Abstract
The incorporation of double dynamic bonds into hydrogels provides an effective strategy to engineer their performance on demand. Herein, novel hydrogels were PREPARED by combining two kinetically distinct dynamic covalent bonds, boronate ester and acylhydrazone bonds, and the synergistic properties of the hydrogels were studied comprehensively. The functional diblock copolymers P(N-isopropyl acrylamide-co-N-acryloyl-3-aminophenylboronic acid)-b-(N-isopropyl acrylamide-co-diacetone acrylamide) (PAD) were prepared via reversible addition−fragmentation chain transfer (RAFT) polymerization. The hydrogel was constructed by exploiting dynamic reaction of phenyboronic acid moieties with polyvinyl alcohol (PVA) and ketone moieties with adipic dihydrazide (ADH) without any catalyst. The active boronate ester linkage endows the hydrogel with fast gelation kinetics and self-healing ability, and the stable acylhydrazone linkage can enhance the mechanical property of the hydrogel. The difference in kinetics endows that the contribution of each linkage to mechanical strength of the hydrogel can be accurately estimated. Moreover, the mechanical property of the hydrogel can be readily engineered by changing the composition and solid content, as well as by controlling the formation or dissociation of the dynamic linkages. Thus, we provide a promising strategy to design and prepare multi-responsive hydrogels with tunable properties.
Highlights
Hydrogels based on dynamic covalent bonds (DCBs) have attracted significant attention due to their excellent performance in self-healing and multi-responsive materials [1,2,3]
The diblock copolymers composed of a phenyboronic acid-bearing (PA) segment and a ketone-bearing (PD) segment were prepared via sequential two-step reversible addition−fragmentation chain transfer (RAFT) polymerization (Scheme 1)
The degree of polymerization (DP) values of the diblock copolymers were calculated by comparing the signals for the PNIPAM protons, the signals at 2.2 ppm (–CH3 protons of the PDAA), and the signals at 1.3–1.9 ppm (–CH– protons of the backbone)
Summary
Hydrogels based on dynamic covalent bonds (DCBs) have attracted significant attention due to their excellent performance in self-healing and multi-responsive materials [1,2,3]. The DCBs-based materials with controllable properties and multiple responsiveness have become increasingly popular because of their application prospects in some complex environments [6,7]. To this end, considerable research has been devoted to the incorporation of multiple DCBs in a single system to enhance the performance and complexities of the material [8,9].
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