Copolymerisation graft

As with other rigid amorphous thermoplastic polymers such as PVC and polystyrene (see the next chapter) poly(methyl methacrylate) is somewhat brittle and, as with PVC and polystrene, efforts have been made to improve the toughness by molecular modification. Two main approaches have been used, both of which have achieved a measure of success. They are copolymerisation of methyl methacrylate with a second monomer and the blending of poly(methyl methacrylate) with a rubber. The latter approach may also involve some graft copolymerisation. 

The common feature of these materials was that all contained a high proportion of acrylonitrile or methacrylonitrile. The Vistron product, Barex 210, for example was said to be produced by radical graft copolymerisation of 73-77 parts acrylonitrile and 23-27 parts by weight of methyl acrylate in the presence of a 8-10 parts of a butadiene-acrylonitrile rubber (Nitrile rubber). The Du Pont product NR-16 was prepared by graft polymerisation of styrene and acrylonitrile in the presence of styrene-butadiene copolymer. The Monsanto polymer Lopac was a copolymer of 28-34 parts styrene and 66-72 parts of a second monomer variously reported as acrylonitrile and methacrylonitrile. This polymer contained no rubbery component. 

Graft copolymerisation of styrene on partially carboxymethylated cotton using gamma radiation. 

The phenomenon of graft copolymerisation dates back to the year 1933 but graft copolymer was officially defined in 1952 by IUPAC. 

Graft copolymerisation is a unique method which is used for modifying the properties of the base polymer. A varieties of new properties can be imparted to the base polymer by implanting a number of suitable polymers. Various methods used for grafting are (i) Chemical method, (ii) Radiation method, and... 

In the second stage of the reaction, the free radical produced on the backbone of the base polymer initiates polymerisation which results in the formation of graft copolymerisation as under ... 

Chen, R. and Kokta, B.V. (1982). Graft copolymerisation of lignosulphonate with methacrylic acid and acrylate monomers. In Graft Polymerisation of Lignocellulosic Fibers, Hon, D.N.S. (Ed.). ACS Symposium Series, 187, pp. 285-299. 

Marchetti, V., Gerardin, P., Tekely, P. and Loubinoux, B. (1998). Graft copolymerisation of acrylic acid onto sawdust using KMn04 as initiator. Hol orschung, 52(6), 654—660. 

Ionic polymerisation is a well-known technique for the preparation of graft copolymers but the fate of these reactions is determined by the reaction conditions. Since the discovery of living polymerisation , (anionic polymerisation) [67] it has become an excellent method for the synthesis of block and graft copolymers. In anionic polymerisation the graft copolymerisation is initiated by the anion generated by the reaction of bases with acidic protons in the polymer chain as shown in Scheme 2. 

Scheme 2 Initiation of graft copolymerisation in case of anionic polymerisation...

This method involves graft copolymerisation using redox initiators [70] or free radical initiators [71, 72, 73] usually in the solution phase, occasionally under the influence of temperature, predominantly in the latter case. Redox systems have extensively been used to generate active sites especially on the natural polymers [74] (like cellulose). Transition metals viz. Cr+6, V+5, Ce+4,... 

Early studies involved the development of a process which could treat all types of papers of varying ages and composition. Graft copolymerisation seemed to offer this potential. The basic concept of graft copolymerisation can be seen in Figure 1. Radical sites are created on the cellulose backbone and these sites allow the... 

Arthur, J. C. Graft Copolymerisation, Advances in Macromolecular Chemistry 1970,. 2, 1-88. 

Burstall, M. L., Mollett, C. C. and Butler, C. E., Graft Copolymerisation as a Method of Preserving Papers Problems and Potentialities, Preprints of the Contributions to the International Institute of Conservation of Historic and Artistic Works (lid), 1984. p 60-63. 

Grafting Procedure and Calculation of Percent Grafting. Graft copolymerisation treatment of KPM rayon yarn and jute fiber were carried out in a well stoppered, Erlenmeyar flask. Fifty millimeter CAS solution of known concentration was kept at a desired temperature. One millimeter MMA was added following immediately by 1.0 gm of KPM rayon yarn, after which the contents were stirred intermittently. After the end of the reaction, the flask were removed from the thermostat and methanol was immediately added. 

Kennedy, J. P. (ed.) Cationic graft copolymerisation. J. Apirf. Polym. Sci. Appl. Polym. Symp. 30 (1977)... 

A.S. Singha, and B.S. Kaith, "Modification of natural polymers-VIII Graft copolymerisation of methylmethacrylate onto cellulose" International Congress of Chemistry and Environment, 2001. 

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