Use of Activated Enol Esters for in vitro Polyester Synthesis

Use of Activated Enol Esters for in vitro Polyester Synthesis 

Much of the earlier work carried out on lipase-catalyzed condensation polymerizations focused on the use of activated diacids such as enol esters (see also Table 4.1). This was due to the belief that such activation was necessary to achieve 

In addition the Novozym 435-catalyzed bulk polymerization of divinyl adipate and 1,4-butanediol was reported [44]. The highest M, =23 236 in 98.3% yield was obtained after 72 h polymerization at 50 °C. It was found that the product molecular weight was decreased when the reaction was conducted without taking proper precautions to exclude water in reactions that can hydrolyze reactive divinyl ester groups. They also found excellent agreement between their experimental data and that predicted by a mathematical model [66]. 

Russell et al. [38] also studied Novozym 435-catalyzed A-A/B-B type condensation polymerizations to prepare aromatic polyesters and polycarbonates. Polymerizations between divinylesters or dicarbonates with aromatic diols, conducted for 24h in bulk catalyzed by Novozym 435 (lOwt %) at preferably 70°C, gave low molecular weight polycarbonates and polyesters. The aromatic diols included 1,2-benzenedimethanol, 1,3-benzenedimethanol, 1,4-benzenedimethanol, 2,6-pyridinedimethanolor4,4-isopropylidenebis(2-(2,6-dibromophenoxy)ethanol) and bisphenol-A. The Mw of polycarbonates and polyesters did not exceed 5200 and 3500 (yields 35%), respectively. When various isomers of benzenedimethanol 

Russell et al. [43] studied lipase-catalyzed polymerizations of activated diesters and fluorinated diols. The effects of reaction time, continuous enzyme addition, enzyme concentration, and diol chain length were studied to determine factors that might limit chain growth. Potential limiting factors considered were enzyme inactivation, enzyme specificity, reaction thermodynamics, hydrolysis of activated esters and polymer precipitation. The polymer molecular weight at 50°C steadily increased and then leveled off after 30h at Mw 1773. 

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