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Skin hyperpigmentation disorders due to abnormal melanin production induced by ultraviolet (UV) irradiation are both a clinical and cosmetic problem. UV irradiation stimulates melanin production in melanocytes by increasing intracellular cAMP. Expression of heat shock proteins (HSPs), especially HSP70, is induced by various stressors, including UV irradiation, to provide cellular resistance to such stressors. In this study we examined the effect of expression of HSP70 on melanin production both in vitro and in vivo. 3-Isobutyl-1-methylxanthine (IBMX), a cAMP-elevating agent, stimulated melanin production in cultured mouse melanoma cells, and this stimulation was suppressed in cells overexpressing HSP70. IBMX-dependent transcriptional activation of the tyrosinase gene was also suppressed in HSP70-overexpressing cells. Expression of microphthalmia-associated transcription factor (MITF), which positively regulates transcription of the tyrosinase gene, was up-regulated by IBMX; however, this up-regulation was not suppressed in HSP70-overexpressing cells. On the other hand, immunoprecipitation and immunostaining analyses revealed a physical interaction between and co-localization of MITF and HSP70, respectively. Furthermore, the transcription of tyrosinase gene in nuclear extract was inhibited by HSP70. In vivo, UV irradiation of wild-type mice increased the amount of melanin in the basal layer of the epidermis, and this increase was suppressed in transgenic mice expressing HSP70. This study provides the first evidence of an inhibitory effect of HSP70 on melanin production both in vitro and in vivo. This effect seems to be mediated by modulation of MITF activity through a direct interaction between HSP70 and MITF.

Synthesis of N doped TiO2 films were conducted by the atmospheric controlled pulsed laser deposition (AC-PLD) method to generate visible light active photocatalytic films. In this method, the anion doped TiO2 films were synthesized on a quartz substrate by the irradiation of a pulsed Nd:YAG laser on a TiO2 target in the presence of gaseous nitrogen containing reagents at reduced pressure. For nitrogen doping, the use of CH3CN was found to be more effective than the use of NH3. The visible light absorption properties of the films were very sensitive to the CH3CN partial pressure during ablation. When using CH3CN, nitrogen and an equal quantity of carbon was uniformly doped into the TiO2 films. The resultant films showed better catalytic performance than those which were either un-doped or doped using NH3. The formation of nitrogen doped TiO2 is discussed by relating experimental results to thermodynamic considerations. It is also suggested that stronger reducing agents such as carbon are required for doping nitrogen into TiO2 films.

A Paraconiothyrium sp. WL-2 of Mn-oxidizing fungus is highly tolerant to Mn2+ ions, and capable of oxidizing more than 380 mg dm−3 of Mn2+ ions, leading to the formation of a large amount of insoluble Mn(III, IV) oxides. The biogenic Mn oxides were characterized by X-ray diffraction, FT-Infrared spectroscopy, elemental analysis, measurement of specific surface area, scanning electron microscopy, and measurement of zeta potential, in comparison with the synthetic Mn oxides. It was found that the biogenic Mn oxide is poorly crystalized birnessite, with higher porosity and much more weakly bounded Mn(II) on the surface than the synthetic Mn oxide. Cobalt(II) ions were sorbed and incorporated as Co(III) into the structure of the biogenic Mn oxide. Sorption efficiency in the biogenic Mn oxide was 5.6 times as high as that in the synthetic ones. Relation of the relased Mn2+ ions to the immobilized Co suggested that Mn(IV) is preferentially used as oxidants over Mn(III) in the biogenic Mn oxide, and emphasized that the existence of Mn(III) in the biogenic Mn oxide activates the geochemical cycles of Mn and the other involved elements in environments.

A sulfur-doped titanium dioxide thin film was prepared by pulsed laser deposition in the atmosphere controlled in carbon disulfide partial pressure. Optical and spectroscopic analyses demonstrated that the doped sulfur atom successfully triggered visible light sensitization by substituting with the lattice oxygen of titanium dioxide, which can absorb ultraviolet light only. As a result, photocatalytic hydrogen evolution activity of sulfur-doped titanium dioxide thin film was remarkably increased, compared with un-doped one. Moreover, an investigation on increase of the substrate temperature during laser ablation revealed that stabilization of sulfur atom in titanium dioxide was attained, resulting in high photocatalytic activity.

