Polymeric films transparent

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. 

Thus, varying the frequency of an applied electric field at a given temperature, one may pass over from homeotropic orientation of the sample (transparent film) to the mode of EHD instability and reverse. This reveals interesting perspectives for controlling the optical properties of polymeric films. 

While transparency is preferred in polymeric films, the covering power is an important factor in textiles. 

The novel water-soluble dye 64 shows sufficient stability for potential application in molecular-based beacons for cancer detection using optical imaging <2005BCC735>. An optochemical ozone sensor with a quantitation limit of 0.03 ppm and accuracy exceeding 8% has been obtained by immobilization of the novel soluble indigo derivative 65 in permeable transparent polymeric films of polydimethylsiloxane-polycarbonate <2005MI1628>. 

Imaginative applications of polymers to fenestration can also be used for flat-plate collectors. A transparent, coated polymeric glazing which transmits the solar spectrijm but returns the Infrared radiation effectively Increases the Insulation provided by the glazing, because the Infrared radiation generated Inside the structure Is retained. A polymeric film which changes from transparent to opaque when heated above a transition temperature acts as an automatic window shade which could help control stagnation temperatures [9]. 

Lee and Sotzing [112] then used a similar approach for the synthesis of the unfunctionahzed thieno[3,4-fi]thiophene (76) and its corresponding polymer 1 in 2001 (Scheme 12.18). The electro-polymerized films are deep blue in the neutral state, but colorless and transparent in the oxidized state. Films grown on ITO give optical spectra with a transition at 846 nm. The onset of this transition (1459 nm) corresponds to an of 0.85 eV [112,113]. This agrees well with the value of 0.8 eV determined from the difference of the redox onsets in the polymer CV. 

In all cases, the films were obtained by oxidative electropolymerization of the cited substituted complexes from organic or aqueous solutions. The mechanism of metalloporphyrin Him formation was suggested to be a radical-cation induced polymerization of the substituents on the periphery of the macrocycle. As it was reported for the case of polypyrrole-based materials ", cyclic voltammetry and UV-visible spectroscopy with optically transparent electrodes were extensively used to provide information on the polymeric films (electroactivity, photometric properties, chemical stability, conductivity, etc.). Based on the available data, it appears that the electrochemical polymerization of the substituted complexes leads to well-structured multilayer films. It also appears that the low conductivity of the formed films, combined with the cross-linking effects due to the steric hindrance induced by the macrocyclic Ugand, confers to these materials a certain number of limitations such as the limited continuous growth of the polymers due to the absence of electronic conductivity of the films. Indeed, the charge transport in many of these films acts only by electron-hopping process between porphyrin sites. 

If the sample has a smooth, planar surface so that good physical contact with an infrared-transparent, higher refractive index prism/plate may be achieved, it can be examined by an infrared reflection technique, for example, one using attenuated total reflection, multiple internal reflection. It should be borne in mind, when examining polymeric films, that the sample may be a laminate and hence examination may give very different spectra from reflection at the two surfaces and also from transmission techniques. A coating or paint may be directly applied to a transparent plate for transmission or reflection techniques. 

The interference pattern in the infrared spectra of thin polymeric films may give rise to difficulties when attempting to observe weak bands. This problem can be overcome in several ways, the simplest being to place the film on an infrared transparent (in the region of interest) plate or simply, when casting a film, to leave it adhered to the transparent plate and to examine it directly allowing for compensation if necessary. It should be borne in mind that the infrared spectra of laminates may also exhibit an interference as a result of the interaction of reflections at boundaries and radiation transmitted directly. 

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