Masahiro Teraguchi

Optical Properties and Blue and Green Electroluminescence in Soluble Disubstituted Acetylene Polymers

Intense photoluminescence (PL) was observed in soluble disubstituted polyacetylenes such as poly(1-phenyl-2- p-adamantylphenyl acetylene (PDPA-Ad) at 530 nm, poly(1-phenyl-2- p-triphenylsilylphenyl acetylene) (PDPA-TPSi) at 530 nm and poly(1-hexyl-2-phenyl acetylene) (PHxPA) at 455 nm, although they are considered to be derivatives of trans-polyacetylene. In monosubstituted acetylene polymers such as poly( o-trimethylsilylphenyl acetylene) (PTMSiPA), PL was negligible. Green and blue light emissions were observed from an electroluminescent (EL) device having soluble poly(diphenyl acetylene) (PDPA) derivatives (PDPA-Ad and PDPA-TPSi) and PHxPA as emission layers, respectively. EL emission is clearly observable under normal room illumination conditions. The electronic energy structures of the disubstituted PA derivatives are also discussed to interpret PL and EL characteristics.

Optical properties of disubstituted polyacetylene thin films

We have studied the optical properties of thin films of novel disubstituted acetylene polymers such as poly(1-phenyl-2-p-nbutylphenylacetylene) (PDPA-nBu) and poly(1-n-hexyl-2-phenylacetylene) (PHxPA), that show high photoluminescence (PL) quantum efficiency in comparison with unsubstituted or monosubstituted polyacetylene. The polarization dependence of PL and Raman scattering of PDPA-nBu and PHxPA have been studied in order to clarify the emission mechanism. Assuming the model of short polyene conjugation length in the acetylene polymers, we estimate the average conjugation length from the respective stretching vibration frequency of the carbon=carbon double bond. The emission mechanism of PHxPA and PDPA-nBu is discussed in relation with the electronic excited states of these polymers # 2001 Elsevier Science B.V. All rights reserved.

Synthesis of conjugated polymers with azobenzene moieties in the main chain

Poly(phenylenevinylene)-based conjugated polymers with azobenzene groups in the main chains were prepared by the Pd-catalyzed coupling polymerization of divinylarenes with dihaloarenes. The Pd-catalyzed coupling polymerization of 4,4′-divinylazobenzene with dihaloarenes such as 1,3-dibromobenzene, 1,4-dibromo-2,5-dihexylbenzene, 4,4′-dibromoazobenzene, and 4,4′-diiodoazobenzene resulted in polymers with poor solubility. In contrast, soluble polymers containing azobenzene moieties in the main chains were attainable from divinylbenzenes with 4,4′-dihaloazobenzenes if either or both of the monomers possessed hexyl groups on the aromatic rings. The number-average molecular weight of the polymer exceeded 10,000 under optimized conditions, and the polymer showed a remarkably redshifted absorption in the visible region (456 nm). 1H NMR and IR spectra supported that the polymers having only trans-geometry for the double bonds.

Study of high permeability polymers by means of the spin probe technique

Abstract The spin probe technique was systematically applied to study a family of high permeability and high free volume glassy polymers. Rotation correlation times τ c or frequencies ν=1/τ c of 2,2,6,6-tetramethylpyperidine-1-oxyl (TEMPO) were measured in amorphous teflons — random copolymers of tetrafluoroethylene and 2,2-bistrifluoromethyle-4,5-difluoro-1,3-dioxole, polyacetylenes and polynorbornenes. Polymers distinguished by unusually high, for the glassy state, permeability and free volume exhibit large rotational mobility of TEMPO. The correlation times correspond to fast rotation of the spin probe previously observed only in rubbery polymers. Correlations between the frequency ν and gas permeability and diffusion coefficients were observed. However, in some polymers, the spin probes rotation rate is also sensitive to side-chain local mobility, which does not affect translational diffusion coefficients of gas molecules in polymers.

Donor polymer (PAT6) — acceptor polymer (CNPPV) fractal network photocells

Abstract Unique characteristics such as quenching of photoluminescence and improvement of photovoltaic effect were observed in donor polymer-acceptor polymer composites, PAT6-CNPPV system and PDPATPSi-CNPPV system. Electronic energy structures of these polymers were determined and these characteristics are interpreted in terms of photoinduced charge transfer between donor polymer (PAT6 and PDPATPSi) and acceptor polymer (CNPPV) and formation of fractal network .

