Cationic copolymerization of anethole: Reactivity of geometric isomers of α,β-disubstituted ethylenes

Cationic copolymerizations of anethole were carried out under various conditions in order to confirm the relative reactivities of its geometric isomers. trans-Anethole was more reactive than cis-anethole in copolymerizations with p-methoxystyrene or styrene, but less reactive in the mutual copolymerization of cis- and trans-anethole; i.e., the trans isomer was more reactive to a growing chain end with little steric hindrance. Thus the intrinsic reactivity of an olefinic double bond to carbonium ion is greater for the trans isomer than for the cis isomer. This idea is supported by ¹³C NMR spectra, since the signal of the olefinic β-carbon of the trans isomer is at higher field than that of the cis isomer. The behavior of anethole was compared with the results observed in vinyl ethers, where the cis isomer was always more reactive irrrspective of the structure of the growing chain end. In addition, the dependence of monomer reactivity ratios on polymerization conditions is discussed.     

Selective vinyl cationic polymerization of monomers with two cationically polymerizable groups. I. p-isopropenylphenyl glycidyl ether: An epoxy-functionalized α-methylstyrene

p-Isopropenylphenyl glycidyl ether (IPGE), a monomer of dual cationic functionality (isopropenyl and epoxy), was polymerized by a variety of initiators, and optimum conditions were established for its selective vinyl cationic polymerization. The hydrogen iodide/iodine (HI/I₂) initiating system or iodine polymerized selectively the isopropenyl group in CH₂Cl₂ at a low temperature (?78°C), to produce soluble poly(IPGE) with epoxy pendants. Under these conditions, the number-average molecular weight of the polymers was inversely proportional to the initial initiator concentration, indicating the formation of long-lived propagating species. Soluble poly(IPGE) was also obtained at ?15 and ?40°C by HI/I₂ or iodine. However, at these higher temperatures, transfer and/or termination reactions took place to give olefin-terminated polymers, in which some of the pendant epoxy groups were consumed. BF₃OEt₂ (a metal halide) and CF₃SO₃H (a strong protonic acid) polymerized both epoxy and isopropenyl groups of IPGE and yielded crosslinked insoluble polymers.     

Regulated interaction between polypeptide chain elongation factor-1 complex with the 26S proteasome during <Emphasis Type="Italic">Xenopus</Emphasis> oocyte maturation

Background  

During Xenopusoocyte maturation, the amount of a 48 kDa protein detected in the 26S proteasome fraction (p48) decreased markedly during oocyte maturation to the low levels seen in unfertilized eggs. The results indicate that the interaction of at least one protein with the 26S proteasome changes during oocyte maturation and early development. An alteration in proteasome function may be important for the regulation of developmental events, such as the rapid cell cycle, in the early embryo. In this study, we identified p48.     

Polymerization of tert-alkylacetylenes by Mo- and W-based catalysts

Polymerization of three tert-alkylacetylenes (3,3-dimethyl-1-pentyne, 3,3-dimethyl-1-nonyne, 1-adamantylacetylene) by Mo- and W-based catalysts provided new polymers in virtually quantitative yields. In contrast, Ziegler catalysts did not polymerize these monomers. Every polymer had a form of white solid, and had alternating double bonds along the main chain. Though some of poly(3,3-dimethyl-1-pentyne)s contained a toluene-insoluble fraction, the polymer was totally soluble when proper polymerization conditions were chosen. The molecular weights of soluble fractions were as high as 3 × 10⁵. Poly(3,3-dimethyl-1-nonyne) was also partly insoluble in toluene, and the quantity of soluble fraction was less than that of poly(3,3-dimethyl-1-pentyne). The geometric structure of these two polymers could be controlled by the choice of suitable polymerization conditions. Poly(1-adamantylacetylene) was insoluble in any organic solvents. Copolymerization of 1-adamantylacetylene with suitable comonomers afforded soluble copolymers.     

Polymerization of phenylacetylene by WCl6·Ph4Sn: Synthesis of high polymer achieved by selection of solvents

Phenylacetylene was polymerized by WCl₆·Ph₄Sn (1:1) in 1,4-dioxane to provide in high yield a polymer whose molecular weight reached 1 × 10⁵. The polymerization also proceeded in other oxygen-containing solvents (ethers, esters, and ketones) but the polymer molecular weights were lower than 1 × 10⁴. Certain hydrocarbon solvents such as cyclohexene, tetralin, and indan also afforded high-molecular-weight polyphenylacetylene [M _n = (5–8) × 10⁴], as compared with those (M _n ≤ 1.5 × 10⁴) obtained in conventional aromatic hydrocarbons like benzene. A high polymer (M _n = 1.6 × 10⁵) was also formed from β-naphthylacetylene in 1,4-dioxane. It was inferred that the active hydrogens of these solvents prevent the formed polymer from being decomposed by a radical mechanism and/or modify the nature of active species.     

