Synthesis, Characterization, and Enzymatic Degradation Studies on Novel Network Aliphatic Polyesters

Network polyesters were prepared from1,1,1-trimethylolethane (Ye), 1,1,1-trimethylolpropane (Yp), 1,2,3,4-butanetetrol (Xe), and d -glucitol (Zs) with aliphatic dicarboxylic acids containing different numbers of methylene groups (HOOC(CH 2 ) n - 2 COOH, n =4, 6−14, 16, and 20). Prepolymers prepared by melt polycondensation were cast from dimethylformamide solution and postpolymerized at 230 °C for 4 h to form a network. The resultant films were transparent, flexible, and insoluble in organic solvents. The network polyesters obtained were characterized by infrared absorption spectra, wide-angle X-ray diffraction analysis, density measurement, thermomechanical analysis, differential scanning calorimetry, and tensile test. The enzymatic degradation was estimated by the weight loss of the network polyester films in a buffer solution with lipase enzymes at 37 °C. The enzymatic degradation for Ye n films was compared with that for the network polyester films of glycerol (Yg) or pentaerithritol (Xp) with various aliphatic dicarboxylic acids reported earlier. 11,12 After the incubation in Rhizopus delemar lipase solution for 2 days, the weight loss was hardly observed for Ye4−7, while it increased drastically for Ye8−13 (13−15 g/m 2 ) and then decreased gradually for Ye14−20. Other lipases of porcine pancreas and Psedomonas cepacia hardly degraded Ye n films. The degradation rate for 10 series films was decreased as follows:Yg10 >Ye10 > Yp10 = Xe10 > Xp10 > Zs10, corresponding to the increase in the number of hydroxyl groups in the polyhydric alcohols.