Shiomoto S, Higuchi H, Yamaguchi K, Takaba H, Kobayashi M. Spreading Dynamics of a Precursor Film of Ionic Liquid or Water on a Micropatterned Polyelectrolyte Brush Surface.
LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021;
37:3049-3056. [PMID:
33667098 DOI:
10.1021/acs.langmuir.0c03260]
[Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Time evolution of the microscopic wetting velocity of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI) or water on a micrometer-scale line-patterned surface with a poly(3-sulfopropyl methacrylate) brush and a hydrophobic perfluoroalkyl monolayer was precisely measured by direct observation using optical microscopy and a selective dyeing method over a long period (178 days). When a liquid droplet was placed on the dyed line-patterned brush surface, the liquid penetrated and spread into the polymer brush layer, forming a precursor thin film that extended beyond the macroscopic contact line. The elongation proceeded in two stages by an adiabatic process followed by a diffusive process. The elongation distance X increased with time in proportion to t2.6 for water and t0.81 for EMI-TFSI during the adiabatic process. In a diffusive process, the advancing velocity of the precursor film was markedly reduced to be expressed as X ∝ t0.66 for water and X ∝ t0.21 for EMI-TFSI, indicating that the diffusive process was affected by the energy dissipation of the wetting system. The high viscosity and the strong molecular interaction of EMI-TFSI with the polymer brush gave a large entropy change during the wetting process to result in a slower spreading velocity.
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