Responsive Smart Polymers

5 g of n-isopropylacrylamide and 20 ml of distilled water are placed in a 100 ml flask and stirred for 15 min under nitrogen. 640 mg of butanediol diacrylate (BDDA) is added to the mixture. 0.5 mol% of sodium disulflte and 0.5 mol% of potassium peroxodisulfate are dissolved in 1 ml water and added to the solution. The reaction mixture is stirred 1 h under nitrogen. After 1 h a white solid precipitates. The solid is filtered out and dried at 70 C. Yield quantitative. The polymer is soluble in water below 32 C and precipitates from aqueous solution above that temperature. 

One of the more recently developed material classes is that of thermo-responsive polymers. This accounts mainly for those polymers showing a so-called lower critical solution temperature (LOST) or - to a much less extent - an upper critical solution temperature (UCST), meaning polymers that change their solution status significantly upon temperature changes. In general, this behaviour is the result of a delicate balance of hydrophilic and hydrophobic groups in the polymer. The major 

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Filipcsei, G., Csetneki, I., Szilagyi, A. and Zrtnyi, M. Magnetic Field-Responsive Smart Polymer Composites. Vol. 206, pp. 137-189... 

Magnetic Field-Responsive Smart Polymer Composites... 

Filipcsei G, Csetneki I, Szilagyi A, Zrinyi M (2007) Magnetic field-responsive smart polymer composites. Adv Polym Sci 206 137-189... 

Jochum, F. D., Theato, P. Temperature- and light-responsive smart polymer materials. ChenLSQ, ., 2013,42, 7468-7483. 

A novel approach to immobilization of enzymes via covalent attachment is the use of stimulus-responsive smart polymers, which undergo dramatic conformational changes in response to small alterations in the environment, such as temperature, pH, and ionic strength [401 03], The most prominent example is a thermo-responsive and biocompatible polymer (poly-iV-isopropyl-acrylamide), which exhibits a critical solution temperature around 32°C, below which it readily dissolves in water, while it precipitates at elevated temperatures due to the expulsion of water molecules from its polymeric matrix. Hence, the biolransformation is performed under conditions, where the enzyme is soluble. Raising the temperature leads to precipitation of the immobilized protein, which allows its recovery and reuse. In addition, runaway reactions are avoided because in case the reaction temperature exceeds the critical solution temperature, the catalyst precipitates and the reaction shuts down. 

Materials that show a shape-memory effect can be deformed into a temporary shape and afterwards they can recover their original shape on exposnre to an external stimulus [65,66]. Shape-memory polymers (SMPs) are stimuli-responsive smart polymers that have dual shape, which responds to application of an external stimulus. SMP is conventionally processed to receive its permanent shape. Afterward, the polymer is deformed and the intended temporary shape is fixed [67,68]. This process is called programming. These polymers basically consist of two phases, fixed points or frozen... 

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