Grafted polymers chitosan

The author also prepared a second derivative by hydroxymethylating chitosan with paraformaldehyde and post-reacting with the lipase inhibitor tetrahydrosterastin. Other graft polymer derivatives of the current invention are described (1). 

Cationic polymers, such as poly(L-lysine) (PEL), polyethylenimine (PEI), chitosan, polyamidoamine (PAMAM) dendrimers, poly(2-dimethylamino) ethyl methacrylate, and polyphosphoesters, condense DNA to form compacted polyplexes. ° The size and the stability of polyplexes depend on the ratio of cations vs. anions, temperature, ionic strength, and the solvent. Stability of polyplexes can be enhanced by conjugating PEG to the polycations or by using PEG-containing block or graft polymers that form micelles. Small cationic peptides are also able to condense DNA, however, six-consecutive-cations is the minimal requirement to achieve this effectively. 

The possibility of grafting synthetic polymer to chitosan has attracted much attention in the last years as a new way to modify the polysaccharide and develop practically useful derivatives. Graft copolymerization reactions introduce side chains and lead to the formation of novel types of tailored hybrid materials composed of natural and synthetic polymers. Grafting chitosan is a common way to improve chitosan properties such as formation of inclusion complexes [99], bacteriostatic effect [100], or to enhance adsorption properties [101, 102]. Although the grafting of chitosan modifies its properties, it is possible to retain some interesting characteristics such as mucoadhesivity [103], biocompatibility [104,105] and biodegradability [106]. 

Chitin, a waste material from crab and shrimp processing, is poly(N-acetyl-D-glucosamine). The de-acetylated form, chitosan, is primarily used in water purification but is also used as a chemical feedstock. For example, chitosan can be depolymerized to the monomer, which is used as a hair-setting agent in shampoo and hair conditioner. In the future, graft polymers of chitosan may form biodegradable films. Already, carboxymethylated chitin is approved as a food wrap. 

Another class of materials are the thermoreversible gels obtained when LCST polymers such as PNIPAm [150-152], PEOP [153], or methylcellulose [154] are grafted on chitosan. Figure 4.4 shows the variation of mechanical moduli to stepwise periodic changes in temperature from 10 to 30 °C. 

Graft copolymers are polymers produced when molecular fragments belonging to others polymers have been inserted into their side chains (Hazer and Steinbiichel 2007). The condensation reaction between the carboxy-terminal groups of certain PHAs poly[(/ )-3-hydroxybutyrate] poly[(/ )-3-hydroxybutyrate-co-(l )-3-hy-droxyvalerate] or PHO and the amine function of chitosan resulted in grafting of PHA polymers onto chitosan (Fig. 2). These grafted polymers formed opaque, viscous solutions in water and, once dried, afforded strong elastic films (Yalpani et al. 1991 Arslan et al. 2007). 

Hu SG, Jou CH, Yang MC (2003) Antibacterial and biodegradable properties of polyhydroxyal-kanoates grafted with chitosan and chitooUgosaccharides via ozone treatment. J Appl Polym Sci 88 2797-2803... 

Jayakumar, R., Prabaharan, M., Reis, R.L., and J.F. Mano. 2005. Graft copolymerized chitosan—Present status and applications. Carbohydrate Polymers 62 142-215. 

Chen, S. and Wang, Y. 2001. Study on P-cyclodextrin grafting with chitosan and slow release of its inclusion complex with radioactive iodine. J. Appl. Polym. Sci. 82 2414-2421. 

Wu C. -S. A comparison of the structure, thermal properties, and biodegradabUity of polycaprol-actone/chitosan and acryhc acid grafted polycaprolactone/chitosan. Polymer 46 (2005) 147. 

Chitosan, having a similar chemical backbone as cellulose, is a linear polymer composed of a partially deacety-lated material of chitin [(l-4)-2-acetamide-2-deoxy-/3-D-glucan]. Grafting copolymer chains onto chitosan can improve some properties of the resulting copolymers [48-50]. Yang et al. [16] reported the grafting reaction of chitosan using the Ce(IV) ion as an initiator, but no detailed mechanism of this initiation has been published so far. 

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