Sorption of Co(II) on the biogenic Mn oxide produced by a Paraconiothyrium sp.-like strain was investigated. The biogenic Mn oxide, which was characterized to be poorly crystalline birnessite (Na4Mn(III) 6Mn(IV) 8O27 ·9H2O) bearing Mn(III) and Mn(IV) in the structure, showed approximately 6.0-fold higher efficiency for Co(II) sorption than a synthetic Mn oxide. XP-spectra of Co 2p for the biogenic and synthetic Mn oxides after Co(II) sorption indicate that Co was immobilized as Co(III) on the surface of Mn oxides, clearly suggesting that redox reaction occurs between Co(II) ions and each Mn oxides. The Co(II) ions would be initially sorbed on the vacant sites of the surface of biogenic Mn oxide, and then oxidized to Co(III) by neighbor Mn(III/IV) atoms to release Mn(II). For the synthetic Mn oxide, release of Mn(II) was negligibly small because the oxidant is only Mn(IV) in ramsdellite (γ-MnO2). The Mn(II) release from the biogenic Mn oxide during Co(II) adsorption would be not only from weakly bounded Mn(II), but also from redox reaction between Mn(III/IV) and Co(II) ions.

We have measured absorption, photoluminescence, and photoluminescence excitation spectra, and the photoluminescence time response for films of silylene-biphenylene copolymer, ((C 6 H 4 ) 2 (Si(CH 3 ) 2 ) m ) n with m =1,2,4, and 6. The excitation spectra clearly reveal that the lowest absorption band in each copolymer consists of two bands, i.e., a band at 4.7 eV and a band of which energy depends on m . Since the latter band is absent in the copolymer with m =1, the former band is attributed to the lowest π − π * transition in biphenylene subunits. The latter band is attributed to the lowest σ − σ * transition in the silylene subunits, considering its dependence on m . In contrast to the result for solution, the peak energy of photoluminescence band is independent of m . The band has a Stokes shift of more than 1 eV and a large band width of 0.5 eV. The time responses of photoluminescence intensity consist of more than two decay components and the intensity decays more slowly at smaller energy. The large Stokes shift is explained as due to excimer formation between biphenylene subunits. In order to explain the energy dependence of time responses, energy migration is discussed.

We have measured the absorption, photoluminescence, photoluminescence excitation spectra and the time response of luminescence intensity of the permethyl-hexasilane ( Si 6( CH 3)14) glass and permethyldodecasilane ( Si 12( CH 3)26) in 3-methylpentane solution. The Si 6( CH 3)14 oligomer shows a strong lattice relaxation in the photo-excited state and we have determined the parameters in configuration coordinate of Si 6( CH 3)14 oligomer. The luminescence is attributed to the self-trapped exciton state. The Si 12( CH 3)26 oligomer has several conformers at room temperature and only one conformer at 77 K. The Si 12( CH 3)26 shows a weak lattice relaxation at room temperature and form free excitons at 77 K.

We report here the measurements of the absorption spectra, photoluminescence spectra and the time response of the luminescence intensity in poly(di-n-hexylsilane) film at 2 K. The excitation energy dependence of the luminescence peak and the rise time of 70 ps are observed. In order to explain these results, numerical diagonalization of a one-dimensional Frenkel exciton Hamiltonian with disorder has been carried out, and the luminescent process is formulated with the assumption that the exciton does not change the site by phonon scattering. We have estimated the transition dipole moment μ0 = 0.92 × 10−29 C m and the transition time ctr = 1.2 × 1012 s−1. We also discuss the role of hidden structures at the low-lying exciton states which appear in the site representation of exciton wave functions.

The laser chemical vapor deposition (CVD) using dichloromethyl phenylsilane as a monomer gave a polysilane film on a substrate. The micropatterns of the polysilane with the resolution of about 300 μm were formed by laser projection CVD through a photomask. The silylene was observed by laser flash photolysis of dichloromethyl phenylsilane as a transient intermediate during the photochemical reaction. The transient absorption spectrum and the molecular orbital (MO) calculation suggest the formation of the methylphenylsilylene by the cleavage of the Si Cl bond of the dichloromethylphenylsilane. The elemental composition by XPS spectra showed the higher Si:C ratio of the polysilane film compared to the monomer, which implies the existence of the silicon network structure. The time-resolved emission spectra of the polysilane film were similar to that of the network polysilane. The optical band gap of polysilane film was decreased with increasing laser excitation power.

