Understanding radiation-thermal aging of polydimethylsiloxane rubber through molecular dynamics simulation

Abstract

The effect of radiation-thermal aging on the structure and properties of polydimethylsiloxane (PDMS) rubber at the micro-scale was investigated through molecular dynamics simulation. The aged PDMS models were constructed by incorporating the aging-induced chemical changes (hydroxyl groups, cross-linking, and scission of main chain). The simulation results show that the introduction of hydroxyl groups and cross-linking in molecular chains lower the chain mobility and the diffusion of the chains and oxygen molecules owing to the strong intermolecular interactions and long-chain structure, respectively. The introduction of short chains caused by the scission of main chains can enhance the mobility, diffusion, and flexibility of the chains and the diffusion range of oxygen molecules, resulting in the decrease in the free volume and Tg. In addition, the hardening effect of cross-linking and the softening effect of scission of main chain collectively contribute to the degradation of mechanical properties of the PDMS rubber.