Study on wettability and capillary pressure of organic nanoporous crystals

Abstract

Research on wettability and water adhesion by surface roughness and chemical composition have been actively conducted. However, these studies remained in surface chemistry, and little research has been conducted on bulk materials. In our work, organic materials which are composed of pyrene and alkyl chain groups are crystallized to 3D structures(orthorhombic and monoclinic) at certain conditions. The orthorhombic structures have a regular and periodic nanopores with their pore sizes in the range of 3-5nm depending on the alkyl chain length. With these materials, By the sessile drop method, the increase of hydrophobicity was observed by nanopores. Also, water adhesion phenomenon was observed by powders attached to an adhesive tape.

The Washburn method was also used to investigate capillary pressure. Capillary radii of orthorhombic HYLIONs 12 and 14 are 49.3nm and 95.5nm, respectively. These results mean that those capillary radii include not only nanopores inside of a crystal but also macropores between crystals. With the capillary radii, capillary pressure was calculated. As a result, orthorhombic HYLION 12 has higher values of capillary pressure than those of orthorhombic HYLION 14 for n-hexane, n-deane and n-tridecane. It confirmed that the smaller the nano-pore size, the greater the capillary pressure.