چكيده لاتين :
Biopolymer chitin, the most abundant natural amino polysaccharide, and its most
important derivative, chitosan, are recently considered as the subjects for extensive
worldwide academic and industrial research. In spite of potential applications
of chitin and chitosan, it is necessary to establish efficient appropriate modifications to
explore fully their high potential. A variety of chemical modifications are employed to modify
these carbohydrate polymers. The present article provides a comprehensive review on
one of the most promising approaches to modify chitin and chitosan, i.e., graft copolymerization,
with an emphasis on the synthetic aspects. Both chemically- and radiation-initiated
graft copolymerization of various vinyl monomers onto the trunk polymers are investigated.
Meanwhile, the limited cases of polycondensation and oxidative coupling are presented
as the non-vinyl graft copolymerization methods. Then, the ring-opening graft
copolymerization is described and the cases of the cyclic monomers a-aminoacid N-carboxy
anhydrides and £-caprolactone are investigated. An extensive description of the
"grafting onto" approach is provided. The preformed polymers discussed here for grafting
onto chitin/chitosan include living poly(2-alkyl oxazolines), poly(ethylene glycol)s, block
polyethers, poly(ethylene imine)s, poly(2-hydroxyalkanoate)s, polyurethanes, poly
(dimethylsiloxane)s, and dendrimer-like hyperbranched polymers. Chitin/chitosan multiple
modification including graft copolymerization is also investigated. Regioselective
grafting using derivatives such as 6-iodo-, mercapto-, deoxy(thiosulphato)-chitins, and Ntrichloroacetyl
chitosan are described as suitable approaches to achieve chitin/chitosan
graft copolymers with well-known structures.