Reestimation of the Taft's substituent constant of the pentafluorophenyl group

The Taft's substituent constant of the pentafluorophenyl group (sigma(C(6)F(5))) was reestimated to be 1.50 by correlation between IR spectral data (v(C)(=)(O)) and sigma constants for a series of esters (involving the pentafluorobenzyl group) of 3-phenylpropanoic acid and butanoic acid. The possibility of the disturbance of the correlation by the intramolecular pi-pi interaction between C(6)F(5) and C(6)H(5) groups in pentafluorobenzyl 3-phenylpropanoate was excluded by ab initio and DFT calculations of the stable conformations and their carbonyl frequencies. The reestimated sigma(C(6)F(5)) value was used for calculation of the pK(a) value of pentafluorobenzyl alcohol [14.5 (or 14.3)].     

Processing of β-BaB2O4 Thin Films Through Metal Organics

β-BaB₂O₄ (β-BBO) thin films were successfully synthesized by the sol-gel method using metallo-organic compounds. A stable BBO precursor solution was prepared from barium metal and boron triethoxide or 2,4,6-triethoxycyclotriboroxane in a mixture solvent of ethanol and 2-ethoxyethanol. As-precipitated powder formed by hydrolysis of the precursor solutions crystallized to ψ phase, which was transformed to β phase at higher temperatures. The transformation temperatures of powders from ψ to β phase of the ethoxide system and the boroxane system were 600 and 680°C, respectively. The calcination of precursor films in a mixture gas of water and oxygen was found to decrease the crystallization temperature of β-BBO films on Pt sheet substrates. The precursor films prepared from the ethoxide system and the boroxane system crystallized to β-BBO on Pt (111)/glass substrates at 500 and 550°C, respectively. The BBO films on Pt(111)/glass substrates showed the strong (006) preferred orientation. The β-BBO films on Pt(111)/glass substrates showed the second harmonic generation (SHG) of the 532 nm light on irradiation with 1064 nm light. The SH power from the BBO films was correlated with the fundamental power through the square-law proportionality based on the theory. The SHG efficiency of the BBO films was dependent upon the film thickness.     

Cationic copolymerization of 3,3-bis(chloromethyl) oxetane with vinyl compounds

Copolymerizations of 3,3-bis(chloromethyl)oxetane (BCMO) with some vinyl compounds were carried out with cationic catalysts in various solvents to determine what kind of vinyl compound is able to copolymerize with BCMO. p-Methylstyrene (pMS), 2-chloroethyl vinyl ether (CEVE), α-methylstyrene (αMS), and isobutene (IB) were used as comonomers. The rate of consumption of each monomer was measured by gas chromatrography. Plots of copolymer composition in the copolymerization of BCMO with pMS were characterized by S-shaped curves in several solvents. As poly-BCMO is insoluble and the vinyl polymers are soluble in benzene, the polymers obtained were separated into benzene-soluble and benzene-insoluble fractions, and the composition of each fraction was determined by elemental analysis. It was found that pMS, CEVE and IB formed a copolymer with BCMO, but αMS produced no copolymer with BCMO. Thus the formation of copolymer between a cyclic ether and some vinyl monomers was observed by a cationic mechanism. The cross-propagation mechanism is discussed on the basis of these results.     

Hydrolysis and polycondensation of acid-catalyzed Phenyltriethoxysilane (PhTES)

The effects of acid catalyst, water content and reaction temperature on the hydrolysis and polycondensation of phenyltriethoxysilane (PhTES) were studied using ²⁹Si NMR spectroscopy. The sol catalyzed by hydrochloric acid showed the simultaneous progress of hydrolysis and polycondensation. In addition, the reaction rate was almost independent of reaction temperature. On the other hand, the polycondensation in the PhTES-derived sol mixed with an excess amount of water and acetic acid as a catalyst proceeded after completion of the hydrolysis. In the acetic acid-catalyzed system, the degree of the hydrolysis and polycondensation largely depends on the reaction temperature.