Thermal behavior of poly(styrene-co-methacrylic acid) with poly(4-vinylpyridine) or poly(N,N-dimethyl acrylamide) or poly(N,N-dimethyl acrylamide-co-4-vinylpyridine)

Abstract

Poly(N,N-dimethyl acrylamide) (PDMA), poly(N,N-dimethyl acrylamide-co-4-vinylpyridine) containing 20 mol% of 4-vinylpyridine (PDMA4VP20) and poly(styrene-co-methacrylic acid) containing 8 or 16 mol% of methacrylic acid (PSMA8 and PSMA16) were synthesized by free radical polymerization and characterized by several techniques. Homogeneous phases were observed by simply mixing PSMA8 with PDMA or P4VP in chloroform, while interpolymer complexes were formed in the same solvent when PSMA8 was added to PDMA4VP20 and PSMA16 to PDMA or P4VP, respectively. FTIR spectroscopy analysis confirmed the presence of various carboxyl–pyridine, carboxyl–amide and carboxyl–carboxyl specific interactions that occurred within these systems. Thermal properties of the synthesized copolymers and of their PSMA/P4VP and PSMA/PDMA blends or PSMA/PDMA4VP20 interpolymer complexes were investigated by differential scanning calorimetry and thermogravimetry. A single glass transition temperature Tg, intermediate between those calculated from the weight average values of the pure polymers for miscible blends and higher than those of two constituents of interpolymer complexes, was observed with these systems in the whole initial composition range. The different Tg-composition curves of these systems were analyzed using the well-known Kwei equation which confirmed in agreement with FTIR spectroscopy the presence and nature of specific between the constituents of the various mixtures and their dependence on the density of carboxylic groups within PSMA. A thermogravimetric analysis confirmed different thermal behaviors of the blends compared to the interpolymer complexes.