Synchrotron X-ray In situ Tomography of Thermally Induced Phase Separation of PolyLactic Acid in 1,4 Dioxane solution

We report here the investigation by X-ray in situ tomography of the thermally induced phase separation under cooling of two kinds of polymer solutions: a binary mixture of polylactic acid (PLA) with 1,4-dioxane and a ternary mixture with PLA, 1,4-dioxane, and water. Under cooling, the crystallization of the solvent induces the phase separation with the polymer. The use of PLA was guided by its interesting combination of properties: good mechanical strength, biodegradability, and biocompatibility. Furthermore, the thermal induced phase separation of PLA and 1,4-D-dioxane is extensively used for fabrication of biomedical scaffolds. The in situ synchrotron tomography is here an ideal tool to characterize both the kinetics of formation of the phase separation and the shape of the crystals that are formed for a specific ramp of temperature. Our experimental setup based on a cryocooling system yields a large temperature gradient of 18 degrees C. This gradient that is clearly a limitation of our setup can be nonetheless useful to produce a strong anisotropy in the crystallization and thus anisotropic scaffolds.