Interfacial lubricating effect in phase coarsening of polyethylene/polycaprolactone/polyethylene oxide tri‐continuous polymer blends.

This work aims at studying the mechanism involved in the phase coarsening of ternary tri‐continuous polymer blends. To this aim, the phase coarsening behaviors of a co‐continuous polyethylene (PE)/polyethylene oxide (PEO) blend, and a tri‐continuous PE/polycaprolactone (PCL)/PEO blend during the quiescent annealing process are studied. Rheological characterization showed that the zero‐shear viscosities of PE and PCL phases were similar but much less than the zero‐shear viscosity of the PEO phase. The evolution of the microstructure of the blends during annealing was characterized using a characteristic length scale (λ). It was found that λ in both co‐ and tri‐continuous blends increased linearly in the early stages of annealing but the phase coarsening rate decreased in both systems at longer annealing times. In general, the tri‐continuous blend showed much faster phase coarsening rate. The effects of kinetic and thermodynamic parameters on the observed phase coarsening behaviors are discussed in detail. A new lubricating mechanism is proposed in which the deformation of the PCL layer between PE and PEO phases reduces the effect of high viscosity of the PEO phase and increases the phase coarsening rate in ternary blends. The obtained results provide a new insight into the role of the middle layer in tri‐continuous polymer blends on controlling the phase morphology of these systems. [ABSTRACT FROM AUTHOR]