Preparation of silicon containing polymers—III: Synthesis and characterization of organosilicon azopolyamides

New silicon containing azopolyamides have been prepared from 4,4′-diaminoazobenzene and four structurally related organosilicon acid dichlorides. Polymerization was carried out by the technique of low temperature interfacial polycondensation using methylene chloride-water system. The polymers were yellow to brown in colour. They were characterized by visible and i.r. spectroscopy, X-ray diffraction, solubility and by solution viscosity. Thermal behaviour of these polyamides was studied by dynamic thermogravimetry.     

Internal motion in organosilicon polymers. II. Dimethylpolysilazanes crosslinked through silicon

An investigation of the internal motion in organosilicon polymers by wideline nuclear magnetic resonance has been extended to a pair of dimethylpolysilazanes crosslinked through trifunctional silicon. The data suggest that there is considerable internal motion in all silazanes at 77°K. Evidence is presented for the presence of C₃ rotation of the methyl groups, as well as rotation or torsional oscillation of the Si(CH₃)₂ groups about the polymer backbone. Upon warming the NMR line is seen to narrow, and this is associated with the onset of additional motion, including chain translation and chain flexing or bending. Crosslinking through silicon increases the barrier to chain translation while decreasing the barrier to chain flexing or bending.     

有机硅活性中间体的研究 II. 一些含环丙基的有机硅化合物的合成及其结构

用锂有机物的方法合成了四种含有环丙基有机硅化合物,对上述每种化合物中可能存在着的立体异构进行了分离和和构型测定。     

Effect of structure on the thermal stability of polyimides

Polyimides with different proportions of m-phenylene and p-phenylene (or p,p′-biphenylene) were prepared by polymerizing different molar ratios of m-phenylene diamine and p-phenylene diamine (or p,p′-diaminobiphenyl) with pyromellitic dianhydride in dimethylformamide at 0°C. Chemical cyclodehydration of polyamic acids resulted in the corresponding polyimides. Polymers were characterized by infrared (IR), viscosity, and density measurements. Viscosity and density of polymers decreased with an increase on m-phenylene groups in the backbone. The thermal and thermooxidative stabilities were investigated by dynamic thermogravimetry. Stability decreased when m-phenylene groups were introduced in the backbone.     

Effect of a novel flame retardant containing silicon and nitrogen on the thermal stability and flame retardancy of polycarbonate

A novel flame retardant (PSiN), containing silicon and nitrogen, was synthesized using N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and diphenylsilanediol through solution polycondensation and it was added to polycarbonate (PC). The structure and thermal properties of PSiN were characterized by fourier transform infrared spectroscopy and thermogravimetric analysis (TG) tests. The effect of PSiN on the flame retardancy and thermal behaviors of PC was investigated by limited oxygen index (LOI), vertical burning test (UL-94), and TG tests. The results showed that the flame retardancy and the thermal stability of PC are improved with the addition of PSiN. When 1 mass% PSiN and 0.5 mass% diphenylsulfone sulfonate (KSS) are incorporated, the LOI value of PC is found to be 46, and class V-0 of UL-94 test is passed. The char structure observed by scanning electron microscopy indicated that the surface of the char for PC/KSS/PSiN system holds a firmer and denser char structure when compared with neat PC and PC/KSS system.     

Preparation of silicon-containing polymers. I. Polyimides from dianhydrides and organosilicon diisocyanates

New silicon-containing polyimides have been prepared by the reaction of pyromellitic dianhydride (PMDA) and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) with organosilicon diisocyanates having the following general structure: where R₁ = R₂ = ? CH₃ and ? C₆H₅. Thermal properties of these polyimides were studied were by TG, DTA, and DTG.     

