Bottlebrush Polymers, Networks, and Applications 88 views

Bottlebrush polymers consist of a long linear backbone densely grafted with many relatively short linear side chains, enabling independent encoding of mechanical, physical, and biochemical complexity into a single molecular architecture. Yet using bottlebrush polymers as building blocks to create functional materials requires understanding the deterministic relation between their molecular structure and architectural parameters. This dissertation addresses these challenges through three interconnected directions spanning the molecular structure, mechanical properties, and applications. In the first direction, we investigate the molecular structure of bottlebrush polymers. We discover that chemically incompatible backbones and side chains drive the backbone to fold into a cylindrical core, a phenomenon opposite to all prior understanding, and show that this folding behavior governs macroscopic thermomechanical properties across different distinct structural regimes. We further discover that in linear-bottlebrush diblock copolymers, interfacial penetration of the linear tail into the bottlebrush domain drives anomalously large domain spacing. In the second direction, we elucidate the mechanical properties of bottlebrush polymer networks. We discover a universal strategy to decouple the inherent stiffness-extensibility trade-off of single-network elastomers using foldable bottlebrush polymers as network strands, increasing tensile breaking strain 40-fold while maintaining a constant modulus. We further design photo-clickable bottlebrush polyethylene glycol hydrogels in which crosslink clustering programs tissue-mimicking strain-stiffening behavior. In the third direction, we demonstrate the applications of bottlebrush polymers. We show that bottlebrush polyethylene glycol nanocarriers translocate across human airway epithelium and penetrate the retina following topical administration. We also develop 3D-printable foldable bottlebrush polyethylene glycol networks that yield hydrogels and elastomers with tissue-mimicking moduli and tensile breaking strains up to 1500%. Together, these discoveries establish bottlebrush polymers as a versatile molecular platform for designing soft materials with prescribed mechanical properties and biological functions, with broad implications for tissue engineering, drug delivery, and soft robotics.

PHD (Doctor of Philosophy)

Bottlebrush polymers; Polymer networks; 3D printing; Tissue engineering; Drug delivery; Hydrogels

English

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2026-07-06