Fine Pore-Structure Engineering by Ligand Conformational Control of Naphthalene Diimide-Based Semiconducting Porous Coordination Polymers for Efficient Chemiresistive Gas Sensing

Exploring new porous coordination polymers (PCPs) that have tunable structure and conductivity is attractive but remains challenging. Herein, fine pore structure engineering by ligand conformation control of naphthalene diimide (NDI)-based semiconducting PCPs with π stacking-dependent conductivity tunability is achieved. The π stacking distances and ligand conformation in these isoreticular PCPs were modulated by employing metal centers with different coordination geometries. As a result, three conjugated PCPs (Co−pyNDI, Ni−pyNDI, and Zn−pyNDI) with varying pore structure and conductivity were obtained. Their crystal structures were determined by three-dimensional electron diffraction. The through-space charge transfer and tunable pore structure in these PCPs result in modulated selectivity and sensitivity in gas sensing. Zn−pyNDI can serve as a room-temperature operable chemiresistive sensor selective to acetone.     

Phosphonitrilic Chloride. XXXVIII. Study of Electrical Conductivity of Diisothiocyanophosphazene Polymer and Hexaisothiocyanocyclotriphosphazene

The electrical conductivity of hexaisothiocyanocyclotriphos-phazene NsPs(NCS)₆ and linear diisothiocyanophosphazene polymer (NP(NCS)₂)n was determined. It was found that hexaisothiocyanocyclotriphosphazene is ionic and linear diiso-thiocyanocyclotriphosphazene polymer has predominantly electron conductivity.     

Synthesis of New Polyphosphazenes. The Reactions of Poly(dichlorophosphazene) with Aminotetraalkoxycyclotriphosphazene and Sodium Phenoxide

Abstract

A new poly(organophosphazenes) copolymer was formed from the reaction of aminopentafluoroethoxycyclotriphosphazene, sodium phenoxide, and poly(dichlorophosphazene). The polymer was thermoplastic and the T_g increased with an increasing amount of the phenol group. The T_g of the polymer with aminopentafluoroethoxycyclotriphosphazene attached as a pendant group was similar to the T_g of polyfluoroethoxyphosphazene.     

Liquid crystalline phase transitions in hexakis(4-(4′-heptyloxy)biphenoxy)cyclotriphosphazene

Abstract

Hexakis(4-(4′-heptyloxy)biphenoxy)cyclotriphosphazene (HHCP) was synthesized from hexachlorocyclotriphosphazene and 4-heptyloxy-4′-hydroxybiphenyl. The mesogenicity of HHCP was studied by DSC, FTIR spectroscopy and polarizing microscopy. Enantiotropic smectic C and nematic phases were observed between 450 and 455 K and 455 and 456 K, respectively, on heating, and between 456 and 455 K (nematic) and 455 and 440 K (smectic C) on cooling from the isotropic liquid phase. The introduction of the heptyloxybiphenoxy groups as side chains into cyclotriphosphazene has generated the liquid crystalline phase. FTIR spectroscopy showed that the P=N and P-O-(C) stretching vibrations converted to lower frequencies from 1224 to 1210 cm^?1 and from 920 to 910cm^?1, respectively, at the crystalline (C)-S_c phase transition. This result suggests that the state of the cyclotriphosphazene ring dramatically changes near the C-S_c phase transition.     

Voltammetric Determination of Boric Acid Using the Ternary Complexation System with Salicylaldehyde and H‐Acid

A square‐wave voltammetric method for the determination of boric acid in water has been described based on the new understanding of the electrochemical behavior of boric acid‐Azomethine H complexation. Salicylaldehyde and H‐acid were used as the starting materials of boric acid‐Azomethine H complex and their concentrations were optimized for boric acid determination in water. A glassy carbon electrode, instead of a conventional mercury electrode, was used in the measurement. The detection limit of the proposed method was 0.10 mg B dm^?3. The proposed method was successfully used for boric acid determination in the water from a seawater desalination RO plant.     

The effect of viscoelasticity on the extrusion drawing in film-casting process

The governing rheological property for extrusion drawing in film-casting process is proposed in this study. The experiment of film-casting process using the high-pressure process low-density polyethylene (LDPE) was performed. The non-isothermal viscoelastic simulation of the film casting experiment was also carried out to explain the experimental results. Film width reduction phenomenon in an air gap, so-called neck-in behavior, was investigated by using the simulation of the LDPE and the model fluids exhibiting specific viscoelasticity. The neck-in phenomenon was also examined using theoretical model based on force balance and deformation type of a film. As a result, the neck-in normalized by the air gap was in good correlation with the ratio of planar to uniaxial elongational viscosity rather than the strain hardening nature of uniaxial elongational viscosity.     

Molecular‐Complex Formation of Syndiotactic Polystyrene with Stable Radical Molecules

Summary: The formation of a molecular‐complex crystalline phase of syndiotactic polystyrene (sPS) that contains a stable nitroxide radical compound, 2,2,6,6‐tetramethylpiperidinyl‐N‐oxyl (TEMPO), is confirmed by IR and electron spin resonance (ESR) spectroscopy, X‐ray diffractometry, and thermogravimetric analysis. Through a guest exchange procedure assisted by a plasticizing agent, the original guest (chloroform) contained in the starting clathrate phase is completely replaced by TEMPO. Although the conformational regularity of the sPS helices in the resultant crystalline phase that contains TEMPO is similar to that in the starting clathrate phase, the host lattice expands in the 010 direction. The guest TEMPO molecules exhibit a significantly broadened ESR signal because of their highly concentrated state in the complex crystalline phase.

Thermogravimetric measurement of a powder sample of the sPS/TEMPO complex.