Preparation of silicon-containing polymers IV. Thermally stable organosilicon poly-1,2,4-triazoles

Novel silicon-containing poly-1,2,4-triazoles have been synthesized by the reaction of polyhydrazide precursors and aniline in polyphosphoric acid (PPA) at 260°C. The polyhydrazide intermediates were prepared from aromatic dihydrazides and silicon-containing acid dichlorides via interfacial polycondensation. These polymers and their intermediates were characterized by infrared spectroscopy (IR), solubility, and by solution viscosity. The thermal behavior of these polytriazoles has been studied by dynamic thermogravimetry.     

Ways to improving the thermal stability of organosilicon elastomeric materials

Samples of silicone elastomeric materials based on linear ladder block copolymers containing linear polydimethylsiloxane and ladder phenylsilsesquioxane molecular units have been obtained and investigated. It has been shown that the use of such block copolymers of the brands Lestosil N and Lestosil SM improves the heat resistance of the obtained vulcanizates up to 350°C for a long time.     

Synthesis of organosilicon and organogermanium polymers containing tetraacetylenic groupings in the chain

Conclusions The thermal dehydropolycondensation of bis(diacetylenyl)diphenylsilane and bis(diacetylenyl)diphenylgermane gave polymers containing tetraaeetylene groupings in the chain between the Si and Ge atoms, whose electrophysical and catalytic properties were studied.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2121–2122, September, 1972.     

Synthesis,characterization and thermal degradation kinetics of ferrocene‐containing aramids

Low‐temperature solution‐phase polycondensation of 1,1′‐ferrocenedicarboxylic acid chloride with different aromatic diamines was carried out in tetrahydrofuran in the presence of triethylamine to afford ferrocene‐containing aramids. The products were characterized by their solubilities, inherent viscosities, elemental analysis, FTIR spectroscopy, differential scanning calorimetry and thermogravimetry. All of them were insoluble in common solvents tested, except aramid‐IV (derived from 1,8‐naphthalene diamine), which was slightly soluble in N,N′‐dimethylacetamide, N,N′‐dimethylformamide, dimethylsulfoxide and formic acid. However, all were miscible with concentrated H₂SO₄, forming red‐coloured solutions. These all show a reduction in their solution viscosities at ambient conditions in concentrated H₂SO₄ which may be attributed to their non‐Newtonian behaviour. The glass transition temperature for each aramid was quite high, and stable up to 390 °C. The integral procedural decomposition temperatures for the products were calculated using Doyle's method and were found to be intermediate to that of Nylon 66 (419 °C) and Teflon (555 °C), and the activation energy for decomposition of each product was calculated by the Horowitz and Metzger method. Copyright © 2005 John Wiley & Sons, Ltd.     

Side-chain liquid crystalline polymers with silphenylene-siloxane main chains. II. Preparation and characterization of polymers containing biphenyl mesogens

Side-chain liquid crystalline polymers with poly(silphenylene-siloxane) backbones and 4,4′-biphenyl-containing pendant mesogenic groups have been prepared and characterized. Polymers with spacers having only three methylene groups were not liquid crystalline, LC, but those with spacers having eight methylene groups or more and a long terminal substituent were LC as indicated by an isotropization peak on the shoulder of the melting peak in the DSC thermogram and the appearance of a Schlieren texture on examination by polarized light microscopy. However, the LC behavior could not be confirmed by wide-angle X-ray diffraction, WAXD, because the crystalline pattern apparently remained up to the isotropization temperature, presumably because the melting transition and isotropization are too close. In contrast, polymethylsiloxanes with the same mesogenic side-chains revealed the presence of well-defined smectic phases by WAXD as well as by polarized light microscopy.     

Photodegradation of aramids. II. Irradiation in air

A series of isomeric fully aromatic polyamides (aramids) were photodegraded in the presence of oxygen. Films and fibers of these aramids gave carboxylic acids as the major products when measured by infrared spectroscopy and potentiometric titration. These acids probably resulted from the oxygen interception of the radicals generated by photocleavage of the amide bonds. In contrast to results found upon irradiation in the absence of oxygen, carboxylic acid formation was accompanied by a rapid loss in molecular weight, and a decrease in useful mechanical properties. Quantum yields for carboxylic acid formation were ≤5.5 × 10^?5 mole/einstein and decreased along the aramid series roughly in agreement with increases in T_g. The photo-Fries rearrangement product was observed in aramid fibers irradiated in air, whereas no rearrangement product was seen in films irradiated in air.     

