Photosynthetic membranes III: Influence of photo-cross-linking on permeation and diffusion coefficients of hydrogen and carbon monoxide through asymmetric membranes prepared by photografting of 1,6-hexanediol diacrylate onto cellulose

Abstract

Asymmetric membranes were prepared by photochemical grafting of 28.1 μmol cm −2 of 1,6-hexanediol diacrylate onto cellulose in the form of filter paper, in the presence of 1,2-diphenyl-2,2-dimethoxyethanone as a photoinitiator, the molar ratio of photoinitiator to acrylated monomer being fixed at 0.086. A fixed polychromatic irradiation flux of 20.2×10 −8 einsteins s −1 cm −2 was used. After 10 min irradiation, a nearly quantitative graft yield was reached. By multiple internal reflection IR analysis, a structure with one pendant acrylate group per monomer unit was assigned to the grafted polymer; at longer irradiation times, a further decrease in unsaturation resulting from photo-cross-linking between pendant acrylate groups was observed. Permeabilities P and diffusivities D at 25 °C for hydrogen and carbon monoxide were measured for membrane specimens obtained at different irradiation times. An increase in P reflects a decrease in unsaturation, while the D are independent of irradiation time. The selectivity of them embranes is not influenced by photo-cross-linking.