Curvature Effect in Polydimethylsiloxane Interaction with CO 2 . Insights from Theory.

In this study we employ density functional theory to investigate the binding interaction between polydimethylsiloxane and CO 2 for application in gas separation membranes. The binding strength has been studied systematically as a function of the monomer conformational rotations in the polymer chain. Our work identified major differences between the CO 2 interaction with the helical conformation and the linear conformation of polydimethylsiloxane polymer chains. We have further estimated dependence between the CO 2 binding strength and the polydimethylsiloxane polymer chain curvature by systematically evaluating the CO 2 binding to cyclic polydimethylsiloxane oligomers. The enhanced CO 2 interaction with helical chains and cyclic oligomers was attributed to cooperative, confinement effects, and local electron density distribution at the Si-O-Si fragments. The binding modes were identified using vibration frequency analysis.