Poly , photoreduction

Crosslinked poly(styrene) beads (20) were prepared with contain Ru(bpy)2+ anchored at oligo(oxyethylene) spacer group 50). Vigorous stirring was needed for the suspended complex (20) to sensitize the photoreduction of MV2+ in the presence of... 

EDTA in water. Ru(bpy)2 + and its dicinnamate were immobilized in a membrane prepared from cinnamate of poly(vinyl alcohol) by photocrosslinking 51), and the immobilized complex sensitized the photoreduction of MV2 +. ... 

Titania and silica glass thin films Au, Pt Photoreduction of HAuCl and K.2PtCl4 in ethanol-water in the presence of poly(N-vinyl-2-pyrrolidone) or poly(methyl vinyl ether led to metal particles (sizes depended on solvent composition the smallest, 2.8 nm in diameter, was obtained in 100% alcohol) which were mixed with Ti(i-OC3H7)4 and acetylacetone under N2. Subsequent to 30 minutes of stirring, exposure to moisture produced Ti02-embedded metal particles 74... 

As can be seen from Table 9.12, photochromism is also strongly affected by humidity. It is well known that thiazine and its derivatives undergo photoreduction smoothly in the presence of such activated surfaces as silica gel and alumina with water molecules,37 and that methylene blue is also photochemically reduced in acid solution, even with only available water as the reducing agent38 Therefore the water present in polymer films must produce a thionine-water hydration system, which accelerates the rate of the photoreduction of thionine, as well as promoting the contact of reductants by a plasticizer effect. PVA, used as the matrix, can also play the role of reductant, but its extent may be minor as compared with the added reductant. The effect of water is supported by the fact that a less hydrophilic polymer matrix such as poly(methyl methacrylate) does not exhibit photochromism even though the system contains an appreciable amount of reductants. 

It is noteworthy that the addition of lEE to poly(ABP) (Table 5) does not appreciably change the activity of poly(ABP), thus suggesting that the photoreduction of excited benzophenone chromophores is much more efficient when both ethereal groups and aromatic ketone moieties are attached to the same macromolecule. This behaviour can easily be explained in terms of a higher local concentration of ethereal functions around the benzophenone chromophores in poly(ABP-co-AEE) than in the corresponding poly(ABP)/IEE system. 

Free and polymer-bound 2-benzyloxy-thioxanthone exhibit similar flash photolysis behaviour and the same photoreduction quantum yield in the presence of 2-(A, AT-diethylamino) ethanol. This clearly shows that the polymeric nature does not appear to affect photophysical properties of the thioxanthone moiety. The photoinitiated polymerization of MMA in benzene solution, using BOTX and poly(StX-co-St) in combination with 2-(MA -dieffiylamino) ethanol, indicates that the polymer-bound chromophore seems to operate in the same way and with similar efficiency as the free photoinitiator, at least in conditions of dilute chromophore concentration. 

The photoreduction of aromatic ketones by polymeric systems having tertiary amine end groups provides an ele nt way for the preparation of block copolymers with high efficiency [138]. The method consists of the synthesis of the bifimctional azo-derivative 4,4 -azobis (iV,i -dimethylaminoethyl-4-cyano pentanoate) (ADCP), successively used as fiee radical thermal initiator for the preparation of tertiary amine-terminated poly(styrene). 

The topological control of such polymerization reactions has been the subject of recent extensive reviews,52 and the same phenomenon in 2,5-distyrylpyrazine has been further discussed.53 The true photopolymerization process discussed here is typified by the u.v.-induced polymerization of AW -polymethylenebis-(maleimides) discussed above,51 and a complete study of the kinetics of the process is included in this series of papers. The conclusion is reached that the triplet state of the chromophore is the reactive species this can be quenched by the addition of ferrocene or 3,3,4,4-tetramethyl-l,2-diazetine 1,2-dioxide. The kinetics of a further example of true photopolymerization, the reductive photocopolymerization of diaryl ketones, have been compared with those of the photoreduction of the model compound benzophenone and found to be similar.53 The photoreductive poly-recombination of the diaryl ketones shown in Schemes 2 and 3 has been studied extensively.54... 

Synthesis oxidative electropolymerization of phenazine in acid media in the dark [624], (The photoreduction of phenazine produces 1-hydroxyphenazine, and then poly(l-hydroxyphenazine) is formed.) Dehalogenation polymerization of 2,7-di-bromophenazine [595],... 

The photoreductive dimerization of aromatic diketones to high-molecular-weight poly(benzpinnacols) is an example of the involvement of a reactive ground state produced by a photochemical reaction ... 

Reversible formation of Ag nanoparticles onto transparent polymer films using an electrochemical technique has been reported (Black et al. 2007). It is known that Ag nanoparticles possess special optical properties (El-Noura et al. 2010). During the nanoparticle formation process, some colored Ag clusters appear, which can be photogenerated and stabilized inside a polymer matrix. An optically transparent film is mandatory for controlling the process of particle formation inside polymer film by means of spectroelectrochemistry. Based on this aspect, Ag nanoparticles were prepared by photoreduction of Ag+ ions in transparent cross-linked films made up of poly(vinyl alcohol) and poly(acrylic acid) (Chalal et al. 2012). For achieving nanoparticles with greater reversibility, a redox mediator (TMB +) was used. The principal role of these species is that they supply electrons that help oxidize silver clusters (Black et al. 2007). 

Lin F, Cheng SZD, Harris FW (2002) Aromatic poly(pyridinium salt)s. Part 3. Photoreduction in amide solvents. Polymer 43 3421-3430... 

Kamogawa H, Sato S (1988) Organic solid photochromism by photoreduction mechanism aryl viologens embedded in poly(N-vinyl-2-pyrrolidone). J Polym Sci Part A Polym Chem 26 653-656... 

I. Yu., Grineva, L.G., Polishchuk, A.P., and Chernega, A.N., Products of quaternization of 4,4 -bipyridine with halogenated carboxylic acids. Synthesis, structure and photoreduction in the crystalline state, Russ. J. Gen. Chem., 68, 609, 1998 (d) Suzuki, M., Kimura, M., Hanabusa, K., and Shirai, H., Reversible color changes induced by photosensitized charge separation in partially quaternized poly(l-vinylimidazole)-bound ruthenium(ll) complex and viologen hlms, Eur. Polym. 

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