Thermal Oligomerization of Unsymmetrically B-Trisubstituted Borazines

Toury, Bérangère; Miele, Philippe; Cornu, David; Bonnetot, Β.; Mongeot, H.

doi:10.1515/mgmc.1999.22.4.231

Cited by 16 publications

(15 citation statements)

References 11 publications

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“…[14] We have established that the formation of B±N direct bonds between borazine rings is promoted by the presence of dialkylamino substituents on the starting monomer. Moreover, we have shown that this mechanism is predominant compared to the formation of ±N(R)± bridges between the rings, which is the mechanism usually described for tri(methylamino)borazine thermolysis [12,15] (Fig.…”

Section: Thermal Polycondensation Of 1 2 and 3 Into Oligomeric Precmentioning

confidence: 91%

“…2), in agreement with the results previously reported in the literature for similar compounds. [14,16] The resulting polyborazine 4 exhibits a low average molecular weight (M w = 870), indicating that it should be considered as a light oligomer (hexamer on average). The 11 B NMR spectrum exhibits one broad resonance at d = 24.8, attributed both to boron atoms bound to dimethylamino groups and to boron atoms bound to borazinic rings, consistent with data reported for polymers derived from alkylaminoborazines similar to 1.…”

Section: Thermal Polycondensation Of 1 2 and 3 Into Oligomeric Precmentioning

confidence: 99%

“…We have previously reported that non-symmetrically substituted B-tri(alkylamino)borazines oligomerize under argon via the formation of both ±N(R)± bridges and direct inter-ring B±N bonds between the rings, the formation of the latter being to a large extent dependent on the presence of dialkylamino substituents on the precursors of BN fibers. [14] On the basis of these results, we focused our attention in the work presented here on polyborazines prepared from B-tri(alkylamino)borazines displaying at least one dimethylamino substituent. Moreover, the alkyl groups used were methyl ones in order to improve the ceramic yield.…”

Section: Introductionmentioning

confidence: 99%

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Boron Nitride Fibers Prepared from Symmetric and Asymmetric Alkylaminoborazines

Toury

Miele²,

Cornu

et al. 2002

Adv. Funct. Mater.

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The thermolysis of 2,4,6‐[(CH3)2N]3B3N3H3 (1), 2,4‐[(CH3)2N]2‐6‐(CH3HN)B3N3H3 (2), and 2‐[(CH3)2N]‐4,6‐(CH3HN)2B3‐N3H3 (3) led to polyborazines 4, 5, and 6 respectively. The polymers display direct B–N bonds between borazinic B3N3 rings and, in addition, a proportion of –N(CH3)– bridges for 5 and 6, as clearly underlined by 13C NMR spectroscopy. Melt‐spinning of these three polymeric precursors exemplified that their ease of processing increases in the order 4 < 5 < 6. Nevertheless, polyborazine filaments could be prepared from each of them and a subsequent thermal treatment up to 1800 °C resulted in the formation of crystalline hexagonal boron nitride fibers, which were characterized by X‐ray diffraction analysis, Fourier transform infrared (FTIR) spectroscopy, and Raman spectroscopy. Scanning electron microscopy (SEM) images showed that the ceramic fibers are circular and dense without major defects. The mechanical properties for 4‐derived fibers could not be measured because of their brittleness, whereas measurements on 5‐ and 6‐derived fibers gave tensile strength σR = 0.51 GPa, Young’s modulus E = 67 GPa, and σR = 0.69 GPa, E = 170 GPa, respectively. The improvement in mechanical properties for ceramic fibers prepared respectively from 4, 5, and 6 could be explained to a large extent by the improvement of the processing properties of the preceramic polymers. This evolution could be related to the increased ratio of bridging –N(CH3)– groups between the B3N3 rings within the polymers 4, 5, and 6 and therefore to the functionalities of the starting monomers 1, 2, and 3.

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Section: Thermal Polycondensation Of 1 2 and 3 Into Oligomeric Precmentioning

confidence: 91%

Section: Thermal Polycondensation Of 1 2 and 3 Into Oligomeric Precmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Boron Nitride Fibers Prepared from Symmetric and Asymmetric Alkylaminoborazines

Toury

Miele²,

Cornu

et al. 2002

Adv. Funct. Mater.

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“…Then DMAB was polymerized by heating for 8 h at 1603C under an argon stream (16). A light-brown, glassy polymer was obtained after cooling and characterized using DSC, TGA, and elemental analysis (B, 20.8; N, 47.7; C, 24.6; H, 5.5).…”

Section: Dmab-based Polymer (Iii)mentioning

confidence: 99%

“…To get a &&two-point'' pseudo-linear polymer, an asymmetric borazine, +(CH ) N,+CH NH, B N H , (DMAB) (Fig. 1c) can be prepared and polymerized (1,11,16). In this work, four kinds of processible polymers have been prepared from the borazines described above: a dipentylamine modi"ed polyborazylene (I), a copolymer resulting from the reaction between borazine and MAB (II), a DMAB-based polymer (III), and a MABbased polymer (IV).…”

Section: Introductionmentioning

confidence: 99%