Polymer-grafted nanoparticles (PGNs) with dynamic bonds have been shown to assemble into precise arrays tunable with temperature and the intrinsic properties of the polymer canopy even without an additional polymer matrix. These matrix free materials have significant ramifications in the design of tough and stimulus-responsive coatings, flexible electronics, and functional inks. However, tuning properties for a specific application is often tedious due to challenging synthetic methods. Polybutadienes, containing both 1,2-butadiene and 1,4-butadiene units, are attractive polymers for post-synthesis modification with pendant supramolecular moieties. The reactive nature of the diene bonds permits superior control over pendant group functionality and degree of functionalization.<br/><br/>Herein we show that polybutadiene can be readily functionalized via thiol-ene chemistry. Careful manipulation of reaction conditions and mercaptan structure and composition enables preparation of rubbery and glassy polymer films with dynamic supramolecular interactions ranging from weak (e.g., single H-donor and single H-acceptor) to strong (e.g., guanine and cytosine associative nucleobase pair). Simultaneous modulation of covalent crosslink density with multifunctional thiols allows for further enhancement of energy dissipation under strain. PGNs are fabricated by grafting amine-terminated polybutadiene with the modified pendant groups to carboxy-functionalized nanoparticles. The nanoparticle spacing, self-assembled structure, and nanoscale mechanics of these matrix-free nanocomposites and arrays are readily tuned via simple manipulation of the pendant functional group, degree of functionalization, nanoparticle dimensions, and molecular weight as confirmed by X-ray scattering, microscopy, and atomic force microscopy. Overall, these approaches afford a versatile and scalable preparation of stimuli responsive and tough nanocomposites.

Modular functionalization of polybutadiene with dynamic bonds for matrix free nanocomposites

256th National Meeting (2018)

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