Hydrolysis-Driven Viscoelastic Transition in Amphiphilic Triblock Copolyether Hydrogels with Acetal-Functionalized Endblocks
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Most degradable hydrogels developed for biomedical uses rely on the hydrolytic cleavage of ester groups, but the rheological time-profile of those hydrogels is hard to be predicted due to the randomness in the chain fragments. To settle a model system suited for a predictable mechano-temporal profile, we designed degradable hydrogels based on amphiphilic triblock copolymers containing endblocks functionalized with hydrophobic acetal pendants. The pendant groups are gradually cleaved from the endblock backbone by acidic hydrolysis, leading to a gradual decrease in overall hydrophobicity of the endblock and subsequent gel-to-sol transition. Dynamic mechanical analysis and NMR spectroscopy revealed that the hydrolysis rate can be orthogonally and precisely tuned by changing the chemical structure and hydrophobicity of acetal pendants. Our study provides a rationale for highly controllable degradable hydrogels with a vast tunability in the hydrolysis rate and the mechanical performance.