Polyethers derived from bisphenols and highly fluorinated aromatics

A series of fluorinated aromatic polyethers was synthesized via aromatic nucleophilic substitution of highly fluorinated aromatics (1,2,4,5-tetrafluorobenzene, hexafluorobenzene, and decafluorobiphenyl) with bisphenol AF or bisphenol A. Polymerization with 1,2,4,5-tetrafluorobenzene was not observed, and polymerization of hexafluorobenzene with bisphenol proceeded only if the potassium carbonate–bisphenol ratio was carefully controlled. The polymer condensed from decafluorobiphenyl and bisphenol AF was prepared in 77% yield with an inherent viscosity of 1.01 dL/g. The polymer prepared from the condensation of decafluorobiphenyl with bisphenol A was obtained in 48% yield with an inherent viscosity of 0.28 dL/g. These polymers were very soluble in common organic solvents, formed clear, colorless films, and were thermally stable (> 450°C by TGA). The fully fluorinated polymer exhibited low water uptake (0.3%) and dielectric constant (2.17). © 1992 John Wiley & Sons, Inc.     

Adhesion Behaviour of Organically-Modified Silicate Coatings on Stainless Steel

The mechanical properties of organically modified silicate coatings on stainless steel substrates were investigated, using nano-indentation and simultaneous in situ microtensile testing/optical microscopy. The load-displacement response and fracture behaviour is examined to ascertain the effects of different organic groups on the film properties and adhesion characteristics. The relationship between the morphology and mechanical properties of the films is discussed, and it is demonstrated that the mechanical response of the coatings is significantly influenced by the nature of the organic group attached to the ormocer precursor.     

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.     

Precipitation reactions of thiobenzoylphenylhydroxylamine and its use as a reagent for copper

Thiobenzoylphenylhydroxylamine (TBPHA) quantitatively precipitates copper as Cu(C₁₃H₁₀NSO)₂ which can be used as a weighing form for copper; the gravimetric factor is 0.12217. Iron, aluminium, chromium and commonly accompanying elements do not interfere. Quantitative precipitation and separation of several metals from highly acidic solutions is possible. The precipitation reactions of metals with TBPHA, over a wide range of acidity and in the presence of EDTA, are tabulated. TBPHA is of little value as a colorimetric reagent.     

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.     

History of Heat-Resistant Polymers

Thermally stable polymers can be traced back to the late 1950s when structures were first synthesized which could exist above 300°C in air. Perhaps the first two types of polymers most significant here were aromatic polyamides and polybenzimidazoles. The latter was important because its discovery opened the field of polyheterocycles as heat-resistant backbone functions. The impetus for this field of study was originally aerospace technology (ablation shields, coatings, and adhesives). Since that time, however, other needs have been filled with these types of polymers: high modulus fibers, flame-proof clothing, and reverse osmosis membranes. These new, unexpected advantages have provided the need for further research to replace the decrease in aerospace efforts. Research has continued, not to find a material which is more thermally stable, but to enable better processing of the polymers at hand. This change is due to a plateau seen in thermal stability (up to 600°C in air and up to 800°C in nitrogen by TGA) and to the poor tractibility observed for early heat-resistant polymers. Inorganic polymers have not been investigated in depth for these applications.     

Skew Clifford algebras

We introduce a generalization, called a skew Clifford algebra, of a Clifford algebra, and relate these new algebras to the notion of graded skew Clifford algebra that was defined in 2010. In particular, we examine homogenizations of skew Clifford algebras, and determine which skew Clifford algebras can be homogenized to create Artin-Schelter regular algebras. Just as (classical) Clifford algebras are the Poincaré-Birkhoff-Witt (PBW) deformations of exterior algebras, skew Clifford algebras are the ${\mathbb{Z}}_2$-graded PBW deformations of quantum exterior algebras. We also determine the possible dimensions of skew Clifford algebras and provide several examples.     

Pricing European options with a log Student’s t-distribution: A Gosset formula

The distributions of returns for stocks are not well described by a normal probability density function (pdf). Student’s t-distributions, which have fat tails, are known to fit the distributions of the returns. We present pricing of European call or put options using a log Student’s t-distribution, which we call a Gosset approach in honour of W.S. Gosset, the author behind the nom de plume Student. The approach that we present can be used to price European options using other distributions and yields the Black-Scholes formula for returns described by a normal pdf.     

FTIR Emission Spectra, Molecular Constants, and Potential Curve of Ground State GeO

Extensive new high-temperature, high-resolution FTIR emission spectroscopy measurements for the five common isotopomers of GeO are combined with previous diode laser and microwave measurements in combined isotopomer analyses. New Dunham expansion parameters and an accurate analytical potential energy function are determined for the ground X1Sigma+ state. Copyright 1999 Academic Press.     

Cracking and Decohesion of Sol-Gel Hybrid Coatings on Metallic Substrates

Thin film coatings based on organically modified silanes were synthesized using sol-gel technology. Various mixtures of tetraethoxysilane and glycidoxypropyltrimethoxysilane precursors were used to produce sol-gel coatings on as-received and thermally oxidised copper, aluminium and titanium substrates. The mechanical properties and adhesion behaviour of the coatings were assessed using nano-indentation and microtensile testing, respectively. The relationship between the film structure and its mechanical response is examined. It is shown that the mechanical properties (hardness and Young's modulus) of the coatings are influenced dramatically by the organic substituent and the presence of an oxide layer thermally grown on the substrate material prior to deposition plays an important role on the film/substrate adhesion behaviour.