Cellulose Graft-Polymers

GOX (glucose oxidase), 631, 636, 637 GPC (unsaturated glycerophosphocholine), 737 GPO (l-glycerol-3-phosphate oxidase), 633 Graft polymers cellulose, 698 cross-linking initiators, 706 ozonized polymers, 622 Griesbaum co-ozonolysis, 1,2,4-tiioxane antimalarials, 1331... 

Emulsion polymerizations of vinyl acetate in the presence of ethylene oxide- or propylene oxide-based surfactants and protective coUoids also are characterized by the formation of graft copolymers of vinyl acetate on these materials. This was also observed in mixed systems of hydroxyethyl cellulose and nonylphenol ethoxylates. The oxyethylene chain groups supply the specific site of transfer (111). The concentration of insoluble (grafted) polymer decreases with increase in surfactant ratio, and (max) is observed at an ethoxylation degree of 8 (112). 

An effective method of NVF chemical modification is graft copolymerization [34,35]. This reaction is initiated by free radicals of the cellulose molecule. The cellulose is treated with an aqueous solution with selected ions and is exposed to a high-energy radiation. Then, the cellulose molecule cracks and radicals are formed. Afterwards, the radical sites of the cellulose are treated with a suitable solution (compatible with the polymer matrix), for example vinyl monomer [35] acrylonitrile [34], methyl methacrylate [47], polystyrene [41]. The resulting copolymer possesses properties characteristic of both fibrous cellulose and grafted polymer. 

In grafting reactions initiated by redox processes, there is an interaction of the intermediate products with the substrate polymer chains. There may also be a chain transfer reaction involved. It is sometimes difficult to make a clear distinction between a direct redox reaction and a chain transfer process. Three redox systems have been studied extensively in grafting onto cellulose persulfate ions 1, hydroperoxide/ferrous ions 2> 3 and cerium (IV) ions. ... 

The hydroxyl radicals formed may abstract hydrogen from the cellulose fiber substrate which gives grafting sites and subsequently grafted polymer with monomer present. The HO- radicals may also initiate homopolymerization. This means that reaction (17) is not specific for initiation of grafting. Another disadvantage is that the Fe + ions formed - if not carefully removed -may cause discoloration of the resulting product. 

The Ce + initiation of grafting and the products obtained from polysaccharides has been reviewed repeatedly5>6. Only some studies of the optimal grafting conditions for grafting of cellulose substrates will be treated here2°>29 30> The reactants should be added to the cellulose suspension in the order CeI,+ initiator and then vinyl monomer to increase the yield of grafted polymer. The optimum conditions are not only related to the pH of the reaction medium but to the relations between the Ce + concentra-... 

We have seen that lignin is a highly branched amorphous pol3rmer containing an extremely complex array of structures and that when in situ in the wood, it is a graft polymer with cellulose and hemicellulose to boot. Characterization of lignins thus becomes a problem. 

The chemical methods for grafting polymer side chains onto cellulose backbone molecules make use of the following chemical mechanisms or techniques involving radicals ... 

The mechanism of grafting polymer side chains to cellulose by Cerium (IV) ions is best understood by the oxidation of pinacol with ceric sulphate investigated 1959 by Mino, Kaizerman and Rasmussen... 

Already in 1955 Polymer Corporation (63) had applied for a patent on a process of treating naturally occurring polymeric substances or their derivatives with ozone containing inert gases and subsequently contacting the ozonized substrates with polymerizable monomers. In the presence of redox activators butadiene, acrylonitrile, and styrene were grafted onto cellulose, starch, casein, gelatin, and rubber. 

With adequate swelling vinyl monomers can be satisfactorily grafted to cellulose and its derivatives by the three main methods developed for other polymers (98). These are (1) the mutual or direct method where the polymer is irradiated in the presence of the monomer or monomer vapor, (2) the pre-irradiation (sometimes called post-irradiation grafting) method where the polymer is first irradiated and then brought into contact with the monomer, and (3) the peroxide method in which the polymer is irradiated in air and the resulting polymeric peroxide used to initiate graft polymerization. 

Waltcher, I., R. Burroughs jr., and E. C. Jahn Grafting to cellulose. International congress of pure and applied chemistry, Stockholm, 1953. Burroughs jr., R. The preparation and characterization of a cellulose polystyrene graft polymer. Thesis, State University College of Forestry, Syracuse, N. Y., 1955. 

Zaidan-Hojin Japan Radiation High Polymer Research Association Grafting on Cellulose, Japan. Pat. 3300 62) June 1, 1962 C. A. 58, 11, 544 (1963). 

Chaudhuri, D. K. R., and J. J. Hermans Grafting onto cellulosic macromolecules through chain transfer to mercaptoethyl side chains. I. Experimental procedure and results. J. Polymer Sci. 48, 159 (1960). 

Guthrie, F. K. Bonding in ceric-ion intiated graft polymers of polyvinyl chloride on cellulose. Tappi 46, 656 (1963). 

Graft polymers of cotton cellulose and acrylonitrile initiated by radiation. Text. Res. J. 31, 988 (1961). 

Araki, K., M. Ichino, and T. Hoshino Radiation induced grafting onto cellulose (dry state grafting). Ann. Rep. Japan Assoc. Radiat. Research on Polymers 2, 465 (1960). 

Kobayashi, Y. Gamma-ray induced graft copolymerization of styrene onto cellulose and some chemical properties of the grafted polymer. J. Polymer Sci. 51, 359 (1961). 

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