Elastomers have been widely used in various areas of applications including electronics, automotive industry, and biomedical applications. The polymeric materials with dynamic covalent bonds, called vitrimers, can overcome the challenges associated with current elastomers and allow recyclability of the material while retaining its thermal and chemical stability. Herein, we developed boronic ester-based vitrimers that exhibit tunable dynamics and mechanical performance by variation of the boronic acid structure in the polymer network. For this purpose, dynamic polymer networks were formed by reacting diol-containing tetra-arm poly(amidoamine) and phenylboronic acid terminated tetra-arm poly(ethylene glycol) which possess different substituents adjacent to boronic acid moieties. Varying the substituent adjacent boronic acid unit will significantly impact the binding strength of boronic ester in dynamic crosslinked networks which therefore affect the dynamics and mechanical performance of resulted vitrimers. The presence of electron-rich substituent in polymer structure noticeably decreases the glass transition temperature of the polymer network, provides faster relaxation, and results in elastic vitrimers with prominent recyclability and malleability at lower temperatures. On the other hand, boronic acid-based vitrimers with electron-poor substituents considerably diminish the dynamics of boronic ester exchange, increase the apparent activation energy and relaxation time while improving the mechanical stiffness of resulted vitrimers. The approach may serve as a guide for the rational design of elastomers with well-tunable dynamics and cyclabilities.

Control of dynamics and mechanical properties of elastic vitrimer by tailoring the substituents of boronic ester

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