Chapter 9
Comblike Cyclopolymers of Alkyldiallylamines and Alkyldiallylmethylammonium Chlorides George B. Butler and Choon H. Do Department of Chemistry and Center for Macromolecular Science and Engineering, University of Florida, Gainesville, F L 32611-2046
Water-soluble and comb-like cyclopolymers of alkyldiallylamines (alkyl=decyl and hexadecyl, ADAA) and the corresponding alkyldiallylmethylammonium chlorides (ADAMAC) were prepared by radical polymerization at 4 0 ° C in water solution. The polymers were characterized by NMR and DSC. The monomers were also cyclocopolymerized with diallyldimethylammonium chloride. Although the protonated A D A A and A D A M A C possess long alkyl chains, they cyclopolymerized like those monomers possessing shorter chains, and formed predominantly pyrrolidinium rings. The ring was largely cis-substituted; however, the ratio of the cis- to the trans-substituted peaks varied among the monomers studied. Because the cyclopolymers possess long alkyl side-chains, they showed a side-chain crystallization. The cyclopolymers also formed polymeric micelles.
Since the discovery that radical polymerization of dialkyldiallylammonium salts yields water-soluble cyclopolymers instead of cross-linked polymers (J^ 5), homo- and co-cyclopolymers of various dial lylamine compounds have been extensively studied and their syntheses, kinetics, ring-sizes, properties, and applications have been reviewed (6-11). Cyclopolymerization of the diallylammonium compounds produces mostly ring structures and the content of double bonds is less than 0.1-3% in the case of poly(diallyldimethylammonium chloride, DADMAC) (9). Free dial ly lamines do not polymerize but their protonated and quaternary ammonium salts polymerize by radical initiation (10). Although the piperidinium ring is thermodynamically favorable, the kinetically favorable pyrrolidinium ring exists dominantly in the cyclopolymer of D A D M A C according to NMR spectroscopic studies (11-13). The size of the ring also depends on the size of N-substituted alkyl groups (II). Complete or partial substitution of one of the methyl groups in the poly(DADMAC) with longer alkyl chains which are hydrophobic would be expected to change the properties of the polymers such as viscosity, solubility, and other applicable properties. Recently, for example, cyclopolymers 0097-6156/91/0467-0151$06.00/0 © 1991 American Chemical Society
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of dîallyldidodecylammonium bromide were studied for vesicle formation (14-15). Introduction of long alkyl chains into the cyclopolymers would produce c o m b - l i k e polymers which may show side-chain c r y s t a l l i z a t i o n (16). F u r t h e r m o r e , because the cyclopolymers possess hydrophilic protonated or quaternary ammonium groups and hydrophobic long alkyl chains, the polymers may form polymeric micelles and polymeric aggregates or self-oriented polymeric systems (17-18). Therefore, we became interested in the polymerization of alkyldiallylamines (alkyl=decyl and hexadecyl, A D A A ) and the corresponding alkyldiallylmethylammonium chlorides (ADAMAC). C o p o l y m e r i z a t i o n of A D A A and A D A M A C with D A D M A C , the most common quaternary ammonium monomer, was also studied. We wish to report here the preparation of I) A D A A and A D A M A C and their homopolymerization (Scheme I) and copolymerization with D A D M A C (Scheme 2) and 2) c h a r a c t e r i z a t i o n of the resulting polymers by C N M R spectroscopy, D S C , and microscopy.
Scheme 1. Homocyclopolymerization of alkyldiallylamine (ADAA) and alkykUallylmethylammoninm chloride (ADAMAC).
Scheme 2. Cyclocopolymerizatian of 1) A D A A with D A D M A C and 2) A D A M A C with D A D M A C
Experimental Preparation of A D A A and A D A M A C . A D A A was prepared in high yields (>90%) from dial ly lamine and I -bromoalkanes by heating at II0°C for I O h . A D A M A C was prepared nearly quantitatively by methylating A D A A with CH3CI in acetone solution at 80 C under 600 psi for 8 h in a bomb reactor.
