Graft copolymerizations onto

Graft Copolymerization Onto Natural and Synthetic Polymers... 

There are a considerable number of methods available for effecting graft copolymerization onto preformed polymers, each with its own particular advantages and disadvantages. 

The hydrogen abstraction from —SH groups is faster than from —OH groups. Hebeish et al. [9] and Misra et al. [10,11] reported the chain-transfer method of initiation of graft copolymerization onto cellulosic substrates with azobisisobutyronitrile (AIBN) and benzoyl peroxide (BPO) as initiators. 

Photoinduced free radical graft copolymerization onto a polymer surface can be accomplished by several different techniques. The simplest method is to expose the polymer surface (P-RH) to UV light in the presence of a vinyl monomer (M). Alkyl radicals formed, e.g. due to main chain scission or other reactions at the polymer surface can then initiate graft polymerization by addition of monomer (Scheme 1). Homopolymer is also initiated (HRM-). 

Table 1. Monomers Used for Surface Graft Copolymerization onto Polyolefin Surfaces...

Athawale, V. D., Lele, V. (1998). Graft copolymerization onto starch. II. Grafting of acrylic acid and preparation of its hydrogels. Carbohydrate Polymers, 35,21-27. 

Fu, Z. S., Liang, W. D., Yang, A. M., Wang, Z. G. (2002). Role and relevance of polarity and hindrance of vinyl monomers in graft copolymerization onto potato starch. Journal of Applied Polymer Science, 85, 896-899. 

In this paper graft copolymerization onto both polystyrene and styrene-butadiene block copolymer will be discussed. It will be shown that radical processes do not permit the addition of monomers onto polystyrene and that one must use anionic initiation in order... 

Chemical Initiation of Graft Copolymerization onto Styrene-Butadiene Block Copolymer... 

RESULTS AND DISCUSSION Graft Copolymerization onto Polystyrene... 

Anionic Graft Copolymerization onto Polystyrene. We have been able to initiate graft copolymerization onto polystyrene by the use of anionic initiators but even here the reaction does not proceed as one may expect. Once again one would likely think that the benzylic hydrogen is the most acidic and should be the one removed by a lithium reagent... 

One may perform radical graft copolymerizations onto the butadiene region of copolymers of styrene and butadiene without any reaction occurring at the styrene portions of the copolymer. If the monomer is reactive, reaction of the monomer at an allylic site occurs while for less reactive monomers, the polymeric radical is formed and this adds to the double bond of the polymer. Proof of the site of grafting comes from information about the relative efficiency of different initiators but the most important information is obtained from infrared spectroscopy. One can observe differences in the spectra which can be related to the mode of addition. 

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... 

Iwai, S., T. Kakurai, and T. Noguchi Studies on acrylonitrile-styrene graft copolymerization onto cellulose by ceric salt. J. Soc. Text, and Cell. Ind. (Japan) 19, 547 (1963). 

Sakurada, I., T. Okasa, Hatakeyama, and F. Kimura. Radiation-induced graft copolymerization onto cellulose and polyvinyl alcohol fibers with binary mixtures of comonomers. J. Polymer Sci. C 4, 1233 (1964). 

Manganic ions (Mn +) in aqueous solution have been developed in our laboratories as an initiator for grafting vinyl monomers onto various polysaccharides, e.g. starch (1), cellulose (2) and guaran (3). This research is part of a general program on graft copolymerization onto polysaccharide substrates as described in a review paper (4). The Mn "1" grafting method has been applied as... 

B. Ranby, "New Methods for Graft Copolymerization onto Cellulose and Starch", in "Modified Cellulosics" (Eds. R.M. Rowell and R.A- Young), Acad. Press, New York 1978 p. 171-195. 

B. Ranby and C. Rodehed, "New Graft Copolymerization onto Cellulosic Fibers", in "Review and Preview in Polymer Science. A Tribute to Herman Mark" (Ed. G.A. Stahl), ACS Mon. Ser. 1981. 

The various data obtained for the kinetics of graft copolymerization onto PTFE films demonstrate that this reaction is complicated by the fact that the rate of diffusion of the monomer may become the controlling factor. It seems interesting at this point to compare and discuss together the results obtained with the different monomers. Table I summarizes the data obtained for autoacceleration indexes (/ ), dose-rate exponents (a), and over-all activation energies E, with styrene, acrylic acid, and vinylpyridine. Several conclusions can be derived from an examination of these data. 

The first two modacrylic fibers ever introduced in the United States were Dynel (by Union Carbide) in 1949 and Verel (by Tennessee Eastman) in 1956. The former was a copolymer of 60 percent vinyl chloride and 40 percent acrylonitrile, and the latter was said to be a 50-50 copolymer of vinylidene chloride and acrylonitrile with perhaps a third component graft-copolymerized onto the primary material to secure dyeability. SEF and its version for wigs, Elura , were introduced by Monsanto Fibers in 1972. A few foreign manufacturers are making modacrylic fibers, but the only modacrylic fiber currently in production in the United States is SEF . 

Table XII. Graft Copolymerization onto Nitrile Rubber (B/AN = 70/30)...

Incorporation of hydrophobic poly(vinyl) moieties through graft copolymerization onto natural polysaccharides results in the decrease of base sensitivity... 

B.S. Kaith, A.S. Singha, D. Pathania, and A. Chauhan, "Screening the effect of 2-vinyl pyridine in binary monomeric mixture with methylacrylate for graft copolymerization onto... 

P.Y. Zhang, B. Ranby, Surface modification by continuous graft copolymerization. III. Photoinitiated graft copolymerization onto poly(ethylene terephthalate) fiber surface. Journal of Applied Polymer Science 41 (1990) 1459. 

For cross-linking by y rays, see Section 21.2.1. Inspection of the Gr values shows that, although styrene can be graft-copolymerized onto poly(vinyl chloride), vinyl chloride cannot be grafted onto poly(styrene). In the first case, so many radicals are produced on the polymer chain that practically no homopolymerization occurs. Above the glass transition temperature (amorphous polymers) or the melting point (crystalline polymers), the Gr values of the polymer increase because of increased chain mobility. Thus different effects can be observed by varying the temperature. 

Table 7. Effect of Reaction Time on Graft Copolymerization onto Ethylene-Vinyl p-Nitrobenzoate Copolymer...

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