Synthesis and characterization of carboxyl-terminated poly(lactic acid)

The carboxyl-terminated modified polylactic acid copolymers of P(LA/SA),P(LA/CA) and P(LA/AC) were synthesized via directly melt polycondensation with D,L-racemic lactic acid(D,L-LA) as raw material and stannous octoate as catalyst.The copolymerization reaction was performed at the temperature of 168 ℃ and the pressure of 0.098 MPa using linear heating method.The copolymers were characterized by viscosity-average molecular weight,FT-IR,1H-NMR,DSC,TGA and XRD.The results demonstrate that Tg of the carboxyl-terminated copolymers is lower than PLA,reducing the rigidity of PLA;the copolymers have good thermal stability for one-step thermal decomposition;compared with PLA,the crystallinity of P(LA/SA) and P(LA/AC) decreased,while the P(LA/CA) slightly decreased,so that,by adjusting the ratio of lactic acid and modifier to adjust the mechanical properties.