Vitrimer-like elastomers with rapid stress-relaxation by high-speed carboxy exchange through conjugate substitution reaction
Natsumi Nishiie, Ryo Kawatani, Sae Tezuka, Miu Mizuma, Mikihiro Hayashi, Yasuhiro Kohsaka
Abstract
We report vitrimer-like elastomers that exhibit significantly fast stress relaxation using carboxy exchange via the conjugate substitution reaction of α-(acyloxymethyl) acrylate skeletons. This network design is inspired by a small-molecule model that shows the carboxy exchange reaction even at ambient temperature in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO). The acrylate and acrylic acid copolymers are cross-linked using bis[α-(bromomethyl)acrylates] and doped with 10 wt% DABCO, exhibiting processability to obtain a transparent film by hot pressing. The high-speed bond exchange in the network, validated by stress-relaxation tests, allows quick molding with household iron. In addition, the material is applied as an adhesion sheet for plastic and metal substrates. Because dynamic cross-linking with the proposed bond exchange mechanism can be implemented for any polymer bearing carboxyl pendants, our approach can be applied to versatile backbones, which must thus be meaningful in the practical sense. Fast bond exchange reactions is critical for the design of vitrimer and vitrimer-like materials but are not sufficiently explored. Here, the authors use fast bond exchange between α-(acyloxymethyl)acrylate and carboxylic acid resulting in rapid stress relaxation and excellent processability owing to the highly efficient network rearrangement.