- Bin Zhao, University of Tennessee, Knoxville, TN
Molecular bottlebrushes are composed of polymer side chains densely grafted on a polymer backbone. These complex macromolecules exhibit intriguing structural characteristics and have potential applications in diverse areas such as lubricants and supersoft elastomers. In particular, the brush polymers can take on drastically different conformations, depending on the interactions between side chains and environment. We have embarked on an effort to design and synthesize molecular bottlebrushes that are capable of shape changing in response to external stimuli. I will present our recent work on thermo- and light-responsive, as well as dually responsive, molecular brushes that can undergo shape transitions between wormlike and globular conformations in aqueous solution. A “grafting to” method has been developed that allows for the synthesis of brushes with two or more distinct side chain polymers and facile tuning of the molar ratio of different types of side chains. Dynamic light scattering and atomic force microscopy studies showed that the responsive binary heterografted molecular bottlebrushes exhibited shape changing between worm-like and collapsed yet stable globular nano-objects upon application of an external stimulus. Using dually thermo- and light-responsive homografted molecular brushes, we further demonstrated multiple shape changes in water under different conditions.
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