Smart polymeric materials respond with a considerable change in their properties to small changes in their environment. Environmental stimuli include temperature, pH, chemicals, and light. “Smart” stimuli sensitive materials can be either synthetic or natural. Scientists have made many attempts to develop smart textiles by grafting the copolymerization of environment-responsive polymers (ERP) onto the surface of fabrics. Among the ERPs used for this purpose, poly (N-isopropyl acrylamide) (PNIPAAm) has attracted considerable attention due to its well-defined lower critical solution temperature (LCST) in an aqueous medium of temperature about 32-34°C, which is close to body temperature. This article summaries recent advances in the application of PNIPAAm and its copolymer hydrogels to temperature-sensitive hygroscopic fabrics, and temperature responsive fabrics. Another temperature sensitive hydroxypropyl methyl cellulose (HPMC) polymer is also briefly introduced, with regard to its application in thermally-sensitive water vapour transmission rate (WVTR) for breathable fabric.
Key words: poly (N-isopropyl acrylamide), temperature sensitive, hydrogel, hydroxypropyl methyl cellulose (HPMC), WVTR
In recent years, smart polymer/gels that experience reversible phase transitions to external stimuli have attracted special attention. These polymers/gels undergo reversible volume change in response to a small variation in solution conditions (external stimuli), such as temperature [1-6], pH [1, 7, 8], and solvent composition [9, 10]. Many temperature sensitive polymers such as poly (N-substituted acrylamide), poly (N-vinyl alkylamide), poly (vinyl methyl ether), and poly (ethylene glycol-co-propylene glycol) have been reported so far and they have been utilized in the gel form for diverse technological applications such as in controlled drug delivery, chemical separation and sensors.
Poly (N-isopropyl acrylamide) (PNIPAAm) is an intensively investigated temperature-sensitive polymer which has a simultaneously hydrophilic and hydrophobic structure and demonstrates a low critical solution temperature (LCST) at about 32 oC .In an aqueous solution, the macromolecular chains of PNIPAAm experience reversible solubility and exhibit a significant hydration-dehydration change in response to temperature stimulus. Due to its sharp temperature-induced transition and well-defined LCST, which is close to body temperature, the PNIPAAm (and in particular the PNIPAAm hydrogel) has been widely applied to temperature-sensitive drug delivery systems, separation membranes, and tissue engineering scaffolds. Recently, scientists have made many attempts to develop stimuli-sensitive textiles, or so-called smart textiles, by grafting the copolymerization of environment-responsive polymers (ERP) onto the surface of fabrics. Among the ERPs used for this purpose, PNIPAAm has attracted considerable attention, and research into it may lead to novel temperature-sensitive smart fabrics. In view of the great potential applications of smart fabrics in many areas, we will review the recent achievements in smart fabrics.
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