Multiple-Responsive Chiral Hydrogels from Helical Dendronized Poly(phenylacetylene)s

Abstract

Chiral hydrogels derived from helical polymers are attractive as intelligent chiral materials due to the combination of polymer helicity and hydrogel characteristics. Here, we report the synthesis and characterization of chiral hydrogels from helical thermoresponsive dendronized poly(phenylacetylene)s via dynamic covalent acylhydrazone crosslinking, which are responsive to temperature, pH and redox. Two types of helical copolymers, featuring dendritic oligoethylene glycol (OEG) units terminated with either methoxyl or ethoxyl groups, were employed as precursors to afford distinct overall hydrophilicity. These precursors exhibited unprecedented thermoresponsive behavior attributed to the densely grafted dendritic OEGs, with cloud points (T_cps) primarily governed by the terminal groups (methoxyl versus ethoxyl). To impart multi-responsiveness, a disulfide-containing crosslinker was selected for hydrogel formation. Gelation was conducted at three different temperatures—freezing temperature, room temperature (below T_cp), and elevated temperature (above T_cp)—yielding hydrogels with tunable responsiveness to temperature, pH, and redox conditions. The resulting hydrogels displayed stabilized helicity, along with good self-healing properties, excellent compressibility and robust mechanical performance. Preliminary biocompatibility assays indicated low cytotoxicity, underscoring their potential for biomedical applications.