Gases with a larger molecular diameter diffuse slower across the prepared membrane [21-23].
The gas permeation mechanism through the polymeric membrane is a solution-diffusion and gases with a larger molecular diameter diffuse slower through membrane structure [21-23] and also due to the larger molecular diameter of C[H.sub.4] in comparison with C[O.sub.2] [23, 31, 32], C[O.sub.2] permeability is higher than C[H.sub.4].
In the VHS model, molecular diameter d is defined as a function of relative velocity cr; that is,
In the VSS model, molecular diameter d is defined as
In addition to the laboriousness of existing techniques, accuracy is compromised, with errors accumulating in proportion to the number of fragments to be read.A new strategy involves the use of nanopores - orifices of molecular diameter
that connect two fluid reservoirs.
Thus He, with the smallest molecular diameter
, has the highest permeation rate.
Subsequently, it was shown that diffusivities for gases and vapors in glassy PS and PMMA, in addition to PVC, are strong exponential functions of molecular diameter (5).
Several measures of molecular diameter were used in establishing these correlations: Gas viscosity measurements yield the Lennard-Jones force constant diameters, [d.sub.LJ].
How do molecules of such a liquid shift and roll when they are wedged between moving surfaces only a few molecular diameters