ORIENTATION BEHAVIOR IN UNIAXIALLY STRETCHED POLY(METHYL METHACRYLATE)-POLY(4-VINYLPHENOL) BLENDS

Infrared spectroscopy has been used to investigate the orientation beh avior of poly(methyl methacrylate) (PMMA)-poly(4-vinylphenol) (PVPh) b lends in uniaxially stretched films, for 0-54.5 wt % PVPh blend conten t. The orientation of PVPh chains increases upon addition of the lower T-g PMMA component, whereas the orientation of PMMA chains decreases upon addition of the more rigid PVPh. This behavior is proposed to be related to changes in hydrogen bonds and/or chain entanglements. As th e number of hydrogen bonds formed between PMMA and PVPh increases, the system is rigidified, and the resulting number of chain entanglement decreases, resulting in a lower orientation function Pt of the PMMA ch ains. At the same time, the number of hydrogen bonds between PVPh chai ns decreases, decreasing the number of intractable loops formed by som e of these interactions. The result is a higher orientation of PVPh ch ains in the blends. A method is used to verify that changes in conform ation, and therefore in a angles, are not responsible for this observa tion, through the use of the slope of In (Delta P-2/Delta lambda) vs 1 /T. This slope, which corresponds to the apparent activation energy, D elta E-a, of the orientation-relaxation process, is proposed as a usef ul tool for comparing the behavior of a polymer in a pure state and in various blends.