characterization of metal-containing polyurethanes and polyurethane-ureas based on divalent metal salts of mono(hydroxybutyl)phthalate [M(HBP)2]. The present paper deals with the synthesis and characteriz-
* Corresponding author. Fax: +91-44-235-2870. E-mail address: [email protected] (S. Nanjundan)
ation of metal-containing polyurethanes and polyurethane-ureas derived from calcium, manganese and lead salts of mono(hydroxybutyl)phthalate, digol, hexamethylene bis(o,N-hydroxyethyl-urea) and hexamethylene diisocyanate or toluylene 2,4-diisocyanate.
2. Experimental procedures Metal salts of mono(hydroxybutyl)phthalate [M(HBP)2, M=Ca++, Mn++ and Pb++] were synthesized by the same method as reported in our previous study [29]. Scheme 1 shows the structure for M(HBP)2. Hexamethylene bis (o,N-hydroxyethyl-urea) [HBHEU] was synthesized according to the method reported by Matsuda [10]. 2.1. Synthesis of polymers For the synthesis of metal-containing polyurethane copolymers (Scheme 2) a mixture of M(HBP)2 (0.005 mol) and digol (0.005 mol) in DMF or DMSO (80 ml) was taken in a three necked ¯ask ®tted with a
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 0 9 - 9
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R. Arun Prasath, S. Nanjundan / European Polymer Journal 35 (1999) 1939±1948
Scheme 1
nitrogen inlet, a condenser and a dropping funnel. To this 2±3 drops of di-n-butyltindilaurate (DBTDL) was added as a catalyst. Then 0.01 mol of HMDI or TDI dissolved in 20 mL of DMF or DMSO was added slowly with constant stirring under a stream of nitro-
gen for about 1 h at 80±908C. Then the temperature of the reaction mixture was raised to 1008C and the mixture was stirred for about 4 h. Finally the reaction mixture was allowed to cool and treated with excess of DMF or DMSO. The solution was ®ltered and poured
Scheme 2
R. Arun Prasath, S. Nanjundan / European Polymer Journal 35 (1999) 1939±1948
into a large quantity of vigorously stirred chloroform or acetone to precipitate the polymer. The polymers were washed several time with alcohol and acetone and then dried in vacuo at 60±708C for 1 h. Similarly, metal-containing polyurethane-ureas (Scheme 3) were synthesized by reacting M(HBP)2 (0.005 mol) and HBHEU (0.005 mol) dissolved in 80 mL of DMF or DMSO with HMDI or TDI (0.01 mol) in the presence of 2±3 drops of DBTDL as catalyst.
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2.2. Characterization of the polymers Infrared spectra of the polymers were taken using Perkin-Elmer Model 598 Spectrophotometer at room temperature with KBr disk method. JEOL-GSX 400 MHz spectrometer was used to record 1H NMR spectra in DMSO-d6 solvent using TMS as internal standard. Thermogravimetric analysis (TGA) was carried out in Metler±3000 Thermal Analyser at a heating
Scheme 3
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R. Arun Prasath, S. Nanjundan / European Polymer Journal 35 (1999) 1939±1948
Table 1 Synthesis data and intrinsic viscosity of various metal-containing polyurethanes Polymer
Yield (%)a
External appearance
Intrinsic viscosity
Ca(HBP)2-HMDI-DGb Mn(HBP)2-HMDI-DGb Pb(HBP)2-HMDI-DGc Ca(HBP)2-TDI-DGb Mn(HBP)2-TDI-DGb Pb(HBP)2-TDI-DGc
77 73 65 78 72 68
White powder Dirty white powder Grey powder Yellowish white powder Yellowish white powder Slightly grey powder
0.1252 0.1290 ± 0.1254 0.1274 ±
a
Reaction temperature is 80±1008C, reaction duration is 5 h. DMF was used as solvent for polymer synthesis. c DMSO was used as solvent for polymer synthesis.
b
rate of 208C/min in air atmosphere. A Perkin-Elmer 2400 Carbon-Hydrogen Analyser was used for elemental analysis. Standard analytical methods were used to determine the metal content of dierent polymers. The intrinsic viscosity of the polymers were determined in DMSO at 408C using an Ubbelohde viscometer. Solubility studies were tried in various polar and nonpolar solvents at room temperature.
3. Results and discussion 3.1. Synthesis Metal salts of mono(hydroxybutyl)phthalate are insoluble in most of the organic solvents. Hence the polymerization of the salts, digol or HBHEU with diisocyanates was done in highly polar solvents such as DMF or DMSO. DMF was used as a solvent for the synthesis of calcium and manganese containing polymers, while DMSO was used for the synthesis of lead containing polymers. It was established that the reaction between diols and diisocyanates catalysed by DBTBL takes place via the formation of a ternary complex between the reagents and the catalyst [30]. To avoid cross-linking of the polymers, the mole ratio of
mixtures of diols and diisocyanates was taken as 1:1. After the completion of the reaction, DMF or DMSO was added in large excess to dissolve the linear polymer. Filtration was carried out in order to separate out any cross linked polymer formed. Subsequently the dissolved polymer was reprecipitated by the addition of non-solvents such as acetone or chloroform. With the help of the ionic monomers Ca(HBP)2, Mn(HBP)2 or Pb(HBP)2 and digol six metal-containing polyurethanes were synthesized based on HMDI and TDI. They are coded as Ca(HBP)2-HMDI-DG, Mn(HBP)2HMDI-DG, Pb(HBP)2-HMDI-DG, Ca(HBP)2-TDIDG, Mn(HBP)2-TDI-DG and Pb(HBP)2-TDI-DG. The synthesis data of metal-containing polyurethanes are given in Table 1. Using 1:1 mixture of M(HBP)2 and HBHEU six polyurethane-ureas were synthesized based on HMDI and TDI which are coded as Ca(HBP)2-HMDI-HBHEU, Mn(HBP)2-HMDIHBHEU, Pb(HBP)2-HMDI-HBHEU, Ca(HBP)2-TDIHBHEU, Mn(HBP)2-TDI-HBHEU and Pb(HBP)2TDI-HBHEU. The synthesis data of metal-containing polyurethane-ureas are given in Table 2. 3.2. Characterization Fig. 1 shows the IR spectra of the metal-containing
Table 2 Synthesis data and intrinsic viscosity of various metal-containing polyurethane-ureas Polymer
Yield (%)a
External appearance
Intrinsic viscosity
Ca(HBP)2-HMDI-HBHEUb Mn(HBP)2-HMDI-HBHEUb Pb(HBP)2-HMDI-HBHEUc Ca(HBP)2-TDI-HBHEUb Mn(HBP)2-TDI-HBHEUb Pb(HBP)2-TDI-HBHEUc
75 72 67 72 70 65
White powder Dirty white powder Grey powder Yellowish white powder Yellowish white powder Slightly grey powder
0.1002 0.1150 ± 0.1124 0.1060 ±
a
Reaction temperature is 80±1008C, reaction duration is 5 h. DMF was used as solvent for polymer synthesis. c DMSO was used as solvent for polymer synthesis.
