Chemoenzymatic synthesis of linear poly(sucrose acrylate): Optimization of enzyme activity and polymerization conditions

We have achieved significant improvements in the synthesis of poly(sucrose acrylate). A screen of 15 commercial enzymes was carried out and Alcalase 2T was selected as the best enzyme because of its high activity and selectivity for acylation of sucrose at only one site. The rate of the enzyme catalyzed acylation of sucrose to form sucrose 1'‐acrylate was increased by a factor of ca. 100 compared to previous reports. This rate was increased 10‐fold by treating the as received enzyme by adjusting the pH to the optimum value for the enzyme. An additional 10‐fold increase was achieved by adding a lyoprotectant such as sucrose or poly(ethylene glycol) prior to lyophilizing the enzyme. Significantly higher molecular weights were obtained in aqueous polymerization systems than when N,N‐dimethylformamide (DMF) was used as the solvent. Similarly, higher molecular weights were observed for oxidation/reduction than for azo‐type free radical initiators. We have demonstrated that copolymers of sucrose acrylate and acrylic acid are readily prepared. Finally, by optimization of the polymerization system, we have increased the number‐average molecular weight of the poly(sucrose acrylate) from M̄n = 54 000 to molecular weights M̄n as high as 2 400 000.