The effects of the amount of chain extender

2

2'-(1

3-phenylene)bis(2-oxazoline) (1

3-PBO)

on the synthesis of lactic acid based poly(ester-amide) (PEA) were studied.The carboxyl-terminated lactic acid-succinic anhydride copolymer (P(LA/SA)) was synthesized via directly melt polycondensation of L

D-lactic acid with succinic anhydride and Sn(Ⅱ)octoate as the catalyst at 168℃ and 0.098 MPa by the method of a gradient increased temperature.Then

the PEA was synthesized with P(LA/SA) as prepolymer and 1

3-PBO as extender.High molecular weight polymer was produced within a narrow range of copolymerization parameters.The highest molecular weights were achieved with the molar ratio of oxazoline/carboxyl end groups being 1.0/1.4 at 150℃ and 0.098 MPa for 15 min.The structure were characterized by spectroscopy (FTIR and 1H-NMR) and the properties were investigated by gel permeation chromatography (GPC)

differertial scanning calorimetry (DSC)

X-ray Diffraction (XRD)

thermogravimetric analysis (TGA) and scanning electron microscope (SEM).Results indicated that the highest molecular weight was over 36104 measured by GPC and the chain stiffness presented a tendency upward detected in mechanical properties as a result of the introduction of benzene rings and amide groups into PLA/SA.A distinct improvement in the thermal stability of the resulting polymer with the chain extender was observed compared with the unmodified PLA by TG

just as an one-step thermal decomposition.The crystallinity of the resulting polymer was higher than that of P(LA/SA)

but lower than that of PLA which indicated that the flexibility of the resulting polymer was superior to P(LA/SA).