SYNOPSISThe thermal degradation of poly (N-vinyl-2-pyrrolidone) (PVP) was studied by dynamic thermogravimetric analysis (TGA) in the range 200-600°C under nitrogen and oxygen atmospheres a t various heating rates. The apparent activation energy of the degradative process was determined by the application of kinetic treatments, giving an average value of 242 kj/mol in Nz, whereas in the presence of oxygen, two trends may be considered At relatively low temperatures (200-400°C) and degrees of conversion, a, lower than 0.5, we obtained an average value of 199 kjlmol, whereas in the temperature interval 400-600°C with degrees of conversion higher than 0.5, the value of E, was 306 kjlmol. Isothermal experiments carried out in N2 in the interval 350-400°C gave an average value of E. = 231 kj/mol, in good agreement with that obtained from dynamic treatments. The FTIR spectra of the volatile compounds evolved in degradation experiments carried out in Nz as well as in the presence of oxygen suggest that PVP is thermally degraded, predominantly, by the release of the pyrrolidone side group and the subsequent decomposition of polyenic sequences. 0 1993 John Wiley & Sons, Inc.

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Poly(acryloxyethyl-trimethylammonium chloride-co-2-hydroxyethyl methacrylate) [poly(Q-co-H)] was prepared by free radical polymerization in aqueous solution at 608C using potassium persulfate as initiator. Spectroscopic characterization confirmed the formation of poly(Q-co-H) and the molar fractions of acryloxyethyl-trimethylammonium chloride monomer units incorporated in the copolymers were determined by potenciometric titrations. The monomer reactivity ratios for Q and H are found to be r Q 5 0.04 6 0.01 and r H 5 3.22 6 0.84 using Fineman-Rö ss method and r Q 5 0.06 and r H 5 3.61 using Genetic Algorithms method. Finally we studied reaction between poly(Q-co-H) and sodium alginate by conductimetric measurement.

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Hydrogels are hydrophilic polymers that swell to an equilibrium volume in the presence of water, preserving their shape. The dynamic swelling behavior of poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) [poly(NIPA-co-DMA)] copolymers at 37°C was investigated. It was observed that the swelling degree in the copolymers decreases with the N-isopropylacrylamide content. In addition, the liberation mechanism was found to be Fickian. Diffusion coefficients according to FickЈs law as a function of the N-isopropylacrylamide concentration and results of the release process are reported. The kinetics of cephazoline sodium release from poly(NIPA-co-DMA) hydrogels with different compositions was studied.