Dielectric studies of specific interaction and molecular motion in single-phase mixture of poly(methyl methacrylate) and poly(vinylidene fluoride)

Abstract

It is well known that the miscibility of dissimilar polymers with high molecular weights arises from specific interaction, such as hydrogen bonding. To discuss the influence of the interaction on a side group rotation and main chain motion of poly(methyl methacrylate) (PMMA) in PMMA/poly(vinylidene fluoride) (PVDF) blends, we investigated the dielectric loss ε″ as a function of frequency f. ε″( f) showed a peak at around 10 4 Hz, which is assigned to the β process characteristic of the side group rotation of PMMA below the glass transition temperature ( T g) and the αβ process characteristic of the side group rotation cooperative with the main chain motion above T g. Above T g, the peak frequency f max increased and then decreased with increasing PVDF content (/gf); f max(/ gf) showed a peak at /gf ≈ 10 wt.%. The increase may be interpreted by the acceleration of main chain motion by lowering of T g with increasing the content of the lower T g component (PVDF). Increasing further the PVDF content, the specific interaction seems to restrict the main chain motion and prevails over the T g effect so that the peak appears in the f max(/ gf) curve. f max decreased with increasing annealing time t a, suggesting the increase in restriction with t a. This may imply that the association of dissimilar polymers by the specific interaction is a very slow rate process on a time scale of thousand minutes. Also observed after annealing were broadening of the relaxation time distribution and the appearance of interfacial polarization, suggesting a change in chain conformation from random coil to a locally stretched state to form a nematic domain.