Poly -starch graft copolymers

Although they lack commercial importance, many other poly(vinyl acetal)s have been synthesized. These include acetals made from vinyl acetate copolymerized with ethylene (43—46), propjiene (47), isobutjiene (47), acrylonitrile (48), acrolein (49), acrylates (50,47), aHyl ether (51), divinyl ether (52), maleates (53,54), vinyl chloride (55), diaHyl phthalate (56), and starch (graft copolymer) (47). 

Poly(amino acids)2892 and polypeptides2893 can also be grafted onto starch. Starch was first alkylated in the presence of lithium naphthalene, and then the alkoxy derivatives were reacted with /V-carboxy anhydrides. Poly(amide amines) were produced by reacting amines with dioic acids on starch and then crosslinking with epichlorohydrin or 1,2-dichloroethane 2894 Grafting of starch with a synthetic polymer chain, for instance, polystyryl carboxylate anions prepared by an anionic polymerization, can be carried out on a blend of starch and cellulose functionalized by sulfonation, mesylation, or tosylation. In this manner, cellulose-starch graft copolymers were prepared.2895... 

Graft copolymers of starch with acrylonitrile and 2-acrylamido-2-methylpropanesulfonic acid, after saponification, were claimed to be good sorbents.3092 A composite of saponified acrylonitrile-starch-copolymer with vinyl formal polymers showed very good salt-rejection characteristics and served as membranes.3093 The same material prepared with poly(vinyl chloride) has been used in gaskets for concrete pipes.3057 Saponified acrylonitrile-starch graft copolymers blended with C12-C16 alcohols provided excellent water-retention characteristics.3094... 

Superabsorbent Polymers Superabsorbent polymers (SAP) are now commonly made from the polymerization of acrylic acid blended with sodium hydroxide in the presence of an initiator to form a poly-acrylic acid, sodium salt (sometimes referred to as cross-linked sodium polyacrylate). This polymer, such as polyacrylamide copolymer, ethylene maleic anhydride copolymer, cross-linked carboxy-methyl-cellulose, polyvinyl alcohol copolymers, cross-linked polyethylene oxide, and starch grafted copolymer of polyacrylonitrile to name a few. Superabsorbent polymers are made using one of two primary methods suspension polymerization or solution... 

Synthesis. Graft copolymer was formed in aqueous solution by ceric-ion-initiated, radical polymerization of monomer on starch. Polymerization was conducted in an inert, atmosphere. Details of the synthesis procedure may be found in references 41 to 43 In recovering the polymer product, freeze drying was used with care since freeze drying produces a more dissolvable and useful product but can degrade polymers with molecular weights of 1 million or more. Poly(starch-g-(1-amidoethylene)) Poly(starch-g-(1-amidoethylene))... 

Poly(starch-g-(l-amidoethylene)) copolymer is not a polyelectrolyte and will be a smaller molecule in water than an equal molecular weight, partially hydrolyzed poly(l-amidoethylene). Polyelectrolyte effect should, however, cause the graft copolymer to expand in solution in the same way it causes poly(l -amidoethylene) to expand, so a series of hydrolyzed graft copolymers were prepared from poly(starch-g-(l-amidoethylene))(41-43) and these derivatives were tested to determine the effect of hydrolysis on copolymer properties in solution. 

Graft copolymers of nylon, protein, cellulose, starch, copolymers, or vinyl alcohol have been prepared by the reaction of ethylene oxide with these polymers. Graft copolymers are also produced when styrene is polymerized by Lewis acids in the presence of poly-p-methoxystyrene. The Merrifield synthesis of polypeptides is also based on graft copolymers formed from chloromethaylated PS. Thus, the variety of graft copolymers is great. 

Graft copolymers of starch and vinyl acetate (VA) have been prepared using Co60 irradiation.110 Near-quantitative conversions of monomer to polymer were reported when the radiation dose was l.OMrad, although the grafting efficiency was <50%. Lower radiation doses gave lower conversions and add-ons. When 10% methacrylate was added to the monomer mixture, grafting efficiency was improved to 70%. Selected copolymers were treated with methanolic sodium hydroxide to yield starch-poly(vinyl... 