b
R. Arun Prasath, S. Nanjundan / European Polymer Journal 35 (1999) 1939±1948
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Fig. 1. IR spectra of (a) Mn(HBP)2-HMDI-DG; (b) Pb(HBP)2-HMDI-DG; (c) Ca(HBP)2-HMDI-DG; (d) Mn(HBP)2-TDI-DG; (e) Ca(HBP)2-TDI-DG and (f) Pb(HBP)2-TDI-DG.
polyurethane copolymers. The spectra are essentially identical. The absorption band at 3300±3400 cmÿ1 is due to -NH stretching. The peaks around 1640± 1720 cmÿ1 are attributed to the carbonyl stretching of urethane and ester groups. The carboxylate ion due to the acid salts give raise to two broad bands, a strong asymmetrical stretching band near 1520±1570 cmÿ1 and a weaker symmetrical stretching near 1400 cmÿ1. This con®rms the presence of ionic links in the polyurethanes. IR spectra of metal-containing polyurethane-ureas are identical and are shown in Fig. 2. The broad band between 3300 and 3380 cmÿ1 is attributed to -NH stretching. Peaks between 1650 and 1720 cmÿ1 are attributed to the carbonyl stretching of urethane, urea and ester groups. The two broad bands
at 1400 and 1590 cmÿ1 con®rms the presence of ionic links in the polyurethane-ureas. The 1H NMR spectra of polyurethane copolymers derived from M(HBP)2, digol and diisocyanates (HMDI/TDI) show signals for the -NH protons of urethane groups at 7.71±8.52 ppm. The shift to down ®eld is due to inter and intra molecular H-bonding between the -NH group with a C1O group of the polymer and the S1O group of the solvent. The resonance signals at 6.85±7.63 ppm are attributed to the aromatic protons. The peaks between 4.71±4.85 ppm are attributed to the methyleneoxy group ¯anked between -OCH2- and -CONH- groups. The methyleneoxy group which is ¯anked between -O(CH2)3- and COC6H4- shows peaks for dierent polymers between
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R. Arun Prasath, S. Nanjundan / European Polymer Journal 35 (1999) 1939±1948
Fig. 2. IR spectra of (a) Mn(HBP)2-HMDI-HBHEU; (b) Pb(HBP)2-HMDI-HBHEU; (c) Ca(HBP)2-HMDI-HBHEU; (d) Mn(HBP)2-TDI-HBHEU; (e) Pb(HBP)2-TDI-HBHEU and (f) Ca(HBP)2-TDI-HBHEU.
Fig. 3. 1H NMR spectra of (a) Ca(HBP)2-HMDI-DG and (b) Ca(HBP)2-TDI-DG.
R. Arun Prasath, S. Nanjundan / European Polymer Journal 35 (1999) 1939±1948
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Fig. 4. 1H NMR spectra of (a) Ca(HBP)2-HMDI-HBHEU and (b) Ca(HBP)2-TDI-HBHEU.
4.25 and 4.32 ppm. The other methyleneoxy group ¯anked between -O(CH2)3- and -COHN- shows a peak between 4.08 and 4.21 ppm. The methylene groups which are attached to ether linkages show signals between 3.52 and 3.58 ppm. The methylene groups ¯anked between -OCONH- and -(CH2)4- show signals at 3.20±3.31 ppm in the case of HMDI-based polyurethane copolymers. Methyl groups attached to the aromatic ring show signals at 2.18±2.30 ppm for the TDI-based polyurethane copolymers. The remaining methylene groups in the copolymers show a broad band between 1.18 and 1.72 ppm. Fig. 3 shows the 1H NMR spectra of calcium-containing HMDI-based polyurethane [Ca(HBP)2-HMDI-DG] and TDI-based polyurethane [Ca(HBP)2-TDI-DG]. The 1H NMR spectra of polyurethane-ureas derived from M(HBP)2, HBHEU and diisocyanates (HMDI/ TDI) show signals between 7.86 and 8.65 ppm for the -NH protons of the urethane and urea groups involved in inter and intra molecular H-bonding. The resonance signal between 7.21 and 7.72 ppm is due to aromatic protons. The methyleneoxy group ¯anked between NHCONHCH2- and -CONH- groups show a signal between 4.45 and 4.61 ppm. The resonance signal between 3.93 and 4.21 ppm is due to the methyleneoxy group ¯anked between -(CH2)3- and -CONH- and that attached to the -COC6H4- group. Methylene groups ¯anked between -NHCONH- and -CH2COONHgroups show resonance signal between 3.26 and 3.31 ppm. Methylene groups ¯anked between -NHCONH-
and -(CH2)4- groups and that in the group OCONHCH2- show peaks between 2.93 and 3.15 ppm. Methyl group attached to the aromatic ring of TDIbased polyurethane-ureas shows resonance signal between 2.18 and 2.29 ppm. The peak at 1.59±1.64
Fig. 5. TGA curves of (a) Ca(HBP)2-HMDI-DG; (b) Mn(HBP)2-HMDI-DG and (c) Pb(HBP)2-HMDI-DG.
