Thermal transformations of oligoarylenes

Journal of Thermal Analysis and Calorimetry - Thermal transformations of oligoarylenes, relating to polymers with conjugate systems, have been investigated in air and in vacuo, depending on the...     

Increasing the adhesion of polymers to metals by adding substances with conjugation systems

The electron-donor properties of polymers with conjugation systems (PCS) and their capability of forming -complexes with metals is of interest in relation to adhesion. Small amounts (0.01–0.1%) of substances with polyconjugation systems (polydiphenylbutadiene, polyphenylacetylene, and copolymers of naphthalene and anthracene with benzene) increase the adhesion between aluminum and polymers used as electrical insulation coatings (polyesters, polyimides, and their derivatives). With optimum PCS dosage, the resistance to peeling rises by 15–38%.Institute of Chemical Physics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 2, pp. 365–367, March–April, 1974.     

Synthesis of organic-inorganic polymer structures via the interaction of orthoboric acid with m-phenylene-bismaleimide

The structure and properties of products arising from the reaction of orthoboric acid with m-phenylene-bismaleimide in melt at 200°C have been studied by spectral and physicochemical methods. The data of IR spectroscopy and thermomechanical analysis suggest that, under the chosen conditions, chemical interaction between the reagents occurs. The conversion increases with the time of reaction and the content of m-phenylene-bismaleimide. High-temperature plasticizers, such as diphenyl and triphenylphosphate, unexpectedly favor formation of more rigid polymer structures, whereas a “temporary plasticizer” (decamethylene glycol) hinders interaction between orthoboric acid and m-phenylene-bismaleimide. The temperature corresponding to a 20% weight loss of the polymer synthesized during heating in air at orthoboric acid: m-phenylene-bismaleimide = 80: 20 is 440–445°C, and the carbon-containing fragments are present in the pyrolysate up to 800°C. The polymer samples retain their shape in air for long time and in water vapor for several days. The hydrolytic stability of the products increases with the content of m-phenylene-bismaleimide.     

On the interrelation between microstructure and physicochemical properties of some polyconjugate systems

Soluble oligoarylenes based on naphthalene and anthracene, and fractions of different molecular weights have been studied by electron microscopy. For the examined samples, a definite interrelation is ascertained between microstructure and physicochemical properties, such as density, x-ray parameters, heat of solution, electron paramagnetic resonance (EPR) spectra, and dark conductivity. The molecular-weight distribution of oligoarylenes is shown to decisively influence the degree of packing of macromolecules and their physicochemical properties. This allows interpretation of some anomalous properties of oligoarylenes in comparison with the first members of the corresponding homologous series.     

Low-temperature transformations of orthoboric acid

The thermal transformations of orthoboric acid at 100–105°C in a vacuum (15 ± 5 torr) were studied. The conditions of the formation of β-metaboric acid were determined; β-metaboric acid is a promising product for the preparation of organo-inorganic incombustible polymeric materials with high thermal stability, fairly high hydrolytic stability, and satisfactory elastic properties. The metaboric acid polymorph formed in thermolysis substantially depended on the prehistory of the sample, primarily on microamounts of strongly bound water in orthoboric acid. Thermal treatment of a 1: 1 mixture of “dry” orthoboric acid and boric anhydride gave β-metaboric acid only, thermal treatment of dry orthoboric acid, a mixture of α- and β-metaboric acids, and heating of aqueous solutions of orthoboric acid gave α-metaboric acid only. During storage for three months even in a hermetically closed vessel, dry orthoboric acid absorbed moisture from air, and the products of its thermolysis did not contain β-metaboric acid. Water was absorbed reversibly, and, after thermal treatment of damp orthoboric acid at 60°C in a 10^?2 torr vacuum, the X-ray pattern of the product of its thermolysis again contained β-metaboric acid peaks. Note that α- and β-metaboric acids are unstable and transform back into orthoboric acid during storage.