Side-chain polymer liquid crystals that possess mesogenic donor-π-acceptor chromophores (azobenzene and stilbene derivatives) and a chiral unit were synthesized, and the efficiencies of the second harmonic generation (SHG) of these polymers were investigated. It was found that these polymers exhibited SHG susceptibility without the application of high voltage.

The protonation effect on the first hyperpolarizability β of 2-amino-5-nitropyridine (2A5NP) is examined by Hyper-Rayleigh Scattering (HRS). Using the HRS technique, the β value of the protonated 2A5NP in acetone is determined to be 22.5 × 10−30 esu, small in comparison to the value for the neutral form. The measurement is repeated in 1,4-dioxane and methanol solutions to examine the influence of the solvent on β. β depends on the reaction field, which is written as a function of the dielectric constant of the solvent, the variation of β in methanol is inconsistent. From this, it is deduced that the first hyperpolarizability of 2A5NP decreases more significantly by hydrogen bond solvent interactions than by protonation.

Side-chain polymer liquid crystals that possess mesogenic donor-π-acceptor chromophores (azobenzene and stilbene derivatives) were synthesized, and the efficiencies of second harmonic generation (SHG) were investigated. SHG susceptibility was found to be stabilized in liquid crystalline polymers. Hyperpolarizabilities (β) of chromophores of the polymers were also investigated by the hyper Rayleigh scattering method, and it was found that the β value of the polymers was nearly twice of that of the corresponding monomers. The magnitude of the β of polymers was affected by the length of the spacer unit that connects the chromophore (mesogen) to the polymer main chain.

Third-order nonlinear susceptibilities (χ(3)) for thin films of oligo- and polygermanes were measured in the range of 0.6—86 × 10−12 esu. A measured χ(3)of 86 × 10−12 esu for a polygermane–polysilane random copolymer, coploy(methylphenylsilylene/methylphenylgermylene), was the largest ever reported for transparent polymers in the visible spectral region.

The thin films of semiconducting polymers such as poly(N-vinylcarbazole), polythiophene, polypyrrole, and polyaniline were formed by the laser chemical vapor deposition (CVD). The 355-nm laser excitation of N-vinylcarbazole deposited on a quartz substrate gave the poly(N-vinylcarba-zole) film with the molecular weight Mw=11860 (Mw/Mn=7.18). The sandwich excimer/second excimer emission ratio of the time-resolved emission spectra suggested the isotactic structure of the poly(N-vinylcarbazole) film prepared by the laser CVD. The micropatterns of the poly(N-vinylcarbazole) with the resolution of about 20μm were formed by the laser irradiation through a photomask. The laser flash photolysis of the N-vinylcarbazole showed the generation of the radical cation, which suggests the cationic polymerization mechanism. The optical band gap of polythiophene film was decreased with increasing laser excitation power.

Rechargeable cells with a sulfur cathode, a lithium anode and a nonaqueous electrolyte operating at ambient temperature have been extensively studied as a possible application of sulfur combined with nonaqueous solvent. However, the behavior of the chemical species formed by the reduction of sulfur with alkali metals in nonaqueous solvent has not yet been clarified. In this report, sulfur is reduced in tetrahydrofuran (THF) by alkali metals (M: Na, K, Li and Cs), by anthracene radical anions or by diphenylethylene dimer dianions with alkali metal counter cations mainly under the experimental condition of [S 8 ] [M] > 0.25 . The system produced by the reduction is the yellow solution consisting of polysulfide dianions (Sm2−, m > 1) and radical anions (Sn−, n > 1) which changes into a blue solution by the addition of hexamethylphosphoric triamide with a much higher polarity than THF. The influence of the kind of alkali metal, the temperature and the addition of solvents such as crown ether on the behavior of the chemical species formed are examined by ultraviolet (uv)-visual electronic spectra, electron spin resonance (ESR) spectra and Raman spectra measurements. In addition, γ-irradiation with 60Co was carried out to reduce sulfur in glassy solid 2-methyl-THF at — 196 °C. Furthermore, the reaction between the yellow solution and aliphatic bromide is investigated. As a result, it is revealed that the yellow species is S42−, the blue species is S3− and several polysulfide dianions and radial anions are in a state of equilibrium.

