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(CH2)
n
-
2COOH, 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 Yen films was
compared with that for the network polyester films of glycerol (Yg) or pentaerithritol (Xp) with various
aliphatic dicarboxylic acids reported earlier.
,
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/m2) and then decreased gradually for Ye14−20. Other lipases of porcine pancreas and
Psedomonas cepacia hardly degraded Yen 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.