Synthesis of spiroisoindolinones by palladium-catalyzed heterocyclization of 2-iodobenzoyl chloride with ketimines

2-Iodobenzoyl chloride reacts with ketimines in acetonitrile at 100° under carbon monoxide pressure in the presence of a catalytic amount of a palladium catalyst together with triethylamine to afford the corresponding spiroisoindolinones in high yields.     

Preparation of Polyacrylonitrile Microfibers Using Gelation and Phase Separation During the Solution Polymerization of Acrylonitrile

Polyacrylonitrile (PAN) microfibrils were prepared directly via the solution polymerization of acrylonitrile at specified ratios of controlling solvent dimethyl sulfoxide (DMSO) to non‐solvent tert‐butyl alcohol. At first, gel formation occurred due to the interaction between DMSO and the cyano groups of PAN. The microfibrillar structure was then formed through the phase separation of PAN molecules from the gel. It is shown that very small variations in the solvent/non‐solvent ratio facilitate a major change in the gelation and phase separation processes.     

Particle Loaded Monolithic Sol‐Gel Columns for Capillary Electrochromatography: A New Dimension for High Performance Liquid Chromatography

Particle‐loaded (3 μm, octadecylsilica) monolithic sol‐gel columns have been prepared and selected characteristics measured. Several electrical properties may be calculated from simple current measurements in the column as a whole. Resistivity in the packed segment is approximately three times that in open segments, resulting in a 60% increase in field strength in the packed regions compared to the capillary with no packing. The surprisingly high specific permeability of these sol‐gel columns is characteristic of 8‐μm particles, which allows their operation in the microLC mode at pressures as low as 69 kPa where their efficiency is about 50,000 plates per meter and in the CEC mode where efficiency is about 106,000 plates per meter at 5 kV. There is a relatively rapid loss of efficiency with increasing linear velocity beyond 0.2 mm/s in microLC mode, which may be due to additional diffusion processes in the inter‐particulate voids. A rapid loss of efficiency above 0.5 mm/s is also observed in the CEC mode, for the same reasons. Chromatographic retention behavior in either separation mode is characteristic of conventional octadecylsilica particles, indicating that analytes have significant access to the surface within the pores of the immobilized bonded phase.     

Phase behaviors of nematic liquid crystal/linear polymer systems: Effect of specific interactions

A new model has been proposed that takes into account the specific interaction between nematic liquid crystal and polymer. A generalized lattice fluid model was employed to describe the specific interaction between liquid crystal and polymer. The proposed model postulates that a specific interaction between dissimilar components in a mixture has both an energetic and an entropic component. A degeneracy parameter and an interaction parameter are also discussed, followed by a comparison of the experimental data to the model. The results show that that a specific interaction plays an important role in the phase behaviors of the given systems. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4128–4136, 2000     

Thermal stress analysis for polyimide thin film: The effect of solvent evaporation

We propose a stress model to account for the thermal stress caused by a mismatch of isobaric expansivity, solvent evaporation, and imidization. The evaporation strain term is given as functions of a viscosity, and solvent weight fraction. The proposed model is in very good agreement with experimental data and gives useful information about the analysis of the thermal stress caused in polymeric films.     

Surface studies of polyethers with well‐defined segmental length

Two series of polyethers were synthesized by the polymerization of 1, n‐dibromoalkane (n = 4, 6, 8, 10, 12, 14 and 18) with bisphenol‐A (BA) and 4, 4'‐(hexafluoroisopropylidene) diphenol‐A. The length of the flexible aliphatic segment changes from 4 Å to 21 Å (corresponding to 4 to 18 CH₂ groups). X‐ray photoelectron spectroscopy (XPS), time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and atomic force microscopy (AFM) were used to characterize the surfaces of the polyethers. The influence of the length of the flexible aliphatic segments on the surface composition of the BA and 6FBA polyethers was investigated. The intensity ratios of the characteristic SIMS peaks of the flexible segments to those of the rigid segments were related to the length of the flexible segments and the XPS results confirmed that the SIMS intensity ratios can be used to determine the surface compositions. AFM was utilized to investigate the crystallization process of the BA polymer with n = 8. The appearance of nuclei, the generation of primary lamellae and the formation of spherulites were observed dynamically. Nuclei appeared first as 10 nm dots, some disappeared and a few could grow into lamellae. The lamellae that developed from the nuclei bred more lamellae, which in turn induced secondary nucleation and branching of lamellae and finally led to a spherical appearance.