The synthesis and properties of crystalline polymers of the type of poly‐p‐xylenes and polyphenylene methyl derivatives

Abstract

AbstractFor the purpose of obtaining polymeric hydrocarbons of enhanced thermostability, linear polymers of regular structure of the type (CH2ArCH2)n and (ArCH2)a with aromatic units in the chain were synthesized. Polymers of the first type were obtained by reaction of metallic sodium with the dichloromethyl derivatives of benzene, m,‐ and p‐xylenes, diphenylmethane, diphenyl and naphthalene in dioxane medium at 20–25°C. The m‐xylene derivative had a CH2Cl group in the m‐position and the others, dichlorides in the p‐ or p,p′‐positions. The polymers were precipitated from the solutions on forming and after removal of excess sodium with the aid of methanol and elimination of the low molecular impurities they appeared as colorless powders of the composition of hydrocarbons, at times containing chlorine. X‐ray analysis of the polymers revealed the presence of a crystalline structure the degree of which varied, depending upon the structure. The polymers differed greatly in solubility and melting points. Thus naphthalene and diphenyl derivatives, evidently being crosslinked three‐dimensional polymers, did not dissolve even in boilling α‐bromonaphthalene and decomposed above 300° and 550° without melting, while derivatives of other hydrocarbons dissolved in bromonaphthlene, melted, and probably were linear polymers of low molecular weight. The m‐xylene derivative was distinguished by low crystallinity, low melting point (130–135°C.) and easily dissolved in chloroform even in the cold. Diphenylmethane derivatives with a more clearly expressed crystallinity melted at 250–255°C. and began to dissolve in α‐bromonaphthaline only at 130°C. p‐Xylene derivatives, like poly‐p‐xylylene, were highly crystalline and melted at 350°, but began to dissolve in bromonaphthalene only at 235°. The molecular weight of the soluble polymers could be determined (according to Rast's method) only for the soluble m‐xylene derivative, which, depending upon the conditions of formation, varied from 1850 to 4000. Polymers of the second type were obtained by polycondensation of aromatic hydrocarbons with paraform and also with the dichloro‐, dioxy‐, and diacetoxymethyl derivatives of aromatic hydrocarbons in boiling glacial acetic acid containing sulfuric acid. In this way starting from p‐xylene and durene one could obtain high‐melting crystalline polymers with melting points above 250 and 320°, dissolving only in high boiling solvents. Condensation of durene with dichloromethyl derivatives of p‐ and m‐xylene as well as with p‐xylylene chloride led to the formation of high melting polymers of the type (ArCH2Ar′CH2)n containing two different aromatic units in the chain.