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Emission measurements were performed on a series of σ−π conjugated organosilicon copolymers, −[(SiMe2)mA]n− (m = 1, 2, 3, 4, and 6), with alternating dimethylsilylene and π-conjugated units (A = phenylene, diphenylene, and anthranylene) in various solvents. The copolymers with m ≥ 2 exhibit a broad emission ascribable to an intramolecular charge transfer (CT) excited state resulting from the charge transfer between the dimethylsilylene and aromatic units. The solvatochromism of the emission spectra was observed for the organosilicon copolymers, where the emission maximum shifted to longer wavelength in polar solvents. The influence of the dimethylsilylene chain-length and the π-conjugated unit on the CT emission was investigated. The molecular orbital calculations on a model compound suggest that the vibronically structured emission is attributed to the π-character of the aromatic unit, and the structureless broad emission is ascribed to the σ-character of the Si−Si bond in the excited states. The emissio...

Copolymers of N-dodecylacrylamide (DDA), which form LB multilayers, and N-vinylcarbazole (Cz) with various copolymer compositions were prepared to investigate the photophysical behavior of the carbazole chromophore in a monolayer and LB multilayers. In LB multilayers, the emission spectra changed with the number of layers deposited. The excimer emission increases in the LB multilayers of a Y-type LB structure which have a head-to-head arrangement, due to effective energy migration between Cz chromophores. Inter- and intralayer energy transfer in the LB multilayers is suggested by the increase in the excimer emission up to the deposition of six layers

Axially chiral binaphthalene chromophores (BN) can be incorporated into polymer Langmuir-Blodgett (LB) films as comonomers of N-alkylacrylamides which have an excellent ability to form stable monolayers and LB multilayers. The spreading behavior of the copolymers of (S)-2-methoxy-1,1'-binaphthalen-2'-yl methacrylate ((S)-MeBN) or (S)-2-hydroxy-1,1'-binaphthalen-2'-yl methacrylate ((S)-HOBM) with N-decyl-(DA), dodecyl-(DDA), or tetradecylacrylamide (TDA) was investigated by a measurement of the surface pressure-area isotherms. The isotherms show that the copolymers, especially DDA copolymers, form a stable condensed monolayer on pure water and the axially chiral binaphthalene chromophore is dispersed uniformly, having its own surface area on water when the mole fraction of BN is less than ca. 20 mol%

Linear, branched, and network polysilanes were synthesized by the copolymerization of dichloromethylphenylsilane and trichlorophenylsilane. The influence of the Si-skeleton on absorption and emission spectra was investigated. The sharp σ-σ * absorption band (λ max 334 nm) of linear poly(methylphenylsilylene) changed into a broad one with branching. The shift of the absorption edge to a longer wavelength (410 nm) suggests that the increase of a-conjugation is due to the silicon network structure. The sharp emission (λ max 355 nm) of linear PMPS also shifted to the broad emission (λ max 471) for network poly(phenylsilyne)

Electron-tranfer of the excited carbazole chromophore in poly(N-dodecylacrylamide-co-N-vinylcarbazole)s (DDA/Cz) polymer monolayers by three different N-stearyl para-substituted pyridinium derivatives (X-Py) (p-COCH 3 , p-COOCH 3 , and p-CONH 2 ) has been investigated in Langmuir-Blodgett (LB) assembly systems by using a steady-state emission quenching method. Three different mixed monolayers of the pyridiniums with stearic acid (St) are in direct contact with the DDA/Cz monolayers having various Cz contents to investigate the influence of the redoc potentials of the quenchers and the effect of energy migration between the Cz chromophores on the electron-transfer quenching in the LB films

The transient absorption spectra obtained by the flash photolysis for the solution of nonalternating poly[(pentamethyldisilyl)styrene sulfone]s in THF showed the formation of benzyl radical as a transient intermediate whereas the spectra of the alternating polymer did not show the formation of this radical but theformation of the p-(pentamethyldisilyl)styrene monomer. The decay curve for an alternating polymer exhibited fast depropagation after the flash photolysis.

