Phenylboronic Acid Modified Sodium Alginate-Poly(Vinyl Alcohol) Shape Memory Hydrogel Based On Supramolecular Interactions

As one of the most important stimuli-responsive polymeric materials,shape memory polymers(SMPs) have attracted tremendous attention. Supramolecular SMPs will bring new breakthrough because of the reversible and dynamic supramolecular interactions.A simple strategy is provided to construct novel supramolecular hydrogels with both self-healing and shape memory properties in this paper. Firstly, Alg-PBA was prepared by grafting 3-aminophenylboronic acid(PBA) onto sodium alginate(Alg) in the presence of 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride(EDC·HC l). The signals of phenyl groups and B-O stretching were observed in the 1H NMR spectrum and FTIR spectroscopy of Alg-PBA, indicating 3-aminophenylboronic acid was successfully grafted onto alginate. The content of phenylboronic acid groups in the polymer was calculated to be 28%. Alg-PBA-PVA supramolecular hydrogel was prepared by mixing the solution of Alg-PBA and 10 % PVA(Alg-PBA : PVA= 6:1 w:w), then 100 μL of 0.1 M Na OH aqueous solution was added, and hydrogel was formed immediately after stirring.The Alg-PBA-PVA hydrogel possess self- healing capacity due to the dynamic nature of PBA–diol ester bonds in the hydrogel network structure. The destructed hydrogel can heal autonomously in 30 s. The self- healing behavior of the supramolecular hydrogel was further evaluated by rheological measurements.Di- and trivalent cations such as Ca2+ can chelate with the Alg to cross- link the polymers; the interactions between Ca2+ and alginate therefore play the role of a ??temporary crosslink‘‘. The hydrogels are capable of maintaining their temporary shape as a result of the interaction between Ca2+ and alginate, resulting in the shape memory behavior of the Alg-PBA-PVA hydrogel. Ca2+ can be either extracted by CO32-or complexed by a competitive ligand such asEDTA·2Na, thereby contributing to the reversible shape memory effect. Meanwhile,the Alg-PBA-PVA hydrogel show good performance at the microscale. Based on the advantages of two supramolecular interactions, we have offered a simple and universal approach in the design and fabrication of novel supramolecular hydrogels with both self- healing and shape memory properties.Another strategy is provided to construct a novel p H- and sugar-induced shape memory hydrogel based on dynamic phenylboronic acid(PBA)–diol interactions formed by PBA modified sodium alginate(Alg-PBA) and PVA. The dynamic PBA–diol ester bonds serve as temporary cross- links and stabilize the deformed shape of the hydrogel. The disassociation of the PBA–diol ester bonds is explored in acidic conditions and aqueous solutions of glucose and fructose, which endow the hydrogel with shape memory performances.