Branced oligogermynes were prepared both by Wurtz coupling reactions of alkyl- and phenyl-trichlorogermanes with sodium metal and by the reaction of alkyltrichlorogermanes using of samarium(II) diiodide. Upon ultraviolet irradiation of oligo(phenylgermyne) in air, the germanium–germanium bond in an oligo(phenylgermyne) film changed into a digermoxane chain. The laser flash photolysis of the oligo(phenylgermyne) film showed the formation of a germyl radical as a reactive intermediate during photodegradation. The formation of germanium carbide (Ge–C) and germanium dioxide (GeO2) was observed upon a heat treatment of unirradiated and irradiated oligo(phenylgermyne) films, respectively. A relatively high-resolution GeC/GeO2 micropatterning was obtained by combining the photochemical and thermal properties of branced oligogermynes.

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...

The electrochemical behaviour of the silylene-phenylene, silylene-thienylene, silylene-diphenylene and silylene-anthranylene copolymers was investigated using cyclic voltammetry. The oxidation potentials of these organosilicon copolymers decreased with increasing dimethylsilylene chain length. The change of the oxidation potential was explained by considering the σ-π conjugation between the dimethylsilylene chain and the π unit. The cyclic voltammograms of the organosilicon copolymers showed the characteristics of an irreversible system. The absorption spectra showed the degradation of the Si-Si chain of the organosilicon copolymers by electrochemical oxidation. The molecular orbitals' were calculated to discuss the σ-π conjugation state and to identify the oxidation site in the polymer chain.

We report here measurements of the photo-luminescence spectra and the time response of the σ-conjugated polymer, poly(methylphenylsilane), film at 2 K. The site-selective luminescence and the time response are discussed in terms of the exciton band model and localized states in disordered system.

Poly(phenylsilyne) and poly(phenylgermyne), which have a network Si- and Ge-skeleton, were synthesized by electrochemical reduction of trichlorophenylsilane and trichlorophenylgermane, respectively. The poly(phenylsilyne) showed broad absorption and emission bands that are characteristic of silicon network polymers. Similarly broad absorption and emission bands were observed for the poly(phenylgermyne). Radical anions and radical cations of poly(phenylsilyne) and poly(phenylgermyne) were produced by pulse radiolysis. The radical ions of these network polymers showed broad transient absorption bands from the UV to the IR region. Within 200 ns after pulse radiolysis, the absorption band of the radical cation in the UV region decreased, whereas the band in the IR region increased. The time-dependent spectral change of the radical cation suggests the formation of a change resonance band of the delocalized positive charge on the σ-conjugated polymer chain. In contrast to the radical cation, the radical anion of the network polymers did not show a spectral change.

High‐resolution micropatterning of SiC/SiO2 was achieved by combining the photochemical and thermal properties of poly(phenylsilyne) having Si‐network structure. The laser flash photolysis of poly(phenylsilyne) film showed the formation of silyl radical as an intermediate during photodegradation. The XPS spectrum of the Si—Si chain changed into that of the siloxane chain by photo‐oxidation in air. FT‐IR spectra showed the formation of SiC and SiO2 by the heat treatment of unirradiated and irradiated poly(phenylsilyne) films, respectively. SiC/SiO2 micropatterning was obtained by the heat treatment of poly(phenylsilyne) film after ultraviolet irradiation with a photomask.

Silylene-phenylene and silylene-thienylene copolymers were prepared by the reactions of α,ω-dichloropermethylated oligosilanes with 1,4-dilithiobenzene and 2,5-dilithiothiophene respectively. All the copolymers were soluble in a wide range of organic solvents. The influence of the chain length of the dimethylsilylene unit in the copolymer backbone on the electronic absorption spectra was investigated. The enhancement of σ-π conjugations between the dimethylsilylene units and the π-conjugated units with increasing dimethylsilylene chain length was suggested by the thermochromism.