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R. Arun Prasath, S. Nanjundan / European Polymer Journal 35 (1999) 1939±1948
Fig. 6. TGA curves of (a) Ca(HBP)2-TDI-DG; Mn(HBP)2-TDI-DG and (c) Pb(HBP)2-TDI-DG.
(b)
ppm is attributed to the -(CH2)2- group which is attached between -OCH2- and -CH2O- groups. Other methylene protons in the polyurethane-ureas show
Fig. 7. TGA curves of (a) Ca(HBP)2-HMDI-HBHEU; (b) Mn(HBP)2-HMDI-HBHEU and (c) Pb(HBP)2-HMDI HBHEU.
Fig. 8. TGA curves of (a) Ca(HBP)2-TDI-HBHEU; (b) Mn(HBP)2-TDI-HBHEU and (c) Pb(HBP)2-TDI-HBHEU.
broad peaks between 1.21 and 1.55 ppm. Fig. 4 shows the 1H NMR spectra of calcium containing HMDIbased polyurethane-urea [Ca(HBP)2-HMDI-HBHEU] and TDI-based polyurethane-urea [Ca(HBP)2-TDIHBHEU]. Figs. 5±8 show the TGA curves of metal-containing polyurethanes and polyurethane-ureas, respectively. Although all the metal-containing polymers are structurally similar, they exhibit dierent behaviour in thermal analysis. Initial decomposition temperature (IDT) of the polymers are found between 150 and 2508C. It is observed that metal-containing polyurethanes have higher IDT than metal-containing polyurethane-ureas. Polyurethane-ureas are expected to be more stable than polyurethanes as the former is stabilized by more hydrogen bondings. The reverse order in this case may be explained based on our ®ndings that the polyurethane copolymers prepared were found to contain less metal than the prepared polyurethane-ureas. It has been reported that the existence of metal promotes the thermal decomposition of urethanes [9] and ureas [22] and with increase in metal content of the polymers the stability decreases. Thermal stability of the metal-containing polymers can be ordered as Pb>Mn>Ca. Initial thermal degradation of polyurethanes and polyurethane-ureas normally proceeds via urethane scission to isocyanate and hydroxyl components [31,32]. Solubility test shows that these metal-containing polyurethane and polyurethane-ureas are insoluble in
R. Arun Prasath, S. Nanjundan / European Polymer Journal 35 (1999) 1939±1948
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Table 3 Analytical data of metal-containing polyurethanes Polymer
Repeating unit
Ca(HBP)2-HMDI-DGa
CaC44H60N4O17
Mn(HBP)2-HMDI-DGa
MnC44H60N4O17
Pb(HBP)2-HMDI-DGb
PbC44H60N4O17
Ca(HBP)2-TDI-DGa
CaC46H48N4O17
Mn(HBP)2-TDI-DGa
MnC46H48N4O17
Pb(HBP)2-TDI-DGb
PbC46H48N4O17
a b
Analytical data found (calculated) (%) C
H
M
47.06 (55.49) 45.88 (54.64) 38.95 (47.25) 49.44 (57.01) 47.54 (56.14) 40.43 (48.64)
5.77 (6.31) 5.65 (6.22) 4.84 (5.38) 4.48 (4.99) 4.34 (4.92) 3.70 (4.26)
2.82 (4.18) 3.72 (5.66) 11.47 (18.4) 2.86 (4.14) 3.62 (5.59) 11.15 (18.22)
DMF was used as solvent for polymer synethsis. DMSO was used as solvent for polymer synethsis.
methanol, ethanol, acetone, ethyl methyl ketone, chloroform, carbon tetrachloride, n-hexane, benzene, toluene, xylenes, tetra hydrofuran and dioxane. While calcium and manganese containing polymers are soluble in DMF and DMSO, lead-containing polymers are insoluble even in the above solvents. The intrinsic viscosity of the soluble polymers in DMSO were found to be low (incorporated in Tables 1 and 2), which con®rms that the ionic links in the polymer chain dissociates into low molecular weight fragments [9,10,24,26]. The intrinsic viscosity of the prepared polyurethanes is higher than that of polyurethaneureas. This may be attributed to the fact that the poly-
urethanes have less metal which leads to less ionic linkage in the polymer chain. Metal-containing polyurethanes show that the experimentally determined percentage value of carbon, hydrogen and metal content is not well within the range of calculated value, while in the case of polyurethane-ureas these values are found to be somewhat low but within the range of calculated value. From this it may be inferred that the reactivity of the ionic diol seems to be much less than that of digol but just less than that of HBHEU towards diisocynates. Tables 3 and 4 show the analytical data of the metal-containing polyurethanes and polyurethane-ureas, respectively.
Table 4 Analytical data of metal-containing polyurethane-ureas Polymer
Repeating unit
Ca(HBP)2-HMDI-HBHEUa
CaC52H76N8O18
Mn(HBP)2-HMDI-HBHEUa
MnC52H76N8O18
Pb(HBP)2-HMDI-HBHEUb
PbC52H76N8O18
Ca(HBP)2-TDI-HBHEUa
CaC54H64N8O18
Mn(HBP)2-TDI-HBHEUa
MnC54H64N8O18
Pb(HBP)2-TDI-HBHEUb
PbC54H64N8O18
a b
DMF was used as solvent for polymer synethsis. DMSO was used as solvent for polymer synethsis.
