A variety of enzymes have been found to acylate sucrose in anhydrous pyridine. The enzymic reaction is highly selective; with trifluoroethylbutyrate as ester donor, enzyme-catalyzed transesterification of sucrose yielded sucrose 1'-butyrate and sucrose 6, 1'-dibutyrate. No sucrose-tributyrates were formed. Using a similar technique, a long-chain linear sucrose polyester has been prepared using Proleather, an alkaline protease from a Bacillus sp. This protease catalyzes the esterification of sucrose with bis(2, 2, 2-trifluoroethyladipate) in a 1:1 ratio to yield a sucrose-containing polyester with M(w) = 2100 and M(n) = 1600 for a polydispersity of 1. 31. Polymers with molecular weights in excess of 13, 000 have been prepared by this enzymic approach, indicating that molecules containing over 30 sucrose units have been produced. The polyester is extremely water soluble and soluble in polar organic solvents. As with the sucrose dibutyrate, the polyester has ester linkages at the C6 and C1' positions on the sucrose. The polyester can be depolymerized using Proleather in aqueous buffer, pH7. After 9 days in aqueous buffer, Proleather catalyzed the breakdown of the polyester to an M(w) of ca. 900. This sucrose-containing polyester may have applications as a water-absorbent, biodegradable plastic for use as diapers and hygienic products, water-treatment chemicals, and components of drug delivery systems.
Communications to the Editor Chemoenzymatic Synthesis of Novel Sucrose-Containing Polymers Typical chemical catalysts provide the chemoselectivity required for the preparation of high molecular weight poly(esters, amides, ols, acrylates, etc.) while enhancing reaction rates. There is an increasing need, however, to impart additional selectivity (e.g., regio-or stereoselectivity) in the synthesis of polymers.1 This is particularly important in the synthesis of optically active polymers or the synthesis of linear polymers from monomers with functionality greater than 2. Recent advances in enzymatic catalysis in nonaqueous media have shown that enzymes are useful catalysts for the synthesis of polyesters and phenolic resins.2•3 Unlike conventional chemical catalysts, enzymes can synthesize polymers with exquisite selectivity.
SYNOPSISStarch-g-poly (methyl acrylate) ( S-g-PMA) copolymers containing 55-60% PMA were prepared from cornstarch, high amylose cornstarch, and waxy cornstarch with ceric ammonium nitrate initiation. Graft copolymers were characterized with respect to % PMA homopolymer, % conversion of monomer to polymer, grafted PMA content, grafting frequency, and the molecular weight and molecular weight distributions of PMA grafts. Variables investigated in the graft copolymerization reaction were nitric acid concentration, ceric ion-to-starch ratio, reaction time, gelatinization of the starch, and reactant concentration in water. At high reactant concentrations, high conversions of methyl acrylate to grafted PMA could be obtained in less than 0.5 h at 25°C.
SynopsisFree-radical, graft polymerization of acrylamide onto lignin occurs in photolysed, distilled dioxane containing calcium chloride and trace quantities of ceric ion. The yield of the reaction is controlled by the amount of oxygen present during dioxane photolysis, the duration of photolysis, and the amount of calcium chloride in the reaction mixture. Polyacrylamide homopolymer is formed during the reaction and can be removed from the graft copolymer by base dialysis. Side chains of the reaction product can be hydrolyzed to partially hydrolyzed polyacrylamide by solution in aqueous base. Hydrolysis raises the limiting viscosity number of the product by a factor of up to 47. As a drilling mud additive, the ability of the reaction product to lower yield point, lower gel strength, or lower API filtrate volume increases with increasing degree of hydrolysis.
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