Studies on syntheses and physical properties of biodegradable aliphatic poly(butylene succinate-co-ethylene succinate)s and poly(butylene succinate-co-diethylene glycol succinate)s

Biodegradable aliphatic poly(butylene succinate-co-ethylene succinate) PBES and poly(butylene succinate-co-diethylene succinate) (PBDEGS) were synthesized from succinic acid and 1,4-butanediol/diethylene glycol through a direct polycondensation with titanium tetraisoproxide (TTP) and diphenylphosphinic acid (DPPA) as the co-catalysts. GPC and NMR results indicated molecular weight M-n higher than 5.0 x 10(4) and 6.5 x 10(4) for the PBES and PBDEGS copolymers respectively, with ES/DEGS populations spanning the whole comonomer composition, and the BS and ES sequence distributions were found to be in close agreement with the random model. DSC analyses revealed that thermal and crystallization behaviour strongly depended on the corresponding comonomer composition for the PBES and PBDEGS copolymers, and that PDEGS was an amorphous poly(ester-ether). For thermal stability, TGA results indicated that thermal stabilities of the prepared PBDEGS significantly decreased with increasing the DEGS unit composition, while there was no remarked decrease detected for those of the PBES copolyesters. In addition, measurements of mechanical properties showed that incorporation of a small amount of ether groups into the DEGS unit could more remarkably improve the elongation behaviour of the semi-crystalline copolymer than that of the ES unit, and much larger elongation rates were exhibited for the copolymer samples bearing 47, 78 mol% ES and 8, 28 mol% DEGS. (C) 2002 Elsevier Science Ltd. All rights reserved.