UV-induced wrinkle formation owing to the degeneration of the extracellular matrix (ECM) is a major dermatological problem in which abnormal activation of matrix metalloproteinases (MMPs) and elastases have important roles. Heat shock protein 70 (HSP70) has cytoprotective and anti-inflammatory activities. In this study, we examined the effect of HSP70 expression on UV-induced wrinkle formation. Mild heat treatment (exposure to heated water at 42 °C) of the dorsal skin of hairless mice induced the expression of HSP70. The long-term repeated exposure to UV induced epidermal hyperplasia, decreased skin elasticity, degeneration of ECM, and wrinkle formation, which could be suppressed in mice concomitantly subjected to this heat treatment. The UV-induced epidermal hyperplasia, decreased skin elasticity, and degeneration of ECM were less apparent in transgenic mice expressing HSP70 than in wild-type mice. UV-induced fibroblast cell death, infiltration of inflammatory cells, and activation of MMPs and elastase in the skin were also suppressed in the transgenic mice. This study provides evidence for an inhibitory effect of HSP70 on UV-induced wrinkle formation. The results suggest that this effect is mediated by various properties of HSP70, including its cytoprotective and anti-inflammatory activities. We propose that HSP70 inducers used in a clinical context could prove beneficial for the prevention of UV-induced wrinkle formation.

Various aromatic chromophores were incorporated into polymer Langmuir-Blodgett (LB) multilayers as comonomers of copolymers of N -alkylacrylamides (AA). The monolayer formation of the naphthalene copolymers is investigated in detail by measurement of the surface pressure-area isotherms. The fluorescence spectra for the LB multilayers were measured as functions of the deposited layer and the alkyl chain length of AA. The excimer emission intensity increased with increasing number of deposited layers when the effective intralayer and interlayer energy transfer to the excimer forming sites is taking place. The efficiency of vertical energy transfer in the Y-type LB films for naphthalene, pyrene, carbazole and fluorene chromophores was safely judged from the increase in the excimer emission intensity as a function of the type of deposited layer in the fluorescence spectra. The limiting energy transfer distances for each chromophores are correlated with critical energy transfer distances of Forster type.

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

New σ-π conjugated alternating silylene-diacetylene copolymers, –[(SiMe2)m–C≡C–C≡C]n–, m = 1, 3, 4, and 6, were synthesized by the reaction of α,ω-dichloropermethylated oligosilanes with dilithiobutadiyne, LiC≡C–C≡CLi. The IR spectra clearly indicated the presence of diyne unit in the polymer backbone. The influence of the chain length m of the dimethylsilylene unit in the –[(SiMe2)m–C≡C–C≡C]n– backbone on the optical and the electrical properties was investigated.

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%

The formation of amorphous silicon using a silicon network polymer as a precursor was investigated. Poly( n -propylsilyne), which has a silicon network structure, was heat-treated in vacuo. The organic side group of poly( n -propylsilyne) disappeared completely and the optical band gap E g,opt decreased from 2.91 to 1.29 eV by heat-treatment at 400°C. The heat-treated poly( n -propylsilyne) showed a far-infared absorption spectrum similar to amorphous silicon.

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)

Ring-opening radical polymerization has been followed by the flash photolysis method. As an initiator radical, the arylthiyl radical (ArS˙) was used; the addition reaction rate constants of ArS˙ to vinyl monomer containing epoxy-ring such as vinyloxiranes have been determined at first. The rate constant of ring opening reaction of the adduct radical changing to ArSCH2CH CROCH2˙ were determined in the form of the relative values, which were converted to the absolute values. The ring-opening reaction rate constants were ca. 106 s−1, which indicates that the ring-opening rates are faster than usual radical propagation rates. The rate constants for vinyl monomer with 5-member ring (1,4-epoxy-1,4-dihydronaphthalene) were similarly evaluated.

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

Poly(p-tert-butylstyrene), poly(p-tert-butylstyrene sulfone), poly(p-trimethylsilylstyrene), and poly(p-trimethylsilylstyrene sulfone) films were ablated with a 248 nm excimer laser. Emission spectra of decomposed products such as Si atoms and C2 as well as CN molecules were measured, while no information of S atoms was obtained. The effects of contained Si and S atoms upon laser ablation were examined, and the ablation dynamics was discussed.

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.

