Effect of chain mobility on the coarsening process of co-continuous, immiscible polymer blends under quiescent melt annealing
Polypropylene (PP) and five kinds of monodisperse polystyrene (PS) with different terminal relaxation times were used to explore the relationship between the mobility of polymer molecular chains and the coarsening process of immiscible polymer blends with a co-continuous morphology under quiescent melt annealing, at different temperatures. The terminal relaxation time of all neat PP and PS was determined by a rheological approach, to characterize the mobility of molecular chains. Selective dissolution experiment showed that all PP/PS (50/50) blends maintained co-continuous structure during the whole annealing process. Significant coarsening behaviors were observed for all PP/PS blends by scanning electron microscope. A linear time dependence of the size of PS phase was found in all PP/PS blends and the coarsening phenomenon was more obvious with the decrease of the terminal relaxation time of PS phase, because of the increase of the mobility of polymer molecular chains. A direct relationship between the phase coarsening rate and the terminal relaxation time of PS phase was found for the first time and it satisfied the equation (k∝τ^((-1/3.4))). According to this equation, the formula k∝η^(-1/3.4) and k∝Mw^( -1) can be derived, which can provide important significance for the control of phase coarsening process of immiscible polymer blends with co-continuous morphology.