IOSR Journal of Applied Chemistry (IOSR-JAC) e-ISSN: 2278-5736. Volume 4, Issue 3 (May. – Jun. 2013), PP 39-44 www.iosrjournals.org www.iosrjournals.org 39 | Page Chemical Modification of Marine Polysaccharide (Alginate) By Free-Radical Graft Copolymerization― a Short Review A Salisu* 1 ; Ahmedy A. Naim 1 ; M.M. Sanagi 2\ 1 Department of Chemistry, Faculty of science, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor, 2 Ibnu Sina Institute for Fundamental Science Studies, Nanotechnology Research Alliance, Universiti Teknology Malaysia, 81310 Johor Bahru, Johor, Abstract : Because of considerable interest in the preparation of biodegradable materials based on natural polymers, many techniques have been used to modify the physical and chemical properties of natural polymers. Due to the presence of various functional groups on molecular chains, polysaccharides could be readily modified chemically to form polymer hybrid of good composition and functional properties. There have been a number of studies reported for chemical attachments of synthetics polymers. However, grafting of vinyl monomers onto polysaccharides backbone via radical polymerization is often used technique. Alginic acid or alginate is polyuronides, i.e., polysaccharides in which the molecules are built up of uronic acid residues which are obtained from seaweed species of brown algae. Alginate has broad applications in various fields such as pharmaceutical, biomedical, agriculture, and environmental. The present review compiled the studies on the chemical modification of alginate via free- radical graft copolymerization, particularly by generating the free radicals using thermal initiator or electron transfer reaction (redox system) and the potential applications of the grafted copolymers. Keywords: alginate, biodegradable, graft copolymerization, polysaccharide, radicals I. Introduction In recent years there has been an increase interest in biodegradable materials. Biodegradable materials are used in packaging, medicine, agriculture and other applications. Natural polymers such as polysaccharides are available in large quantities from renewable sources. Polysaccharides are carbohydrates that contain many monosaccharide units joined together by glycosidic bonds. The majority of carbohydrates that occur in nature are in the form of polysaccharides. The important roles played by polysaccharides in living organisms are either storage or structural functions. Due to the presence of various functional groups on molecular chains, polysaccharides could be readily modified chemically to form polymer hybrid of good composition and functional properties. The recent investigation of polysaccharide-based materials can be attributed to new synthetic approaches for their modification with the aim to improve their properties for specific applications. These synthetic approaches include the combination of polysaccharides with other polymers. Grafting of vinyl monomers onto polysaccharides via radical polymerization has attracted the interest of many researchers in the last two decades [1]. However, the methods employed for grafting vinyl monomers onto polysaccharides are different from that of grafting non vinyl monomers. Non vinyl graft copolymerization can be achieved through polycondensation reactions; although competitive degradation reaction may severely result to rapid loss of molecular weight in short period of time due to susceptibility of many functional groups of polysaccharides towards acids, bases, and reducing agents or in most cases low yield of product is obtained. Most of the recent researches on the chemical modification of polysaccharides involve the introduction of synthetic polymer on the backbone through grafting techniques. The radical-initiated polymerization has gained considerable attention, and has proven to be useful methods for the industrial production of modified polysaccharides. Recently, many review papers have been published on the modification of polysaccharides. However, this article is intended to bring out the researches on the chemical modification of marine polysaccharide (i.e. alginate) by free- radical graft copolymerization particularly on ―grafting from‖ method with major emphasis on radical formation by thermal or electron transfer reaction (redox system) and their potential application. 1.1 Synthesis And Characterization Of Graft Copolymers Graft copolymer is a macromolecular chain in which one or more blocks are connected to the main chain (called trunk polymer) as side chain(s). Thus, it can be described as having the general structure illustrated schematically in Fig 1., where the main polymer backbone poly(A), commonly referred to as the trunk polymer, has branches of polymer chain poly(B) originating from different points along its length. The simple way to describe this structure is poly(A)-graft-poly(B), which can be further condensed as poly(A)-g- poly(B).