Reversible transparency

Produce thermo reversible transparent gel. Increase the gel strength... 

Gel Networks for Reversible Transparency and Color Control with Temperature. A novel class of polymer gel networks which change both their color and transparency with changing temperature has been developed (61). Starting from a... 

Chromogenic Polymer Gels for Reversible Transparency and Color Control... 

Thermotropic Gel Networks for Reversible Transparency Control with Temperature... 

The semicrystalline, ethylene-based ionomers of commerce are flexible, transparent polymers notable for high strength and elasticity in both soUd and molten states. The ionic bonding is completely reversible (8) and has a strong influence on properties, even at temperatures well above the melting point. 

Note that the definition of R is arbitrary. However, the present choice seems simplest and has a transparent physical interpretation. The work done by the system in an infinitesimal reversible transformation at constant S, N, A, s, and ayiy is given by... 

If the mixture to be separated contains fairly polar materials, the silica may need to be deactivated by a more polar solvent such as ethyl acetate, propanol or even methanol. As already discussed, polar solutes are avidly adsorbed by silica gel and thus the optimum concentration is likely to be low, e.g. l-4%v/v and consequently, a little difficult to control in a reproducible manner. Ethyl acetate is the most useful moderator as it is significantly less polar than propanol or methanol and thus, more controllable, but unfortunately adsorbs in the UV range and can only be used in the mobile phase at concentrations up to about 5%v/v. Above this concentration the mobile phase may be opaque to the detector and thus, the solutes will not be discernible against the background adsorption of the mobile phase. If a detector such as the refractive index detector is employed then there is no restriction on the concentration of the moderator. Propanol and methanol are transparent in the UV so their presence does not effect the performance of a UV detector. However, their polarity is much greater than that of ethyl acetate and thus, the adjustment of the optimum moderator concentration is more difficult and not easy to reproduce accurately. For more polar mixtures it is better to explore the possibility of a reverse phase (which will be discussed shortly) than attempt to utilize silica gel out of the range of solutes for which it is appropriate. 

The mixture is heated to boiling for a few minutes and is spread out to dry at 20" to 60° C. The dried material is insoluble in cold water, but it swells to form a tough gel which is thermally reversible and transparent. Another... 

The protein-containing colloidal solutions of water-in-organic solvents are optically transparent. Hence, absorption spectroscopy, circular dichroism spectroscopy and fluorescence spectroscopy are found to be convenient for studying biocatalysis [53]. The reversed micelles are interesting models for studying bioconversion, since the majority of the enzymes in vivo act inside or on the surface of biological membranes. 

Metallopolymer films have also been prepared by oxidative polymerization of complexes of the type [M(phen)2(4,4 -bipy)2]2+ (M = Fe, Ru, or Os phen= 1,10-phenanthroline, 4,4 -bipy = 4,4 -bipyridine).23 Such films are both oxidatively and reductively electrochromic reversible film-based reduction at potentials below —IV lead to dark purple films,23 the color and potential region being consistent with the viologen dication/radical cation electrochromic response. A purple state at high negative potentials has also been observed for polymeric films prepared from [Ru(L13)3]2+.24 Electropolymerized films prepared from the complexes [Ru(L16)-(bipy)2][PF6]22 and [Ru(L17)3][PF6]226,27 exhibit reversible orange/transparent electrochromic behavior associated with the Run/Ruin interconversion. 

In an example of the construction of such a device, thin films of these materials are deposited on OTEs that are separated by a layer of a transparent ionic conductor such as KCF3SO3 in polyethylene oxide).125 The films can be colored simultaneously (giving deep blue) when a sufficient voltage is applied between them such that the WO3 electrode is the cathode and the PB electrode the anode. Conversely, the colored films can be bleached to transparency when the polarity is reversed, returning the ECD to a transparent state. 

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