On heating films of long-chain alkylamino-1,3,5-triazine-2,4-dithiols, substituted with unsaturated groups in the 6-position, on copper plates in air, the films become partially insoluble in benzene. The polymerization rate and monomer conversion increased with temperature above 80°C and with time. At low temperatures, an induction period was observed. The detailed behavior was dependent upon the number and length of the alkyl chains. Films with high packing density polymerized more slowly. In the presence of azobis(isobutyro)nitrile (AIBN) and benzoyl peroxide (BPO), the rate and conversion increased and the induction period disappeared. The optimum concentration of initiators was approximately 0.0025 mol% of monomer. The polymerization of the films was initiated by oxygen activated with copper, or by radicals derived from AIBN and BPO. It is proposed that the growth of polymer proceeded mainly by the addition of thiyl radicals to unsaturated groups, the insoluble polymers being formed by the coupling of thiyl radicals.

We have measured the time response of luminescence intensity in poly(di-n-hexylsilane) films with the excitation density from 1.2×1018 to 1.1×1020 excitons cm−3 at 2 K. At 1.1×1020 cm−3, we found that the rise time is 1.4±0.5 ps and that the decay is nonexponential. The rise time is attributed to the exciton–exciton scattering time in which initially photo-generated excitons at 4 eV are scattered to the luminescent states at 3.4 eV. The nonexponential decay is ascribed to the bimolecular annihilation of excitons with the rate constant γ2 of (1.0±0.5)×10−8 cm3 s−1. A microscopic mechanism to explain this large γ2 is discussed.

We have measured absorption spectra, luminescence spectra and the time response of luminescence intensity in σ – π conjugated polymers of silylene–biphenylene copolymers in tetrahydrofuran solution at room temperature. In order to investigate the σ -conjugated length dependence of optical properties, we have prepared the three copolymers which have different silylene chain lengths of m =1, 2 and 6. It is found that the excitations are strongly localized at biphenylene units for m =1 and that a strong lattice relaxation occurs for m =2. For m =6, the charge transfer excitation from silylene units to biphenylene units is indicated.

The Q and e values of the radical copolymerization in solution indicate that N-dodecylacrylamide tends to copolymerize with various comonomers with various comonomers via radical copolymerization. This monomer is found to have an excellent ability to prepare a stable monolayer and LB multilayer in the form of polymer.

Ring-opening radical polymerization has been followed by the flash photolysis method. As an initiator radical, the arylthiyl radical (ArS˙) was used; the addition reaction rate constants of ArS˙ to vinyl monomer containing epoxy-ring such as vinyloxiranes have been determined at first. The rate constant of ring opening reaction of the adduct radical changing to ArSCH2CH CROCH2˙ were determined in the form of the relative values, which were converted to the absolute values. The ring-opening reaction rate constants were ca. 106 s−1, which indicates that the ring-opening rates are faster than usual radical propagation rates. The rate constants for vinyl monomer with 5-member ring (1,4-epoxy-1,4-dihydronaphthalene) were similarly evaluated.

It is reported that a very loosely packed monolayer of triazine dithiols on water undergoes oxidative polymerization at remarkably higher rates than close packed or ordered LB films.

The copolymers of [Ru(bpy)2(Vbpy)]2+ and N-dodecylacrylamide (DDA) form a stable condensed monolayer on a water surface and the monolayers could be transferred onto solid supports, yielding the Y-typed (bilayer type) ruthenium(II) complex-containing polymer Langmuir–Blodgett (LB) films.

The reaction rate constants for halogen abstraction of Ph3Sn· and Ph3Si· have been determined by xenon-flash photolysis method. The absolute rate constants for the reactivity of Ph3Sn· with several alkyl halides have been compared with the relative ones; the agreement between the both methods was fairly good. For Ph3Sn·, the rate constant (in unit of mol−1 dm3 s−1) of n-BuCl (5.2×102) was smaller than that of n-BuBr (3.1×106) by a factor of ca. 1⁄104. With changing the alkyl halides, the rate constants for Ph3Si· and Ph3Sn· varied similarly, although the rate constants for Ph3Si· were larger than those for Ph3Sn· by factors of 50–100. The reactivity of alkyl halides increased with a decrease in the bond-dissociation energy of the R–X (X=Cl, Br).

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