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In this study, a series of N -isopropylacrylamide/trimethyl acrylamidopropyl ammonium iodide (NIPAAm/TMAAI) copolymeric gels were prepared from the various molar ratios of NIPAAm, cationic monomer TMAAI, and N , N ′-methylene bisacrylamide (NMBA). The influences of the amount of the cationic monomer in the copolymeric gels on the swelling behaviors in water, various saline solutions, and various temperatures were investigated. Results showed that the swelling ratios of copolymeric gels were significantly larger than those of pure homopolymer NIPAAm gels, and the more the TMAAI content, the higher the gel transition temperature. In the saline solution, results showed that the swelling ratio of pure NIPAAm gel did not significantly change with an increase of the salt concentration until the salt concentration was greater than 0.1 M. The swelling ratios for the copolymeric gels NIPAAm/TMAAI were decreased with increasing of the salt concentration. In various saline solutions, results showed that the anionic effects were greater than cationic effects in the presence of common anion, different cations and common cation, different anions for these hydrogels

The copolymer prepared by copolymerizing styrene and maleic anhydride was imidized with N,N ′-dimethylaminopropyl amine. The styrene- N,N ′-dimethylaminopropyl maleimide (SDMAPM) copolymer obtained was then reacted with propane sultone to yield a styrene-[ N,N ′-dimethyl(maleimidopropyl)ammonium propane sulfonate] (SDMMAPS) copolymer. The cloud point and intrinsic viscosity of this ampholytic SDMMAPS copolymer were determined in aqueous salt solutions. The effects of counter ions on the cloud point and intrinsic viscosity of SDMMAPS were similar to their effects on these properties of other zwitterionic poly(sulfobetaine)s. The Huggins constants for SDMMAPS in aqueous salt solutions, however, were quite different than those of other sulfobetaine homopolymers, such as poly[ N,N ′-dimethyl(acrylamidopropyl) ammonium propane sulfonate], [poly(DMAAPS]. The value of the constant was negative and increased as the intrinsic viscosity and salt concentration increased. This phenomenon is mainly attributed to the presence of the styrene segment, a hydrophobic group, in the SDMMAPS copolymer.

The copolymer prepared by copolymerizing acrylamide with maleic anhydride was imidized with N,N-dimethylaminopropylamine. The obtained acrylamide-N,N-dimethylaminopropylmaleimide (ADAPM) copolymer was then reacted with propane sultone to yield a novel acrylamide-N,N-dimethylmaleimidopropylammonium propanesulfonate (ADMMAPS) copolymer. The properties of this ampholytic ADMMAPS copolymer in aqueous salt solution were studied by measurement of reduced viscosity and intrinsic viscosity. The intrinsic viscosities of this polyampholyte were related to the type and concentration of the added salts. ‘Soft’ salt cations and anions were more easily bound to the quaternary ammonium (R4N+) and sulfonate group (SO−3) of ADMMAPS than were ‘hard’ salt cations and anions. The tendency of the intrinsic viscosity for ADMMAPS in various aqueous salt solutions is similar to that of other zwitterionic poly(sulfobetaine)s. The Huggins constant for ADMMAPS in an aqueous salt solution shows a marked distinction from the sulfobetaine copolymer, styrene-N,N-dimethylmaleimidopropyl-ammonium propane sulfonate (SDMMAPS). This phenomenon is attributed mainly to the presence of the acrylamide/styrene segment, a hydrophilic/hydrophobic group, on the ADMMAPS/SDMMAPS copolymer, respectively.

The properties of ampholytic poly[ N,N′ — dimethyl(acrylamido propyl) ammonium propane sulfonate] (poly(DMAAPS)) in aqueous solution were studied by measurements of cloud point determination and intrinsic viscosity. The minimum salt concentration and intrinsic viscosity of this polyampholyte were related to the type and concentration of added salt. ‘Soft’ salt cations and anions bound more easily to the quaternary ammonium (R 4 N + ) and sulfonate groups (SO 3 − ) of poly(DMAAPS) than ‘hard’ salt cations and anions. For the measurements of cloud point and intrinsic viscosity in aqueous salt solution of various divalent acidic groups, the divalent acidic groups ruptured the ionically crosslinked network of sulfobetaine at a small concentration of salt and the divalent acidic groups attracted the neighbouring polymeric side chains to make the polymeric main chains twist and agglomerate. A similar degree of expansion of the polymeric main chain at the saturated binding concentration of various monovalent salts (LiCl, NaCl, KCl) was observed from measurement of intrinsic viscosity