Responsive Bottlebrush Polymers for Biomedical and Environmental Applications

Amphiphilic bottlebrush copolymers were synthesized as bioinspired analogs of natural mucins and investigated with respect to their self-assembly and properties in aqueous media. Using a “grafting-through” approach, statistical copolymers with molecular weights of up to 600 kDa and narrow dispersity were obtained from hydrophilic oligo(ethylene glycol) methyl ether acrylate (OEGA) and hydrophobic acrylates. This approach allows precise control over self-assembly and thermoresponsive behavior by tuning the copolymer composition. In aqueous solution, the copolymers form unimolecular micelles that exhibit exceptional colloidal stability even at extreme dilution and physiological salt concentrations. Driven by their amphiphilic nature, the copolymers exhibit precisely tunable, fully reversible phase transitions with transition temperatures ranging from 20 to 70 °C. Above the phase transition temperature, well-defined aggregates form at low concentrations, and above the critical gelation concentration, physical hydrogels form, mediated by the terminal methoxy group of the OEGA side chains. Encapsulation studies using pyrene as a model drug revealed high loading capacities, while cell viability assays indicated no significant reduction in metabolic activity. To assess the mucin-like barrier function, the copolymers were examined for their binding affinity toward water-associated environmental contaminants. Polystyrene nanoparticles were successfully removed during temperature-induced gelation, followed by gel syneresis; a combined approach using activated carbon was also explored. Scalability was demonstrated through a jellyfish-mucus-inspired passive filter mechanism that exhibited size-dependent particle binding. The modification of the system with charged comonomers enabled the quantitative removal of charged dyes from aqueous solution and demonstrated the system's versatility. Collectively, these findings establish amphiphilic bottlebrush copolymers as a versatile and synthetically accessible platform that mimics key mucin functions, offering promising prospects for biomedical and environmental applications.