Synthesis and properties of high birefringence liquid crystals: thiophenylacetylene and benzothiazolylacetylene derivatives

We have synthesized and evaluated the physical properties of thiophenylacetylene and benzothiazolylacetylene derivatives in order to obtain higher Δn liquid crystals as compared with analogous phenylacetylene-based compounds. These new materials had poorer liquid crystallinity than the phenylacetylene derivatives. Exchanging the phenyl ring for a benzothiazole ring was effective in increasing Δn, whereas a thiophene ring decreased Δn because of the associated reduction in the anisotropic polarizability. These conjugated hetero rings shifted the UV absorption spectra into the visible region such that they are yellow or brownish in colour.     

Synthesis of Polymers Containing Free Radical Verdazyl

Abstract

In precediig papers the authors have reported on the syntheses of polvrners containing a neYi type of free rarlical verdazyl [1, 2] through the anionic polymerizatim cf vinyl verdazyl monomers [3, 4]. In tNs paper we wish to report on the synthesis of polymer verdazyl by the reaction of verdazyl having amino group I with copolymers of maieic annvdride.     

Five New Steroidal Glycosides from Caralluma dalzielii

Five new pregnane glycosides, caradalzielosides A–E ( 1 – 5 ), were isolated from the aerial parts of Caralluma dalzielii. Their structures were elucidated by extensive 1D‐ and 2D‐NMR spectroscopic analysis as well as by HR‐FAB‐MS experiments.     

Studies of the Polymerization of Diallyl Compounds. XL. Correlation between Addition Modes and Evolution of Carbon Dioxide in the Polymerization of Diailyl Oxalate

The occurrence of head-to-head (HH) addition in the radical polymerization of diallyl oxalate (DAO) was examined under various polymerization conditions. The content of HH linkage in poly (DAO) was reduced in comparison with allyl acetate and diallyl succinate; this may be ascribed to the high polarity of DAO inducing a polar effect on the intermolecular propagation of the growing polymer radical, resulting in reduced HH addition. The correlation between addition modes and evolution of carbon dioxide characteristic of DAO polymerization at elevated temperatures is mechanistically discussed in detail, with special focus on the solvent effect and the reduced dismutation of the cyclized radical compared to the uncyclized one.     

Thermodynamic and kinetic considerations on the morphological stability of “hamburger-like” composite polymer particles prepared by seeded dispersion polymerization

Micrometer-sized, monodisperse, “hamburger-like” polystyrene (PS)/poly(2-ethylhexyl methacrylate)/decane composite particles were obtained by seeded dispersion polymerization of 2-ethylhexyl methacrylate with PS seed particles in the presence of decane. The morphological stability of the hamburger-like particles was investigated based on thermodynamic and kinetic aspects. The hamburger-like morphology was maintained at 60 °C (above glass transition temperature (T _g)) for at least 1 week in spite of less thermodynamic stability than hemispherical morphology. T _g of the particles gradually increased throughout the polymerization due to monomer consumption. Geometric calculation result indicates that the degree of reduction of the interfacial free energy at the early stage of the morphological development is significantly low. From these results, it is concluded the morphological stability of the hamburger-like particles is considerably high because the development from hamburger-like to hemispherical morphologies is retarded by the gradual increase in viscosity inside the particles and the significantly lower interfacial free energy reduction.     

Absolute structures of C-glucosides of resveratrol oligomers from Shorea uliginosa

Two C-glucosides of resveratrol dimers (uliginoside A (1) and hemsleyanoloside B (2)) consisting of enantiomeric aglycones and two C-glucosides of resveratrol trimers (uliginosides B (3) and C (4)) consisting of diastereomeric aglycones were isolated from Shorea uliginosa (Dipterocarpaceae). These structures were elucidated by spectroscopic analysis including NMR experiments, and their absolute configurations were determined based on circular dichroism data. Resveratrol oligomers of C-glucosides with a 1,2-diaryldihydrobenzofuran ring are produced with specific biogenetic routes.     

Tuning of nonvolatile bipolar memristive switching in Co(III) polymer with an extended azo aromatic ligand

We have fabricated a unique memristive device by molecular engineering and demonstrated that the leakage current tuning in the device is 100 times more efficient than that in a standard device. Molecular analogs of the memristive matrices used here are an electrochemically active conjugated Co(III) polymer (CP) and a nonconjugated Co(III) polymer (NCP), which have been synthesized in good yield and characterized by (1)H NMR spectroscopy. Redox switching of an organic-metallic hybrid polymer generates bistable states with a large ON/OFF ratio that supports random flip-flops for several hours. Thus, we provide a synthetic solution to leakage current restriction, one of the fundamental problems faced when fabricating state-of-the-art electronic devices.