Methyl methacrylate-starch graft

In 1962, Kimura, Takitani and Imoto (1) found that an aqueous solution of starch could easily polymerize methyl methacrylate (MMA) and about a half of polymerized MMA grafted on starch. This novel polymerization was called as "uncatalyzed polymerization". Since then, a lot of macromolecule was applied, instead of starch, and many of them were effective to initiate the radical polymerization of MMA. 

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. 

Preparation of grafted starches on synthetic polymers. Ce salts are used to oxidize starch and generate free radicals that react with certain monomers (methyl methacrylates, acrylonitrile, vinyl acetate, acrylamide, etc.)... 

Aluminoxanes suppressed side reactions involving hydrogen transfer. They also formed cyclic structures with starch, giving copolymers that were coated with crystalline polyethylene. A catalyst composed of dicyclopentadienylzirconium dichloride and trimethylaluminium permitted polymerization of ethylene on starch in a toluene suspension at 60 °C for 2h.2806 Graft copolymerization of methyl methacrylate onto starch was also performed with an acetylacetone-copper(II) complex in trichloroacetic acid.2807 The grafting yield and efficiency were proportional to the initiator concentration up to 7.0 x 10-3 mole/L. 

Grafting of methyl methacrylate on starch occurs in an aqueous, saturated starch solution at 85 °C in the presence of carbon tetrachloride or copper(II) ions,2808,2809 and the grafting efficiency could be as high as 72%. At a low concentrations of the vinyl compound, the reaction rate was proportional to its concentration. The reaction rate became independent of concentration at higher concentrations of the vinyl monomer. Grafting in the presence of 0.1M nitric acid and ammonium selenate was also reported.2810... 

When chloroprene was grafted onto cationic aminated starch, a latex was obtained that imparted wet strength to paper and also served as a pressureless adhesive for wood 2951 Starch dialdehyde when grafted with acrylonitrile, methyl methacrylate, or both, produced a biodegradable filler for poly (vinyl chloride) plastics.2942 Starch xanthates grafted with vinyl monomers were also used to produce additives for reinforced foamed rubber.2944,2945... 

Graft copolymers of A and B monomers are named poly(A-g-B) or poly A-grafi-poly B with the backbone polymer -(-A-)/j— mentioned before the branch polymer. Some examples are poly(ethylene-g-styrene) or polyethylene-grq/i-poly styrene and starch-grayi-poly(methyl methacrylate). In the nomenclature of block copolymers, b or block is used in place of g or graft, e.g., poly(A- -B) or poly A-block-po y B, poly(A-b-B-b-A) or poly A-block-po y B-block-po y A, poly(A-b-B-b-C) or poly A-block-poly B-block-poly C, and so on. Thus the triblock polymer (XX) is called poly(styrene- -butadiene-i -styrene) or polystyrene- /cck-polybutadiene-b/ock-polystyrene. For commercial products, such polymers are usually designated by the monomer initials thus, structure (XX) is named SBS block copolymer. 

Copolymers of Vinylidene Chloride. The glass-transition temperatures of these copolymers vary nonlinearly with composition, as is the case for copolymers of methyl methacrylate, but these show a maximum. It is a broad maximum around 105 C at 55-80 wt% acrylonitrile. (The Tg of vinylidene chloride homopolymer is ca -20°C, whereas PAN s is ca 100°C.) Again, sequence distribution explains such behavior (163). These copolymers have good barrier properties and are used for surface Coatings. Acrylonitrile grafting on starch imparts hydrophilic behavior to starch and results in exceptional water absorption capability (164-167). These copolymers can also immobilize enzymes by entrapment or covalent bonding (168). 

Coni, M. Gurruchaga, M. Valero and G.-M. Guzman, Graft polymerization of acrylic monomers onto starch fractions. I. Effect of reaction time on grafting methyl methacrylate onto amylose,/. Polym. Sci. Al, 21 (8) 2573-2580,1983. 

If a suitable monomer is present, grafts are grown from these initiating sites. This method has been applied by Kukani and Mehta to grafting polyacrylonitrile onto cellulose and by Iwakura and Imai to the preparation of poly(vinyl alcohol-gfra/t-methyl methacrylate). More recently, Parker et al have synthesized poly(vinyl alcohol- rq/t-vinylpyridine hydrochloride) and McCormick and Lin have grafted polyacrylamide chains onto starch. 

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