Cellulose-starch graft copolymers

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... 

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... 

Superabsorbent polymers are now commonly made from the polymerization of acrylic acid blended with sodium hydroxide in the presence of an initiator to form a polyacrylic acid, sodium salt (sometimes referred to as cross-linked sodium polyacrylate). Some of the polymers include 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. The latter is one of the oldest SAP forms created. 

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. 

Thakur Kumar Vijay. Cellulose-based graft copolymers. Boca Raton, FL CRC Press, 2015. Thielemans Wim, Belgacem Mohamed N., and Dufresne Alain. Starch nanocrystals with large chain surface modifications. Langmuir. 22 no. 10 (2006) 4804-4810. 

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. 

The graft copolymers of acrylamide, acrylic acid, and cellulose or starch are used as water absorbents and in enhanced oil recovery systems. 

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. 

The PVC-acrylic polymer alloy previously described is characterized by high speed injection moldability and, in sheet form, by deep drawing capability, both of which are the result of low melt viscosity. A cellulose-ethyl acrylate graft copolymer compatibilizes cellulose and PEA, cellulose and PVC, as well as starch and PVC (8). These compositions containing PVC obviously have better flow properties than non-thermoplastic cellulose or starch. However, they also have better flow properties than PVC alone. 

Deshmukh, S. R., Sudhakar, K., and Singh, R. R, Drag-reduction efficiency, shear stability, and hiodegradation resistance of carhoxymethyl cellulose-based and starch-based graft copolymers, J. Appl. Polym. ScL, 43, 1091-1101 (1991). 

Starches are modified chemically in various ways. Some acetate and phosphate esters are produced commercially, as well as hydroxyalkyl and tertiary aminoalkyl ethers. Both unmodified and modified starches are used principally in paper making, paper coating, paper adhesives, textile sizes, and as food thickeners. There are many reports in the literature on graft copolymers of starch. The work is often conducted is search of biodegradable materials for packaging and agricultural mulches. Most chemical modifications of starch parallel those of cellulose. 

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. 

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 ... 

IR spectroscopy is a usefull technique to evaluate if a graft reaction is carry out and also to evaluate grafting yields on graft copolymers. Several research works used IR with this purpose for keratin (Martinez et al 2003 Martinez et al 2008 Kavitha et al 2005), starch (Meshram et al 2009), modified starch (Cao et al 2002), chitosan (Mun et al 2008), carboxymehtyl chitosan (Joshi and Sinha, 2006), cellulose (Zampano et al 2009),... 

Superabsorbent polymers were developed in 1974. Initially, they were mostly graft copolymers of polysaccharides such as starch and cellulose. However, the majority of currently used superabsorbent pol3miers are lightly crosslinked acrylic acid polymers. 

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... 

Hydrolyzed cellulose-polyacrylonitrile (PAN) or starch-PAN graft copolymers. 

---