Thiol-Ene Polymerization of Natural Monomers: A DFT Study

Abstract

This study investigates the thiol-ene reaction mechanism of natural monomers using quantum chemical tools. The structure-reactivity relationship for these monomers is elaborated by the aid of radical stabilization energies (RSEs), intermolecular interactions, the curve-crossing model, Hammond Postulate, and Evans-Polanyi relationships. Geometry optimizations, frequency, and energy calculations are performed at the M06-2X/6-31++G(d,p) level of theory. A crucial parameter for thiol-ene polymerization, which is the ratio of the propagation reaction (k(p)) and the chain transfer reaction (k(ct)) rate constants (k(p)/k(ct)), is calculated in order to elucidate the thiol-ene reaction mechanism. In light of these energetic and kinetic calculations, it is suggested that linalool, d-limonene, terpinolene, and gamma-terpinene are considered natural monomer candidates for thiol-ene polymerization due to their almost equal magnitude of the rate constants (k(p)/k(ct)approximate to 1). The thiol-ene polymerization potential of some specific unsaturated fatty acids is another prominent finding in this study.