Chemical modification of polysulfones and their gas transport properties

摘要

Commercial polysulfones were chemically modified on either ortho-ether or ortho-sulfone sites. The substitution groups were systematically changed from trimethylsilyl (TMS), dimethylphenylsilyl (DMPS) to methyldiphenylsilyl (MDPS) groups. The permeabilities of oxygen and nitrotgen and their ideal separation methyldiphenylsilyl (MDPS) groups. The permeabilities of oxygen and nitrogen and their ideal separation factors were measured. When TMS groups (DS chemical bounds 2.0) were substituted on the ortho-ehter sites, the O2 permeability increased more than five fold compared to that of unmodified polysulfone, whereas the O2/N2 selectivity decreased only marginally from 5.5 to 5.4. From these results we have found that 1) the ortho-ehter substitution is more effective inimproving permeability than the ortho-sulfone substitution and 2) the TMS group is also more effective than the bulkier DMPS group. Even through DMPS and MDPS groups are bulker than TMS group, the intersegmental d-spacing values and gas diffusion coefficients were smaller in the modified polysulfones with MDPS and MDPS groups than in those with TMS. This result can be understood by considering mobility of pendant substituents. According to the dynamic mechanical amnalysis, the g-transition peak for former was higher than that for latter, representing higher mobility of TMS group. Therefore, it was concluded that the mobility of pendant substituents plays a major role in determining the diffusion coefficient instead of their bulkiness.