Studies on syntheses and physical characterization of biodegradable aliphatic poly(butylene succinate-co-ε-caprolactone)s

Biodegradable aliphatic poly(butylene succinate-co-epsilon -caprolactone) (PBSCs) were synthesized through a polycondensation with titanium tetraisoproxide (TTP), diphenylphosphinic acid (DPPA) and stannous octoate (Sn(Oct)(2)) as the novel co-catalysts. By means of gel permeation chromatography (GPC) and nuclear magnetic resonance spectrometer (NMR), it was revealed that the PBSC copolyesters had number average molecular weights Al higher than 5.0 x 10(4), and that the polycondensations were in well agreement with a random copolymerization model. With respect to thermal properties, melting point, heat of fusion and glass transition temperature were found to decrease with increasing the CL/BS unit molar ratio up to 0.92, while thermal stability monotonously decreased with increasing the CL unit population spanning the whole CL unit composition. X-ray diffraction patterns indicated that the BS-rich/CL-rich PBSC organized the corresponding PBS/PCL-type of crystal structure. Moreover, it is worth to note that the PBS copolymerized with an appropriate amount of the minor CL component could significantly increase the fracture elongation of the resultant PBSC, and that mechanical properties of PBSC strongly depended on its CL unit population. In addition, biodegradabilities of PBSCs as well as PBS and PCL were tentatively assessed in a kind of compost soil, and the results suggest that chain flexibility may play an important role in the biodegradation as another factor besides the specificity of unit chemical structure and morphology. (C) 2001 Elsevier Science Ltd. All rights reserved.