Polystyrene-based films containing from 0 to 45 mol % of C60 fullerene are investigated. It is found that the introduction of fullerene increases the molecular packing density of polystyrene
chains, thus affecting the transport of small molecules through the polymer films. Gas diffusion through the composite films
is slower than through the polystyrene films, while the gas-distributing properties of the composites are higher. The dielectric
relaxation method shows that the solution-grown films retain the cluster state of fullerene. When the films containing more
than 0.15 mol % of fullerene are heated above the glass transition temperature of polystyrene away from air, the relaxation
time of the α transition in polystyrene is found to increase. This effect is associated with strong chain interaction via
fullerene molecules incorporated into polystyrene-C60 complexes. The NMR spectroscopy method allows us to observe the typical changes in the composites. 相似文献
Russian Journal of Applied Chemistry - New diffusion membranes were prepared by introducing endofullerenes with encapsulated iron atoms, Fe@C60, into the poly-2,6-dimethyl-1,4-phenylene oxide... 相似文献
A new hybrid gas separation membrane was prepared from poly(2,6-dimethyl-1,4-phenylene oxide) modified with graft copolyimide with side poly(methyl methacrylate) chains. The changes in the membrane structure on introducing up to 15 wt % modifier were evaluated by atomic force microscopy and density measurements. The microphase separation in modified polyphenylene oxide films was demonstrated. Introduction of graft copolyimide leads to an increase in the density of the hybrid films. The gas transport properties of the membranes were evaluated for H2, CO2, O2, O4, and N2. Introduction of up to 10 wt % modifier does not noticeably alter the permeability of the hybrid membranes to all the gases but increases the selectivity in gas separation.
Based on regular star-shaped PSs differing in the structure of the branching center (one or two covalently bound fullerene C60 molecules) and in the number of branchings (6 and 12), homogeneous gas-separation membranes have been produced. The transport behavior of the membranes with respect to several gases, such as H2, He2, N2, CO, CO2, and CH4, has been studied by mass spectrometry. It has been found that the membranes prepared from six-arm PSs are characterized by a smaller density of macromolecular packing than the membranes obtained from 12-arm PCs and, consequently, they possess higher gas permeability. The starshaped PSs demonstrate a higher selectivity factor for separation of the O2/N2 gas pair compared to the corresponding characteristics of the linear PSs. The analysis of gas-separation characteristics by means of the Reitlinger-Robeson diagrams demonstrates that the transport behavior of star-shaped PSs qualitatively surpasses similar parameters of the known polymers in the separation of the CO/N2 gas pair. 相似文献
Separation of aqueous isopropanol solutions by pervaporation using membranes based on composites of a polyimide with an aniline-anthranilic
acid copolymer was studied. 相似文献
Samples of molecular polyimide brushes with poly(methyl methacrylate) side chains with substantially different grafting densities and lengths of side chains are obtained by the atom-transfer radical polymerization of methyl methacrylate using samples of polyimide multicenter macroinitiators with different contents of initiation groups. Strong homogeneous films suitable for use as diffusion membranes for pervaporation separations of liquid mixtures are cast from solutions of polyimide brushes in dimethylformamide. Investigations are performed for films of polyimide brushes with loosely grafted short side chains or densely grafted long side chains as well as for films of a polyimide identical in its chemical structure to the backbone of polyimide brushes. It is shown that all film membranes sorb water moderately and do not sorb isopropanol. For membranes made of the polyimide and the loosely grafted brush, which is close to the polyimide in its properties, the active sorption of acetonitrile is demonstrated. It is found that all membranes exhibit high selectivities for water upon pervaporation of water–isopropanol mixtures. In addition, membranes made of the brush with densely grafted side chains show high productivity. 相似文献
The effect of introduction of the comonomer methylthiirane (MT) into the main chain of polyacrylonitrile (PAN) on the thermal transformations of the macromolecules in dilute DMF solution was studied. For this purpose, statistical copolymers of acrylonitrile and MT were synthetized and their pyrolysis in solution was investigated. It was found that introduction of the thioether group into the main chain of PAN results in essential changes in the thermal behaviour of the copolymers as compared to the homopolymer. The results of rheological, thermal and spectral studies on the solutions suggest that the direction of the thermochemical reaction changes on introduction of the thioether group into the PAN molecule. In such copolymers the reaction will preferably proceed by the -C≡N groups forming conjugated cyclic structures. 相似文献
A process was developed for preparing asymmetric ultrafiltration poly(4,4′-oxydiphenylene)pyromel litimide membranes, involving
wet forming of the membranes from the prepolymer, followed by catalytic solidphase thermal transformation of the prepolymer
into the polyimide. The influence exerted on the structure and characteristics of the membranes by the compositions of the
forming solution and precipitation bath, and also by thermal imidization conditions was examined. The optimal conditions were
determined for preparing asymmetric ultrafiltration poly(4,4′-oxydiphenylene)pyromellitimide membranes exhibiting the water
permeability coefficient of (10−500) × 10−6 m3 m−2 s−1 atm−1 and molecular weight cut-off in the range (5−100) × 103 g mol−1. 相似文献
Experimental data on evaporation of binary mixtures composed of ethanol and water, ethyl acetate and acetic acid, water and acetic acid, and ethyl acetate and water in a wide range of concentrations, across film membranes composed of cellulose myristinate and polyphenylene oxide are presented. 相似文献
The transport properties of membranes based on polyimide-polyaniline composites are studied in the pervaporation separation
of a methanol-toluene binary azeotropic mixture. The morphology of the membranes is investigated by electronic microscopy,
and the wettability of their surface is analyzed by contact-angle measurements. Special attention is given to the study of
sorption and diffusion characteristics of membranes affecting the selectivity and rate of membrane separation. It is found
that the incorporation of polyaniline into the matrix of the aromatic polyimide facilitates a reduction in the density of
the composites relative to that of the nonmodified polyimide. It is shown that the membranes based on the polyimide-polyaniline
composites are more selective with respect to methanol and show lower permeability during pervaporation of the methanol-toluene
mixture than polyimide membranes. 相似文献