Network Formation Kinetics of Poly(dimethylsiloxane) Based on Step-Growth Polymerization

Kinetic study of the step-growth polymerization of hydroxyl-terminated poly(dimethylsiloxane) (PDMS) and triisocyanate has been done in this work. Kinetic Monte Carlo simulations are performed to understand the experimental investigation of the cross-linked network formation. This approach enables us to afford a visualization of the entire network formation in detail and evaluate its characteristic properties. A comparison between the current simulation results and that from classical theories (e.g., Flory and Macosko–Miller theoretical calculations) is done. In addition, the Cole–Poehlein diffusion model based on the free volume theory, involving a parallel summation of the chemical and diffusional rate coefficients, is used to describe the effect of diffusion-controlled mechanism on polymerization. Moreover, the effect of experimental conditions, such as the ratio of [NCO]/[OH] and the molar mass of PDMS, on network formation kinetics is also investigated. The simulation results demonstrate that the [NCO]/[OH] ratios within the range of 1–1.2 and PDMS with lower molar mass are preferred to prepare a polymer network with a high cross-linking density. It is believed that the current kinetic modeling provides a way for better understanding the kinetics and optimizing the experimental conditions.