Click chemistry of natural polymers

In recent years, natural polymers, such as chitosan, cellulose, starch, alginate, collagen, gelatine, chondroitin sulphate, hyaluronic acid, heparin, and so on, have been attracted more and more attentions in different fields for their versatile properties, such as biocompatibility, biodegradability, nontoxicity, econony and environmental friendly. The above natural polymers are also easy to be modified by chemical grafting of new functional groups to promote their properties. Nowadays, click chemistry has become a powerful tool for materials modification by material chemists for their number of advantages such as readily available starting material, high reaction rate, high reliability, mild reaction conditions, high oxygen and moisture stability, good stereoselectivity, high yield, simple workup and easy purification. Click chemistry not only has broad applications in synthetic organic chemistry, but also has been employed in immobilizing small molecules, linear polymers, dendrimers and biological macromolecules into the skeleton of natural polymers. Modification of natural polymers by click chemistry will help to overcome their shortages such as complicated reaction conditions, low selectivity, various side reactions and low yields, and remarkably improve their immobilizing efficiency. In the current chapter, we want to introduce the progress in modification of the natural polymers through the click reactions, and the application of the above composite in different fields.