2019/12/06
Keio University
Kyushu University
Senior Assistant Professor Ayano Chiba of the Faculty of Science and Technology at Keio University, Associate Professor Ryo Akiyama of the Faculty of Science at Kyushu University, and Akio Oshima, a graduate student at the time of the research (who completed his master's degree in March 2019), have discovered a liquid separation method using a crystalline polyolefin membrane and proposed its principle. Generally, liquid separation refers to the extraction of specific molecules from a liquid mixture of multiple types of molecules. While conventional liquid separation using porous membranes has employed a strategy of allowing only molecules smaller than the pores to permeate, this study revealed that in a liquid mixture, there is a strong tendency for larger molecules to selectively enter the porous material. This can be explained by the Asakura-Oosawa theory, a theory of statistical mechanics. In fact, when a crystalline film of the polyolefin isotactic poly(4-methyl-1-pentene) was immersed in a binary mixture of linear alkanes, the longer linear alkane was selectively absorbed into the voids within the crystal. This is considered to be a spontaneous liquid separation based on molecular volume. A well-known conventional method for separation by volume is gel permeation chromatography (GPC), which separates polymers based on their degree of polymerization, i.e., their effective volume. This research provides a new perspective for separating small molecules by their volume.
The results of this research were published in the online edition of the American scientific journal "Langmuir" on Tuesday, December 3, 2019 (US time).
Please see below for the full press release.