Analytical data found (calculated) (%) C
H
M
53.27 (54.74) 52.42 (54.03) 46.51 (47.75) 55.00 (56.25) 54.00 (55.53) 47.30 (49.14)
6.70 (6.71) 6.60 (6.63) 5.85 (5.85) 5.55 (5.59) 5.48 (5.52) 4.88 (4.88)
3.15 (3.51) 4.20 (4.75) 14.00 (15.84) 3.12 (3.47) 4.11 (4.70) 13.04 (15.69)
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R. Arun Prasath, S. Nanjundan / European Polymer Journal 35 (1999) 1939±1948
4. Conclusion Metal salts of mono(hydroxybutyl)phthalate are very useful starting materials for the synthesis of ionic polymers into which the metal is ®rmly incorporated. As M(HBP)2 are insoluble in most of the organic solvents, DMF or DMSO were used as solvent media for the synthesis of polymers. A series of polyurethane copolymers were prepared by reacting a 1:1 mixture of M(HBP)2 and digol with HMDI or TDI. Another series of polyurethane-ureas were prepared by reacting 1:1 mixture of M(HBP)2 and HBHEU with HMDI or TDI. The IR spectra of these polymers, con®rms the presence of ionic linkage. The polymers were characterized by NMR spectra. Thermal studies show that the metal-containing polyurethanes have higher IDT than metal-containing polyurethane-ureas. Also, the intrinsic viscosity of polyurethanes are higher than the polyurethane-ureas. From analytical methods it was found that the metal content in polyurethanes or polyurethane-ureas are found to be less than the value calculated based on equal reactivity of co-monomers. This shows that the reactivity of digol and HBHEU are higher than that of M(HBP)2 towards diisocyanates.
Acknowledgements One of the authors (R.A.P.) thanks the CSIR, India for oering Senior Research Fellowship.
References [1] Matsuda H, Kanaoka Kunio. J Appl Polym Sci 1985;30:1229. [2] Matsuda H. J Appl Polym Sci 1979;23:2603.
[3] Matsuda H, Takechi S. J Polym Sci Polym Chem Ed 1990;28:1895. [4] Matsuda H. J Appl Polym Sci 1978;22:2093. [5] Matsuda H. J Polym Sci; Polym Chem Ed 1977;15:2239. [6] Matsuda H. J Appl Polym Sci 1978;22:3371. [7] Silver JH, Hart AP, Williams EC, Cooper SL, Charef S, Labarre D, Jozefowivz M. Biol Mat 1992;13(6):339. [8] Okkeema AZ, Cooper SL. Biol Mat 1991;12:668. [9] Matsuda H. J Polym Sci; Polym Chem Ed 1974;12:455. [10] Matsuda H. J Polym Sci; Polym Chem Ed 1974;12:469. [11] Matsuda H. J Polym Sci; Polym Chem Ed 1974;12:2419. [12] Matsuda H. J Macromol Sci Chem 1975;A9:397. [13] Matsuda H. J Polym Sci; Polym Chem Ed 1976;14:1783. [14] Matsuda H. J Appl Polym Sci 1976;20:995. [15] Matsuda H. J Macromol Sci Chem 1976;A10:1143. [16] Durairaj B, Venkatarao K. Polym Bull 1979;1:723. [17] Durairaj B, Venkatarao K. Eur Polym J 1980;16:941. [18] Kothandaraman H, Venkatarao K, Raghavan A, Chandrasekaran V. Polym Bull 1985;13:353. [19] Matsuda H. Polym Engng Sci 1987;4:233. [20] Rajalingam P, Radhakrishnan G, Vasudevan C, Tamare Seloy K, Venkatarao K. Polym Com 1990;31:243. [21] Rajalingam P, Radhakrishnan G. Polymer 1992;33:2214. [22] Matsuda H, Takechi S. J Polym Sci, Polym Chem 1990;28:1895. [23] Matsuda H, Takechi S. J Polym Sci, Polym Chem 1991;29:83. [24] Qiu W, Zeng W, Zhang X, Li C, Lu L, Wang X, Yang X, Sanitary BC. J Appl Polym Sci 1993;49:405. [25] Bao Z, Chen Y, Yu L. Macromolecules 1994;27:4629. [26] Zeng W, Qiu W, Liu J, Yang X, Lu L, Wang X, Dai Q. Polymer 1995;36:3761. [27] Lee J, Nishio A, Tomita I, Endo T. Macromolecules 1997;30:5205. [28] Jiang B, Jones Jr WE. Macromolecules 1997;30:5575. [29] Arun Prasath R, Nanjundan S. J Macromol Sci Pure Appl Chem 1998;A35(5):821. [30] Lipatova TE, Bakalo LA, Sivotinskaya AL, Lopationa VS. Vysokomol Soedin 1970;A12(4):911 (in Russian). [31] Beachell HC, Ngoc Son CP. J Appl Polym Sci 1963;7:2217. [32] Rapp NS, Ingham JD. J Polym Sci 1964;A2:689.
Synthesis and characterization of metal-containing polyurethanes and polyurethane-ureas R. Arun Prasath, S. Nanjundan* Department of Chemistry, College of Engineering, Anna University, Guindy, Madras 600 025, India Received 29 September 1998; accepted 25 November 1998
Abstract Metal-containing polyurethanes containing ionic linkages in the main chain were synthesized by the polyaddition reaction of hexamethylene diisocyanate (HMDI) or toluylene 2,4-diisocyanate (TDI) with 1:1 mixtures of divalent metal salts of mono(hydroxybutyl)phthalate [M(HBP)2] and digol [DG]. Similarly polyurethane-ureas were synthesized by reacting the diisocyanates with 1:1 mixtures of hexamethylene bis(o,N-hydroxyethyl-urea) (HBHEU) and M(HBP)2. The polymers were characterized by elemental analysis, thermogravimetric analysis, solubility, visocity and spectral studies. # 1999 Elsevier Science Ltd. All rights reserved.
