Structure–electrical property study of anisotropic polyaniline films

The relationships of the structure and electrical properties of anisotropic HCl‐doped polyaniline (PANI) films cast from N,N′‐dimethylpropylene urea (DMPU) solutions and stretched to different draw ratios were studied. The anisotropic structure of the stretched PANI films was examined by X‐ray diffraction, near‐infrared wave‐guide coupling, and polarized infrared measurements. The PANI emeraldine base (EB) films cast from DMPU solutions had a single‐phase noncrystalline structure, and stretching of the films did not cause crystallization to occur. The transition moment angles of two weakly absorbing infrared bands were determined, and the Hermans' orientation functions for the PANI EB films were calculated. The PANI films were then doped with HCl, and the electrical properties were determined by impedance spectroscopy. With a specially designed test fixture, the in‐plane and through‐plane impedance was obtained. The conductivity along the stretch direction increased with orientation. The in‐plane conductivity was significantly higher than the through‐plane conductivity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 823–841, 2003     

Simple preparation of iron stabilized carboxonium ions. Concurrent complexation,rearrangement and alcohol addition to terminal acetylenes

CpFe(CO)₂[C(OEt)R]BF₄ complexes can be prepared by reaction of CpFe(CO)₂(isobutylene)BF₄ with monoalkylated acetylenes in methylene chloride/ethanol solutions. Methyl propiolate yields methyl trans-2-ethoxy-acrylate, in a reaction catalytic in CpFe(CO)₂(isobutylene)BF₄, and internal acetylenes can be transformed to CpFe(CO)₂(vinyl ether)BF₄ complexes.     

The effect of a coriolis force on Taylor-Couette flow

Taylor-Couette flow subject to a Coriolis force is studied experimentally and numerically. In the experiment, the Couette apparatus is mounted on a turntable with the axis of the cylinders orthogonal to the rotation vector of the turntable. The Coriolis force stabilizes the fluid against the onset of Taylor vortices and alters the velocity fields, both above and below the transition from the initial flow. At small dimensionless turntable frequencies, the transition yields time-independent Taylor vortices which are tilted with respect to the cylinder axis. At larger there is a direct transition to turbulence. We determine the first-order correction to the classical Couette initial flow, to account for the effects of the Coriolis force, by expanding in powers of. We present numerical results for the axial velocity (the only nonvanishing correction term to order) in the infinite-cylinder approximation.     

Experimental and Computational Study of the Thermal Decomposition of 3‐Methyl‐3‐buten‐1‐ol in m‐Xylene Solution

An experimental study of the thermal decomposition of a β‐hydroxy alkene, 3‐methyl‐3‐buten‐1‐ol, in m‐xylene solution, has been carried out at five different temperatures in the range of 513.15–563.15 K. The temperature dependence of the rate constants for the decomposition of this compound in the corresponding Arrhenius equation is given by ln k (s^?1) = (25.65 ± 1.52) ? (17,944 ± 814) (kJ·mol^?1)·T^?1. A computational study has been carried out at the M05–2X/6–31+G(d,p) level of theory to calculate the rate constants and the activation parameters by the classical transition state theory. There is a good agreement between the experimental and calculated rate constants and activation Gibbs energies. The bonding characteristics of reactant, transition state, and products have been investigated by the natural bond orbital analysis, which provides the natural atomic charges and the Wiberg bond indices. Based on the results obtained, the mechanism proposed is a one‐step process proceeding through a six‐membered cyclic transition state, being a concerted and slightly asynchronous process. The results have been compared with those obtained previously by us (Struct Chem 2013, 24, 1811–1816) for the thermal decomposition of 3‐buten‐1‐ol, in m‐xylene solution. We can conclude that in the compound studied in this work, 3‐methyl‐3‐buten‐1‐ol, the effect of substitution at position 3 by a weakly activating CH₃ group is the stabilization of the transition state formed in the reaction and therefore a small increase in the rate of thermal decomposition.     

Structural and Kinetic Aspects of Blood Plasma Protein Adsorption on the Surface of Hydrophobic Polymers

Abstract

Due to the wide use of polymers in medicine, researchers are required to solve a very important problem–to understand the interaction between materials of nonphysiological origin and the surrounding biological liquids, and tissues, particularly blood.     

Fourier Transform Microwave Spectrum and ab Initio Study of Dimethyl Methylphosphonate

The rotational spectrum of dimethyl methylphosphonate (DMMP) has been studied using a pulsed molecular beam Fourier transform microwave spectrometer. The spectrum is complicated by the internal rotation motions of the three methyl tops in the molecule as well as an interconversion motion of the two methoxy groups. Here, we present the microwave spectrum, the ab initio calculations, and the assignment of the rigid-rotor A-symmetry state of the molecule. The rotational constants for this state are A=2828.753(2) MHz, B=1972.360(3) MHz, and C=1614.267(2) MHz. In the following paper, a group theoretical analysis is developed for DMMP. The observed conformation of the molecule has no point-group symmetry and all three electric-dipole selection rules are active, with c-type transitions being the most intense. Ab initio calculations were carried out at both the Hartree-Fock 6-31G* and MP2/6-311G* levels of theory. These calculations indicate that two low-energy conformations are possible separated by energies of less than 170 cm⁻¹. Furthermore, the calculated lowest energy conformer is in agreement with the one observed experimentally. The relative energies of the two low-energy conformers rise from 34 cm⁻¹ at the HF level to 170 cm⁻¹ at the MP2 level.     

Evaporation of a packet of quantized vorticity

We study the diffusion of a packet of quantized vorticity initially confined inside a small region. We find that reconnections fragment the packet into a gas of small vortex loops which fly away. The time scale of the process is in order-of-magnitude agreement with recent experiments performed in 3He-B.