Polyimidines. IV. The synthesis and polymerization of 3,3-diphenyl-6-aminophthalide

The monomer 3,3-diphenyl-6-aminophthalide was synthesized in a 20% yield by the following sequence of reactions: nitration of phthalimide, hydrolysis and dehydration to 4-nitrophthalic anhydride, Friedel–Crafts reaction with benzene to 2-benzoyl-5-nitrobenzoic acid, cyclization with thionyl chloride to the pseudoacid chloride, Friedel–Crafts reaction with benzene, and, finally, reduction of the nitro group to the amino function with Adams catalyst. Although the five-substituted isomer is also possible, it was obtained in yields of only one-fifth to one-tenth of those for the 6-substituted isomer. The 3,3-diphenyl-6-aminophthalide underwent polymerization with difficulty to yield low-molecular-weight polyimidines (inherent viscosity up to 0.68 dl/g) in reasonable yields (32?88%). Because of the rigid character of the backbone and steric crowding, conditions for polymerization were rather severe: 1–2 days at 180–225°C in nitrobenzene or polyphosphoric acid or 350°C in a sealed tube. The addition of sand to the reactants in the sealed tubes caused an increase in yield and molecular weight. The polymers were subjected to thermogravimetric analysis in air and nitrogen. The temperatures at which a 10% weight loss occurred were as high as 440°C in air and 510°C in nitrogen. These stabilities were similar to those encountered for previously synthesized all-aromatic polyimidines.     

Surface ordering at the air–nematic interface. Part 2. A spectroscopic ellipsometry study of orientational order

Spectroscopic ellipsometry has been used to measure enhanced orientational ordering at the nematic–air interface of 8CB as the smectic A phase was approached by cooling from the isotropic phase. The depth profile of the orientational order has been estimated by calculating the ellipsometric parameters for a homeotropic uniaxial surface film on a uniaxial sub‐phase using the Abelès matrix method. This showed that the depth of the enhanced orientationally ordered region was ～10 nm at 0.5°C above the nematic–smectic A transition. This is substantially less than the thickness of the region with surface enhanced smectic order as determined by neutron reflection and a model of the surface structure consistent with both sets of results is proposed.     

Thermally Stable Polymers: Polyoxadiazoles,Polyoxadiazole-N-Oxides,Polythiazoles, and Polythiadiazoles

This review is organized into four sections according to backbone functional group: (1) poly(l₎3,4-oxadiazoles), (2) poly(l,2,4-oxa-diazoles) and poly(l,2,4- and 1,2,5-oxadiazole-N-oxides), (3) poly -thiazoles, and (4) polythiadiazoles. The structures of the principal groups are given below.     

Insight into the Structural Variation and Sodium Storage Behavior of Polyoxometalates Encapsulated within Single-Walled Carbon Nanotubes

The host–guest interaction can remarkably alter the physiochemical properties of composite materials. It is crucial to clarify the mechanism by revealing the influence of the host on the electronic structure of the guest molecules. Herein, we study the structural variation of polyoxometalates (POMs) after being confined in single-walled carbon nanotubes (SWNT). What we found is that in addition to the reported charge transfer from SWNT to POM, an intramolecular electron transfer within a single POM cluster can be observed in the POM@SWNT composites. Moreover, the charge density on the bridged oxygen of POMs is prominently enhanced. The structural change and electron reconfiguration of POMs upon encapsulation in SWNT significantly speed up electron and ion transport, leading to the improved electrochemical performance for sodium ions storage.