Synthesis and properties of new block copolymers based on polydimethylsiloxane and tetraphenylethylene-containing polyimide

New polydimethylsiloxane (PDMS)-polyimide block copolymers were synthesized by the solution polycondensation of aminopropyl-terminated polydimethylsiloxane, 1,1-bis(4-aminophenyl)-2,2-diphenylethylene, and 3,3′,4,4′-benzophenonetetracarboxylic dithioanhydride in pyridine. New 1,3-bis(3-aminopropyl)tetramethyldisiloxane (BADS)-based random copolyimides were also prepared. The inherent viscosities of all the random and block copolyimides were in the range of 0.13–0.90 dL/g in N-methyl-2-pyrrolidone. These copolymers were soluble in N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and m-cresol. All the BADS-based random copolymers and PDMS-containing copolymers with PDMS content above 42 wt % were soluble in tetrahydrofuran and chloroform. Transparent or somewhat cpaque films were prepared by casting from the reaction solutions. The BADS-based random copolyimides had one glass transition temperature (T_g) in the whole composition ranges, which showed single phase nature of the copolymers. On the other hand, the PDMS-polyimide block copolymers had double T_gS, indicating phase-separated morphology. The block copolymers containing PDMS content above 73 wt % behaved like a high temperature elastomer. © 1993 John Wiley & Sons, Inc.     

Microstructure and electric properties of elastomeric ionene-TCNQ salts

The elastomeric ionene polymers characterized by the alternating structure of the rigid polycation segments that contained 4,4′-bipyridilium rings and the flexible polypropyleneoxide (PPO) segments were prepared as a function of chain length of the PPO segments. From the measurements of dynamic mechanical properties and x-ray diffraction patterns of these ionenes and their 7,7,8,8-tetracyanoquinodimethane (TCNQ) salts, a microheterogeneous structure of the PPO segments and the polycation-TCNQ salts segments in the TCNQ salts was estimated. On the basis of this microstructure a change in the conductive and dielectric properties with an increase on the weight fraction of the PPO segments the TCNQ salts (W_f) were discussed. For the simple salts the values of resistivity (ρ) and activation energy of conduction (E_a) were increased with the increase in the value of W_f. The values of ρ for the complex salts also increased with the increase in the value of W_f, whereas the values of E_a were nearly constant (ca. 0.07 eV) until the value of W_f reached 0.8. Strong interaction between \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm TCNQ}^{-\atop\cdot}$\end{document} and TCNQ° molecules facilitated the formation of the continuous conduction columns and did not change their structure and properties. Dielectric constant (ε) of the TCNQ salts attained 10²?10⁴. The dielectric behavior was consistent with the conductive behavior, and the appearance of the high ε values was caused by polarization of carrier electrons of the TCNQ salts in the conductive paths isolated or interrupted by the PPO segments. As the W_f value increased, the ε values of the TCNQ salts decreased. The decrease in the number of these paths accompanied by the increase in the W_f value led to reduced ε values.     

Evaluation of nitric oxide chemical ionization mass spectra of substituted benzenes

Nitric oxide chemical ionization mass spectra of substituted benzenes obtained with the Townsend discharge technique were studied. There were four kinds of base peaks in the mass spectra, i.e. [M + NO]⁺˙, M⁺˙, [M ? H]⁺ and [M ? OR]⁺ (R = H, CH₃). The formation of the specific ion [M + NO]⁺˙ was highly dependent on the kind of substituent, and it was produced more abundantly in the case of substitutions involving electron-accepting groups. The measure of [M + NO]⁺˙ production was evaluated from the value of the ratio [M + NO]⁺˙/M⁺˙. In mono-substitutions, it was clarified that the ratios of [M + NO]⁺˙/M ⁺˙ were correlated with the Hammett substituent constant s?_p or the electrophilic substituent constant s?_p⁺. Monosubstitutions (C₆H₅R) and toluene substitutions (CH₃C₆H₄R) could be classified into six groups in terms of base peak species, [M + NO]⁺˙/M⁺˙ ratios and substituents. In disubstitutions, the mass spectral patterns were governed by the combination of substituents. Mass spectral distinctions among ortho, meta and para isomers could be made in many cases.     

Nickel-catalyzed cross-coupling of silyl enol ethers with grignard reagents. Regio- and stereocontrolled synthesis of olefins

The substitution of the siloxy group in silyl enol ethers with Grignard reagents to form olefins is accomplished by use of nickel acetylacetonate or phosphine-nickel complexes as catalysts, the stereo- and regiochemistry of coupled olefins depending upon the nature of the catalyst and reaction conditions employed.     

Preparation and properties of polyarylates and copolyarylates from phenylindanedicarbonyl chloride and bisphenols

A series of polyarylates having inherent viscosities of 0.4–1.1 dL/g was prepared by the two phase polycondensation of 1,1,3-trimethyl-3-(4-chloroformylphenyl)indanecarbonyl chloride with various bisphenols in an organic solvent–aqueous alkaline solution system in the presence of a phase transfer catalyst. Similarly, copolyarylates of high molecular weights were prepared from a mixture of the phenylindanedicarbonyl chloride, terephthaloyl chloride, and 2,2-bis(4-hydroxy-phenyl)propane. All the polyarylates were characterized by their amorphous nature and high solubility in organic solvents. They gave transparent and tough films by the solution casting. The films had tensile strength of 33–46 MPa, elongation at break of 3–16%, and tensile modulus of 1.2–1.6 GPa. These polyarylates had glass transition temperatures in the range of 205–310°C, and began to decompose at ca. 350°C in air.     

