full text article in - Institute of Solid State Chemistry and

full text article in - Institute of Solid State Chemistry and

Solid State Ionics 141–142 Ž2001. 231–236
www.elsevier.comrlocaterssi
Polymerization of m-NH 2 C 6 H 4COO anions in the intercalation
compounds of aluminium hydroxide
wLiAl 2 žOH /6 xw m-NH 2 C 6 H 4COOx P nH 2 O
V.P. Isupov ) , L.E. Chupakhina, M.A. Ozerova, V.G. Kostrovsky, V.A. Poluboyarov
Institute of Solid State Chemistry and Mechanochemistry of SB RAS, Kutateladze-18, NoÕosibirsk 630128, Russia
Abstract
The intercalation compounds of aluminium hydroxide wLiAl 2 ŽOH. 6 xwNH 2 C 6 H 4COOx P nH 2 O containing aminobenzoic
anions are synthesized for the first time. When heated in air, the intercalate containing m-aminobenzoic acid anions
undergoes polymerization in the interlayer space, resulting in the formation of polymeric macromolecules. The product is
investigated by means of XRD, IR and Raman methods, ESR and optical spectroscopy. A polymerization mechanism is
proposed that includes the diffusion of oxygen molecules through the system of micropores in the interlayer space of the
intercalate into the contact region of two anions, oxidation of anions and the formation of macromolecules. The character of
the orientation of macromolecules in the interlayer space of polymerization product is considered. q 2001 Elsevier Science
B.V. All rights reserved.
MAT: wLiAl 2 ŽOH. 6 xw m-NH 2 C 6 H 4 COOx P nH 2 O; wLiAl 2 ŽOH. 6 xw o-NH 2 C 6 H 4 COOx P nH 2 O; wLiAl 2 ŽOH. 6 xw p-NH 2 C 6 H 4 COOx P nH 2 O
Keywords: Polyaniline; Layered double hydroxides; Intercalation compounds; Aminobenzoic acid
1. Introduction
Organic–inorganic hybrid materials, composed of
the layered inorganic matrix with organic polyconjugated macromolecules in the interlayer space, are the
subject of rather thorough attention of researchers for
the recent 10–15 years w1–14x. The attention to the
synthesis of these compounds is connected with the
possibility to obtain well-ordered conducting poly-
)
Corresponding author. Tel.: q7-3832-363837; fax: q7-3832322847.
E-mail address: [email protected] ŽV.P. Isupov..
mers in the interlayer space, which is difficult to
achieve when polymerization is performed in solution. These polymers can possess interesting
physicochemical properties. There are several approaches to the synthesis of these compounds. One
of them involves preliminary synthesis of intercalates containing guest monomeric molecules in the
interlayer space Že.g. aniline, etc... At the second
stage of the synthesis, interlayer polymerization of
the intercalated organic molecules is carried out.
Since polymerization is connected with the oxidation
of organic molecules, for the reaction to proceed,
either oxidative properties of the host matrix are
necessary ŽFeOCl, V2 O5 P nH 2 O, VOPO4 , etc.., or
0167-2738r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved.
PII: S 0 1 6 7 - 2 7 3 8 Ž 0 1 . 0 0 7 5 1 - 2
232
V.P. IsupoÕ et al.r Solid State Ionics 141–142 (2001) 231–236
the treatment of intercalation systems with oxidative
reagents Žoxygen of the air, ferric chloride, copper
chloride, etc... Aniline and its derivatives are most
often used as organic molecules. The analysis of
literature shows that in every case, intercalated
molecules are present in the interlayer space either as
neutral molecules or cations. Studies of the interlayer
polymerization of anions are missing from literature.
Because of this, the goal of the present study was to
investigate the possibility of the interlayer polymerization of the anions of m-, o- and p-aminobenzoic acids. Intercalation compounds of aluminium with lithium salts wLiAl 2 ŽOH. 6 xwNH 2 C 6 H 4COOx P nH 2 O belonging to double hydroxides,
synthesized by us for the first time, were used as the
matrix.
2. Experiments
The synthesis of intercalation compounds containing the anions of o-, p- and m-aminobenzoic acids
was carried out by the interaction of aqueous solutions of their sodium salts with the intercalation
compound wLiAl 2 ŽOH. 6 xCl P pH 2 O ŽLDH-Cl. w15x.
The initial wLiAl 2 ŽOH. 6 xCl P pH 2 O was synthesized
by treating the crystal modification of aluminum
hydroxide Žgibbsite. with the aqueous solution of
lithium chloride w16x. The treatment of LDH-Cl with
aqueous solutions of NH 2 C 6 H 4 COONa was carried
out in vessels under continuous mixing at a temperature of 758C for 4 h. The concentration of the initial
salt was 0.44 M. The solid products of the interaction were isolated by filtering, washed with distilled
water and dried in air. The Li, Al and Cl contents of
the solid phase was determined. In some cases,
carbon, nitrogen, and hydrogen were determined by
burning the samples. In order to study the phase
composition of the synthesized intercalates, as well
as their polymerization products, we used X-ray
phase analysis with the DRON-3 diffractometer, CuK a-radiation, within the angle range 2 u s 4–308. In
order to study polymerization in the synthesized
samples, we used IR, Raman and ESR spectroscopy.
