Invariance of the local segmental relaxation dispersion in polycyclohexylmethacrylate/poly-α-methylstyrene blends

Dielectric spectroscopy was carried out on polycyclohexylmethacrylate (PCHMA) and its blend with poly-α-methylstyrene (PaMS) as a function of temperature and pressure. When measured at conditions whereby the local segmental relaxation time for the PCHMA was constant, the dispersion in the loss spectra had a fixed shape; that is, the relaxation time determines the breadth of the relaxation time distribution, independently of T and P. This result is known for neat materials and could be observed for the blend herein due to the nonpolar character of the PaMS and the degree of thermodynamic miscibility of the blend.