Mixing POEGMA precursor polymers with different LCSTs leads to linear changes in macroscopic gel properties (e.g. mechanics, swelling) but non-linear changes in properties dependent on gel microstructure (e.g. protein adsorption, cell adhesion).

The physicochemical properties of injectable hydrogels are typically modified by altering the chemistry of the precursor polymer and/ or the amount or type of cross-linker, both of which can lead to hydrogels with altered mechanics, swelling, degradation, and other key physical properties. Herein, we describe an alternative approach to tune the properties of injectable hydrogels (here, based on hydrazone cross-linked poly(oligoethylene glycol methacrylate), or POEGMA) by altering the architecture of the precursor polymers through branching. Hydrogels prepared using highly branched precursor polymers had nearly identical chemical compositions but exhibited markedly different physical properties relative to linear precursor hydrogels on which we have previously reported. Specifically, increasing the degree of branching resulted in increased degradation time and stiffness but decreased gelation time and gel swelling. The mechanical properties of highly branched hydrogels are relatively insensitive to the mass concentration of precursor polymer used to prepare the gels, in contrast to hydrogels prepared with linear precursors; furthermore, gels prepared from only highly branched precursors exhibit substantially prolonged degradation times compared to all-linear or linear−highly branched hydrogels. Overall, introducing branching in the precursor polymers is demonstrated to provide an alternate strategy to tune injectable hydrogel properties while decoupling otherwise coupled properties (e.g., polymer concentration and mechanics).

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