Graft copolymers like 1-27 are named aspoly(A-g-B) with the backbone polymer mentioned before the branch polymer. Examples are poly(ethylene- -styrene) or starch-g-polystyrene. In block copolymer nomenclature b is used in place of g and the polymers are named from an end of the species. Thus the triblock macromolecule 1-53... 

Graft copolymers of A and B monomers are named poly(A-g-B) or poly -graft-po y B with the backbone polymer -(-A-) - mentioned before the branch polymer. Some examples are poly(ethylene-g-styrene) or polyethylene-gra/it-polystyrene and starch-gra/ir-polystyrene. In the nomenclature of block copolymers, b or block is used in place of g or graft, e.g. poly(A-b-B) or poly A-block-poly B, poly(A-6-B-6-A) or poly A-6/ocik-poly B-blocic-po y A, poly(A-b-B-6-C) or poly A-6/ock-poly B-block-po y C), and so on. Thus the triblock polymer (XXIV) is called poly(styrene-6-butadiene-b-styrene) or polystyrene-6/ocA -polybutadiene-6/ock -polystyrene. When such polymers are articles of commerce they are usually designated by the monomer initials thus, structure (XXIV) would be named SBS block copolymer. 

Graft copolymers were also produced by bubbling alkylene oxides through starch solutions in dimethyl sulfoxide in the presence of potassium naphthenate.2888,2889 Another approach involved grafting polyethylene oxide) to starch. Polyethylene oxide) was converted into a chloroformate derivative and subjected to a reaction with starch alkoxide 2890 Poly(alkylene glycol) could be grafted onto starch by means of cyclic aliphatic acid anhydride in the presence of 4-toluenesulfonic acid 2891 The products were water soluble. 

In the context of this chapter, the use of thermoplastic starch in blends with thermoplastic resins is of the main interest. As shown in Table 16.11, several blends have been developed, e.g., with vinyl alcohol copolymers (EVAl), polyolefins, aliphatic polyesters such as poly-e-caprolactone (PCL) and its copolymers, or polymers of glycols (e.g., 1,4-butanediol) with succinic, sebacic, adipic, azelaic, decanoic or brassihc acids, PCL + PVC. Compatibilization is possible by amylose/EVAl V-type complexes, starch grafted polyesters, chain extenders like diisocyanates, epoxies, etc. [Bastioli et al., 1992, 1993]. 

Ozone treatment of polymers can also cause hydroperoxidation of labile hydrogens. It can, however, also cause extensive degradation of the backbone polymers, because attacks by ozone on double bonds in the backbones converts them to unstable ozonides. Starch can be ozonized to form graft copolymers. The same is true of cellulose, poly(vinyl chloride), and polyethyl-ene. Hydroperoxides form without noticeable degradation. This allows subsequent preparations of graft copolymers. 

Another example is formation of graft copolymers of formaldehyde with starch, dextrin, and poly(vinyl alcohol)This procedure is also carried out in two steps. Potassium naphthalene is first reacted with the backbone polymer in dimethylsulfoxide. The formaldehyde is then introduced in gaseous form to the alkoxide solution. 

A similar reaction can be used to form graft copolymers of poly(ethylene oxide) on cellulose acetate. Poly (ethylene oxide) can also be grafted to starch. For instance, a preformed polymer terminated by chloroformate end groups can be used with potassium starch alkoxide ... 

Additional aging effects could be found for graft copolymers (starch-acrylamide copolymers [36], synthetic amylose [36],poly(acrylamide-co-methacryloxyethyl-N,N,N,-trimethylammoniumchloride) PAAm/M [30] and poly(acrylamide-co-sodium-2-sulfoethylmethacrylate) [37]. 

Graft copolymers of A and B monomers are named poly(A-g-B) or poly A-graft-poly B with the backbone polymer -(-A-), — mentioned before the branch polymer. Some examples are poly(ethylene-g-styrene) or polyethylene-grayi-polystyrene and starch-gro -poly(methylmetha-... 

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