Origins of Specialty Polymers

Specialty polymers are typically water-soluble polymers that come from three origins, natural, semisynthetic, and synthetic macromolecules. Natural polymers are plant or animal based materials such as cellulose and proteins. Semisynthetic polymers are modified natural polymers manufactured by chemical derivatization of natural organic macromolecules, generally based on polysaccharides. Synthetic polymers are obtained by the polymerization of monomers synthesized from petroleum or natural gas precursors.

Natural and Semisynthetic Polymers A significant number of water-soluble polymers are derived from biological sources, biopolymers . Biopolymers are an abundant and diverse class of polymers that includes polysaccharides , polynucleotides , and proteins . Since these polymers perform unique biological functions, they have specific microstructures and are often monodisperse.

Polysaccharides are a diverse class of biological macromolecules with a wide range of structural and behavioral characteristics . They are biodegradable, cyclolinear, polyhydroxyl compounds that are widely used in industry. Industrial polysaccharides have traditionally been extracted from renewable resources like starch and gums from plant seeds.

Solution properties, such as solubility, viscosity, and phase behavior, are highly dependent on the macrostructure of the chain and the chemical microstructure of the repeat units. The presence of acidic or basic functionality causes pH, electrolyte, and temperature-dependent behavior. The unique behavior of polysaccharides includes the ability to form hydrogels and lyotropic liquid crystals. These properties are largely due to hydrogen bonding and the intramolecular and/or intermolecular association of hydrophobic groups. The hydrophobic association has been shown to significantly modify the rheology of a system and is widely applied to many commercial materials such as paints, inks, personal care, and pharmaceuticals.

Polynucleotides are biopolymers that carry genetic information involved in the processes of replication and protein synthesis . An essentially infinite number, of proteins can be made by assembling the 20 amino acids in various microstructural combinations and sequence lengths. The 20 amino acids contain four major types of side chains, i.e., hydrophobic, hydrophilic, basic and acidic. Most polypeptides and proteins are water-soluble or water-swellable. The solubility of proteins varies considerably based on composition and condition of ionic strength, pH, and concentration. Those with the highest density of polar groups or electrolyte character are the most soluble. Therefore, solubility in water is lowest at the isoelectric point and increases with increasing basicity or acidity.

Polynucleotides are utilized extensively in medical, industrial, and agricultural applications. The development of recombinant DNA techniques has led to the ability to clone genes and has facilitated the production of a large numbers of proteins with significant commercial potential . Among the first genetically engineered proteins are insulin, the pituitary growth hormone, and interferon. Other water-soluble proteins are isolated from biological sources in a more traditional manner for a number of commercial applications. Enzymes are used as detergent additives to hydrolyze polysaccharides and proteins, to isomerize various glucose and sucrose precursors, and for mineral recovery. Supported enzymes are becoming commercially significant for large-scale substrate conversion of macromolecules.

Commercial Advantages of Natural and Semisynthetic Polymers Natural and semisynthetic polymers have some commercial advantages over many synthetics, particularly in food applications.

· FDA Status — Many have been assigned "generally recognized as safe" (GRAS) status by the US Food and Drug Administration (FDA).

· Ease of Production –

ü The processes for producing natural polymers are frequently simpler, involving harvest and refinement through chemical and mechanical operations.

ü Semisynthetics involve chemically derivatizing natural macromolecules instead of complex polymerization of monomers.

ü The facilities for producing them, therefore, are less capital-intensive, and the equipment can be more flexible.