Ceric Ion-Initiated Grafting of Poly(Methyl Acrylate) onto Chitin

Chitin and its derivatives: Structural properties and biomedical applications

Chitin, a polysaccharide that occurs abundantly in nature after cellulose, has attracted the interest of the scientific community due to its plenty of availability and low cost. Mostly, it is derived from the exoskeleton of insects and marine crustaceans. Often, it is insoluble in common solvents that limit its applications but its deacetylated product, named chitosan is found to be soluble in protonated aqueous medium and used widely in various biomedical fields. Indeed, the existence of the primary amino group on the backbone of chitosan provides it an important feature to modify it chemically into other derivatives easily. In the present review, we present the structural properties of chitin, and its derivatives and highlighted their biomedical implications including, tissue engineering, drug delivery, diagnosis, molecular imaging, antimicrobial activity, and wound healing. We further discussed the limitations and prospects of this versatile natural polysaccharide.

Chitosan Derivatives: Introducing New Functionalities with a Controlled Molecular Architecture for Innovative Materials

The functionalization of polymeric substances is of great interest for the development of innovative materials for advanced applications. For many decades, the functionalization of chitosan has been a convenient way to improve its properties with the aim of preparing new materials with specialized characteristics. In the present review, we summarize the latest methods for the modification and derivatization of chitin and chitosan under experimental conditions, which allow a control over the macromolecular architecture. This is because an understanding of the interdependence between chemical structure and properties is an important condition for proposing innovative materials. New advances in methods and strategies of functionalization such as the click chemistry approach, grafting onto copolymerization, coupling with cyclodextrins, and reactions in ionic liquids are discussed.

Graft copolymerization of methyl methacrylate onto mercaptochitin and some properties of the resulting hybrid materials

The graft copolymerization of methyl methacrylate onto mercaptochitin and some properties of the resulting graft copolymers have been studied. Methyl methacrylate was efficiently graft copolymerized onto mercaptochitin in dimethyl sulfoxide, and the grafting percentage reached 1300% under appropriate conditions. Although the side-chain ester groups were resistant to aqueous alkali, hydrolysis could be achieved with a mixture of aqueous sodium hydroxide and dimethyl sulfoxide. Subsequent treatment with acetic anhydride in methanol transformed the sodium carboxylate groups into carboxyl groups. Although the graft copolymers exhibited an improved affinity for organic solvents, those having sodium carboxylate or carboxyl units were characterized by a much more enhanced solubility and were soluble in common solvents. The hygroscopic nature of chitin decreased with an increase in the grafting extent but increased significantly upon hydrolysis of the ester groups. The enzymatic degradability of the graft copolymers, as evaluated with lysozyme, was also dependent on the grafting extent and much higher than that of the original chitin. DSC measurements revealed the presence of a glass transition phenomenon, which could be ascribed to the poly(methyl methacrylate) side chain.