Dynamics of spinodal decomposition coupled with chemical reaction in thermosetting phenol-formaldehyde resin-based solutions and its application in monolithic porous materials

Abstract

A model comprised of a rate equation for polymerization and cross-linking reaction and the time-dependent Ginzburg–Landau equation for spinodal decomposition was utilized to describe reaction-induced spinodal decomposition (RISD). The effects of initial composition, curing temperature, and scaled diffusion coefficient and rate constant on the RISD dynamics were investigated numerically in thermosetting phenol-formaldehyde resin (PF)-based polymer solutions. As the initial composition increased, the final morphology varied from the regular droplet-like to interconnected pattern, and then transformed into another droplet-like one. The greater initial composition or higher curing temperature contributed to accelerate the RISD dynamics and caused the smaller dominant wavelength. When the curing point was determined, the increase of scaled diffusion coefficient gave rise to reduction of characteristic size and maximum structure factor, while the raise of scaled rate constant merely resulted in acceleration of the curing reaction. Based on the theoretical analyses, experiments were carried out to verify the influence of initial composition and curing temperature on the morphology of monolithic porous carbons. The results were in good agreement with the theoretical analyses and can provide guidance for synthesizing monolithic porous polymer and carbon materials with tunable pore morphology.