Title: Reversible Bonds, Phase Equilibrium, and Self-Assembly in Telechelic Polymer Blends
Reactive polymer blends form a large class of industrially and academically important materials, including thermoplastic polyurethanes (TPUs) and epoxy materials. The urethane bond present in TPUs can dissociate at elevated temperatures, leading to an equilibrium distribution of block polymers with varying block lengths and compositions. Experimental investigation of this reversibly bonding system is difficult due to competing kinetic and thermodynamic phenomena that affect phase separation, self-assembly, and materials properties. We use field-theoretic approaches to study the thermodynamic behavior of a model system of a binary blend of telechelic homopolymers that can form reversible AB-type bonds at chain ends. Previous field-based studies of reversibly-bonding polymer systems have been limited by the computational demand of accounting for an infinite number of possible reaction products in a spatially inhomogeneous self-assembled structure. We demonstrate that newly developed theoretical models and numerical methods enable the simultaneous computation of phase equilibrium, reaction equilibrium and self-assembly via self-consistent field theory. Phase diagrams are computed at a variety of physically relevant conditions and are compared with non-reactive analogs. We briefly survey extensions of this approach to network systems and comment on unresolved numerical challenges.