Biodegradable polymers from sugars

Therefore, all the above mentioned are attractive materials for sustained current research and development, especially in view of the scarcity of synthetic chemicals, and the environmental issues that are increasingly important to modem society. 

2 Biodegradable polymers obtained from monosaccharides and disaccharides 

There has been a worldwide realization diat nature-derived monosaccharides, disaccharides, oligosaccharides and polysaccharides can provide us with the raw materials needed for the production of numerous industrial consumer goods (Kunz, 1993 Varma, 2003 Pacitti, 2003). This section will deal with the role of sugar molecules anchored like pendants onto a synthetic polymer, reminiscent of the crown ether type molecules pendant on polystyrene and other synthetic chains which created a whole new area of research with far-reaching outcomes (Gokel and Durst, 1976 Varma, 1979 Varma et al, 1979 Smid et al, 1979a, Shah and Smid, 1978 Smid et al, 1979b Varma and Smid, 1977). 

The base catalyzed adsorption of poly(vinyl alcohol) in DMSO with reducing carbohydrates to obtain pseudopolysaccharides through a chemically and enzymatically inert ether linkage has been reported (Kraska and Mester, 1978), They are useful in the solid phase syntheses of glycosides, as potential carriers of drugs and they also serve as a useful probe in the study of protein- 

7 Growth pattern of soil bacteria on sugar-linked poly(styrene maleic anhydride) polymers. Weight losses after 28 days for samples 3 and 4 were 10%. 

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Biodegradable polymers from sugars 181 Table 7.2 Cellulose, hemicellulose, and lignin contents of some major plant biomass... 

The most fundamental classification of polymers is whether they are naturally occurring or synthetic. Common natural polymers (often referred to as biopolymers) include macromolecules such as polysaccharides e.g., starches, sugars, cellulose, gums, etc.), proteins e.g., enzymes), fibers e.g., wool, silk, cotton), polyisoprenes e.g., natural rubber), and nucleic acids e.g., RNA, DNA). The synthesis of biodegradable polymers from natural biopolymer sources is an area of increasing interest, due to dwindling world petroleum supplies and disposal concerns. 

The C4 aldol intermediate of the Weizmann process is also key in the aerobic fermentation of sugars to poly(3-hydroxybutyric acid) or PHB (-0[-CH(CH3)-CH2-COO - [70]. This natural and biodegradable polymer is produced inside microorganisms, e.g., Ralstonia eutropha. A complex processing is required to extract and purify the polymer granules from the microorganism. 

One of the anticipated growth areas for industrial uses of plants is in development of non-brittle, durable polymers from renewable plant feedstocks (in both biodegradable and non-biodegradable forms). Starch and sugars are currently used commercially as feedstocks for polyester production utilising microbial monomer and polymer fermentation systems (see Chapter 5 for more information). 

Polylactic acid (PLA) is a biodegradable polymer derived from lactic acid. It is a highly versatile material and is made from 100% renewable resources like corn, sugar beet, wheat and other starch-rich products. Polylactic acid exhibits many properties that are equivalent to or better than many petroleum-based plastics, which makes it suitable for a variety of applications. 

The carboxylic acids and amines link to form peptide bonds, also known as amide groups. Proteins are the condensation polymers made from amino acid monomers. Carbohydrates are also condensation polymers made from sugar monomers such as glucose and galactose. Condensation polymerization is occasionally used to form simple hydrocarbons. This method, however, is expensive and inefficient, so the addition polymer of ethene, i.e., polyethylene, is generally used. Condensation polymers, unlike addition polymers, may be biodegradable. The peptide or ester bonds between monomers can be hydrolyzed by acid catalysts or bacterial enzymes breaking the polymer chain into smaller pieces. The most commonly known condensation polymers are proteins and fabrics such as nylon, silk, or polyester. 

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