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Talk- Guest Speaker - Bin Zhao

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What
  • cmb seminar
When Nov 13, 2017
from 11:00 AM to 12:30 PM
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Stimuli-Responsive Shape-Changing Linear Molecular Bottlebrushes


Bin Zhao

Department of Chemistry, University of Tennessee, Knoxville, TN 37996

 

 

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. Inspired by the triggered unraveling of the von Willebrand Factor, a protein in our body, from a non-sticky globular to a sticky stretched state in the blood clotting process, 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 in this talk 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 to prepare molecular bottlebrushes using the copper(I)-catalyzed azide-alkyne cycloaddition “click” reaction; the modular nature and the high grafting efficiency of this method allow 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. To stabilize the collapsed globular state, a permanently water-soluble polymer was introduced to the brushes as 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. The conformational transitions were exploited to control the interactions between the brushes and environment. Using dually thermo- and light-responsive homografted molecular brushes, we further demonstrated multiple shape changes in water under different conditions.

Webpages: https://www.chem.utk.edu/Faculty/bzhao; https://www.chem.utk.edu/zhao/

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