Gas transport and dynamic mechanical behavior in modified polysulfones with trimethylsilyl groups: effect of degree of substitution

Abstract

Trimethylsilyl (TMS) groups were introduced with controlled degree of substitution (DS) onto the phenylene rings of various polysulfones. The introduction of TMS groups resulted in a marked increase in oxygen permeabilities with small concurrent decreases in oxygen/nitrogen permselectivities. Although TMS groups are bulky, they are highly mobile and are expected to reduce chain packing as evidenced by larger specific volumes and d-spacings with increasing DS. The higher is DS, the greater the reduction in the chain packing that occurs. Dynamic mechanical analyses of sub-glass-transition relaxation, i.e., ␥-relaxation behavior, showed that the TMS groups affected the local chain motion. In particular, the motion of unsubstituted phenylene rings increases with DS. Therefore, both the loosened chain packing and the increased local motion by substitution of TMS may result in the increase in the gas permeability.

Polysulfone/Cellulose Acetate Butyrate Environmentally Friendly Blend to minimize the Impact of UV Radiation

“…The storage modulus E' curve for PSF and the PSF/0.2% CAB blend showed three main regions, but in the glassy region there is a significant appearance of the three deformation phases (secondary dispersion at 82.6/23.9°C , γ-relaxation at 90.4/30-40°C and β-relaxation at 187/164°C) for pure PSF and the PSF/0.2% CAB blend, respectively. It was clear that adding CAB to PSF led to significant changes in molecular motion, so that two γ-relaxation processes were observed (30-40°C ) because the substituent in the CAB component introduced phenylene rings [30]. At 187/164°C, the E' curve for pure PSF and PSF/0.2% CAB went into the transition region with a steep slope in order to meet with the tanδ curve at the glass transition temperature (T g ) region for each curve, after that went into the rubbery region.…”

Novel polyoxadiazoles with non-coplanar ortho-linked structures as highly CO2 permselective membranes

“…The introduction of rigid and bulky packing-disrupting units into the backbone has been proposed as the most effective way of enhancing diffusivity and selectivity through hindrance of packing of the relatively rigid backbones and reduction of the rotational mobility around the exible groups. [15][16][17][18][19] A large number of polymeric materials including polyimides, 20,21 poly(amide-imide)s, 22 polybenzimidazoles, 23 polycarbonates, 24 and polysulfones 25 have been investigated and developed as promising membranes for CO 2 separation applications. However, these membranes were found to develop shortcomings including limited thermal and chemical stability together with suffering from the usual trade-off between the desirable properties of selectivity and permeability.…”