1. Introduction Ionic polymers have emerged in large extent that possess a wide range of properties leading to variety of applications as aqueous thickeners, impregnants, textile sizers, adhesives [1,2], additives [3], resins [4,5], catalysts [6] and in the ®eld of medicine [7,8]. Diols containing ionic linkages between COOÿ and M++ are of interest and useful as difunctional ionic monomers which are used as starting materials for the synthesis of ionic polymers in which the metal is ®rmly incorporated in the backbone of the polymer chain [9±24]. Metallo-polymers containing metal in the backbone of the polymer chain have been studied [25±28]. The previous report [29] from this laboratory was synthesis and characterization of metal-containing polyurethanes and polyurethane-ureas based on divalent metal salts of mono(hydroxybutyl)phthalate [M(HBP)2]. The present paper deals with the synthesis and characteriz-
* Corresponding author. Fax: +91-44-235-2870. E-mail address: [email protected] (S. Nanjundan)
ation of metal-containing polyurethanes and polyurethane-ureas derived from calcium, manganese and lead salts of mono(hydroxybutyl)phthalate, digol, hexamethylene bis(o,N-hydroxyethyl-urea) and hexamethylene diisocyanate or toluylene 2,4-diisocyanate.
2. Experimental procedures Metal salts of mono(hydroxybutyl)phthalate [M(HBP)2, M=Ca++, Mn++ and Pb++] were synthesized by the same method as reported in our previous study [29]. Scheme 1 shows the structure for M(HBP)2. Hexamethylene bis (o,N-hydroxyethyl-urea) [HBHEU] was synthesized according to the method reported by Matsuda [10]. 2.1. Synthesis of polymers For the synthesis of metal-containing polyurethane copolymers (Scheme 2) a mixture of M(HBP)2 (0.005 mol) and digol (0.005 mol) in DMF or DMSO (80 ml) was taken in a three necked ¯ask ®tted with a
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 0 9 - 9
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R. Arun Prasath, S. Nanjundan / European Polymer Journal 35 (1999) 1939±1948
Scheme 1
nitrogen inlet, a condenser and a dropping funnel. To this 2±3 drops of di-n-butyltindilaurate (DBTDL) was added as a catalyst. Then 0.01 mol of HMDI or TDI dissolved in 20 mL of DMF or DMSO was added slowly with constant stirring under a stream of nitro-
gen for about 1 h at 80±908C. Then the temperature of the reaction mixture was raised to 1008C and the mixture was stirred for about 4 h. Finally the reaction mixture was allowed to cool and treated with excess of DMF or DMSO. The solution was ®ltered and poured
Scheme 2
R. Arun Prasath, S. Nanjundan / European Polymer Journal 35 (1999) 1939±1948
into a large quantity of vigorously stirred chloroform or acetone to precipitate the polymer. The polymers were washed several time with alcohol and acetone and then dried in vacuo at 60±708C for 1 h. Similarly, metal-containing polyurethane-ureas (Scheme 3) were synthesized by reacting M(HBP)2 (0.005 mol) and HBHEU (0.005 mol) dissolved in 80 mL of DMF or DMSO with HMDI or TDI (0.01 mol) in the presence of 2±3 drops of DBTDL as catalyst.
1941
2.2. Characterization of the polymers Infrared spectra of the polymers were taken using Perkin-Elmer Model 598 Spectrophotometer at room temperature with KBr disk method. JEOL-GSX 400 MHz spectrometer was used to record 1H NMR spectra in DMSO-d6 solvent using TMS as internal standard. Thermogravimetric analysis (TGA) was carried out in Metler±3000 Thermal Analyser at a heating
Scheme 3
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R. Arun Prasath, S. Nanjundan / European Polymer Journal 35 (1999) 1939±1948
Table 1 Synthesis data and intrinsic viscosity of various metal-containing polyurethanes Polymer
Yield (%)a
External appearance
Intrinsic viscosity
Ca(HBP)2-HMDI-DGb Mn(HBP)2-HMDI-DGb Pb(HBP)2-HMDI-DGc Ca(HBP)2-TDI-DGb Mn(HBP)2-TDI-DGb Pb(HBP)2-TDI-DGc
77 73 65 78 72 68
White powder Dirty white powder Grey powder Yellowish white powder Yellowish white powder Slightly grey powder
0.1252 0.1290 ± 0.1254 0.1274 ±
a
Reaction temperature is 80±1008C, reaction duration is 5 h. DMF was used as solvent for polymer synthesis. c DMSO was used as solvent for polymer synthesis.
b
rate of 208C/min in air atmosphere. A Perkin-Elmer 2400 Carbon-Hydrogen Analyser was used for elemental analysis. Standard analytical methods were used to determine the metal content of dierent polymers. The intrinsic viscosity of the polymers were determined in DMSO at 408C using an Ubbelohde viscometer. Solubility studies were tried in various polar and nonpolar solvents at room temperature.
