C. Duriez et al. / Journal of Organometallic Chemistry 657 (2002) 107Á
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113
1
NH and NH3 correspond to positive signals and NH2 as
negative one, tertiary nitrogen atom do not lead to any
resonance because they are not bounded to proton). The
chemical shifts were explained in ppm and proton and
carbon spectra were obtained from C6D6 solutions. The
following abbreviations are used: d, doublet; s, singlet; t,
triplet; q, quadruplet; br, broad. The IR spectra were
recorded on a FTIR Nicolet Magna 550 spectrophot-
ometer in KBr pellets. The ceramic yield was determined
using a TGA B70 apparatus and the study was
performed under ammonia up to 600 8C and then
under nitrogen up to 1000 8C with a 2 8C minꢁ1
heating rate. DCS analysis were ran on a TA 8000
Mettler-Toledo under an Ar atmosphere. SEM images
were obtained from a JEOL 55 CF (CMEABG Lyon).
X-ray powder diffraction (XRD) were obtained with
stretch.); 1194 (NC); 1029 (NH); 715 (BN bend). H-
NMR (ppm): d 1.50 (s, br, 1H, (BNHCH3); 2.5 (s, br,
3H, (NHCH3)), 2.66 (s, br, 1H (NH cycle)). 11B-NMR
(ppm): d 25.9 (s, br). 14 N-NMR (ppm): d ꢁ
1N (NHCH3)); ꢁ
(ppm): d 27.5 (s, br (NHCH3).
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377.4 (s, br,
321.9 (s, br, 1N (NH cycle). 13C-NMR
/
3.3.3. Synthesis and characterisation of the copolymer
The reaction of copolymerisation was performed in a
Schlenk vessel under controlled atmosphere. The MAB,
a waxy compound, and the borazine, clear liquid, were
mixed together under a vigorous magnetic stirring. As
soon as the mixing has been done, a gas evolved
characterised as mainly hydrogen. After 36 h, the
copolymer was allowed to cold down to room tempera-
ture (r.t.) and then the product was kept at ꢁ20 8C to
/
CuÁ
/
Ka radiation using a Philips PW 3710/3020 dif-
fractometer equipped with a monochromator.
avoid a chemical evolution. The copolymer was very
waxy and the stirring was not very efficient after few
hours. IR (cmꢁ1): n 3447, 3250 (NH); 2934 (CH); 2483
(BH); 1445 (CH); 1404 (BN stretch.); 1101 (NC); 1029
3.3. Preparation of the studied compounds
(NH); 700Á
br (BH)), 27.1 (s, br (BN3)), ꢁ
NMR (ppm): d ꢁ254, ꢁ251, ꢁ
276, ꢁ
286 (B2NH). 13C-NMR (ppm): d 27.5 (s, br
(NHCH3), 34.1 (s, ÃNCH3Ã).
/
650 (BN bend). 11B-NMR (ppm): d 31.2 (d,
17.5 (q, br (BH3)). 14N-
253, ꢁ257, ꢁ266,
3.3.1. Synthesis and characterisation of borazine
/
The borazine was prepared using a two steps classical
method. In a first step, NH3BH3 was prepared from
NH4CO3 and KBH4 through an exchange reaction
performed in THF [15,17]. IR (cmꢁ1): n 3315 (NH);
2350 (BH); 1375 (BN str.); 785 (BN bend). H-NMR
(ppm): d 1.47 (q, 3H, JHB
/
/
/
/
/
ꢁ
/
/
/
/
1
3.4. Preceramisation and ceramisation conditions
1
ꢂ
/
94 Hz (BH3); 4.07 (br t,
22.4
373.6 (q,
70 Hz). The amine borane NH3BH3 was the
1
3H, JH14Nꢂ
/
34 Hz (NH3). 11B-NMR (ppm): d ꢁ
94 Hz). 15N-NMR (ppm): d ꢁ
/
The crude polymer fibres were transformed into
ceramic fibres by a two steps thermal and chemical
treatment using two different apparatus. First, a pre-
ceramisation; was performed from r.t. up to 1000 8C in
a classic ovens fitted with a silica tube, this operation
was run under reactive ammonia flow (1 l hꢁ1) up to
600 8C and then under nitrogen flow. Ammonia was
used to strip the organic parts of the copolymer, as
showed in previous work [25]. The heating rates used
were 18 minꢁ1 up to 600 8C and then 58 minꢁ1 up to
1000 8C. Then the fibres were transferred into a high
temperature oven where the were heated up to 1800 8C
with a heating rate of 108 minꢁ1 under a nitrogen
atmosphere.
1
(q, JBH
ꢂ
/
/
1JNH
ꢂ
/
pyrolysed in glyme as described in the literature [16,17].
It was purified by low pressure distillation leading to
pure monomer. IR (cmꢁ1): n 3460 (NH); 2496 (BH);
1
1425 (BN str.); 745 (BN bend). H-NMR (ppm): d 4.53
133 Hz (BH); 5.54 (t, 3H, 1JH14Nꢂ
(q, 3H, 1JHB
ꢂ
/
/
54 Hz
133 Hz). 15 N-
ꢂ67 Hz).
(NH). 11B-NMR (ppm): d 30.4 (d, 1JBH
ꢂ
/
1
265.8 (q, JNH
NMR (ppm): d ꢁ
/
/
3.3.2. Synthesis and characterisation of the MAB
MAB was prepared from TCB and methyl amine
CH3NH2. TCB was commercially unavailable so it was
prepared in the laboratory using the standard method
using the reaction between BCl3 and NH4Cl in
C6H5CH3 [18]. To a suspension of NH4Cl in refluxing
C6H5CH3, BCl3 was slowly added, the addition rate was
rule by the reflux of BCl3. After the reaction, TCB was
recovered from C6H5CH3 with a 60% yield from BCl3.
IR (cmꢁ1): n 3450, 3416 (NH); 1438 (BN stretch); 1031
4. Conclusion
A new route to BN ceramic fibres has been demon-
strated through the use of a melt spinnable copolymer
based borazine backbone. The addition of a small
amount of AB to borazine followed by an appropriated
chemical treatment, yielded to a new precursor exhibit-
ing the required physical properties to be easily extruded
and spanned into thin polymer fibres. The ceramic yield
of this copolymer was kept high by the low AB addition
which was proved to be sufficient to improved the
reological properties of polyborazylene. The crude fibres
1
(NH); 743 (BCl); 704 (BN bend). H-NMR (ppm): d
5.29 (t, br, (NH). 11B-NMR (ppm): d 29.7 (s). TCB was
reacted with MeNH2 at low temperature in a ratio 1/8
leading to the formation of MAB and CH3NH3Cl which
was separated by filtration. MAB was recovered by
evaporation of C6H5CH3 [21,22]. IR (cmꢁ1): n 3446,
3250 (NH); 2922, 2830 (CH); 1514 (CH); 1420 (BN