Optical properties and electroluminescence characteristics of polyacetylene derivatives dependent on substituent and layer structure

Abstract Intense photoluminescence (PL) is observed in di-substituted polyacetylene derivatives even though solitonic mid-gap absorption is observed upon doping, contrary to non-substituted trans-polyacetylene and mono-substituted polyacetylene in which strong PL is not observed. Intense green and blue electroluminescence (EL) is realized utilizing poly(diphenylacetylene) derivatives and poly(1-alkyl-2-phenylacetylene) derivatives, respectively. Greenish-blue emission is also observed in poly (1-chloro-2-phenylacetylene) derivatives. The dependence of wavelength and intensity of PL and EL on the molecular structure of substituents is clarified in detail. The effects of molecular alignment and layer structure on the EL characteristics are also discussed. Upon intense light excitation, remarkable spectral narrowing due to stimulated emission is also observed in these di-substituted polyacetylene derivatives.

Exciton dynamics in disubstituted polyacetylenes

Exciton dynamics in luminescent poly(diphenylacetylene) (PDPA) derivatives with different substituents have been studied by time-resolved photoluminescence (PL) spectroscopy. Although their absorption and PL spectra are almost similar, PL of PDPA-nBu decays single-exponentially, whereas PL of PDPA-SiMe 3 decays faster with a suppressed exponential decay function indicating exciton dissociation, In the case of PDPA-nBu mixed with a non-luminescent polyphenylacetylene (PPA) derivative, PL decay of PDPA-nBu is significantly shortened. The experimental results show the influences of side chains on exciton confinement in the backbone/main chain. Efficient PL in PDPA-nBu is a result of effective exciton confinement on the main chain, but excitons migration or energy transfer to another main chain segments may take places.

Local mobility of substituted polyacetylenes measured by quasielastic neutron scattering and its relationship with gas permeability

Abstract Local mobility of three substituted polyacetylenes was investigated by means of a quasielastic neutron scattering technique aiming at elucidating the origin of gas permeability of these polymers. It was found that the local flux, which is defined as the product of the relaxation rate Γ, and the mobile fraction f m , increases with the gas permeability coefficient. This suggests that the local flux is an important factor controlling gas permeability.

Synthesis and properties of polyacetylenes with adamantyl groups

Three disubstituted acetylenes with an adamantyl group—1-(p-adamantylphenyl)-2-chloroacetylene (ClpAdPA), 1-(p-adamantylphenyl)-1-propyne (pAdPP), and 1-(p-adamantylphenyl)-2-phenylacetylene (pAdDPA)—polymerized in good yields in the presence of MoCl5- or TaCl5-based catalysts. The highest weight-average molecular weights of poly(ClpAdPA), poly(pAdPP), and poly(pAdDPA) reached 3.6 × 105, 1.1 × 106, and 6.0 × 106, respectively. The polymers were yellow to white solids and completely soluble in toluene, chloroform, and so forth. These polymers thermally were fairly stable, and the onset temperatures of weight loss in air were over 360 °C. Poly(pAdPP) and poly(pAdDPA) provided free-standing films by solution casting, and their oxygen permeability coefficients (PO2) at 25 °C were 8.6 and 55 barrers [1 barrer = 1 × 10−10 cm3 · (STP) · cm/(cm2 · s · cm Hg)], respectively, which are relatively small compared to those of other substituted polyacetylenes.

Gas permeability and hydrocarbon solubility of poly[1‐phenyl‐2‐[p‐(triisopropylsilyl)phenyl]acetylene]

The effects of film thickness, physical aging, and methanol conditioning on the solubility and transport properties of glassy poly[1-phenyl-2-[p-(triisopropylsilyl) phenyl]acetylene] are reported at 35 °C. In general, the gas permeability coefficients are very high, and this polymer is more permeable to larger hydrocarbons (e.g., C3H8 and C4H10) than to light gases such as H2. The gas permeability and solubility coefficients are higher in as-cast, unaged films than in as-cast films aged at ambient conditions and increase to a maximum in both unaged and aged as-cast films after methanol conditioning. For example, the oxygen permeability of a 20-μm-thick as-cast film is initially 100 barrer and decreases to 40 barrer after aging for 1 week at ambient conditions. After methanol treatment, the oxygen permeabilities of unaged and aged films increase to 430 and 460 barrer, respectively. Thicker as-cast films have higher gas permeabilities than thinner as-cast films. Propane and n-butane sorption isotherms suggest significant changes in the nonequilibrium excess free volume in these glassy polymer films due to processing history. For example, the nonequilibrium excess free volume estimated from the sorption data is similar for as-cast, unaged samples and methanol-conditioned samples; it is 100% higher in methanol-conditioned films than in aged, as-cast films. The sensitivity of permeability to processing history may be due in large measure to the influence of processing history on nonequilibrium excess free volume and free volume distribution. The propane and n-butane diffusion coefficients are also sensitive to film processing history, presumably because of the dependence of diffusivity on free volume and free volume distribution.