PERMEABILITY OF OXYGEN THROUGH MEMBRANES OF POLY(CYCLOHEXYL ACRYLATE)

The permeability of oxygen through membranes of poly(cyclohexyl acryla te) at temperatures in the vicinity of the glass transition temperatur e (T(g)) is determined using an electrochemical experiment. The diffus ion coefficient of the gas follows Arrhenius behaviour with an activat ion energy of 22 kcal mol-1, a surprisingly high value if it is consid ered that the range of activation energies observed in most systems is 1-20 kcal mol-1. The interpretation of the free volume of the membran e at T(g) suggests that the critical volume necessary for permeation o f the gas to take place is nearly four times lower than the value of t his parameter for the mechanical and dielectric processes. It is sugge sted that bulky side groups may aid the transport of gas in the glassy state but presumably hinder it in the rubbery state.