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Smart polymers or stimuli-responsive polymers are high-performance polymers that change according to the environment they are in. Such materials can be sensitive to a number of factors, such as temperature, humidity, pH, the wavelength or intensity of light or an electrical or magnetic field and can respond in various ways, like altering colour or transparency, becoming conductive or permeable to water or changing shape (shape memory polymers). Usually, slight changes in the environment are sufficient to induce large changes in the polymer’s properties. Smart polymers appear in highly specialised applications and everyday products alike. They are used for the production of hydrogels, biodegradable packaging, and to a great extent in biomedical engineering. One example is a polymer that undergoes conformational change in response to pH change, which can be used in drug delivery. The nonlinear response of smart polymers is what makes them so unique and effective. A significant change in structure and properties can be induced by a very small stimulus. Once that change occurs, there is no further change, meaning a predictable all-or-nothing response occurs, with complete uniformity throughout the polymer. Smart polymers may change conformation, adhesiveness or water retention properties, due to slight changes in pH, ionic strength, temperature or other triggers. Another factor in the effectiveness of smart polymers lies in the inherent nature of polymers in general. The strength of each molecule’s response to changes in stimuli is the composite of changes of individual monomer units which, alone, would be weak. However, these weak responses, compounded hundreds or thousands of times, create a considerable force for driving biological processes. ==Stimuli== Several polymer systems respond to temperature, undergoing an lower critical solution temperature phase transition. One of the better-studied such polymers is poly(N-isopropylacryamide), with a transition temperature of approximately 33 °C. Several homologous N-alkyl acrylamides also show LCST behavior, with the transition temperature depending on the length of the hydrophobic side chain. Above their transition temperature, these polymers become insoluble in water. This behavior is believed to be entropy driven. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Smart polymer」の詳細全文を読む スポンサード リンク
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