Enzyme-catalyzed transesterification of vinyl esters on cellulose solids

Enzyme-catalyzed transesterification of several cellulose solids in organic media have been investigated. Several protease enzymes were made soluble in organic media through ion-paired enzyme-surfactant complexes. Subtilisin Carsberg was found to be catalytically active in the transesterification of cellulose with vinyl propionate and vinyl acrylate in anhydrous pyridine. The ester carbonyl groups in acylated cellulose derivatives were confirmed by Fourier transform infrared spectroscopy. The surfaces of these cellulose derivatives became hydrophobic as demonstrated by increased water-contact angles. The enzyme-catalyzed transesterification was confirmed to regioselectively target the primary hydroxyl group of cellulose by reactions on specifically substituted cellulose. The cellulose esters from enzyme-catalyzed transesterification could be hydrolyzed partially by the same enzyme in aqueous media, and were thus biodegradable. Surface grafting of cellulose acrylate was demonstrated using azobisisobutylonitrile-initiated polymerization of acrylonitrile in dimethylformamide. Polyacryonitrile (PAN)-g-cellulose shows a differ ent thermal behavior from cellulose, homopolymer PAN, and PAN/cellulose blends. The grafted PAN on PAN-g-cellulose at a 16% grafting add-on is incapable of cyclization. (C) 2001 John Wiley & Inc, Inc.