Degradable Crystalline Triblock Copolymers, Linear and Cross-Linked, for Emulsion-Templated Porous Monoliths via Ring-Opening Polymerization

Abstract

PolyMIPEs are macroporous polymers templated within medium internal phase emulsions (MIPEs), emulsions with 30 to 74 vol % internal phase. Here, degradable crystalline triblock copolymers (TBCs), linear and cross-linked, based on poly(ethylene glycol) (PEG) midblocks of various molecular weights (MWs) and polycaprolactone (PCL) endblocks were synthesized via ring-opening polymerization (ROP) within oil-in-oil emulsions. The effects of the PEG MW, cross-linking, and synthesis conditions on the macromolecular architecture, phase-separated structure, crystallinity, porous structure, properties, and degradation were investigated. Emulsion-templated polymers are almost always cross-linked to prevent collapse. Here, remarkably, robust porous monoliths were generated from the linear TBCs, with crystallization providing the mechanical stiffness and strength needed to prevent collapse. Increasing the PEG MW in the linear TBCs increased the phase-separated microdomain spacing and crystallinity, while reducing the average void diameter, modulus, and degradation time. Cross-linking the TBCs reduced the extent of microphase separation, average void diameter, and crystallization, while increasing the modulus. The versatility of these TBC-based polyMIPEs lies in the ability to design the macromolecular architecture, the phase-separated structure, and the properties through the selection of the midblock macroinitiator and the endblock monomers without the need for cross-linking.