Polystyrene Hybrid-Vitrimer Based on the Hemiacetal Ester Exchange Reaction

Vitrimer materials, which are permanently cross-linked but reshapable polymers, are a class of materials of growing interest due to their potential in recycling and sustainable development. More precisely, vitrimers derived from commodity polymers could have a drastic impact on plastic consumption in the upcoming years. Here, the development of a polystyrene-based vitrimer harnessing the recently discovered hemiacetal ester exchange reaction of carboxylic acid is presented. 1,4-Cyclohexanedimethanol divinyl ether was reacted with 4-vinylbenzoic acid (VBA) to form a divinyl species containing two hemiacetal ester functions. This dimer was then copolymerized with styrene, butyl acrylate, and VBA to form a cross-linked material presenting pendent acid groups. This material exhibited three distinct behaviors at different temperature regimes: below 80 °C, despite the exchange reactions able to occur at this temperature, the cross-linked material behaved as a frozen material due to the hydrogen bonding formed by the carboxylic acid pendent groups. Between 80 and 130 °C, the vitrimer behavior was demonstrated by rheological creep experiments. At higher temperatures, the dissociation of the hemiacetal ester groups led to the loss of the covalent cross-linking.