Synthesis,structure, and properties of poly[1‐(trimethylgermyl)‐1‐propyne]

Polymerization of 1‐(trimethylgermyl)‐1‐propyne (TMGP) with TaCl₅ and NbCl₅ produced a colorless polymer in high yields, whose molecular weight reached about 3 × 10⁵–14 × 10⁵. The molecular weight distribution of the poly(TMGP) with NbCl₅ in cyclohexane was somewhat narrow (M_w /M_n = ∼1.54). The TaCl₅‐based poly(TMGP) dissolved in toluene, chloroform, cyclohexane, carbon disulfide, carbon tetrachloride, tetrahydrofuran, hexane, and so forth; the NbCl₅‐based polymer was less soluble and did not dissolve in hexane, despite its lower molecular weight. The cis contents of the NbCl₅‐ and TaCl₅‐based poly(TMGP)s determined by ¹³C NMR were 67 ± 5 and 28 ± 3%, respectively. The onset temperature of the weight loss of poly(TMGP) in air was 350 °C, indicating fair thermal stability. The oxygen permeability coefficient (P) of poly(TMGP) at 25 °C was 7800 barrer after the methanol conditioning, and the permeability was fairly stable to aging. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2964–2969, 2000     

Synthesis,geometric structure,and properties of poly(phenylacetylenes) with bulky para-substituents

Phenylacetylenes (PAs) with bulky substituents (adamantyl, tert-butyl, and n-butyl groups) at the para-position polymerized in good yields with Fe, Rh, Mo, and W catalysts. The formed polymers were soluble, and their number-average molecular weights were in the range of thousands to hundred thousands. Whereas it is known that the poly(PA) obtained with the Fe catalyst is an insoluble cis-cisoidal polymer, the present polymers formed with the same catalyst were totally soluble in many solvents such as benzene and CHCl₃. The ¹H- and ¹³C-NMR and DSC data revealed that both of the polymers formed with the Fe and Rh catalysts had virtually all-cis structures, while those with the Mo and W catalysts had cis-rich and trans-rich structures, respectively. Cis-cisoidal and cis-transoidal structures of para-substituted poly(PAs) could not be distinguished because of their good solubility. The bulky substituents raised the temperature of cis–trans isomerization and improved the thermal stability of the polymers. Poly(p-t-BuPA) showed gas permeability higher than that of poly(PA). © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 3157–3163, 1998     

Preparation and characterization of fluorine‐containing aromatic condensation polymers. VII. Aromatic polyacetals and copolyacetals from 2,2‐bis(4‐hydroxyphenyl)‐1,1,1,3,3,3‐hexafluoropropane and/or 2,2‐bis(4‐hydroxyphenyl)propane and 2‐(trifluoromethyl)benzal chloride

A series of fluorine‐containing aromatic homopolyacetals and copolyacetals with a wide range of unit ratios were synthesized by the solution polycondensation of 2,2‐bis(4‐hydroxyphenyl)‐1,1,1,3,3,3‐hexafluoropropane (bisphenol AF), 2,2‐bis(4‐hydroxyphenyl)propane (bisphenol A), or both with 2‐(trifluoromethyl)benzal chloride, and the effect of fluorine substitution on the properties of these polymers is discussed in relation to the fluorine contents. High molecular weight polyacetals with reduced viscosities of 0.43–0.97 dL/g were obtained in high yields with potassium hydroxide as a base, 18‐crown 6‐ether as a catalyst, and N‐methyl‐2‐pyrrolidinone as a medium at 100 °C for 3 h. Regardless of the fluorine contents, these polymers all were highly soluble in various solvents, including benzene, chloroform, ethyl acetate, and tetrahydrofuran, and afforded colorless, transparent, and tough films by solution casting. The temperatures of 5% weight loss and 10% weight loss under nitrogen both increased significantly and monotonously with increasing fluorine content, whereas the glass‐transition temperatures were scarcely affected by fluorine substitution. The dielectric constant at 1 MHz of the bisphenol AF‐based homopolyacetal was 2.43, which was remarkably lower than the value of the bisphenol A‐based homopolyacetal, 2.68. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1873–1879, 2000     

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. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1474–1484, 2000     

A chain geometry prediction of polystyrene and polyarylate block copolymer by a kinetic simulation model

The chain geometry of polystyrene (PS) and polyarylate (PAr) block copolymer was predicted by the simulation of the kinetics of the block‐copolymerization route. The simulation model consisted of a combination of two models. In the first model, the kinetics of the free‐radical polymerization of carboxyl‐terminated telechelic PS (COOH‐PS‐COOH) was simulated for the determination of the molecular weight distribution. In the second model, the kinetics of the PS and PAr block copolymerization with COOH‐PS‐COOH was simulated by a Monte Carlo computation, with each reacting functional group assigned by an integer. The number‐average and weight‐average molecular weights and the composition of the PS‐PAr block copolymer, as calculated by the simulation models, were in good agreement with the experimental data. From this agreement, plausible predictions for the chain geometry (i.e., the type of block copolymer and length of each segment) were obtained that were practically impossible to analyze experimentally. The simulation results showed that more than 80 wt % of the block copolymer synthesized by this method was a composite of various types of multiblock copolymers and that the length of the PAr segment was almost the same as that of the homo‐PAr obtained as a by‐product. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 299–309, 2000     

Adsorption-induced bending of polypyrrole films and its application to a chemomechanical rotor

We have discovered that polypyrrole films undergo rapid and intensive bending in the solid state. Bending was induced by the reversible and anisotropic adsorption of various substances in the vapor state. The speed and direction of bending largely depended on the adsorbate used. By using this phenomenon, we have devised an experimental “chemomechanical rotor” capable of transducing a chemical free energy change directly into a continuous rotation. © 1996 John Wiley & Sons, Inc.     

Strained Lattice Organic Thin Film Growth by Molecular Beam Epitaxy

Abstract

Strained lattice organic thin film which possessed distinct lattice structure from the bulk crystal was formed by molecular beam epitaxy (MBE). In situ infrared (IR) spectroscopic characterization was carried out to clarify the as-grown film structure under several growth conditions. The growth condition for parallel orientation of the flat molecules was discussed under the interrelation between the molecule-substrate interactions and the intermolecular interactions.     

Characteristics of Wavelength Tunable Femtosecond Soliton Pulse Generation Using Femtosecond Pump Laser and Polarization Maintaining Fiber

We have investigated both experimentally and numerically the characteristics of wavelength tunable femtosecond soliton pulse generation using a pulse width variable fiber laser and two different types of polarization maintaining fibers. The generated soliton shows the feature of the pulsewidth becoming almost constant at - 250 fs under any conditions of the pump pulse for 220m fiber. High conversion efficiency from pump pulse to a generated soliton pulse accounting for as much as 73% can be obtained. This efficiency decreases with increase in the input power or wavelength shift. A superior conversion efficiency and broad wavelength shift can be obtained by using a more shortened pump pulse. In the numerical calculations, it is predicted that under a condition of constant power of pump pulse, the maximum wavelength shift is achieved when the soliton number N is -1.4. The difference of mode field diameter and the group velocity dispersion (GVD) coefficient β₂ affect the wavelength shift and conversion efficiency. Using the fiber with small mode field diameter and small absolute value of GVD coefficient β₂, a high conversion efficiency and large wavelength shift can be obtained.