3. Results and discussion 3.1. Synthesis Metal salts of mono(hydroxybutyl)phthalate are insoluble in most of the organic solvents. Hence the polymerization of the salts, digol or HBHEU with diisocyanates was done in highly polar solvents such as DMF or DMSO. DMF was used as a solvent for the synthesis of calcium and manganese containing polymers, while DMSO was used for the synthesis of lead containing polymers. It was established that the reaction between diols and diisocyanates catalysed by DBTBL takes place via the formation of a ternary complex between the reagents and the catalyst [30]. To avoid cross-linking of the polymers, the mole ratio of
mixtures of diols and diisocyanates was taken as 1:1. After the completion of the reaction, DMF or DMSO was added in large excess to dissolve the linear polymer. Filtration was carried out in order to separate out any cross linked polymer formed. Subsequently the dissolved polymer was reprecipitated by the addition of non-solvents such as acetone or chloroform. With the help of the ionic monomers Ca(HBP)2, Mn(HBP)2 or Pb(HBP)2 and digol six metal-containing polyurethanes were synthesized based on HMDI and TDI. They are coded as Ca(HBP)2-HMDI-DG, Mn(HBP)2HMDI-DG, Pb(HBP)2-HMDI-DG, Ca(HBP)2-TDIDG, Mn(HBP)2-TDI-DG and Pb(HBP)2-TDI-DG. The synthesis data of metal-containing polyurethanes are given in Table 1. Using 1:1 mixture of M(HBP)2 and HBHEU six polyurethane-ureas were synthesized based on HMDI and TDI which are coded as Ca(HBP)2-HMDI-HBHEU, Mn(HBP)2-HMDIHBHEU, Pb(HBP)2-HMDI-HBHEU, Ca(HBP)2-TDIHBHEU, Mn(HBP)2-TDI-HBHEU and Pb(HBP)2TDI-HBHEU. The synthesis data of metal-containing polyurethane-ureas are given in Table 2. 3.2. Characterization Fig. 1 shows the IR spectra of the metal-containing
Table 2 Synthesis data and intrinsic viscosity of various metal-containing polyurethane-ureas Polymer
Yield (%)a
External appearance
Intrinsic viscosity
Ca(HBP)2-HMDI-HBHEUb Mn(HBP)2-HMDI-HBHEUb Pb(HBP)2-HMDI-HBHEUc Ca(HBP)2-TDI-HBHEUb Mn(HBP)2-TDI-HBHEUb Pb(HBP)2-TDI-HBHEUc
75 72 67 72 70 65
White powder Dirty white powder Grey powder Yellowish white powder Yellowish white powder Slightly grey powder
0.1002 0.1150 ± 0.1124 0.1060 ±
a
Reaction temperature is 80±1008C, reaction duration is 5 h. DMF was used as solvent for polymer synthesis. c DMSO was used as solvent for polymer synthesis.
b
R. Arun Prasath, S. Nanjundan / European Polymer Journal 35 (1999) 1939±1948
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Fig. 1. IR spectra of (a) Mn(HBP)2-HMDI-DG; (b) Pb(HBP)2-HMDI-DG; (c) Ca(HBP)2-HMDI-DG; (d) Mn(HBP)2-TDI-DG; (e) Ca(HBP)2-TDI-DG and (f) Pb(HBP)2-TDI-DG.
polyurethane copolymers. The spectra are essentially identical. The absorption band at 3300±3400 cmÿ1 is due to -NH stretching. The peaks around 1640± 1720 cmÿ1 are attributed to the carbonyl stretching of urethane and ester groups. The carboxylate ion due to the acid salts give raise to two broad bands, a strong asymmetrical stretching band near 1520±1570 cmÿ1 and a weaker symmetrical stretching near 1400 cmÿ1. This con®rms the presence of ionic links in the polyurethanes. IR spectra of metal-containing polyurethane-ureas are identical and are shown in Fig. 2. The broad band between 3300 and 3380 cmÿ1 is attributed to -NH stretching. Peaks between 1650 and 1720 cmÿ1 are attributed to the carbonyl stretching of urethane, urea and ester groups. The two broad bands
at 1400 and 1590 cmÿ1 con®rms the presence of ionic links in the polyurethane-ureas. The 1H NMR spectra of polyurethane copolymers derived from M(HBP)2, digol and diisocyanates (HMDI/TDI) show signals for the -NH protons of urethane groups at 7.71±8.52 ppm. The shift to down ®eld is due to inter and intra molecular H-bonding between the -NH group with a C1O group of the polymer and the S1O group of the solvent. The resonance signals at 6.85±7.63 ppm are attributed to the aromatic protons. The peaks between 4.71±4.85 ppm are attributed to the methyleneoxy group ¯anked between -OCH2- and -CONH- groups. The methyleneoxy group which is ¯anked between -O(CH2)3- and COC6H4- shows peaks for dierent polymers between
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Fig. 2. IR spectra of (a) Mn(HBP)2-HMDI-HBHEU; (b) Pb(HBP)2-HMDI-HBHEU; (c) Ca(HBP)2-HMDI-HBHEU; (d) Mn(HBP)2-TDI-HBHEU; (e) Pb(HBP)2-TDI-HBHEU and (f) Ca(HBP)2-TDI-HBHEU.
Fig. 3. 1H NMR spectra of (a) Ca(HBP)2-HMDI-DG and (b) Ca(HBP)2-TDI-DG.
R. Arun Prasath, S. Nanjundan / European Polymer Journal 35 (1999) 1939±1948
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Fig. 4. 1H NMR spectra of (a) Ca(HBP)2-HMDI-HBHEU and (b) Ca(HBP)2-TDI-HBHEU.
