Poly film reversible addition

Also, water-soluble poly(vinyl alcohol) was modified by thymine derivatives. This yielded a material that reversibly photodimerizes upon UV irradiation. Photocrosslinking experiments of this polymer were carried out in the film state on quartz plates by irradiation with light at 280 nm. The poly(vinyl alcohol) containing thymine units were found to be more light sensitive than uracil units in a similar polymer. In addition, photodimerization reaction of an ester derivative of the thymene substituted poly(vinyl alcohol) was found to be faster than that of an acetal derivatives, but the sensitivity was lower, because... 

Fig. 2.4 a Schematic of the film deposition process using slides and beakers. Steps 1 and 3 represent the adsorption of a polyanion and polycation, respectively, and steps 2 and 4 are washing steps. The four steps are the basic buildup sequence for the simplest film architecture (A/ B) . The construction of more complex film architectures requires only additional beakers and a different deposition sequence, b Simplified molecular picture of the first two adsorption steps, depicting film deposition starting with a positively charged substrate. Counterions are omitted for clarity. The polyion conformation and layer interpenetration are an idealization of the surface charge reversal with each adsorption step, c Chemical structures of two t3q>ical polyions, the sodium salt of poly(styrene sulfonate) and poly(allylamine hydrochloride). Reproduced with kind permission of Ref. [32]... 

The direct electrochemistry of redox proteins such as ferredoxin and blue copper protein was studied. The additional effect of poly(L-lysine) on the redox behaviour of horse heart cyt c at functional electrodes has been reported Electropolymerized films such as PAn undergo redox reactions producing a colour change. This is described in Sect. 5.2. The anodic oxidation of poly(iV-vinylcarbazole) films was shown to involve initially the cross-linking of the polymer chains by oxidation of the carbazole moieties and dimerization of the resulting pendant carbazole cation radicals The resulting dimeric carbazole unit is more easily oxidized than the monomer and undergoes a further (reversible) two-electron oxidation. 

It is important to note the effect of toluene vapor on the Vis/UV spectrum of a thin film of poly(3-hexylthiophene) spun from a chloroform solution on to a microscope slide (8, 49). A small piece of the slide together with attached film was placed in a cuvette in the spectrometer with air in the reference cuvette and its spectrum was recorded. The film was removed, a few drops of toluene were placed in both cuvettes and the film was carefully suspended in a cuvette and its spectrum was again measured after five minutes. There was no change in the spectrum after an additional 20 minutes in the cuvette. The film was removed and permitted to remain in the air for five minutes. As can be seen from Figure 20, toluene vapor results in a partly reversible effect on the Vis/UV spectrum of the poly(3-hexylthiophene). We have found that gas desorption is frequently slower than gas adsorption in systems of this type we have not yet determined whether a longer period in air would result in greater reversibility. 

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