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C y c l o p o l y m e r i z a t i o n of A D A A and A D A M A C . A D A A ' H C I was c y c l o p o l y m erized or c o c y c l o p o l y m e r i z e d with D A D M A C in 40-50 wt % aqueous solution at 4 0 ° C for 24 h using 2,2 -azobis(N,N'-dimethyleneisobutyramidine)dihydrochloride ( A B D M B A ) as radical initiator. A f t e r polymerization, the solution was neutralized with 3 Ν (Nte^COg The polymer which separated was washed with water, then dissolved in a small amount of CHCI3 and reprecipitated into acetone. The copolymers were purified by dialysis lîsing a membrane of 8,000 molecular weight c u t o f f . The yields were higher than 20%. A D A M A C was homopolymerized or copolymerized with D A D M A C using A B D M B A as initiator at 40°C in 40-50 wt% aqueous solution, by following a similar procedure to polymerization of A D A A ' H C I . A f t e r polymerization, the polymer was purified by dialysis using a membrane of 8,000 c u t o f f m o l e cular weight. The yields were in the range of 10%. l
Iλ Characterization. C N M R spectra were recorded on a Varian 200 X L N M R Spectrometer at ambient temperature using CDCI3 or D2O as solvents. Melting points of side-chain c r y s t a l l i z a t i o n were measured using a P e r k i n E l m e r D S C - 7 . The heating rate was 2 ° C / m i n . Optical micrographs were obtained by using a Nikon Optiphot microscope. Results and Discussion ,
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P o l y ( A D A A ) and Its Copolymers. By comparison with the C N M R spectra of the monomer and its quaternary ammonium chloride (Figure I), the peaks of poly(decyldiallylamine, D D A A ) were assigned (Figure 2). The spectrum of
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poly(hexadecyldiqllylamine, H D D A A ) was very similar to that of poly( D D A A ) . Two C N M R peaks around 39-43 ppm represent C - 3 and C - 4 of the pyrrolidine ring (10,12), and consequently indicate that p o l y ( A D A A ) possesses the pyrrolidine ring structure (I and 2). The ratio of the two ,
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( a ) . Poly(HDDAA) C-11 C-14
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C N M R spectra of (a) p o l y ( H D D A A ) and (b) p o l y ( D D A A ) in CDCI3.
peaks also indicates c i s - and trans-substitutions of the ring (10,12), and the spectra show that the ratios are 3:1 (cis:trans) or less. These ratios are reduced from 5:1, the ratio observed in the cyclopoiymer of m e t h y l d i a l l y l amine. This difference is probably due to steric hindrance of the bulky alkyl groups, but the cis-pyrrolidine ring structure is still dominant.
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The positions of C - 6 , C - 7 , C - 2 , and C - 5 in the N M R spectra may also support the above conclusions. However, they are obscured and overlapped with the peaks from C - 6 , C - 7 , and C - 1 0 which appear between 26 and 27 ppm and those from C - 2 , C - 5 , and C - 8 which appear around 55-59 ppm. The copoly mers prepared from A D A A and D A D M A C also possess pyrrolidine rings and are random copolymers rather than block copolymers or mixtures of homopolymers. This conclusion is based on the N M R spectra, the melting points of side-chains, and the formation of m i c e l l e s . If a mixture of homopolymers or a block copolymer had been obtained, the depression of T m due to dilution would be linear and s m a l l . It also would be observed in a wide range of the composition. Furthermore, such structures would not be expected to form polymeric micelles since the homopolymer showed no tendency to do so. P o l y ( A D A M A C ) and Its Copolymers. Although d e c y l - and h e x a d e c y l - d i a l l y l methylammonium chlorides ( D D A M A C and H D D A M A C ) possess long alkyl chains, .they form polymers possessing pyrrolidinium ring structures a c c o r d ing to ' ^ C N M R spectra (Figure 3). C - 3 and C - 4 appear around 37-40 ppm
9. BUTLER & DO
70 F i g . 3. CDCI .
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C N M R spectra of (a) p o l y ( H D D A M A C ) and (b) p o l y ( D D A M A C ) in
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and indicate that it is composed of pyrrolidinium rings (3) (13); the c i s - and trans-substitution ratios are 2:1 or less. If piperidinium rings (4) had been formed in addition to the pyrrolidinium ring, the methylene carbon atom ( C 4) of the piperidinium ring would appear around 35-41 ppm (13). The methyl carbon atom attached to the nitrogen atom shows two peaks 48.5 and 52 ppm and C - 2 , C - 5 , and C-8 show three peaks between 64 and 70 ppm. C-6 and C 7 appear around 24-28 ppm.
