Significant glass-transition-temperature increase through hydrogen-bonded copolymers

The role of hydrogen bonding in promoting intermolecular cohesion and higher glass-transition temperatures of polymer is a subject of longstanding interest. A series of poly(vinylphenol-co-vinylpyrrolidone) copolymers were prepared by the free-radical copolymerization of acetoxystyrene and vinylpyrrolidone; this was followed by the selective removal of the acetyl protective group, with corresponding and significant glass-transition-temperature increases after this procedure. The incorporation of acetoxystyrene into poly(vinylpyrrolidone) resulted in lower glass-transition temperatures because of the reduced dipole interactions in its homopolymers. However, the deacetylation of acetoxystyrene to transform the poly(vinylphenol-co-vinylpyrrolidone) copolymer enhanced the higher glass-transition temperature because of the strong hydrogen bonding in the copolymer chain. The thermal properties and hydrogen bonding of these two copolymers were investigated with differential scanning calorimetry and Fourier transform infrared spectroscopy, and good correlations between the thermal behaviors and IR results were observed. (C) 2002 Wiley Periodicals, Inc.