Polymers liquid/polymer gels

Ionic liquids have already been demonstrated to be effective membrane materials for gas separation when supported within a porous polymer support. However, supported ionic liquid membranes offer another versatile approach by which to perform two-phase catalysis. This technology combines some of the advantages of the ionic liquid as a catalyst solvent with the ruggedness of the ionic liquid-polymer gels. Transition metal complexes based on palladium or rhodium have been incorporated into gas-permeable polymer gels composed of [BMIM][PFg] and poly(vinyli-dene fluoride)-hexafluoropropylene copolymer and have been used to investigate the hydrogenation of propene [21]. 

Chauvin et al. reported the asymmetric hydrogenation of acetamidocinnamic acid to (S)-phenylalanine with a cationic chiral rhodium catalyst in [C4-mim][SbF6] ionic liquid, more recently the 2-arylacryhc acid has been produced with a reasonable 64% yield using a chiral ruthenium catalysts in [C4-mim][BF4] ionic hquids. Palladium catalysts immobilized in an ionic liquid-polymer gel membrane containing either [C2-mim][CF3S03] or [C2-mim][BF4] have also been reported as catalysts for heterogeneous hydrogenation reactions. 

Fuller, J., A.C. Breda, and R.T. Carlin. 1998. Ionic liquid-polymer gel electrolytes fi om hydrophilic and hydrophobic ionic liquids. / Electroanal Chem 459 29-34. 

P. Wang, S. M. Zakeeruddin, I. Exnar, M. Gratzel, (2002) "High efficiency dye-sensitized nanocrystalline solar cells based on ionic liquid polymer gel electrolyte." Chem. Commun., 2972-2973. 

The ESR working window in which the ESR line shapes are sensitive to rotational reorientation depends on the anisotropy of the A- and g-tensors of the radical for nitroxides, the range for Xp, is 10 -10 s, which means that the technique is applicable to polymer solutions, polymer gels, and solid polymers at temperatures close to or above Tg. At the X-band ESR frequency ( 9 GHz), the rotational dynamics in most liquids is usually sufficiently fast, that is, Xp,Aco 1 [where Am is a measure of the magnitude of the orientation-dependent part of the spin Hamiltonian ffj(t)] such motions (Xjj < lO s) fall within the motional narrowing (fast-motional) regime. For slower dynamics (Xp,Am > 1), more complicated slow-motional spectra are observed. ... 

Key words Theory - phase separation - polymers - liquid crystals - gels... 

J. Fuller, A. C. Breda, R. T. Carlin, Ionic liquid-polymer gel electrolytes. J. Electrochem. Soc. 1997a, 144(4), L67. 

The use of polymeric catalytic membranes in distributor/contactor-type reactors for hydrogenation or oxidation reactions has been widely described in several former and recent reviews. Mixed-matrix membranes of PDMS hlled with Pd particles, composite membranes of ionic liquid-polymer gels filled with Pd/C, ° ionic liquids containing rhodium complexes and supported in polystyrene sheets in a corrugated configuration, have been used for the selective gas-phase hydrogenation of hydrocarbons in contactor-type membrane reactors. 

Carlin R T and Fuller J (1997), Ionic liquid-polymer gel catalytic membrane , Chem Commun, 1345-1346. 

Solvated polymers are approaching "gels" in properties, depending on the mobility of the molecules. In some cases the action of a binder and of a separator are combined. By extraction of one of the components and refilling the voids with a liquid, a two-phase system can be created (Bellcore). There are irreversible and re-... 

The structure of water at the PVA/quartz interface was investigated by SFG spectroscopy. Two broad peaks were observed in the OH-stretching region at 3200 and 3400 cm , due to ice-like and liquid-like water, respectively, in both cases. The relative intensity of the SFG signal due to liquid-like water increased when the PVA gel was pressed against the quartz surface. No such increase of the liquid-like water was observed when the PVA gel was contacted to the hydro-phobic OTS-modified quartz surface where friction was high. These results suggest the important role of water structure for low friction at the polymer gel/solid interfaces. 

Polymer gels and ionomers. Another class of polymer electrolytes are those in which the ion transport is conditioned by the presence of a low-molecular-weight solvent in the polymer. The most simple case is the so-called gel polymer electrolyte, in which the intrinsically insulating polymer (agar, poly(vinylchloride), poly(vinylidene fluoride), etc.) is swollen with an aqueous or aprotic liquid electrolyte solution. The polymer host acts here only as a passive support of the liquid electrolyte solution, i.e. ions are transported essentially in a liquid medium. Swelling of the polymer by the solvent is described by the volume fraction of the pure polymer in the gel (Fp). The diffusion coefficient of ions in the gel (Dp) is related to that in the pure solvent (D0) according to the equation ... 

The polymer at the gel point is in a critical state [3], and the name critical gel [4] is appropriate for distinguishing polymers at the gel point from the various materials which commonly are called gels. The critical gel has no intrinsic size scale except for the size of its oligomeric building block, and molecular motions are correlated over large distances. The combination of liquid and solid... 

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