writer：Tao Yu, Jie Ren, Shuying Gu, Ming Yang.
keywords：poly(lactic acid), poly(e-caprolactone) diols, polycondensation, chain extension, copolymer
source：期刊
specific source：Polymers for Advanced Technologies. 2010, 21: 183-188
Issue time：2010年
Biodegradable copolymers of poly(lactic acid)-block-poly(e-caprolactone) (PLA-b-PCL) were successfully prepared by two steps. In the first step, lactic acid monomer is oligomerized to low molecular weight prepolymer and copolymerized with the (e-caprolactone) diol to prepolymer, and then the molecular weight is raised by joining
prepolymer chains together using 1,6-hexamethylene diisocyanate (HDI) as the chain extender. The polymer was carefully characterized by using H-NMR analysis, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The results of 1-H-NMR and TGA indicate PLA-b-PCL prepolymer with number average molecular weights (Mn) of 4000–6000 were obtained. When PCL-diols are 10 wt%, copolymer is better for chain extension reaction to obtain the polymer with
high molecular weight. After chain extension, the weight average molecular weight can reach 250,000 g/mol, as determined by GPC, when the molar ratio of –NCO to –OH was 3:1. DSC curve showed that the degree of crystallization of PLA–PCL copolymer was low, even became amorphous after chain extended reaction. The product exhibits superior mechanical properties with elongation at break above 297% that is much higher than that of PLA chain extended products.