Lipase-Catalyzed Synthesis and Properties of Silicone Aromatic Polyesters and Silicone Aromatic Polyamides

Candida antarctica lipase B (CALB) immobilized on a macroporous acrylic resin (Novozym 435) was used to enzymatically synthesize silicone aromatic polyesters (SAPEs) and silicone aromatic polyamides (SAPAs) M toluene under mild reaction conditions. The SAPEs were synthesized using alpha,omega-(dihydroxyalkyl)terminated poly(dimethylsiloxane) (HAT-PDMS, molar mass M-n = 2500 g mol(-1) and the SAPAs were synthesized using alpha,omega-(diaminopropyl)-terminated poly(dimethylsiloxane) (APT-PDMS, having two different molar masses. M-n, 1000 and 4700 g respectively). Each of the polymers was made by a transesterification reaction with dimethyl terephthalate (DMT) in toluene (1:2 w/v ratio of monomers to solvent) at a temperature in the range of 80-90 degrees C under vacuum. Toluene was employed as the solvent in order to solubilize the DMT in the reaction mixture. The methanol byproduct was recovered from the reaction mixture along with the toluene by applying vacuum, and thus the transesterification reaction was driven forward. The enzymatically synthesized polymers were characterized by GPC, FTIR, H-1 NMR, XRD, DSC, and TGA. Higher molar masses were obtained for the SAPEs compared to those of the SAPAs, even though similar reaction conditions were used. The thermal properties of the resulting polymers were seen to depend on the molar masses of the SAPEs and the SAPAs. Both types of polymer were found to be amorphous liquids at room temperature. However, below room temperature the SAPA samples were found to be a sticky wax-like material which contained a crystal-like phase that showed a melting endotherm by DSC analysis. The absence of a melting endotherm in the SAPEs and the relatively low melting point of the SAPAs may be attributed to the presence of lone chain highly flexible PDMS segments in the polymers.