Synthesis And Crystallization Of PLLA With Different Initiators

Poly(lactic acid) (PLA) presents outstanding biodegradability and biocompatibility. It is instructive to study the influence of end group on the crystallization of PLLA for its modification and application. In this work, isopropanol,phenol,1-hydroxypyrene were used as initiators and 1,8-Diazabicyclo[5.4.0]undec-7-ene(DBU) as catalyst for ring-opening polymerization of 1-lactide, three kind of PLLA with different initiators were synthesized. Isothermal and nonisothermal crystallization of these PLLA were studied by using differential scanning calorimeter (DSC) and polarizing microscope (POM). DSC results show that the crystallization rates of PLLA with different initiators were obviously different:PLLA with isopropanol as initiator(IPA)>PLLA with phenol as initiator(PLLA(phenol))>PLLA with 1-hydroxypyrene as initiator(PLLA(pyrene)). POM results show that the nucleation rate and spherulitegrowth rate of PLLA with different initiators were also different and followed the same rules. This may due to different steric hindrance effect of the end group of PLLA molecular chains. Besides, the physical cross-linking and the existence of DBU may also get crystallization rate slow down. Therefore, the research of this topic will provide a more comprehensive understanding of PLLA crystallization.