Biocatalytic synthesis of fluorinated polyesters

The biocatalytic synthesis of fluorinated polyesters from activated diester s and fluorinated diols has been investigated. The effects of time, continu ous enzyme addition, enzyme concentration, and diol chain length were studi ed to determine the factors that would limit chain extension, such as enzym e inactivation, enzyme specificity, the equilibrium position for the reacti on, hydrolytic side reactions, and polymer precipitation. An enzyme screen demonstrated that only Novozym 435, an immobilized lipase from Candida anta rctica, was effective in producing the fluorinated polyester. Molecular wei ght and polydispersity analyses were performed by means of gel permeation c hromatography. End group analysis was accomplished through the use of matri x-assisted laser desorption/ionization time-of-flight mass spectroscopy. Po lymer molecular weight steadily increased and then leveled off after approx imately 30 h, with a weight average molecular weight of approximately 1773. The majority of the polymer chains were terminated with either hydroxyl or vinyl groups. Polymers that were synthesized from bulk monomers had higher molecular weights, but high enzyme concentrations were required. Enzyme sp ecificity toward shorter chain fluorinated diols appeared to be the governi ng factor in limiting chain growth. However, polymer molecular weight incre ased further (M-w= 8094) when a fluorinated diol that contained an addition al methylene spacer between the fluorine atoms and hydroxyl groups was used .