The application of functional hydrogels in various scientific fields such as bioengineering, drug delivery, soft robotics, etc., is continuously growing. However, developing hydrogels that simultaneously possess good mechanical and self-healing properties remains a challenge. Schiff base bonds have attracted much attention due to their dynamic nature finding use in the fabrication of crosslinked self-healing materials. In this work, such dynamic systems have been developed investigating multifunctional benzaldehyde amphiphilic crosslinkers in conjunction with glycol chitosan to form hydrogels. The polymeric crosslinkers were fabricated by a two-step process utilizing aqueous copper-mediated reversible deactivation radical polymerization (Cu-RDRP) to synthesize narrow dispersity ‘ABA’ telechelic copolymers from a bifunctional PEG initiator. The A blocks were comprised of random copolymers of dimethyl acrylamide (DMAc) and hydroxyethyl acrylamide (HEAm), at certain molar ratios. Polymers were then modified by post-functionalization yielding multifunctional benzaldehyde crosslinkers able to self-assemble in water. Aqueous solutions of these crosslinkers spontaneously formed hydrogels when mixed with glycol chitosan due to the <i>in situ</i> formation of imine bonds. Hydrogels were characterized while additional comparisons were made with a commonly used bifunctional PEG crosslinker. Finally, the effect of introducing partially reduced graphene oxide (GO) nanosheets was also examined leading to certain enhancements in both mechanical properties (2.0 fold increase in modulus and 1.4 fold increase in strain) and self-healing efficiencies (&gt;99% from 60% by rheology) relative to the pristine polymer materials. Based on our findings, we envision the use of such materials as platforms for the controlled delivery of hydrophobic amine substances for several applications.

Investigating the self-healing and mechanical properties of dynamic glycol chitosan hydrogel nanocomposites

ACS Fall 2021

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