Many natural biomacromolecules, such as von Willebrand factor, utilize shape changing from compact folded to extended conformations to perform their functions. Stimuli-responsive molecular bottlebrushes are excellent candidates for mimicking the behavior of these natural polymers. Here we present the synthesis of thermosensitive binary heterografted linear molecular brushes and their temperature-induced shape transitions between extended worm-like and collapsed yet stable globular conformations in water. These bottlebrushes are composed of a thermosensitive water-soluble polymer and poly(ethylene oxide) (PEO) as side chains, where PEO serves as a stabilizer for the collapsed state. A “grafting to” method is developed to make molecular brushes by clicking alkyne end-functionalized side chain polymers onto an azide-bearing backbone polymer. At a concentration of 1.0 mg/g, the aqueous solution of binary heterografted molecular bottlebrushes remained clear upon heating through the lower critical solution temperature (LCST), in contrast to the homografted thermosensitive bottlebrushes in water at the same concentration, which turns cloudy. Atomic force microscopy study reveals shape transitions between an worm-like morphology below the LCST and a globular conformation above the LCST. We further demonstrate that the shape changing of binary heterografted brushes can be exploited to control the interaction between the brushes and their environment by incorporating a functional group into the thermosensitive side chains.

Thermosensitive shape-changing binary heterografted linear molecular bottlebrushes

254th National Meeting (2017)

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