Effect of chemical structure of organics on pore wetting

Abstract

Pore wetting is significant for understanding fluid behaviour in porous media. In this paper, a range of organics with similar surface tensions were used to investigate the effect of chemical structure on glass pore wetting. We measured contact angles of organics in a single glass capillary. Our results indicate that the chemical structure of organics does significantly affect the contact angle in a single glass pore. The amphiphiles have similar surface tensions, but their contact angles vary greatly with their chemical structures. The amphiphiles with functional groups have larger contact angles than the non-polar organics, and in the order of θ–OH>θ–NH2≈θ–COOH. The contact angle of amphiphile in a glass pore increases with the straight alkyl chain length. The straight alkyl chain contributes to the pore contact angle most and the side chain on the carbon of backbone tends to reduce the pore contact angle. The symmetrical molecular structure gives the smallest contribution on the pore wetting. In addition, the contact angles of amphiphiles were also measured in a hydrophobic PMMA (poly(methyl methacrylate)) pore, and compared with those in a hydrophilic glass pore. The results indicate that the chemical structure has no contribution on hydrophobic pore wetting.