Abstract
Here we report an ABA triblock copolymer that can express microscopic autonomous formation and break-up of aggregates under constant condition to generate macroscopic viscoelastic self-oscillation of the solution. The ABA triblock copolymer is designed to have hydrophilic B segment and self-oscillating A segment at the both sides by RAFT copolymerization. In the A segment, a metal catalyst of chemical oscillatory reaction, i.e., the Belousov-Zhabotinsky (BZ) reaction, is introduced as a chemomechanical transducer to change the aggregation state of the polymer depending on the redox states. Time-resolved DLS measurements of the ABA triblock copolymer confirm the presence of a transitional network structure of micelle aggregations in the reduced state and a unimer structure in the oxidized state. This autonomous oscillation of a well-designed triblock copolymer enables dynamic biomimetic softmaterials with spatio-temporal structure.
Highlights
Living body, and is recognized as a chemical model for understanding several non-equilibrium phenomena in nature
We first prepared a random copolymer of NIPAAm and NAPMAm and attached the Ru(bpy)[3] metal catalyst with an activated ester (i.e., Ru(bpy)3-NHS) to the amino side-chain of NAPMAm26,27
The arrangement of NIPAAm and Ru(bpy)[3] groups along the polymer chain is highly random because the electron densities of the propagation terminals of the polymers with NIPAAm and NAPMAm during polymerization process are comparable due to the similarity of the main-chain chemical structure; Ru(bpy)3-NHS is attached to the amino side-chain after random copolymerization
Summary
Living body, and is recognized as a chemical model for understanding several non-equilibrium phenomena in nature. The resultant triblock copolymers show low temperature unimolecular dissolution and high temperature micellization owing to the lower critical solution temperature (LCST)-type thermosensitivity of NIPAAm. The aggregation temperature strongly depends on the redox state of the Ru(bpy)[3] incorporated into the self-oscillating segment because of hydrophilicity changes of the metal center (Fig. 1(a)).
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