Acrylonitrile, cellulose grafting with

Improvement in the solvent and oil resistance of rubbers can be achieved via grafting of acrylonitrile onto rubber [140-142] and rubber blends [143]. The careful control of the degree of grafting allows vulcanized rubber with high-mechanical properties compared with ungrafted vulcanized rubber to be obtained. Also, acid resistance [144] and resistance to microbiological attack [145,146] was improved for cellulose grafted with acrylonitrile, and increases in base resistance were also noted for MMA and a mixture of MMA and ethyl acrylate [13],... 

Partial carboxymethylation of wood pulp significantly increases its susceptibility toward grafting with acrylonitrile using the ceric ion as the initiator 146]. Studies dealing with grafting of various vinyl monomers, such as acrylonitrile, methylmethacrylate, and acrylamide, onto partially carboxymethylated cotton cellulose using tetravalent cerium as the initiator have been reported [47]. 

Studies in the grafting of mixed monomers to cellulose have also been reported by Sakurada (113). Binary mixtures studied included butadiene with styrene or with acrylonitrile, and styrene with acrylonitrile. Remarkable increases in rate in the case of mixed monomer similar to those found by RAPSON were found in many cases. For example, about 10% of butadiene increased the grafting yield about ten fold. Similar results were found with the addition of acrylonitrile to butadiene and to styrene. Ternary mixtures of monomers were also investigated by both Rapson (109) and Sakurada (113). The large increases in rate with certain mixtures were interpreted by Sakurada as due to a particular balance of gd effects akin in many ways to popcorn polymerization. The effects were found also with polyvinyl alcohol but not with polyethylene where gel effects would perhaps be less prominent. 

This observation has been used by Kargin, and Plate (127) who initiated polymerization and grafting with the help of mechanically disrupted inorganic materials. Many metals, oxides, and salts which never normally act as initiators, when mechanically disrupted, are able to initiate polymerization of styrene, methyl methacrylate, acrylonitrile, and other vinyl monomers. The surface of the active inorganic substance can also be used as a site for grafting to already existing polymer chains if joint dispersion of polymer and monomer, such as cellulose and styrene, is performed. 

The ozonization method has been extended to the most varied polymer/monomer systems, such as polybutadiene-03 with acrylamide, methyl methacrylate or styrene, cellulose-03 with styrene or acrylonitrile (127), starch-03 with styrene (126). In this last case the formation of some homopolystyrene as side-product has been mentionned by the authors. The starch-styrene graft copolymers are claimed to be good emulsifiers for water-oil suspensions. 

Much effort has been devoted over the last few years to preparing branched cellulose or cellulose derivatives, by combining the cellulose backbone with a synthetic polymer which confers desirable properties. The length of these branches or grafts varies considerably, depending on the copolymerization conditions. The most widely used monomers are acrylic and vinyl monomers, with the following order of reactivity [16] ethyl acrylate > methyl methacrylate > acrylonitrile > acrylamide > styrene. 

By using this technique acrylamide, acrylonitrile, and methyl acrylate were grafted onto cellulose [20]. In this case, oxidative depolymerization of cellulose also occurs and could yield short-lived intermediates [21]. They [21] reported an electron spin resonance spectroscopy study of the affects of different parameters on the rates of formation and decay of free radicals in microcrystalline cellulose and in purified fibrous cotton cellulose. From the results they obtained, they suggested that ceric ions form a chelate with the cellulose molecule, possibly, through the C2 and C3 hydroxyls of the anhy-droglucose unit. Transfer of electrons from the cellulose molecule to Ce(IV) would follow, leading to its reduction... 

Graft copolymerization of acrylonitrile with various vinyl comonomers such as methyl acrylate, ethyl acrylate, vinyl acetate, and styrene onto cellulose derivatives using ceric ion was studied [24]. The results showed that... 

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. 

Daniel, Moore, and Segro (49) further investigated the graft polymerization of acrylonitrile to paper. They found that in grafted products having add-ons up to 53% neither cellulose nor polyacrylonitrile could be extracted with respective solvents. 

Guzman (53) investigated the ceric ion initiated grafting of acrylonitrile, acrylamide, methyl methacrylate, styrene, vinyl acetate, methacrylate, acrylic anhydride, and isoprene to cellulose. Intense grafting was obtained with acrylonitrile, acrylamide, methacrylate and acrylic anhydride. 

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. 

Also other oxidants have been used successfully to initiate graft copolymerization onto cellulose substrates. Toyo Rayon (79) achieved grafting by pretreatment of viscose rayon fibers with potassium permanganate-sulfuric acid and contacting it subsequently with acrylonitrile. Methyl methacrylate is being grafted to rayon when heated together with potassium bromate, as claimed by Asahi Chemical Industry... 

In the late fifties Regie Nationale des Usines Renault (86) described the preparation of allyl ethers through reaction of alkali cellulose with allyl halides in carbon tetrachloride or benzene. With products having degrees of substitution between 0.2 to 0.8 graft copolymerization could be achieved when activated by pretreatment with air or ozone or by initiation with peroxide catalysts with styrene, acrylonitrile, vinyl acetate, or acrylates. 

Fig. 4. UV grafting of acrylonitrile to cellulose film in dimethyl formamide solution with 10% water and 0.01 M 2,7 anthraquinone sodium disulfonate (112). — in air, C —in vacuo...

Hagemeyer, H. J., and E. L. Oglesby, assigned to Eastman Kodak Company Graft copolymers of acrylonitrile and other ethenoid monomer with a hydroxyl-containing cellulose derivative and their preparation. U. S. 2, 865, 872 (December 23, 1958). 

---