Naoto Tsutsumi

Nonlinear optical (NLO) polymers. 3. NLO polyimide with dipole moments aligned transverse to the imide linkage

This paper presents a new class of nonlinear optical (NLO) polyimide for second harmonic generation (SHG). This new class of NLO polyimide consists of 2,4-diamino-4‘-nitroazobenzene (2R-DIAMINE) with 3,3‘4,4‘-benzophenonetetracarboxylic dianhydride, in which the NLO dipole moment is aligned transverse to the main chain. 2R-DIAMINE was prepared from m-phenylenediamine with p-nitroaniline. The time dependence of the decay was found to be well-fitted by a Kohlrausch−Williams−Watts stretched exponential function. The difference of the orientational relaxation among the samples with different glass transition temperatures can be compared using the scaling relation of τ = A‘ exp[(T0 − T)/T] in which τ is the relaxation time and T0 is the effective transition temperature for SHG activity. T0 is in good agreement with the corresponding glass transition temperature. Enhanced orientational stability of the aligned NLO chromophore is ascribed to the rigid structure of the polyimide backbone. For the orientational re...

Synthesis and enzymatic degradation of poly(tetramethylene succinate) copolymers with terephthalic acid

Abstract Poly(tetramethylene succinate/terephthalate) copolymers were prepared by melt polycondensation of succinic acid (4) and dimethyl terephthalate (T) with 1,4-butanediol (4G). The structure and physical properties of these copolymers were characterized by 1H NMR, solution viscosity, differential scanning calorimeter and tensile test. The enzymatic degradation was performed in a buffer solution with Rhizopus delemar lipase at 37°C. The highest degradation rate was observed for T-17 film due to the depressed crystallinity. T-17 film uniaxially drawn with draw ratio of three times showed the larger tensile strength as well as the much faster degradation rate compared with 4G4 film.

Thin-film waveguiding mode light extraction in organic electroluminescent device using high refractive index substrate

The redistribution of thin-film waveguiding emitted light from an organic electroluminescent (EL) layer using high refractive index substrates has been investigated. The internally emitted light can be classified in terms of three modes: external, substrate, and indium-tin-oxide (ITO)∕organic modes. According to classical ray optics theory, the ITO∕organic mode emission can be completely redistributed to the substrate mode when the refractive index of the substrate becomes larger than that of the emitting layer. The redistributed substrate mode emission should be able to be easily extracted by an uneven surface, such as a microlens array. With this understanding, we prepared organic EL devices in which the substrate refractive index was varied over a range. However, redistribution of the ITO∕organic mode emission to the substrate mode was not observed experimentally in our EL devices. In addition, there was no difference in the luminous intensity improvement between glass (n=1.52) substrate and high refra...

Improvement of coupling-out efficiency in organic electroluminescent devices by addition of a diffusive layer

We demonstrated that the diffusive layer laminated to glass substrate surface increased the light output of organic electroluminescent devices by extracting and reemitting light trapped in the substrate of such devices. Lamination of the diffusive layer improved the efficiency of the coupling-out factor, which was also changed by the thickness of the electron transporting layer (ETL). High total emitting flux for the sample with ETL thickness around quarter wavelength optical thickness (QWOT) was not improved significantly by lamination of the diffusive layer. Conversely, low total emitting flux for the sample with ETL thickness around 2QWOT without the diffusive layer was largely increased by the lamination of the diffusive layer, which was due to the extraction of waveguided light from the substrate mode. As the results, large dependence of total emitting flux on ETL thickness was significantly minimized by the lamination of diffusive layer. In addition, lamination of the diffusive layer also significan...

Real-time three-dimensional holographic display using a monolithic organic compound dispersed film

Organic holographic materials such as photorefractive polymers are one of the promising candidates for the next generation three dimensional (3D) real-time display. Recently, we found that polymer composite of monolithic organic compound of 3-[(4-nitrophenyl)azo]-9H-carbazole-9-ethanol (NACzE) (30 wt%) doped transparent polymethylmethacrylate (PMMA) had capability of recording and displaying new images within a few seconds and fixed at ten seconds and viewing for a longer time without applying electric field. Here, we present 3D holographic display using monolithic organic compound NACzE dispersed transparent PMMA film sandwiched between two glass plates with size of 7.5 × 5 cm2. The thickness of film is ca. 50 μm. Images are easily and completely erased by over recording and it is accelerated by slight heating.

Biodegradability of poly(ethylene terephthalate) copolymers with poly(ethylene glycol)s and poly(tetramethylene glycol)

Poly(ethylene terephthalate) copolymers were prepared by melt polycondensation of dimethyl terephthalate and excess ethylene glycol with 10-40 mol% (in feed) of poly(ethylene glycol) (E) and poly(tetramethylene glycol) (B), with molecular weight (MW) of E and B 200-7500 and 1000, respectively. The reduced specific viscosity of copolymers increased with increasing MW and content of polyglycol comonomer. The temperature of melting (T m ), cold crystallization and glass transition (T g ) decreased with the copolymerization. T m depression of copolymers suggested that the E series copolymers are the block type at higher content of the comonomer. T g was decreased below room temperature by the copolymerization, which affected the crystallinity and the density of copolymer films. Water absorption increased with increasing content of comonomer, and the increase was much higher for E1000 series films than B1000 series films. The biodegradability was estimated by weight loss of copolymer films in buffer solution with and without a lipase at 37°C. The weight loss was enhanced a little by the presence of a lipase, and increased abruptly at higher comonomer content, which was correlated to the water absorption and the concentration of ester linkages between PET and PEG segments. The weight loss of B series films was much lower than that of E series films. The abrupt increase of the weight loss by alkaline hydrolysis is almost consistent with that by biodegradation.

