Fabrication of scaffold using thermally induced phase separation in poly(lactic acid)/dialkyl phthalate system

Abstract

The purpose of this study is to understand the thermally induced phase in poly(lactic acid) (PLA)/dialkyl phthalate system, control the final morphology, and subsequently fabricate the PLA scaffold suitable for cell culture. Both poly(DL-lactic acid) (PDLLA) and poly(L-lactic acid) (PLLA), which are stereoisomers of PLA, were used and a series of dialkyl phthalate, in which the length of alkyl chain was changed from the methyl to hexyl, was employed to control the interaction between the polymer and solvent. Thermally induced phase separation was adopted as fabrication method because the morphology could be tailored by adjustment of the process parameter such as polymer concentration, quenching temperature and quenching method. To control the final morphology, it is essential to understand the phase separation behavior. For this reason, we investigated the relationship between the liquid-liquid phase separation and crystallization in PLA/dialkyl phthalate system through phase diagram in chapter 2. Experimental phase diagrams, which were composed of the liquid-liquid phase separation temperature and crystallization temperature, for poly(lactic acid)/dialkyl phthalate systems were constructed. From the phase diagram, it is confirmed that when the molecular weight of PLLA is increased, the liquid-liquid phase separation occurs at a higher temperature and the crystallization temperature remains almost constant. And as the number of carbon atoms of alkyl chain in the phthalate was decreased, liquid-liquid phase separation temperature decreased considerably while crystallization temperature was not significantly influenced. The final morphology of PLLA solutions was investigated by changing the variables of the TIPS process. The pore size increased when quenching temperature and solvent quality were decreased, which allow liquid-liquid phase separation to progress further before crystallization. When the polymer concentration was low and the PLLA molecular weight wa...