Enzymatic synthesis of silicone fluorinated aliphatic polyesteramides

The enzymatic synthesis of silicone fluorinated aliphatic polyesteramides (SFAPEAs) is reported. These materials were synthesized by incorporating both the fluorinated aliphatic segments and the dimethylsiloxane segments into the same linear chain backbone. Immobilized lipase B from Candida antarctica (Novozym-435) was used to catalyze the reactions to prepare fluorosilicones containing both amide and ester linkages. Simultaneous reactions of an amidation between α,ω-aminopropyl terminated poly(dimethylsiloxane) (APDMS) and diethyl adipate (DEA) and a transesterification between diethyl adipate and four different fluorinated alkanediols (FADs), respectively were conducted. The condensation reactions were carried out in the bulk, in the temperature range 70-90 °C and under reduced pressure (50 mmHg vacuum gauge). The molar masses of the synthesized fluorosilicones were determined by GPC analysis. The effect of the chain length of the FADs on the molar mass build up of the respective polymers was investigated. The highest molar mass fluorosilicones were obtained with the 3,3,4,4,5,5,6,6-octafluoro 1,8-octanediol (OFOD) monomer, which has an additional methylene (-CH2-) spacer between the fluorocarbon chain (-CF2-)n and the hydroxyl end groups (-OH) when compared to the other three FAD monomers namely - 2,2,3,3-tetrafluoro 1,4-butanediol (TFBD), 2,2,3,3,4,4-hexafluoro 1,5-pentanediol (HFPD) and 2,2,3,3,4,4,5,5-octafluoro 1,6-hexanediol (OFHD). The formation of amide and ester linkages during the polymerization was confirmed by FTIR and 1H NMR spectroscopy. A series of copolymers were synthesized by varying the feed ratios of FAD to APDMS. Fluorinated polyesters (FPEs) and silicone polyamides (SPAs) were also enzymatically synthesized under similar reaction conditions. The DSC analysis revealed that the fluorosilicones were semi-crystalline, principally due to the presence of the FPE segments. The FPEs were found to be white solids at room temperature. However, the SFAPEA's were found to be viscous materials due to the presence of highly flexible silicone segments in the backbone chain. The crystallinity was seen to disappear completely for the SFAPEA's with greater than 15 mol% of silicone content. The TGA analysis revealed that thermal degradation/depolymerization characteristics of the fluorosilicones improved with increased silicone content. We envisage that these new fluorosilicones have potential for a variety of low surface energy applications.