Melt-Fabricated Photoreactive Block Copolymer Micelles\nas Building Blocks for Tunable Elastomeric Hydrogels

Abstract

Soft,\nconformally shaped thermoplastic elastomer (TPE) hydrogels\nproducible from a moldable precursor material are desirable in many\nbiomedical, surgical, and pharmaceutical applications. An innovative\nclass of hydrogel networks was developed by employing photocurable,\nmoldable solutions of melt-assembled spherical micelles formed from\nω-anthracenyl­polystyrene-<i>b</i>-poly­(ethylene\noxide) diblock copolymer. Photoinduced [4 + 4] cycloaddition (λ\n= 365 nm) of terminal anthracene groups populating the hydrophilic\ncorona of each micelle was used to produce polystyrene-<i>b</i>-poly­(ethylene oxide)-<i>b</i>-polystyrene triblock copolymer\ntethers or network strands among adjacent micelles. Structural uniformity\nin the micelle population was confirmed by small-angle X-ray scattering\n(SAXS), cryogenic transmission electron microscopy (cryo-TEM), and\ndynamic light scattering (DLS). Homogeneous dispersal of the assembled\nmicelle building blocks in water resulted in spreadable or moldable\nphotoactive micelle solutions, studied for their stability in solution\nand ability to rapidly form elastomeric hydrogels once irradiated.\nOnce in molds, these solutions of varied concentration were irradiated\nto form soft TPE hydrogels with dynamic shear modulus controllable\nwith irradiation time (triblock copolymer content), exhibiting prescribed\nshape consistent with high-fidelity conformal fill.