Thermodynamics of multiblock polymers at immiscible polymer/polymer interfaces

When two dissimilar polymers are mixed, the low entropy of mixing tends to produce a phase separated system of droplets of the minority phase within the majority matrix. The resulting interfaces are weak due to the low penetration of one polymer into the other phase, posing a challenge for mechanical recycling of plastic waste. One solution to this challenge is to compatibilize the interface with multiblock polymers, which lower the interfacial tension and "stitch together" the interface to provide mechanical strength. I will discuss our recent results on modeling the activity of multiblock polymers at interfaces. The first part of the presentation will focus on coarse-grained molecular dynamics simulations of linear and graft multiblock polymers for weakly entangled, glassy matrices. The mechanisms of deformation and failure will be described, with an emphasis on the unique behavior obtained for graft copolymers. The second part of the presentation will focus on self-consistent field theory calculations of the critical micelle concentrations (CMC) in these systems. The CMC sets a thermodynamic limit on the amount of copolymer that can be adsorbed to the interface and thus limits its ability to act as a compatibilizer.