Natural thermo-sensitive polymers

Chemical structure of chitosan, a natural thermo-sensitive polymer. 

Natural polymers have also been used as thermo-sensitive hydrogels, either on their own or in combination with other synthetic polymers. Popular natural polymers include chitosan, cellulose derivatives, dextran, xyloglucan and gelatin (Klouda and Mikos 2008). Chitosan is a polysaccharide derived from the shells of crustaceans and is produced by deacetylation of chitin, basically through the removal of the acetyl group using a concentrated NaOH solution (Fig. 11.5). The main advantage of chitosan for medical and pharmaceutical applications is its biocompatibility and inertness when in contact with human cells (Kumar et al. 

Self-organization of amphiphilic (co)polymers has resulted in assemblies such as micelles, vesicles, fibers, helical superstructures, and macroscopic tubes [174, 175]. These nanoscale to macroscale morphologies are of interest in areas ranging from material science to biology [176]. Stimuli-responsive versions of these assemblies are likely to further enhance their scope as smart materials. Thermo- or pH-sensitive polymer micelles [177] and vesicles [178] have been reported in which the nature of the functionality at the corona changes in response to the stimulus. Some attention has been also paid to realize an environment-dependent switch from a micelle-type assembly with a hydrophilic corona to an inverted micelle-type assembly with a lipophilic corona [179]. 

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