C o p o l y m e r i z a t i o n of A D A M A C with D A D M A C yields random copolymers possessing pyrrolidinium rings. Thus ' C N M R peaks of the methyl groups attached to the quaternary nitrogen atom and C - 3 and C-4 regions of p o l y ( D D A M A C - c o - D A D M A C ) made f r o m 1:1 monomer feed are identical with those of p o l y ( D A D M A C ) (Figure 4) and this result indicates that the copolymer possesses pyrrolidinium ring structure like a p o l y ( D A D M A C ) . The formation of polymeric micelles (see below) suggests that the copolymer is a random copolymer rather than a mixture of homopolymers of each components or a block copolymer. 3
Side-Chain C r y s t a l l i z a t i o n . P o l y ( H D D A A ) and its derivatives and copolymers exhibit endothermic peaks due to the melting of side-chains between 30-50°C (Figure 5). These results indicate that hexadecyl groups c r y s t a l l i z e in the side-chains. Apparently, p o l y ( H D D A A ) and its HCI salt show more tendency to c r y s t a l l i z e than its quaternary ammonium chloride, poly( H D D A M A C ) . The limits of the composition of the copolymers and sidechain c r y s t a l l i z a t i o n will be examined further. P o l y ( D D A A ) and its HCI salts, however, do not show side-chain c r y s t a l l i z a t i o n c l e a r l y .
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70
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F i g . 4. C N M R spectra of (a) p o l y ( D D A M A C - c o - D A D M A C ) and (b) poly( D A D M A C ) in D 0 . 2
F i g . 5. D S C Thermograms of p o l y ( H D D A A ) and its derivatives.
9. BUTLER & DO
Cyclopolymers of Alkyldiallylamines
Formation of Polymeric Micelles. Optical micrograph shows polymeric micelles of I μ m size (Figure 6a) and polymeric aggregates of < 10 y m size (Figure 6b) formed from an aqueous solution of poly(DDAA-co-DADMAC). Although this shows that the cyclopolymers can form polymeric micelles, their properties and the ranges of the copolymer compositions where the copolymers are able to form micelles have not been fully investigated yet.
Fig. 6. Optical micrograph of (a) polymeric micelles and (b) polymeric aggregates formed from aqueous solution of poly(DDAA-co-DADMAC). Acknowledgments Financial support of this work was provided by the Department of Energy, Office of Basic Energy Sciences under Grant No. DE-FG05-84ER45104 for which we are grateful. We are also grateful to Dr. H. C. Aldrich, Dept. of Microbiol., Univ. of Fla., for permission to use his microscope to obtain the micrograph shown in Figure 6. Literature Cited 1. 2. 3. 4. 5. 6. 7. 8.
Butler, G. B.; Ingley, F. L. J. Am. Chem. Soc. 1951, 73, 895. Butler, G. B.; Goette, R. L. J. Am. Chem. Soc. 1952, 74, 1939. Butler, G. B.; Johnson, R. A. J. Am. Chem. Soc. 1954, 76, 713. Butler, G. B.; Angelo, R. J. J. Am. Chem. Soc. 1956, 78, 4797. Butler, G. B.; Angelo, R. J. J. Am. Chem. Soc. 1957, 79, 3128. Butler, G. B. in IUPAC, Polymeric Amines and Ammonium Salts; Goethals, E. J., Ed; Pergamon; New York, 1980; p. 125. Butler, G. B. Acc. Chem. Res. 1982, I5, 370. Ottenbrite, R. M.; Ryan, W. S., Jr. lnd. Eng. Chem. Prod. Res. Dev. 1980, 19, 528.
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9. 10. 11. 12. 13. 14. 15. 16. 17. 18.
Jaeger, W.; Hong, L. T.; Philipp, B.; Reinisch, G.; Wandrey, Ch. in IUPAC, Polymeric Amines and Ammonium Salts; Goethals, E. J., Ed; Pergamon; New York, 1980; p. 155. Solomon, D. H.; Hawthorne, D. G. J. Macromol. Sci.-Rev. Macromol. Chem. 1976, C15, 143. Ottenbrite, R. M.; Shillady, D. D. in IUPAC, Polymeric Amines and Ammonium Salts; Goethals, E. J., Ed; Pergamon; New York, 1980; p. 143. Johns, S. R.; Willing, R. I.; Middleton, S.; Ong, A. K. J. Macromol. Sci.-Chem. 1976, A10, 875. Lancaster, J. E.; Baccei, L.; Panzer, H. P. J. Polym. Sci., Polym. Lett. Ed. 1976, 14, 549. Babilis, D.; Dais, P.; Margaritis, L. H.; Paleos, C. M. J. Polym. Sci., Polym. Chem. Ed. 1985, 23, 1089. Babilis, D.; Paleos, C. M.; Dais, P. J. Polym. Sci., Polym. Chem. Ed. 1988, 26, 2141. Plate, Ν. Α.; Shibaev, V. P. J. Polym. Sci., Macromol. Rev. 1974, 8, 117. Fendler, J. H.; Tundo, P. Acc. Chem. Res. 1984, 17, 3. Ringsdorf, H.; Schlarb, B.; Venzmer, J. Anqew. Chem. Int. Ed. Engl. 1988, 27, 113.
RECEIVED June 4, 1990
