Fmoc-phenylalanine as a building block for hybrid double network hydrogels with enhanced mechanical properties, self-recovery, and shape memory capability

Abstract

Based on thermoreversible sol–gel transitions of simple amino acid, fluorenylmethoxycarbonyl-modified phenylalanine (Fmoc-F), a hybrid double-network (DN) hydrogel, has been fabricated by combining a self-assembled Fmoc-F gel and a covalent polyacrylamide (PAAm) network. Up to 2 wt% Fmoc-F can be incorporated into DN hydrogels (90 wt% water) to form thinner and shorter nanofibers within the PAAm gel network than in pure Fmoc-F hydrogels; this indicates strong interaction between two gelators. Fmoc-F self-assembly also provides sacrificial bonding to effectively dissipate stretching energy, resulting in increased tensile modulus and yield strength of DN gels by 3437% and 737%, respectively, when compared with pure PAAm hydrogel. The relatively small increase of 133% and 177% in tensile strain and strength, respectively, of DN gels could be attributed to the time-independent discontinuous dissociation of the Fmoc-F self-assembly for energy dissipation. DN hydrogels also exhibit temperature-sensitive shape memory and self-recovery performance because of thermoreversible Fmoc-F self-assembly. • A novel DN gel was prepared by introducing thermoreversible Fmoc-F self-assembly into PAAm hydrogel. • A reinforcing mechanism of DN gel was proposed. • Energy dissipation mechanism mainly depends on discontinuous dissociation of Fmoc-F self-assembly. • DN gels exhibit temperature-sensitive shape memory and self-recovery performance.