Side-Chain Length and Dispersity in ROMP Polymers with Pore-Generating Side Chains for Gas Separations
Francesco M. Benedetti, You-Chi Mason Wu, Sharon Lin, Yuan He, Erica Flear, Kayla R. Storme, Chao Liu, Yanchuan Zhao, Timothy M. Swager, Zachary P. Smith
Abstract
Bottlebrush polymers with flexible backbones and rigid side chains have shown ultrahigh CO 2 permeability and plasticization resistance for membrane-based gas separations. To date, this class of polymers has only been studied with polydisperse side chains. Herein, we report gas transport properties of a methoxy (OMe) functionalized polymer synthesized via ringopening metathesis polymerization (ROMP) with uniform sidechain lengths ranging from n = 2 to 5 repeat units to elucidate the role of both side-chain length and dispersity on gas transport properties and plasticization resistance. As side-chain length increased, both Brunauer-Emmett-Teller (BET) surface area and gas permeability increased with minimal losses in gas selectivity. Increased plasticization resistance was also observed with increasing side-chain length, which can be attributed to increased interchain rigidity from longer side chains. Controlling the side-chain length provides an effective strategy to rationally control and optimize the performance of ROMP polymers for CO 2 -based gas separations.