Exploitable Flexible Honeycomb Structured Porous Films from Sol−Gel Cross-Linkable Silicone Based Random Branched Copolymers

Abstract

This work describes the novel use of silicone based random branched copolymers, PEGDMA-ran-PMMA-ran-PMPS and PEGDMA-ran-PMMA-ran-PTRIS, in “breath figure” technique formation of honeycomb structured porous films. These branched copolymers compounds are prepared by a facile, one-pot conventional free radical copolymerization technique that is economic and scalable for industry exploitations. The branched copolymers compounds are soluble in organic solvents and high in molecular weights and were taken to high monomer conversions without gelling or cross-linking. The degree of branching and molecular weights of branched copolymers compounds was readily controlled by varying the feed concentrations and ratios of the monomers methyl methacrylate (MMA), 3-(trimethoxysilyl)propyl methacrylate (MPS), or 3-[tris(trimethylsiloxy)silyl]propyl methacrylate (TRIS), the cross-linker and ethylene glycol dimethacrylate (EGDMA), and the chain transfer agent 1-dodecanthiol (DDT) during copolymerization. The presence of alkoxysilane precursors (i.e., PMPS) inside honeycomb structured porous films prepared from PEGDMA-ran-PMMA-ran-PMPS random branched copolymers enables cross-linking of the film via the sol−gel process to improve properties of the film. Cross-linked porous films have enhanced properties including higher flexibility without breakage, higher solvent resistance, and thermal stabilities up to 85 °C. The observed phase transitions of thermal sensitive PNIPAAm solution deposited inside the pores of these cross-linked porous films exhibited the thermal conductivity property of honeycomb structured porous films. These flexible, thermally and chemically stable honeycomb structured porous films may find applications as thermal sensors or low-cost conformal digital display when coupled with thermal sensitive or light emitting materials inside the pores of these films.