UC Santa Barbara

From the robust underwater adhesion of marine mussels to rapid camouflage in cephalopods, the chemical and structural motifs found in marine organisms are instructive for rational design of synthetic nanomaterials. This dissertation describes the development of three bioinspired assembly methods of synthetic copolymers into hierarchically structured constructs for photonic and therapeutic applications.

First, a catechol-based dip coating platform has been developed for the facile preparation of composite films from aqueous solutions. The sequential layer-by-layer assembly of a mussel inspired polymeric binder with oxide nanoparticles — SiO2 and TiO2 — utilizes the exceptional adhesion properties of catechol moieties. This modular assembly of well-defined building blocks demonstrates tunability over film thickness and refractive indices, enabling the preparation of multilayered optical coatings such as Bragg stacks.

To prepare responsive, internally structured particles for photonic applications, block copolymers (BCPs) were assembled in droplets. In this system, pH responsive ellipsoidal particles were designed to emulate the structure of the light reflective cells used by squid for dynamic coloration. Functional surfactants were used to direct the assembly of lamellar forming polystyrene-b-poly(2-vinylpyridine) (PS-P2VP) within emulsion droplets to achieve axially stacked lamellae after solvent evaporation. Selective cross-linking of the P2VP domain leads to pH sensitive hydrogel domains connecting glassy PS discs. This ability to tune the refractive index contrast between the two alternating BCP domains, suggests progress towards colloidal Bragg reflectors for photonic materials.

In the final system, well-defined microgels were produced using a microfluidic device in combination with coacervate-driven crosslinking of poly(ethylene-oxide) based ionic triblock copolymers. This strategy enables the additional incorporation of charged cargo into the microgel. When the payload functional group and the microgel dimensions are varied, distinct cargo release profiles are observed. This mild and non-covalent assembly method represents a promising new approach to produce tunable BCP microgels as scaffolds for colloidal biomaterials in therapeutics and regenerative medicine.