Irradiation aqueous polysaccharide

Water radiolysis is the main effect of the y-irradiation of diluted aqueous solutions. In the case of diluted aqueous solutions of polysaccharides, "OH and H atoms formed from water radiolysis are able to abstract hydrogen atoms from the polymer to form the macroradicals (reactions (31.3) through (31.5)). The subsequent reactions of macroradicals can be chain scission (reaction (31.6)), hydrogen transfer, inter- and intramolecular recombination, and disproportionation of macroradicals. Chain scission leads to a decreasing in the molecular weight of the polymer. 

Xyloglucan (XG), a water-soluble food grade polysaccharide extracted from tamarind seed mucilage, has been reported as a substrate for the graft copolymerization of acrylonitrile (AN) [37]. Polymerization was initiated with XG both conventionally by ceric ions in an aqueous medium under atmosphere and also under microwave irradiation. In the microwave initiated grafting reaction where no initiator was used, 92.5%G was achieved using 0.5 M acrylonitrile, XG (1 g/200 ml (H O)), temperature 60°C and microwave power 150 W in 120 s. Conventionally, xmder same monomer and polysaccharide concentration, 76%G was achieved in 24 h using ceric ammonium nitrate (0.001 M) as initiator at 40°C. 

It is worth mentioning that if the aqueous solutions saturated with air are exposed by ionized irradiation, additional particles O and CO are formed that participate in polysaccharide radiolysis as well. The majority of researchers confirm that the reactivity of the radical particles formed during irradiation decreases in the series OH >e >C02 >02 [73]. 

The effects of y-radiation on the depolymerization and selected physical properties of amylose in the solid state and in solution have been investigated under conditions of graft copolymerization. Irradiation furnished an alkali-sensitive material (G-value for scission 2.8), most likely owing to the presence of a j8-alkoxycarbonyl structure. The G-value (1.3) obtained on irradiation of solid amylose at 0 °C under nitrogen is lower than values previously reported for amylose and other polysaccharides. A solution of amylose in water was protected against y-radiation by the addition of DMSO (G-value of 2.3 vs. 30). A solvent system of DMSO-acetic acid-water degraded y-irradiated amylose less than did aqueous DMSO. 

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