Viscometric investigations on the intermolecular interactions between poly(methyl methacrylate) and poly(vinyl acetate) in various solvents

Viscometric behavior of poly(methyl methacrylate) (PMMA) (referred to as the guest polymer) in various solvents containing poly(vinyl acetate) (PVAc) (referred to as the host polymer) at constant concentration was thoroughly investigated. It has been found that, using PVAc and tetrahydrofuran (THF) to form polymer solvent of (PVAc+THF), the intrinsic viscosity of PMMA in polymer solvent was less than in pure solvent of THF, indicating that repulsive interaction between PMMA and PVAc existed in THF. With the increasing of the concentration of PVAc in polymer solvent of (PVAc+THF), the intrinsic viscosity of PMMA decreased, indicating that repulsive interaction between PMMA and PVAc increased in concentrated polymer solvent. On the contrary, if using PVAc and chloroform, or, PVAc and cyclohexanone to form polymer solvent, the intrinsic viscosity of PMMA in polymer solvent is larger than in pure solvent of chloroform or cyclohexanone, indicating that attractive interaction between PMMA and PVAc existed in either chloroform or cyclohexanone. With the increase of the concentration of PVAc in polymer solvent, the intrinsic viscosity of PMMA increased accordingly, and reached its maximum at the concentration of 0.2 g/dl in polymer solvent of (PVAc+chloroform) or 0.3 g/dl in polymer solvent of (PVAc+cyclohexanone). With the further increase of the concentration of PVAc in polymer solvent, the intrinsic viscosity of PMMA, either in (PVAc+chloroform) or in (PVAc+cyclohexanone), decreased. On this occasion, the increased concentration-dependent intermolecular excluded volume effect is believed to be dominant, resulting in the contraction of PMMA coils and thus the decrease of the intrinsic viscosity of PMMA in polymer solvent. Viscometric behavior of PMMA/PVAc blends with the weight ratio of 1/1 in various solvents was also investigated and several criteria to predict polymer–polymer compatibility by viscosity measurement were determined to interpret the phase behavior of PMMA/PVAc blends cast from different solvents.