Synthesis, characterization, and enzymatic degradation of network aliphatic copolyesters

Network copolyesters were prepared from glycerol (Yg) and sebacic acid (10) with 10–90 mol % of either succinic acid (4), 1,12-dodecanedicarboxylic acid (14), 1,18-octadecanedicarboxylic acid (20), or terephthalic acid (T). Prepolymers prepared by melt-polycondensation were cast from dimethylformamide solution and postpolymerized at 230–250°C for various periods of time to form a network. The resultant films were transparent, flexible, and insoluble in organic solvents. The network copolyesters obtained were characterized by infrared absorption spectra, wide angle X-ray diffraction analysis, density measurement, thermomechanical analysis, differential scanning calorimetry, and tensile test. The enzymatic degradation was estimated by weight loss of the network copolyester films in a buffer solution with Rhizopus delemar lipase at 37°C. The weight loss due to the enzymatic degradation was decreased with increasing comonomer content, and the copolyesters with Yg4, Yg20 and YgT more than 50 mol % were not degraded by lipase enzyme at all. On the contrary, Yg-10/14 films were degraded appreciably over whole range of comonomer composition. With increasing comonomer content, the heat distortion temperature increased gradually, while the tensile strength and Youngs modulus were not changed much.

Poly(ethylene terephthalate) copolymers with a smaller amount of poly(ethylene glycol)s and poly(butylene glycol)s

Abstract Poly(ethylene terephthalate) copolymers were prepared by melt polycondensation of dimethyl terephthalate and excess amount of ethylene glycol with 2–20 mol% of poly(ethylene glycol) (E) or poly(butylene glycol) (B), where the molecular weights (MW) of E and B are 200–7500 and 1000–3000, respectively. Reduced specific viscosity of copolymer increased with increasing MW and the content of polyglycol comonomer. Temperatures of glass transition (Tg), cold crystallization and melting (Tm) decreased with increasing MW of polyglycol and comonomer content, and their decrease is more remarkable for E-type copolymers than for B-type ones. Tm depression of copolymers suggested that these copolymers are block-type at higher comonomer content. Tg was decreased below room temperature by the copolymerization, which affected the crystallinity and density of the copolymer films. Water content and dye uptake increased with increasing comonomer content, and their increase is higher for E1000 copolymer film than for B1000 one. Alkali resistance increased for B1000 copolymer film, whereas it decreased remarkably for E1000 one. Tensile properties of drawn (3x) film were remarkably affected by the decrease of the Tg of the copolymer, and E1000 5 mol% copolymer film showed high tensile recovery. Shrinkage in boiling water increased for E1000 drawn film, whereas it decreased for B1000 one. Thermal stability increased and then decreased with increasing comonomer content and it was lower for B-type copolymer than for E-type one.

Amplified spontaneous emission and distributed feedback lasing from a conjugated compound in various polymer matrices

This letter presents amplified spontaneous emission (ASE) and distributed feedback (DFB) lasing of the conjugated compound, 1,4-bis[2-[4-[N,N-di(p-tolyl)amino]phenyl] vinyl]benzene, in various polymer matrices of poly(methylmethacrylate), poly(styrene) (PS), poly(vinyl butyral), poly(N-vinyl carbazole), and poly(methyl phenylsilane). Effective and large ASE intensity, lowest threshold, and maximum optical gain were measured in the PS matrix. Sharp DFB lasing with full width at half-maximum=0.6 nm was measured at 490 nm. The lasing wavelength of 490 nm was fitted well by the theoretically calculated value of 491 nm.

Synthesis and enzymatic degradation of regular network aliphatic polyesters

Abstract Regular network aliphatic polyesters were prepared from glycerol (Yg) and a series of various length aliphatic dicarboxylic acids (HOOC-(CH2)n−2-COOOH, n = 4–10, 12 and 14). Prepolymers prepared by melt polycondensation were cast from dimethylformamide solution and post-polymerized at 230°C for various times to form a network. The resultant films were transparent, flexible and insoluble in organic solvents. The degree of reaction (DR) estimated from the infrared absorbance of -OH and >CH2 or >CH groups increased with increasing post-polymerization time and length of methylene chain. The heat distortion temperature also increased with increasing post-polymerization time and was 55, 28, 15, 6, 0, −1, −5, 4 and 32°C for Yg4, Yg5, Yg6, Yg7, Yg8, Yg9, Yg10, Yg12 and Yg14 post-polymerized for 4 h, respectively. Wide angle X-ray scattering patterns showed a distinct single diffraction peak, suggesting some ordered structure due to the establishment of a regular network. Density, water absorption and weight loss by alkali hydrolysis decreased with increasing methylene chain length. The enzymatic degradation was estimated by weight loss of the network films in a buffer solution of lipase at 37°C. The films of Yg4, Yg5, Yg6 and Yg7 showed no weight loss, but the weight loss increased greatly for Yg8, Yg9 and Yg10, and then decreased abruptly for Yg12 and Yg14. This suggests that the enzymatic degradation is affected by network structure, which allows the lipase to penetrate, and by the concentration of the enzymatically degradable ester linkage.