Preparation of poly (L-lactic acid) with aligned structures by unidirectional freezing

Honeycomb monolith structured porous poly (L-lactic acid, PLA) was simply fabricated by employing a unidirectional freeze-casting technique. Dimethyl sulfoxide (DMSO) was used as a solvent for PLA, and the solution was unidirectionally frozen. The DMSO was nucleated in the solution and was grown in the freezing direction. The PLA was solidified and structured with the DMSO crystal as a template. Then DMSO was leached by water, ethanol, or the mixture of them, and subsequently the porous PLA was dried by oven. It was found that the freeze-casting protocol can significantly influence the morphological features such as the tube diameter and wall thickness of tube can be tuned by varying of PLA concentration, freezing temperature, and the nature of leaching solvent. Because DMSO has a special solubility of a number of polymers, this method may be a general way for designing and preparing aligned porous materials.