4.25 and 4.32 ppm. The other methyleneoxy group ¯anked between -O(CH2)3- and -COHN- shows a peak between 4.08 and 4.21 ppm. The methylene groups which are attached to ether linkages show signals between 3.52 and 3.58 ppm. The methylene groups ¯anked between -OCONH- and -(CH2)4- show signals at 3.20±3.31 ppm in the case of HMDI-based polyurethane copolymers. Methyl groups attached to the aromatic ring show signals at 2.18±2.30 ppm for the TDI-based polyurethane copolymers. The remaining methylene groups in the copolymers show a broad band between 1.18 and 1.72 ppm. Fig. 3 shows the 1H NMR spectra of calcium-containing HMDI-based polyurethane [Ca(HBP)2-HMDI-DG] and TDI-based polyurethane [Ca(HBP)2-TDI-DG]. The 1H NMR spectra of polyurethane-ureas derived from M(HBP)2, HBHEU and diisocyanates (HMDI/ TDI) show signals between 7.86 and 8.65 ppm for the -NH protons of the urethane and urea groups involved in inter and intra molecular H-bonding. The resonance signal between 7.21 and 7.72 ppm is due to aromatic protons. The methyleneoxy group ¯anked between NHCONHCH2- and -CONH- groups show a signal between 4.45 and 4.61 ppm. The resonance signal between 3.93 and 4.21 ppm is due to the methyleneoxy group ¯anked between -(CH2)3- and -CONH- and that attached to the -COC6H4- group. Methylene groups ¯anked between -NHCONH- and -CH2COONHgroups show resonance signal between 3.26 and 3.31 ppm. Methylene groups ¯anked between -NHCONH-
and -(CH2)4- groups and that in the group OCONHCH2- show peaks between 2.93 and 3.15 ppm. Methyl group attached to the aromatic ring of TDIbased polyurethane-ureas shows resonance signal between 2.18 and 2.29 ppm. The peak at 1.59±1.64
Fig. 5. TGA curves of (a) Ca(HBP)2-HMDI-DG; (b) Mn(HBP)2-HMDI-DG and (c) Pb(HBP)2-HMDI-DG.
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Fig. 6. TGA curves of (a) Ca(HBP)2-TDI-DG; Mn(HBP)2-TDI-DG and (c) Pb(HBP)2-TDI-DG.
(b)
ppm is attributed to the -(CH2)2- group which is attached between -OCH2- and -CH2O- groups. Other methylene protons in the polyurethane-ureas show
Fig. 7. TGA curves of (a) Ca(HBP)2-HMDI-HBHEU; (b) Mn(HBP)2-HMDI-HBHEU and (c) Pb(HBP)2-HMDI HBHEU.
Fig. 8. TGA curves of (a) Ca(HBP)2-TDI-HBHEU; (b) Mn(HBP)2-TDI-HBHEU and (c) Pb(HBP)2-TDI-HBHEU.
broad peaks between 1.21 and 1.55 ppm. Fig. 4 shows the 1H NMR spectra of calcium containing HMDIbased polyurethane-urea [Ca(HBP)2-HMDI-HBHEU] and TDI-based polyurethane-urea [Ca(HBP)2-TDIHBHEU]. Figs. 5±8 show the TGA curves of metal-containing polyurethanes and polyurethane-ureas, respectively. Although all the metal-containing polymers are structurally similar, they exhibit dierent behaviour in thermal analysis. Initial decomposition temperature (IDT) of the polymers are found between 150 and 2508C. It is observed that metal-containing polyurethanes have higher IDT than metal-containing polyurethane-ureas. Polyurethane-ureas are expected to be more stable than polyurethanes as the former is stabilized by more hydrogen bondings. The reverse order in this case may be explained based on our ®ndings that the polyurethane copolymers prepared were found to contain less metal than the prepared polyurethane-ureas. It has been reported that the existence of metal promotes the thermal decomposition of urethanes [9] and ureas [22] and with increase in metal content of the polymers the stability decreases. Thermal stability of the metal-containing polymers can be ordered as Pb>Mn>Ca. Initial thermal degradation of polyurethanes and polyurethane-ureas normally proceeds via urethane scission to isocyanate and hydroxyl components [31,32]. Solubility test shows that these metal-containing polyurethane and polyurethane-ureas are insoluble in
R. Arun Prasath, S. Nanjundan / European Polymer Journal 35 (1999) 1939±1948
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Table 3 Analytical data of metal-containing polyurethanes Polymer
Repeating unit
Ca(HBP)2-HMDI-DGa
CaC44H60N4O17
Mn(HBP)2-HMDI-DGa
MnC44H60N4O17
Pb(HBP)2-HMDI-DGb
PbC44H60N4O17
Ca(HBP)2-TDI-DGa
CaC46H48N4O17
Mn(HBP)2-TDI-DGa
MnC46H48N4O17
Pb(HBP)2-TDI-DGb
PbC46H48N4O17
a b
Analytical data found (calculated) (%) C
H
M
47.06 (55.49) 45.88 (54.64) 38.95 (47.25) 49.44 (57.01) 47.54 (56.14) 40.43 (48.64)
5.77 (6.31) 5.65 (6.22) 4.84 (5.38) 4.48 (4.99) 4.34 (4.92) 3.70 (4.26)
2.82 (4.18) 3.72 (5.66) 11.47 (18.4) 2.86 (4.14) 3.62 (5.59) 11.15 (18.22)
DMF was used as solvent for polymer synethsis. DMSO was used as solvent for polymer synethsis.
methanol, ethanol, acetone, ethyl methyl ketone, chloroform, carbon tetrachloride, n-hexane, benzene, toluene, xylenes, tetra hydrofuran and dioxane. While calcium and manganese containing polymers are soluble in DMF and DMSO, lead-containing polymers are insoluble even in the above solvents. The intrinsic viscosity of the soluble polymers in DMSO were found to be low (incorporated in Tables 1 and 2), which con®rms that the ionic links in the polymer chain dissociates into low molecular weight fragments [9,10,24,26]. The intrinsic viscosity of the prepared polyurethanes is higher than that of polyurethaneureas. This may be attributed to the fact that the poly-
urethanes have less metal which leads to less ionic linkage in the polymer chain. Metal-containing polyurethanes show that the experimentally determined percentage value of carbon, hydrogen and metal content is not well within the range of calculated value, while in the case of polyurethane-ureas these values are found to be somewhat low but within the range of calculated value. From this it may be inferred that the reactivity of the ionic diol seems to be much less than that of digol but just less than that of HBHEU towards diisocynates. Tables 3 and 4 show the analytical data of the metal-containing polyurethanes and polyurethane-ureas, respectively.
