Role of Nonbond Interactions in the Glass Transition of Novolac-Type Phenolic Resin: A Molecular Dynamics Study

Abstract

Nonbond interactions, such as hydrogen bonds and π–π/p-π interactions, have a decisive effect on the physical properties of phenolic-rich polymers, such as the novolac-type phenolic resins. To study the influence of nonbond interactions on the glass transition temperature (Tg) of novolac resins, both the molecular dynamics and experimental approaches were applied. The results show that, compared with the o-p′ type novolac, the o-o′ type novolac models have relatively lower gyration radiuses and higher Tg values because more intramolecular hydrogen bonds can be formed in the o-o′ type novolac models. As there are fewer hydrogen bonds formed in o-p′ type novolac, the π–π and p-π interactions, which decrease with the degree of polymerization and temperature, strongly influence the glass transition of o-p′ type novolac. These results provide a new perspective on the structural-property relationship of phenolic resin.