Kinetic and ESR studies on radical copolymerization of p-tert-butoxystyrene and di-n-butyl maleate in benzene

The copolymerization of p-tert-butoxystyrene (TBOSt) (M₁) and di-n-butyl maleate (DBM) (M₂) with dimethyl 2,2′-azobisisobutyrate (MAIB) in benzene at 60°C was studied kinetically and by means of ESR spectroscopy. The monomer reactivity ratios were determined to be r₁ = 2.3 and r₂ = 0 by a curve-fitting method. The copolymerization system was found to involve ESR-observable propagating polymer radicals under practical copolymerization conditions. The apparent rate constants of propagation (k_p) and termination (k_t) at different feed compositions were determined by ESR. From the relationship of k_p and f₁ (f₁ = [M₁]/([M₁] + [M₂])) based on a penultimate model, the rate constants of five propagations of copolymerization were evaluated as follows; k₁₁₁ = 140 L/mol s, k₂₁₁ = 3.5 L/mol s, k₁₁₂ = 61 L/mol s, k₂₁₂ = 1.5 L/mol s, and k₁₂₁ = 69 L/mol s. Thus, a pronounced penultimate effect was predicted in the copolymerization. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1449–1455, 1998     

Synthesis and characterization of highly fluorescent polythiophene derivatives containing polystyrene sidearms

In this study, macroinitiators with different content of atom‐transfer radical polymerization (ATRP) functional group on polythiophene backbone were first prepared by the copolymerization of 3‐[1‐ethyl‐2‐(2‐bromopropionate)]thiophene and 3‐hexylthiophene with various feed ratio. Then poly [3‐hexyl‐2,5‐thienylene‐co‐3‐[1‐ ethyl‐2‐(2‐[poly(styrene)]propionate)]‐2,5‐thienylene] (PTTBr‐PS) with different graft density were obtained by ATRP of styrene from these macroinitiators in anisole. The degree of polymerization of PS sidearm (DP_PS) was controlled by polymerization time. The structures of obtained graft copolymers were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (¹H NMR) and differential scanning calorimetry (DSC). Introduction of the PS sidearms onto the backbone of polythiophene was an attempt to trap the polythiophene backbone in a “solution‐like” conformation, thus inhibit the packing of polythiophene backbone and result in the improvement of fluorescent property in solid state. This was verified by the UV–vis and fluorescence analyses. Besides, it was also found that the optical property of PTTBr‐PS graft copolymer was dominated by its graft density and independent on the degree of polymerization of its PS sidearm. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1003–1013, 2008     

A novel direct N-alkenylation of nitrogen-containing heterocycles with magnesium alkylidene carbenoids

Treatment of magnesium alkylidene carbenoids, which were generated from 1-chlorovinyl p-tolyl sulfoxides with isopropylmagnesium chloride at −78 °C in toluene, with N-lithio nitrogen-containing heterocycles (e.g., indole, indazole, phenothiazine, and phenoxazine) gave N-alkenylated products in moderate to good yields. The intermediate of this reaction was found to be the alkenyl anion, which could be trapped with iodoalkanes using CuI as a catalyst to give the heterocycles having fully substituted alkenes on the nitrogen. The alkenyl anion intermediate could be trapped also with benzoyl chloride and phenyl isocyanate. This reaction offers a quite novel and direct N-alkenylation of nitrogen-containing heterocycles.     

Enhancement and suppression of vibrational coherence in degenerate four-wave-mixing signal generated from dye-doped polymer films

Vibrational coherence in the degenerate four-wave-mixing (DFWM) signal generated from polymer films doped with a dye, oxazine 4 (Ox4), at 10 K was investigated. It was found that the amplitudes of some low-frequency oscillations (<400 cm(-1)) were enhanced when the delay between the first and second femtosecond pulses was set out of phase with the oscillation period. Frequency and reorganization energy dependence was investigated by computer simulation based on the response function formalism which considers all the possible Liouville space pathways for the DFWM signal. It was revealed that low-frequency oscillations with weak coupling to the optical transition can be enhanced in the stimulated photon echo signal compared to the transient grating signal.     

Studies on the nematic-isotropic phase transitions in liquid crystals

Compressibility-pressure relations in the region of nematic-isotropic phase transitions under constant temperature were studied, and the value of critical exponent was estimated.     

Study of the energy and charged multiplicity dependence of inclusiveπ− production in π−p interactions up to fermilab energies

Using new data from 100 $\text{GeV}\text{c π}{}^{\mathrm{?}}$ interactions, we find the energy dependence of the invariant cross-section in the target fragmentation (central) region to be consistent with an $\text{A + Bs}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{(C + Ds}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>4</mtext>}}\text{)}$ behavior. The leading particle peak near x = + 1 exhibits a width in x which becomes smaller with increasing energy and an integrated cross section which is approximately energy independent.     

Synthesis of silylene and silyl(silylene)metal complexes

In 1987, two research groups published the first-ever reports on the synthesis of silylene complexes and presented structural evidence. Since then, a range of synthetic methods have been developed and a number of silylene complexes have been prepared. In 1988, we reported on the first base-stabilized bis(silylene) complexes that can be regarded as being masked silyl(silylene) complexes. These complexes occupy a unique position among silylene and silyl(silylene) complexes in that they provide a convenient tool for studying the reactivity of coordinated silylenes. They are stable enough to be isolated, but the bond between the silylene silicon atom and the internal base can easily be cleaved by thermal perturbation to generate real silyl(silylene) complexes. To date, a number of base-stabilized bis(silylene) complexes have been prepared in which the central metals range from group 5 to group 9. Only two base-free silyl(silylene) complexes have been prepared. One is prepared by reacting a platinum complex with a stable silylene; the other is produced by the photolysis of a tungsten complex in the presence of a hydrodisilane.     

Adsorption of phenol in flow systems by a monolithic carbon cryogel with a microhoneycomb structure

Adsorption of phenol from an aqueous solution in batch and continuous flow systems using carbon gels with a microhoneycomb structure (carbon gel microhoneycombs, CMHs) was studied. The obtained monolithic CMHs had fairly straight channels, 25–45 μm in diameter, and the thickness of the walls which form the channels was around 5 μm. The CMHs showed 370 times lower hydraulic resistance when compared with a column packed with particles having the same diffusion path length as it. The obtained CMHs have a hierarchical micro-meso porous structure giving BET surface area in the range of 513–1070 m²·g^?1.When used for phenol adsorption from an aqueous solution, the CMHs quickly adsorbed phenol at first, and then, the uptake gradually increased, which indicates that the adsorption mechanism is based on not only simple physisorption. The phenol adsorption capacity increased with the increase in carbonization temperature of the CMH and the decrease in its hydrophilicity. CMHs carbonized at temperatures higher than 1073 K showed the highest phenol adsorption capacity which was around 160 mg·g^?1. The CMHs could continuously adsorb phenol from aqueous solutions, and their length of unused bed (LUB) values depended on operation conditions but were in the range of 0.3–0.7 cm. The experimental results indicated that carbon cryogels with a microhoneycomb structure have a high potential to be used for effective separation of phenol.