Dynamic covalent cross-linked polymer gels through the reaction between side-chain β-keto ester and primary amine groups.

Abstract

A dynamic covalent gel network was constructed via the coupling reaction between the pendant primary amine groups of poly(l-leucine methacryloyloxyethyl ester) (P(H2N-Leu-EMA)) and the side-chain β-keto ester functionalities of poly(2-(acetoacetoxy)ethyl methacrylate) (PAEMA) by varying the molar ratios of P(H2N-Leu-EMA)/PAEMA and the concentration of polymers in different solvents at room temperature. Fourier transform infrared (FT-IR) spectroscopy and solid-state 13C nuclear magnetic resonance (NMR) study confirmed the newly formed enamine bonds in the polymeric gel. Rheological studies showed that the mechanical strength of gels increased with increasing weight percentage (wt.%) of polymers in solution. Furthermore, polymer gels can be transferred to the mixture of starting polymer solutions by regulating the pH of the system, which can be further transformed into the gel state by adding an external base.