Polythiourethanes Crosslinked with Dynamic Disulfide Bonds: Synthesis via Nonisocyanate Approach, Thermomechanical and Reprocessing Properties

Abstract

Polythiourethanes (PTUs) crosslinked with dynamic disulfide bonds are synthesized via a nonisocyanate approach. First, a difunctional five-membered cyclic trithiocarbonate (1) is synthesized via the reaction of diglycidyl ether of bisphenol A (DGEBA) with carbon disulfide (CS₂ ). Thereafter, the step-growth polymerizations of 1 with α,ω-diamino poly(propylene oxide)s with various molar masses are carried out to obtain a series of linear poly(mercapto thiourethane)s. These linear poly(mercapto thiourethane)s are readily crosslinked upon formation of disulfide bonds, which are generated via radical coupling reaction with the side mercapto groups. These crosslinked PTUs can be tailored into the materials from thermosetting plastics to crosslinked elastomers, depending on the molar masses of α,ω-diamino poly(propylene oxide)s. More importantly, these crosslinked PTUs display excellent reprocessing properties at elevated temperatures, which is attributable to the metathesis reaction of dynamic disulfide bonds.

Keywords: crosslinking; dynamic disulfide bonds; polythiourethane; reprocessing properties.