Molecular conformation and macroscopic properties of brush-like polymers are controlled by well-defined architectural parameters including side-chain length, grafting density, and crosslink density. Loosely grafted comb-like macromolecules behave as flexible linear chains that overlap and entangle, whereas densely grafted bottlebrushes behave as worm-like filaments possessing distinct shape and self-disentangled organization. Relatively large dimensions and discrete assembly of bottlebrushes allowed imaging of individual molecules both as single species and within dense films by atomic force microscopy (Figure a). Steric repulsion between long and dense side chains may induce conformational transitions and even cause scission of covalent bonds. In block-copolymer bottlebrushes, the same steric repulsion regulates dimensions of microphase separated domains and generates structural coloration (Figure b). Herein we will first present assorted visuals of different bottlebrush systems and then discuss their implications for fundamental understanding and practical applications of these unique macromolecules. From many interesting applications such as membranes and drug delivery, the ability of brush elastomers to precisely replicate the deformation response of soft tissues is particularly noteworthy. Brush architecture imposes significant shifts in mechanical properties of bottlebrush assemblies such as melts, elastomers, and gels. We will discuss the distinct tactility of brush materials by examining quantitative correlations between the brush parameters and specific materials mechanical characteristics such as modulus, elongation-at-break, strength, and firmness.

How we see and sense bottlebrushes

ACS Spring Meeting 2021

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