INSITU CONDUCTIVITY ELECTROCHEMISTRY OF CONDUCTIVE POLYMERS - POLY(3-METHYLTHIOPHENE) AND POLYTHIOPHENE

In situ monitoring of conductivity and potential response of conductive polymers during electrochemical process had been described. A renewable carbon fibre array ring-glassy carbon disk electrode was used for this purpose. Poly(3-methylthiophene) and polythiophene were investigated with this method, and some 5 orders in magnitude of conductivity changes were observed during the electrochemical redox process.

THE RING-BANDED SPHERULITE STRUCTURE OF POLY(EPSILON-CAPROLACTONE) IN ITS MISCIBLE MIXTURES WITH POLY(STYRENE-CO-ACRYLONITRILE)

The structure of the PCL spherulite in poly(epsilon-caprolactone)/poly(styrene-co-acrylonitrile) (PCL/SAN) blends was investigated by optical microscopy and small angle light scattering. The spherulite structure with a Maltese cross has been observed in pure PCL. Similar PCL/SAN blends exhibited not only spherulites with a Maltese cross, but also distinct extinction rings. The H(v) light scattering pattern especially caused diffraction rings in PCL/SAN blends but not in pure PCL. The spherical symmetry of spherulite PCL becomes more incomplete and the twist of the lamella becomes more irregular with increasing SAN content. It is found that the spherulite structure of PCL/SAN blends is dependent on the crystallization temperature and the concentration of SAN in PCL/SAN blends.

DILUTE SOLUTION PROPERTIES OF RING-SHAPED POLYSTYRENE II. THE SECOND VIRIAL COEFFICIENTS

Using a low angle laser light scattering photometer (LALLS) the second virial coefficients(A_2) of ring-shaped and linear polystyrene (RPS and LPS) samples were determined in both toluene and butanone solutions. The A_2 of RPS in the good solvent (toluene) is smaller than that of LPS with the same molecular weight, but in the poor solvent (butanone) these two are very close. For RPS in the molecular weight range of 4×10~4——2.2×10~5, we haveA_(2r)=1.28×10~(-2)M_w~(-0.283) (Toluene 25℃) and A_(2r)=5.06×10~(-2...

Study on the structure of C-phycocyanin in Spirulina platensis with scanning tunneling microscope

The C-phycocyanin (C-PC) trimmer was isolated from the blue-green alga Spirulina platensis, and scanning tunnelling microscope (STM) was used to investigate its structure, High resolution STM images of C-PC were obtained. From the STM images, it could be observed that the C-PC molecules were disk-like in shape and the subunits of C-PC arranged in ring-like pattern with a channel in the center. After filter treatment, the folding of the polypeptide chains could be. seen clearly. This is the first time to observe directly the topography of phycobiliprotein, and the results showed STM to be a powerful tool for the structural study of phycobiliproteins.

Skeleton-rearranged pentacyclic diterpenoids possessing a cyclobutane ring from Euphorbia wallichii

Two novel rearranged trachylobane diterpenoids, designated as wallichanol A (2) and wallichanol B (3), consisting of an unprecedented pentacyclic skeleton named wallichane with a cyclobutane ring, and a new ent-trachylobane diterpenoid, 3-oxo-ent-trachyloban-17-oic acid (1), were isolated from the roots of Euphorbia wallichii. Their structures were elucidated by comprehensive analysis of 2D-NMR spectroscopic data, with the stereochemistry of 1 confirmed by X-ray crystallographic study. All of these compounds potently block osteoclastogenesis in vitro, suggesting a potential therapeutic application in prevention of osteoporosis.

Effect of pore ring number of zeolites on catalytic performance of Mo/Zeolite in methane aromatization under non-oxygen condition

The catalytic behavior of Mo-based zeolite catalysts with different pore structure and size, particularly with 8 membered ring ( M R), 10 M R, coexisted 10 and 12 M R, and 12 M R, was studied in methane aromatization under the conditions of SV=1500 ml/(g.h), p=0.1 MPa and T = 973 K. It was found that the catalytic performance is correlated with the pore structure of the zeolite supports. The zeolites that possess 10 MR or 10 and 12 MR pore structure with a pore diameter equal to or slightly larger than the dynamic diameter of benzene molecule, such as ZSM-5, ZSM-11, ZRP-1 and MCM-22, are fine supports. Among the tested zeolite supports, MCM-22 exhibits the highest activity and selectivity for benzene. A methane conversion of 10.5% with benzene selectivity of 80% was achieved over Mo/MCM-22 catalyst. The Mo/ERS-7 catalyst with 8 MR (0.45 nm) does not show any activity in methane dehydro-aromatization, while Mo/JQX-1 and Mo/SBA-15 catalysts with 12 MR pore exhibit little activity in the reaction. It can be concluded that the zeolites with 10 MR pore or coexisted 10 and 12 MR, having pore size equal to or slightly larger than the dynamic diameter of benzene molecule, are fine supports for methane activation and aromatization.

Experimental investigation of an unstable ring resonator with 90-deg beam rotation for a chemical oxygen iodine laser

We report the experimental results of an unstable ring resonator with 90-deg beam rotation for a kilowatt class chemical oxygen iodine laser (COIL). The distributions of near-field phase and far-field intensity were measured. A beam quality of 1.6 was achieved when the COIL average output power was approximately 5 kW. (C) 1999 Optical Society of America.

Lewis acid assisted ring-closing metathesis of chiral diallylamines: An efficient approach to enantiopure pyrrolidine derivatives

Lewis acid assisted ring-closing olefin metathesis (RCM) of chiral diallylamines, using the second generation RCM ruthenium-based catalyst, leads to enantiopure pyrrolidine derivatives in 79-93% yields under very mild conditions. The scope of the olefin metathesis has been expanded.