DMTA AND FTIR INVESTIGATION OF THE PHASE-BEHAVIOR OF POLY(METHYL METHACRYLATE) POLY(4-VINYLPHENOL) BLENDS

The phase behavior of poly(methyl methacrylate) (PMMA)/poly(4-vinylphe nol) (PVPh) blends was investigated using differential scanning calori metry (DSC), dynamic mechanical thermal analysis (DMTA), small-angle X -ray scattering (SAXS), and Fourier transform infrared (FTIR) spectros copy. Only one glass transition was observed by DSC in both pure state s and blends. However, two loss tangent maxima observed in DMTA relaxa tion spectra indicate the existence of two phases in the blends. Therm al treatments were found to influence both the number of hydrogen bond s and the proportion of both phases in the blends: quick quenching lea ds to a lower concentration of hydrogen bonds and to an increase in th e quantity of the minor phase. This minor phase gives rise to a tan de lta peak appearing at low temperature. It has been assigned to domains composed of isotactic-like PMMA segments and PVPh (phase-i). The T-g determined by the major loss tangent maximum exhibits positive deviati on from linearity in the T-g-composition curve and is likely due to th e domain of syndiotactic-like PMMA. sequence with PVPh (phase-s). Usin g DMTA and X-ray scattering measurements, it is estimated that less th an 2% phase-i with average domain size 30 Angstrom is dispersed in a p hase-s matrix. This type of approach could be used to characterize sub tle differences in the behavior of optically active hydrogen-bond-form ing polymer blends related to tacticity.