| 概 要 |
Many kinds of stimuli-responsive polymer gels that respond to temperature, pH, electricity, light, and specific molecules, etc., have been developed. Especially, from the late 1980s, new functional gels have been developed as intelligent or smart gels, and their applications have been demonstrated. As typical examples, actuator (artificial muscle), drug delivery systems, tissue engineering, purification or separation systems, biosensor, shape memory materials, molecular recognition systems, etc., have been extensively studied. Further, gels have played important roles in the field of micromachines and nanotechnology recently. Not only new synthetic methods to give unique functions by molecular design in nano-order scale including supramolecular design, but also the design and construction of micro or nanomaterial systems with the biomimetic functions have been attempted.
In addition to stimuli-responsive behaviors, one of characteristic and important behaviors in living systems is autonomous oscillation, that is, spontaneous changes with temporal periodicity (called "temporal structure") such as heartbeat, brain waves, pulsatile secretion of hormone, cell cycle, and biorhythm. Although many stimuli-responsive polymer and gel systems inspired by living systems have been studied so far, there are few studies on polymer and gel systems undergoing self-oscillation under constant condition without any on-off switching of external stimuli. If such autonomous systems can be realized by using completely synthetic polymers, unprecedented biomimetic materials may be created.
Under this concept, as a novel biomimetic gel, we developed gels with an autonomous self-oscillating function like a heart muscle, which was firstly reported in 1996. We designed the "self-oscillating gel" by utilizing the oscillating reaction, called the Belousov-Zhabotinsky (BZ) reaction which is well known as a chemical model of the TCA cycle. The self-oscillating polymer is composed of a poly(N-isopropylacrylamide) network in which the metal catalyst for the BZ reaction is covalently bonded. In a closed solution containing the reactants other than the catalyst, the polymer gel undergoes spontaneous cyclic swelling-deswelling changes without any on-off switching of external stimuli. Their potential applications include several kinds of functional material systems, such as biomimetic actuators, autonomous mass transport systems, functional fluids, etc. In my talk, recent progress on the novel polymer gels is introduced.
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