Orientation Behavior in Uniaxially Stretched Poly(methyl methacrylate)−Poly(4-vinylphenol) Blends

Abstract

Infrared spectroscopy has been used to investigate the orientation behavior of poly(methyl methacrylate) (PMMA)−poly(4-vinylphenol) (PVPh) blends in uniaxially stretched films, for 0−54.5 wt % PVPh blend content. The orientation of PVPh chains increases upon addition of the lower Tg 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 the 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 P2 of the PMMA chains. At the same time, the number of hydrogen bonds between PVPh chains decreases, decreasing the number of intractable loops formed by some of these interactions. The result is a higher orientation of PVPh chains in the blends. A method is used to verify that changes in conformation, and therefore in α angles, are not responsible for this observation, through the use of the slope of ln (ΔP2/Δλ) vs 1/T. This slope, which corresponds to the apparent activation energy, ΔEa, of the orientation−relaxation process, is proposed as a useful tool for comparing the behavior of a polymer in a pure state and in various blends.