Tg. Knudstrup et al., PRESSURE-DRIVEN FLOW EXPERIMENTS IN MOLECULARLY NARROW, STRAIGHT PORES OF MOLECULAR DIMENSION IN MICA, Langmuir, 11(3), 1995, pp. 893-897
Hexane, dodecane, hexadecane, and OMCTS to (octamethylcyclotetrasiloxa
ne) were forced to flow through track-etched mica membranes in a serie
s of pressure drop-flow rate experiments. The sizes of membrane pores
ranged from semiaxis sizes of about 30 Angstrom to about 300 Angstrom.
The track-etched pores in a particular mica membrane are practically
identical in cross section and in length, and their number can be accu
rately estimated, permitting the flow through a membrane to be predict
ed and compared to measurements. If the alkanes and OMCTS had strongly
physisorbed to the pore walls, this physisorption would have been exp
ected to lower the flow rate expected for a given pressure drop and bu
lk fluid viscosity. No such results of strong physisorption were obser
ved, even in the smallest mica pores, where they would be expected to
manifest themselves if present. These results are contrasted with resu
lts from the surface-force apparatus, where strong physisorption effec
ts have been reported for fluids confined in molecularly narrow region
s between sheets of mica.