Fourier‐transform infrared studies of polymer blends. III. Poly(β‐propiolactone)‐poly(vinyl chloride) system

Fourier‐transform infrared (FTIR) studies of the poly(β‐propiolactone) (PPL)‐poly(vinyl chloride) (PVC) blend system are presented. PPL‐PVC blends are observed to be incompatible in the molten (80°C) and solid (25°C) states, over the entire range of compositions. This is in marked contrast to our previous results of the poly(ϵ‐caprolactone)‐PVC blend system which was shown to be compatible in the amorphous state. The results of both studies are compared and discussed with particular reference to the detection of intermolecular interactions by FTIR and correlation with compatibility in polyester‐PVC blends. The role of the chemical interactions in the compatibilization of polymer blends is discussed in terms of thermodynamic considerations. Finally, it is well known that changes in refractive index of polymer blend compositions can cause frequency shifts of infrared bands, which are particularly relevant to the interpretation of residual peaks obtained by difference spectroscopy. The FTIR results of the PPL‐PVC blends are germane to this subject and are discussed.