Molecular properties of amorphous high polymers. II. An interpretation of gaseous diffusion through polymers

A cell model is extended in order to interpret gaseous diffusion data through thin films of amorphous polymers. An amorphous polymer is again characterized as a homogeneous one component phase containing N identical n ‐center polymer segments. A sorbed gas molecule is visualized as occupying an equilibrium position in a homogeneous lattice and behaving as a three dimensional harmonic oscillator trapped by surrounding bundles of parallel polymer segments. A diffusion “jump” is assumed to occur when four parallel polymer segments separate sufficiently to create a cylindrical void into which the gas molecule can move. Equations are developed which relate the activation energy for gaseous diffusion, the activation energy for self diffusion and the length of an average polymer segment to the molecular properties of the polymer. Gaseous diffusion data from various literature sources are successfully analyzed on this basis.