Polyimidines,a new class of polymers. II. Polyhexamethylenetetraphenyldithiopyromellitimidine

Polyimidines have been shown to be soluble, thermally stable polymers. In searching for an alternate synthetic method the thio analog of this system has been discovered. The brightly colored (red-orange) perthio derivatives of 3,3-diphenylphthalide and 3,3,5,5-tetraphenyipyromellitide were synthesized from their oxo analogs with P₂S₅. The model compound thioimidines were synthesized by reacting 3,3-diphenyldithiophthalide with aniline and with 1,6-hexane diamine and by reacting 3,3,5,5-tetraphenyltetrathiopyromellitide with aniline and n-hexylamine. The polymerization of tetraphenyltetrathiopyromellitide occurred readily with 1,6-hexanediamine in boiling carbon tetrachloride with complete cyclization. This reaction gave an 80% yield with inherent viscosities up to 0.89 and molecular weights up to approximately 11,000. Thermogravimetric analysis showed a 2% weight loss at 200°C and 10% weight loss at 300°C with rapid decomposition above 300°C. Although the polythioimidine was less thermally stable than its oxo analog, it was much more soluble in common solvents (aromatic and chlorinated aliphatic hydrocarbons) and more readily synthesized in higher yield.     

Synthesis of poly(benzylidene phthalide)s: A new class of polymers

Pyromellitic dianhydride (PMDA) was condensed with different aromatic diacetic acids via a Perkin reaction to produce new polymers containing the benzylidenephthalide group in the backbone. Yields ranged from 50 to 90% with inherent viscosities ranging from 0.07 to 0.37 dL/g. Polymerizations at 275°C for 4 h using p-phenylenediacetic acid and PMDA gave the polymer with highest inherent viscosity. However, polymerization under identical conditions of p,p′-diphenyl ether diacetic acid, each with PMDA, yielded poor results. For these two monomers the best polymerization conditions were 250°C for 8 h. In general, the most thermally stable polymer was derived from the diphenyl ether diacetic acid monomer (308°C). This polymer was obtained in highest yields and gave the greatest amount of pyrolytic residue in argon (67%).     

Polyimidines. VIII. Condensation of 3,5-dibenzylidenepyromellitide-1,7-dithione with m-xylylenediamine

A new pyromellitimidine-forming monomer, 3,5-dibenzylidenepyromellitide-1,7-dithione, was synthesized by thionation of 3,5-dibenzylidenepyromellitide using phosphorus pentasulfide in boiling chloro- or bromobenzene. Polymerization of this monomer with m-xylylenediamine (MXDA) in chlorobenezene at 95°C afforded poly(dihydroxydibenzylpyromellitimidinethione) with inherent viscosities of 0.23–0.51 dL/g in yields from 73 to 84%. Subsequent dehydration was accomplished by thermal methods or in a polar aprotic solvent such as dimethylformamide (DMF) using acid catalyst. Hydrated and dehydrated polymers were soluble in N-methyl-2-pyrrolidinone (NMP), m-cresol, and dioxane, and partially soluble in chloroform. Very brittle films could be cast from NMP solution. Thermogravimetric analysis of the dehydrated polymer showed a 10% weight loss in nitrogen atmosphere at 460°C     

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.