A pressure and temperature study on solubility and micelle formation of sodium perfluorodecanoate in aqueous solution

Both the critical solution temperature (CST, or the Krafft temperature) and the critical solution pressure (CSP, or the Tanaka pressure) were determined for sodium perfluorodecanoate (NaPFDe) in water, and the result shows that the Krafft temperature is raised with the increase in the Tanaka pressure. A thermodynamic analysis has been made on the data for the critical micellization concentration (cmc) and of the solubility at various temperatures and pressures. The estimated change in the partial molal volume, resulting from micelle formation from the singly dispersed state and from the hydrated solid state, was found to be conspicuously higher for NaPFDe compared to hydrocarbon surfactants. This has been ascribed to the more pronounced role of carbon chain-water interactions and water structure effects of the fluorocarbon surfactants.     

Aromatic polydiketopiperazines

Aromatic polydiketopiperazines have been prepared from bis-2-chloroacetamides of aromatic diamines in the presence of an epoxide as HCl acceptor and a quaternary ammonium halide catalyst. The structures of the polymers were characterized by infrared and NMR spectra. These polymers were soluble in organic acids such as formic acid, dichloroacetic acid, and trifluoroacetic acid but insoluble in common organic solvents such as dimethylformamide, dimethylacetamide, and dimethyl sulfoxide. Thermogravimetric analysis indicated that these polymers decomposed at 300–340°C.     

Phase Behavior and Thermal Properties for Binary Blends of Bacterial Poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate)s with Narrow‐Comonomer‐Unit Compositional Distribution

The miscibility and the effect of compositional distribution on physical properties were investigated for binary blends of biosynthesized poly(3‐hydroxybutyrate) [P(3HB)] and comonomer compositionally fractionated poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate)s [P(3HB‐co‐3HH)] with narrow compositional distribution. Biosynthesized P(3HB‐co‐3HH) samples were compositionally fractionated using solvent (chloroform)/nonsolvent (n‐heptane) mixtures. The binary blends of fractionated P(3HB‐co‐3HH)s with different 3HH unit content were prepared by casting from solution in chloroform. The miscibility and the thermal properties of these blends were analyzed by differential scanning calorimetry (DSC). It was found that the two components are miscible in the amorphous phase when the difference in 3HH unit content between the two component polymers of these blends is less than 20 mol‐%, subsequently they are immiscible when the difference is larger than 30 mol‐%. By comparing the thermal properties of the binary blends of fractions, with those for the fractions themselves, and with those for the bacterially as‐produced unfractionated copolyesters, the effects of compositional distribution on the properties of copolyesters were discussed.

Glass transition temperatures of blends PHB/H10, H10/H20, and PHB/H20 versus total 3HH unit content in the blends. The solid lines are the best fits of the experimental results of the P(3HB‐co‐3HH) fractions with narrow compositional distribution.     

Epitaxial heterostructures: side-to-side Si-ZnS, Si-ZnSe biaxial nanowires, and sandwichlike ZnS-Si-ZnS triaxial nanowires

Epitaxial semiconducting heterostructures: side-to-side Si-ZnS, Si-ZnSe biaxial nanowires, and sandwichlike ZnS-Si-ZnS triaxial nanowires were grown via a simple two-stage thermal evaporation of mixed SiO and ZnS or SiO and ZnSe powders under a precise temperature control. Each nanowire had a uniform diameter of 40-120 nm and length ranging from several to several tens of micrometers. Subnanowires of Si, ZnS, and ZnSe within them had a diameter of 20-50, 40-60, and 20-50 nm, respectively. The optical property (nanoscale cathodoluminescence) was also investigated from these new structures. It is proposed that the Si nanowires formed through disproportionation of SiO to Si in the first evaporation stage and then served as one-dimensional nanoscale substrates (or templates) for an epitaxial growth of ZnS or ZnSe nanowires in the following thermal evaporation of ZnS or ZnSe powders. The present results suggest that the simple method might be useful for the synthesis of many other heterostructures containing Si and II-VI or III-V semiconducting composite nanowires to meet the growing demands of nanoscale science and technology.     

Preparation and properties of aromatic polyesters and copolyesters containing phenylindane unit

Aromatic polysters and copolyesters of high molecular weights with phenylindane units were prepared from combinations of 3-(4-hydroxyphenyl)-1,1,3-trimethyl-5-indanol and bisphenol A with isophthaloyl and terephthaloyl chloride by two-phase polycondensation in a nitrobenzene-water system with various phase-transfer catalysts. The phenylindane-containing polyesters and copolyesters were amorphous and readily soluble in a wide range of solvents that included chloroform, m-cresol, tetrahydrofuran, and dimethylformamide. The glass transition temperatures of the phenylindane-derived polyisophthalate and polyterephthalate were 235 and 253°C, respectively, which were higher than those of the corresponding bisphenol A analogs by some 50°C. These polymers began to lose weight around 400°C in air and nitrogen atmospheres.