| PLA stereocomplexatio, due to the peculiarly strong interaction between L-lactyl unit sequences and D-lactyl unit sequences improved the melt temperature. sc-PLA have a Tm above 220 ℃, being much higher than the Tm of PLLA or PDLA. The high heat-resistance has been attracting much attention.PLA-based stereo diblock compolymers PLLA-TMC and PDLA-TMC can also formed stereocomplexation in solution. The heat-resistance, mechanical properties and degradable properties have largely been enhanced by the adding of TMC units.PLA homopolymer and PLA-TMC diblock copolymers were prepared by ring-opening polymerization of appropriate monomer feeds, using stannous octoate as catalyst. The polymers were characterized by GPC, FTIR,1H NMR and DSC.Blending stereo diblock PLLA-TMC and PDLA-TMC solutions to prepared PLA-based stereocomplexation (sc-PLAX(L/H)) by solution casting, X means molar rations of TMC, L and H respercively represent low molecular weight polymers and high molecular weight polymers. The thermal properties and crystal structure were characterized by DSC and XRD. The results show that TMC units enchanced stereocomplextion degree. The chain segement of PLLA and PDLA decreased with the increasing of TMC molar ratio, shorter chain segement increased the chance of interaction between PLLA and PDLA than long chain segement. We also used DMA and tensile test to analysis polymer mechanical properties. Compared with sc-PLA, PLA-based diblock stereocomplexation exhibited higher toughness.Various solution cast films of sc-PLAX(L/H) were allowed to degrade at 37 ℃ in the presence of proteinase K, and the degradation behavior was monitored by weight loss, water absorption, DSC and SEM. With degradation, the mass loss increase,33% of mass loss is detected after degradation 204 h. The degradation rate increased with TMC molar ratio.The chains of amorphous region fold into crystalline region, which results in an increase of the drgree of crystallinity. |
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