Self-assembly of cholesterol tethered within hydrogel networks

Abstract

Cholesterol self-assembles into weakly ordered aggregates when tethered to a crosslinked hydrogel network of poly(ethylene glycol) (PEG). PEG-diacrylate and cholesterol-PEG-acrylamide (PEG-chol) were co-polymerized in organic solvent and transferred to water for equilibrium swelling. Small-angle x-ray scattering revealed self-assembled cholesterol structures not present during network synthesis. At lower ratios of PEG-tethered cholesterol to PEG (<12% cholesterol based on total solid content), cholesterol aggregates into the dense, weakly ordered crosslink junctions of the PEG network. The hydrogel networks exhibited classic affine behavior during compressive mechanical testing, and cholesterol aggregation enhanced the elastic modulus. At high PEG-chol to PEG ratios (12–20% cholesterol based on total solid content), cholesterol self-assembles into domains with lamellar-like meso-ordering. The structural transition causes network deswelling and significantly reduces material brittleness upon deformation.