N-Vinylcarbazole (Cz), being nonamphiphilic, has been introduced into Langmuir-Blodgett (LB) film as a comonomer of N-dodecylacrylamide (DDA) which has an excellent ability to form monolayer and B multilayer. The spreading behaviors of the DDA/Cz copolymers with various Cz contents on a water surface were investigated by a measurement of the surface pressure-surface area isotherms

Etude de la cinetique, l'extinction par le methylviologene du complexe Ru(bpy) 3 2+ photoexcite dans des solutions aqueuses de poly(styrenesulfonate de sodium) et de copolymere styrenesulfonate de sodium/methacrylate de butyle. Les resultats montrent qu'un microdomaine constitue d'environ 43 unites styrenesulfonate est forme au voisinage du complexe sur la chaine de polymere, tout comme un domaine micellaire, et que l'extinction a lieu par concentration du viologene dans ces domaines. La taille de ces microdomaines est qua independante de la concentration et de la masse moleculaire du polymere

Photoinduced electron transfer of tris(4,7-diphenyl-1,10-phenanthroline)ruthenium (Ru(dpphen){sub 3}{sup 2+}) to stearyl viologen (SV{sup 2+}) in barium stearate LB assembly systems was investigated by a steady-state quenching method. The electron transfer from the excited state of Ru(dpphen){sub 3}{sup 2+} to SV{sup 2+} across two barium stearate monolayers was impossible by electron tunneling during the lifetime of Ru(dpphen){sub 3}{sup 2+*}. Even when the monolayer of the ruthenium complex is in direct contact with the layer of SV{sup 2+} quencher at the hydrophilic interface, the quenching of the ruthenium complex had low efficiency, indicating that Ru(dpphen){sub 3}{sup 2+} is located at a more hydrophobic region. In an assembly where both Ru(dppneh){sub 3}{sup 2+} and SV{sub 2+} exist within the same monolayer, the quenching efficiency depended strongly on the two-dimensional density of SV{sup 2+}. A good linear relationship of 1n (I{sub 0}/I) {minus} 1 vs the distance between the quencher molecules, which is calculated from the two-dimensional density, was obtained. This shows that electron-transfer rate decreases exponentially with distance and supports the conclusion that the electron-transfer quenching proceeds via an electron-tunneling mechanism. The half-quenching distance, which is defined as the distance giving half the emission intensity, was found to be 1.8 nm.

Three kinds of 6-(stearylamino)-1,3,5-triazine-2,4-dithiol (ST) and 6-(cis-9-octadecenylamino)-1,3,5-triazine-2,4-dithiol (OL) films, a cast film, and a LB film, were prepared and polymerized under UV light irradiation. The polymerization rate was influence by films structures and obeyed the rate equation of pseudo-first-order reaction for ST film and paraboric law for OL films

Le facteur de separation de la membrane composite preparee pour le systeme O 2 /N 2 atteint 2 entre 10 et 70 o C, avec une vitesse de permeation de l'oxygene variant entre 10 −4 et 10 −3 cm 3 /cm 2 s. cm Hg

Les resultats montrent que l'effet de l'hydrophobicite du dialkylviologene (l'effet de la longueur de la chaine alky) sur l'efficacite de l'extinction du complexe Ru(bpy) excite varie fortement avec le milieu reactionnel (solution aqueuse de poly (styrenesulfonate de sodium), de polystyrene latex ou solution organique)

Etude par cette methode des phenomenes de transition dans le processus d'agregation de ce copolymere greffe

Latex forme de p-styrenesulfonate de sodium, methacrylate de dodecyle et d'une tres petite quantite de vinylcarbazole

Etude de cette extinction pour des complexes RuL 3 2+ avec L=bipyridyle-2,2', phenanthroline-1,10 et diphenyle-4,7 phenanthroline-1,10. Observation d'une cinetique d'une extinction de pseudo 1er ordre pour les cations monovalents et multiexponentielle pour les cations divalents

Incorporation de polyvinylcarbazole, polyvinylnaphtalene et polystyrene dans une couche LB sous forme d'une couche monomoleculaire avec un acide gras, dispersion du polymere dans la couche monomoleculaire

The photogalvanic effect was studied for the Ru(bpy)/sub 3//sup 2 +/-benzenethiolate anion system. The illuminated electrode showed a negative potential against the dark one. The photocurrent was proportional to both light intensity and concentration of Ru(bpy)/sub 3//sup 2 +/, and the action spectrum coincided with the electronic absorption spectrum of Ru(bpy)/sub 3//sup 2 +/. The current generation mechanism was in agreement with the kinetic mechanism proposed for the previous flash photolysis study. The photogalvanic effect in this system is attributable to the formation of Ru(bpy)/sub 3//sup +/ from the electron transfer quenching of Ru(bpy)/sub 3//sup 2 +/ by benzenethiolate anion.

Dynamique des reactions de desexcitation des etats photoexcites de Ru(phen) 3 2+ et Ru(dppphen) 3 2+ par C n V 2+ (n=1, 2, 3, 4 et 6 pour CH 3 , C 2 H 5 , C 3 H 7 , C 4 H 9 et C 6 H 13 ) en solution micellaire de SDS. Etude par photolyse laser eclair. C n V 2+ est totalement solubilise en phase micellaire. La reaction de desexcitation est un processus de transfert d'electron du complexe de Ru (II) excite a C n V 2+ sur la surface du micelle SDS