Starch derivatives graft copolymers

Etherification and esterification of hydroxyl groups produce derivatives, some of which are produced commercially. Derivatives may also be obtained by graft polymerization wherein free radicals, initiated on the starch backbone by ceric ion or irradiation, react with monomers such as vinyl or acrylyl derivatives. A number of such copolymers have been prepared and evaluated in extmsion processing (49). A starch—acrylonitrile graft copolymer has been patented (50) which rapidly absorbs many hundred times its weight in water and has potential appHcations in disposable diapers and medical suppHes. 

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. 

Ce Ion Initiation. Initiation of grafting with Ce ions was introduced by Mino et al. 7. The process has been widely studied and even applied to industrial production of cellulose and starch graft copolymers. A mechanism is derived from model experiments with low molecular weight vicinal diols in acid aqueous solution. The first step (22) is OH OH... 

Other useful modifications include acetylation, hydroxyethylation, hydro-xypropylation, cationic starches, succinate, and substituted succinate derivatives of starch. In starch-grafted copolymers, free radicals are initiated on the starch that then act as macroinitiators for the acryl or vinyl monomers. These products are used in firefighting fluids, electrolyte solutions for alkaline batteries, wound dressing, and so on. 

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. 

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... 

For these reasons there has been renewed interest in starch-based plastics in recent years. Earlier studies of starch esters and ethers (3-10) indicated that they had inadequate properties in comparison with cellulose derivatives for most applications. More recently, starch graft copolymers (2), starch plastic composites (11,12), and starch itself (13-17) have been proposed as plastic materials. 

The first attempts to produce a graft copolymer of poly(amino acids) onto the natural polymers, such as cellulose, starch, and their derivatives, were carried out by Zilka and Avny in 1965. Sodium methoxide was known to be an initiator of NCA polymerization. Therefore, they proposed to use alkoxide derivatives of polysaccharides as macroinitiators for the graft copolymerization of NCA s of a-amino acids. All known methods for production of alkoxide derivatives of natural polymers, such as the reaction of polyhydroxy polymers with sodium metal in liquid ammonia, or exchange reactions between lower alkoxides and polyhydroxy polymers, - were unsatisfactory for the subsequent graft copolymerization of NCAs, because any residual base would lead to homopolymerization. In addition, alkoxide derivatives of cellulose acetate and nitrocellulose could not be obtained by these conventional methods due to chemical degradation. Zilka et al., finally found that the reaction of alkali metal naphthalenes [20] with polyhydroxy polymers in either... 

The synthetic polyacrylates derived from acrylic acid, and the graft copolymers from starch and acrylic acid have emerged as the absorbent polymers of choice. This is in no small part due to economic factors, as a glance at any chemical marketing periodical will show acrylic acid as one of the least expensive water soluble monomers. In addition, the properties of acrylic acid make it relatively easy to polymerize, and to polymerize to products of high molecular weight. The importance of these latter properties will become clear in the next section. 

Different types of floeculants can be prepared by aminomethylation the amino-methyl derivatives of polyacrylamide represent the most widely adopted class of compounds, which includes high-molecular-weight floeculants (502, 517 in Table 38, 562 in Table 40), and has been widely patented. The large amount of research on these pnxlucts is concerned, in particular, with is(x lcctric points, the content of functionalized co-units, the extent of amido groups hydrolysis, and the use of copolymcrs. -"- Applications of acrylamide copolymers grafted onto starch or other polysaccharides arc also considered. ... 

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