Phase separation and viscoelastic behavior of semicompatible polymer blends: Poly(vinylidene fluoride)/poly(methyl methacrylate) system

Abstract

Thermal and dynamic mechanical analyses of variously processed blends of poly(vinylidene fluoride) (PVF2) and poly(methyl methacrylate) (PMMA) were carried out to elucidate the effects of lower-critical-solution-temperature (LCST) behavior reported earlier by Paul on the morphologies and properties of this system. The two components are miscible in the blends with PVF2 content ϕw<0.6. Such blends exhibit single glass transition at Tg’s, which follow the Gordon-Taylor scheme. On the other hand, the blends with ϕw>0.6, prepared by melt-mixing and annealing at 200°C for a sufficiently long period of time, exhibit two Tg’s and two Tm’s, implying a four-phase morphology. In such blends an LCST-type phase separation has taken place at a temperature as low as 200°C to give an amorphous mixture with ϕw≅0.6 and a nearly pure PVF2 melt. Quenching of such melts leads to a four-phase morphology composed of a mixed amorphous phase with Tgࣅ55°C, an imperfect crystalline phase grown out from the mixture and hence having a low Tm, and a nearly pure semicrystalline PVF2 domains similar to form II crystals with Tg≅40°C and a higher Tm. © 1981 The Society of Polymer Science, Japan.