Boron–nitrogen polymers. I. Mechanistic studies of borazine pyrolyses

Abstract

Pyrolyses of B‐triamino‐N‐triphenyl‐, B‐triamino‐N‐trimethyl‐, and B‐trianilino‐borazines were performed between 150 and 300°C. Initial stages of degradation were accompanied by liberation of ammonia in addition to the expected aniline or methylamine; this was most pronounced for the methyl borazine. Aniline elimination proceeded more readily with the B‐anilino than the B‐amino isomer. Data obtained support a ring opening mechanism resulting in telomerizaton accompanied by aniline liberation and formation first of singly then doubly bridged dimers and finally doubly bridged tetramers. Thermal exposure up to 1000°C failed to give pure boron nitride; carbon was invariably retained.

Thermal Oligomerization of Unsymmetrically B-Trisubstituted Borazines

“…Although the structures of the ultimate polymers are probably complex and cross-linked, the process of direct B-N link establishment occurs when the borazine boron atoms bear mono-and dialkylamino groups. These conclusions, consistently with those of Paciorek et al stated above [8], are a crucial point for the choice of the polymerization process and for the identification of the most suitable borazines for preceramic polymer elaboration. In this undertaking, further works are in progress to determine the molecular weights of the oligomers and the influence of others thermolysis conditions on the structure of the obtained polyborazines.…”

“…These compounds were heated under vacuum for 20 h at 140-145 °C whereas the evolved gas were continuously trapped at low temperature. In these cases, no NH 3 liberation has been observed during thermolysis that excludes any ring opening mechanism described by Paciorek et al [8] and Toeniskoetter and Hall [9]. Spectroscopic data are consistent with the presence of borazine rings in the oligomers.…”

Formation, Structure and Properties of Boron Nitride Fibers from Polymer Precursors

“…Company, Sol I, and nitrided products of Sol 1, were obtained with a as poly(ethylene oxide) or poly(N-vinylpyrrolidinone) [9,10,11]. ReRigaku D/Max-B system operating at 45kV and 100 mA ( Figure 4).…”

“…Polyborazines in which a nitrogen atom of one borazine ring is linked to a nitrogen atom of a second borazine nucleus are unknown. Poly(borazinyl amines) which consist of borazine rings linked through borons of adjacent rings by -N(H)-or * -N(R)-groups have been synthesized [9,10,12,13,[19][20][21][57][58][59]. Poly(borazinyl oxides) have been reported in which the borazine rings are linked by oxygen [60].…”

“…Significant among these are precursors for fiber structures of materials such as boron nitride, which can offer the combination of high specific modulus and specific strength, high temperature (oxidation) resistance and optical transparency over a broad range of the electromagnetic spectrum. In spite of the important advances in the chemistry of precursor polymer materials for these ceramic structures [5][6][7][8][9][10][11][12][13][14][15], significant issues * pertaining to continuous fiber formation and thermochemical conversion and consolidation remain to be resolved in developing a satisfactory process for the formation of boron nitride fibers. These are related to choice of precursor materials and precursor fiber formation route, and the effects of these fields and environments during fiber formation and its subsequent conversion to boron * nitride.…”