Effect of organosilicon chain-transfer agents on the heat resistance of vinyl polymers

The effect exerted on the resistance of polymers to thermal oxidation degradation by organosilicon hydrides used as chain-transfer agents in polymerization of styrene, methyl methacrylate, and vinyl acetate was examined.     

Thermal stability of P-N containing polymers

The thermal stability of a number of P-N containing polymers was studied employing softening range, thermogravimetry and differential scanning calorimetry. The products generally exhibited better weight retension than their carbon counterparts showing poor low temperature stability but moderate high temperature (to 1000°) stability. Degradation to about 300° occurs via nonoxidative routes whereas above 300° degradation occurs by oxidative routes in air. Most stability plateaus are kinetically controlled. Other commonalities and possible degradative routes are given.

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Zusammenfassung Die thermische Stabilität einer Anzahl P-N-haltiger Polymere wurde durch die Untersuchung des Erweichungsbereichs, die thermogravimetrische Analyse und die Differential-Abtastkalorimetrie geprüft. Die Produkte erwiesen im Allgemeinen eine bessere Konstanz des Gewichts als ihre kohlenstoffhaltigen Analoge mit geringer Stabilität bei niedrigen, doch mäßiger Stabilität bei hohen Temperaturen (bis zu 1000°C). Die Zersetzung bis zu 300°C erfolgt auf nicht-oxidativem Wege, während bei Temperaturen über 300°C die Zersetzung in Luft sich auf oxidativem Wege vollzieht. Die meisten Stabilitätsplateaus sind kinetisch bedingt. Andere Einzelheiten und mögliche Zersetzungswege werden angeführt.

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Résumé Etude de la stabilité thermique dans le domaine du ramollissement de plusieurs polymères contenant P et N, par thermogravimétrie et par analyse calorimétrique différentielle (DSC). Les produits conservent généralement d'autant mieux leur stabilité pondérale que leurs équivalents carbonés possèdent une faible stabilité thermique à basse température mais une stabilité modérée à haute température (jusqu'à 1000°C). Jusqu'à 300°C, la dégradation se produit par un processus non oxydant alors qu'au-dessus de cette température et dans l'air, la dégradation s'effectue par le biais de l'oxydation. La plupart des paliers thermogravimétriques sont contrôlés cinétiquement. D'autres voies de dégradation possibles sont également signalées.

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P-N , , . , , ( 1000°C) , , . 300°C , 300°C — . . .

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The author is pleased to acknowledge partial support of this research by an American Chemical Society — Petroleum Research Fund Grant 7814-B1,3 and a University of South Dakota Research Fund Grant.     

Kinetics of thermal decomposition of polymers. II

The rate equations for the thermal decomposition of a polymer by a random scission reaction followed by rapid depolymerization of a constant number of monomer units from both fragments together with rapid evaporation of low molecular weight species are solved by using a different approach from that used by previous workers. The results obtained are more specific and differ slightly from previous treatments.     

Heat-resistant polymers containing bipyridyl units. II. Polyamide-imides

Polyamide-amic acids containing bipyridyl units were prepared by polymerization of various bipyridyl diamines with trimellitic anhydride acid chloride. These polymers were converted to polyamide-imides by thermal cyclization. The resulting polyamide-imides exhibited very good solubility in organic solvents.     

Chemistry of organosilicon compounds: CIV. Syntheses of novel organoelement heterocycles containing titanium and silicon

Four new dicyclopentadienyltitanium(IV) metallocycles, Cp₂TiCH₂XCH₂ (X = SiMe₂OSiMe₂, SiMe₂CH₂SiMe₂, SiMe₂SiMe₂, and SiMe₂SiMe₂SiMe₂) are prepared and characterized.