The Promoting Effect of Reactive Comb Compatibilizer on the Formation of Co-Continuous Structure in PVDF/PLLA Blends

While many kinds of reactive compatibilizers (RCs) have been artificially created for reducing interfacial tension in immiscible polymer blends, the effect of RCs on co-continuity formation (preferred in application) remains controversial. In this work, we selected the previously reported poly(vinylene fluoride)/poly(L-lactic acid)/reactive comb compatibilizer (PVDF/PLLA/RCC) blend system as the model system, in which the reaction between epoxy groups in RCC and terminal carboxyl groups in PLLA upon blending can produce glycidyl methacrylate (GMA)-PLLA side chains located at the PVDF/PLLA interface. By manipulating PVDF/PLLA composition ratio and RCC content, a half-U-shaped co-continuous phase diagram with an upward opening was obtained, suggesting a promoting effect of RCC on PVDF/PLLA co-continuity. This can be attributed to both the high viscosity of PLLA/RCC and the inhibited PVDF phase coalescence. On the one hand, owing to the significantly increased viscosity of PLLA/RCC relative to neat PLLA, the decreased viscosity ratio of PVDF to PLLA(/RCC) can lower the co-continuous PVDF/PLLA composition ratio. On the other hand, the coalescence of PVDF phase in PVDF/PLLA/20%RCC can be effectively inhibited due to the addition of RCC, opposite to the inclined PLLA phase coalescence in the neat PVDF/PLLA blend with high PVDF fraction (e.g., 80%). Our results provide guidance for evaluating and selecting RCs for a specific immiscible polymer blend in practical application.