Dominant Factor of Bond-Exchange Rate for Catalyst-Free Polyester Vitrimers with Internal Tertiary Amine Moieties

Catalyst-free vitrimers have attracted attention for practical application of the vitrimer concept, which requires fundamental knowledge of physical property tuning. We prepared catalyst-free vitrimers by cross-linking amorphous polyesters bearing COOH side groups with tetraepoxy compounds bearing tertiary amines (4,4'-methylenebis(N,N-diglycidylaniline), abbreviated as Mb-epoxy). The obtained network possessed ester and OH groups, and the amino moieties worked as internal catalysts for trans-esterification-based bond exchange. The competing effect of cross-link density and concentration of amines was investigated for samples with different fractions of Mbepoxy, revealing that cross-link density, which governs chain mobility, was the dominant factor in the determination of bond-exchange rate.