Table 4 Analytical data of metal-containing polyurethane-ureas Polymer
Repeating unit
Ca(HBP)2-HMDI-HBHEUa
CaC52H76N8O18
Mn(HBP)2-HMDI-HBHEUa
MnC52H76N8O18
Pb(HBP)2-HMDI-HBHEUb
PbC52H76N8O18
Ca(HBP)2-TDI-HBHEUa
CaC54H64N8O18
Mn(HBP)2-TDI-HBHEUa
MnC54H64N8O18
Pb(HBP)2-TDI-HBHEUb
PbC54H64N8O18
a b
DMF was used as solvent for polymer synethsis. DMSO was used as solvent for polymer synethsis.
Analytical data found (calculated) (%) C
H
M
53.27 (54.74) 52.42 (54.03) 46.51 (47.75) 55.00 (56.25) 54.00 (55.53) 47.30 (49.14)
6.70 (6.71) 6.60 (6.63) 5.85 (5.85) 5.55 (5.59) 5.48 (5.52) 4.88 (4.88)
3.15 (3.51) 4.20 (4.75) 14.00 (15.84) 3.12 (3.47) 4.11 (4.70) 13.04 (15.69)
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4. Conclusion Metal salts of mono(hydroxybutyl)phthalate are very useful starting materials for the synthesis of ionic polymers into which the metal is ®rmly incorporated. As M(HBP)2 are insoluble in most of the organic solvents, DMF or DMSO were used as solvent media for the synthesis of polymers. A series of polyurethane copolymers were prepared by reacting a 1:1 mixture of M(HBP)2 and digol with HMDI or TDI. Another series of polyurethane-ureas were prepared by reacting 1:1 mixture of M(HBP)2 and HBHEU with HMDI or TDI. The IR spectra of these polymers, con®rms the presence of ionic linkage. The polymers were characterized by NMR spectra. Thermal studies show that the metal-containing polyurethanes have higher IDT than metal-containing polyurethane-ureas. Also, the intrinsic viscosity of polyurethanes are higher than the polyurethane-ureas. From analytical methods it was found that the metal content in polyurethanes or polyurethane-ureas are found to be less than the value calculated based on equal reactivity of co-monomers. This shows that the reactivity of digol and HBHEU are higher than that of M(HBP)2 towards diisocyanates.
Acknowledgements One of the authors (R.A.P.) thanks the CSIR, India for oering Senior Research Fellowship.
References [1] Matsuda H, Kanaoka Kunio. J Appl Polym Sci 1985;30:1229. [2] Matsuda H. J Appl Polym Sci 1979;23:2603.
[3] Matsuda H, Takechi S. J Polym Sci Polym Chem Ed 1990;28:1895. [4] Matsuda H. J Appl Polym Sci 1978;22:2093. [5] Matsuda H. J Polym Sci; Polym Chem Ed 1977;15:2239. [6] Matsuda H. J Appl Polym Sci 1978;22:3371. [7] Silver JH, Hart AP, Williams EC, Cooper SL, Charef S, Labarre D, Jozefowivz M. Biol Mat 1992;13(6):339. [8] Okkeema AZ, Cooper SL. Biol Mat 1991;12:668. [9] Matsuda H. J Polym Sci; Polym Chem Ed 1974;12:455. [10] Matsuda H. J Polym Sci; Polym Chem Ed 1974;12:469. [11] Matsuda H. J Polym Sci; Polym Chem Ed 1974;12:2419. [12] Matsuda H. J Macromol Sci Chem 1975;A9:397. [13] Matsuda H. J Polym Sci; Polym Chem Ed 1976;14:1783. [14] Matsuda H. J Appl Polym Sci 1976;20:995. [15] Matsuda H. J Macromol Sci Chem 1976;A10:1143. [16] Durairaj B, Venkatarao K. Polym Bull 1979;1:723. [17] Durairaj B, Venkatarao K. Eur Polym J 1980;16:941. [18] Kothandaraman H, Venkatarao K, Raghavan A, Chandrasekaran V. Polym Bull 1985;13:353. [19] Matsuda H. Polym Engng Sci 1987;4:233. [20] Rajalingam P, Radhakrishnan G, Vasudevan C, Tamare Seloy K, Venkatarao K. Polym Com 1990;31:243. [21] Rajalingam P, Radhakrishnan G. Polymer 1992;33:2214. [22] Matsuda H, Takechi S. J Polym Sci, Polym Chem 1990;28:1895. [23] Matsuda H, Takechi S. J Polym Sci, Polym Chem 1991;29:83. [24] Qiu W, Zeng W, Zhang X, Li C, Lu L, Wang X, Yang X, Sanitary BC. J Appl Polym Sci 1993;49:405. [25] Bao Z, Chen Y, Yu L. Macromolecules 1994;27:4629. [26] Zeng W, Qiu W, Liu J, Yang X, Lu L, Wang X, Dai Q. Polymer 1995;36:3761. [27] Lee J, Nishio A, Tomita I, Endo T. Macromolecules 1997;30:5205. [28] Jiang B, Jones Jr WE. Macromolecules 1997;30:5575. [29] Arun Prasath R, Nanjundan S. J Macromol Sci Pure Appl Chem 1998;A35(5):821. [30] Lipatova TE, Bakalo LA, Sivotinskaya AL, Lopationa VS. Vysokomol Soedin 1970;A12(4):911 (in Russian). [31] Beachell HC, Ngoc Son CP. J Appl Polym Sci 1963;7:2217. [32] Rapp NS, Ingham JD. J Polym Sci 1964;A2:689.