IR spectra were recorded with Specord-751R
spectrophotometer in KBr tablets within the wavelength range of 400–4000 cmy1 . Raman spectra
were recorded with RFS-100rS spectrometer. ESR
spectra were recorded with JES-3BX spectrometer at
temperatures 300 and 77 K both in air and in vacuum. Thermal analysis in Ar flow was carried out
with a derivatograph of a 1500Q Paulic–Paulic–
Erdey.
3. Results and discussion
3.1. The synthesis of intercalation compounds of
aluminium hydroxide containing the anions of
aminobenzoic acid isomers
The interaction of wLiAl 2 ŽOH. 6 xCl P pH 2 O with
aqueous solution of NaŽ m-NH 2 C 6 H 4 COO. results in
complete removal of chlorine from the solid phase at
relatively small increase of lithium to aluminium
atomic ratio. The data of chemical analysis point to
the appearance of the anions of aminobenzoic acid in
the products. The presence of aminobenzoic acid
anions is also confirmed by the IR spectrum of the
synthesized compound, which contains intense bands
at 1373 and 1533 cmy1 attributed to stretching vibrations of the carboxylic group, as well as less intense
bands at 1250 and 1306 cmy1 that can be attributed
to the stretching vibrations of C`N bond of primary
amine ŽFig. 1. w17x. X-ray diffraction patterns of the
obtained compound exhibit intense new reflections
multiple to each other, which is the evidence of the
layered character of the formed structure ŽFig. 2..
The interlayer distance for the new compound is
Fig. 1. IR-spectra: wLiAl 2 ŽOH. 6 xw m-NH 2 C 6 H 4 COOxPnH 2 O Ž1.,
wLiAl 2 ŽOH. 6 xw m-NH 2 C 6 H 4 COOxPnH 2 O heated in air Ž2..
V.P. IsupoÕ et al.r Solid State Ionics 141–142 (2001) 231–236
233
the solid phase. As the first approximation, anion
exchange reaction can be described as:
LiAl 2 Ž OH . 6 Cl P pH 2 O
q Na Ž m-NH 2 C 6 H 4 COO . q aq
s NaCl q LiAl 2 Ž OH . 6
= w m-NH 2 C 6 H 4 COO x P nH 2 O.
Fig. 2. XRD patterns: wLiAl 2 ŽOH. 6 xClP pH 2 O Ž1., wLiAl 2 ŽOH . 6 xw m-NH 2 C 6 H 4 COO x P nH 2 O Ž2 ., wLiAl 2 ŽOH . 6 xw mNH 2 C 6 H 4 COOxPnH 2 O heated in air at 908C Ž3..
˚ which is 7.8 A˚ more than the interabout 15.5 A,
layer distance for LDH-Cl. Thus, the interaction of
wLiAl 2 ŽOH. 6 xCl P pH 2 O with aqueous solution of
NaŽ m-NH 2 C 6 H 4 COO. leads to the anion exchange
of chloride ions for the anions of m-aminobenzoic
acid with the conservation of the layered structure of
Qualitatively similar results on anion exchange were
obtained for the sodium salts of p- and o-aminobenzoic acids. In these cases, the interaction resulted
in qualitatively complete exchange of chloride ions
for the anions of organic acids with the formation of
layered intercalates.
The structure of wLiAl 2 ŽOH. 6 xCl P pH 2 O can be
represented as alternating hydroxide layers wLiAl 2ŽOH. 6 xq and layers containing Cly-anions and water
molecules w18x. Intercalation of large anions leads to
the increase of interlayer distance D ŽTable 1.. The
˚ . obtained by
size of gallery height Ž L s D y 4.8 A
subtracting the thickness of aluminium hydroxide
˚ . from the interlayer distance size shows
layer Ž4.8 A
that the anions in the interlayer space are located so
that the planes of benzene rings are perpendicular to
the planes of aluminium hydroxide layers ŽFig. 3..
Besides, larger gallery height in comparison with the
anion size allows to assume that there are voids of
molecular size between the hydrophobic part of the
anion and the hydroxide layer. These voids are connected to each other and are partially occupied by
water molecules. The presence of water is confirmed
by the data of thermal analysis. The estimates of the
amount of water present in the interlayer space of
intercalate containing m-aminobenzoate give approximately two molecules. Thus, the obtained intercala-
Table 1
The interlayer distance Ž D ., gallery height Ž L. and size of anions Ž S . for the initial LDH-Cl and intercalates containing aminobenzoic acid
anions
˚.
X ŽA
D
L
S
Cly
7.6
2.8
2.8
Compounds— wLiAl 2 ŽOH. 6 x X P nH 2 O
m-NH 2 C 6 H 4 COOy
p-NH 2 C 6 H 4 COOy
o-NH 2 C 6 H 4 COOy
15.5
10.7
8.7
15.3
10.5
9.6
14.7
9.9
8.7
234
V.P. IsupoÕ et al.r Solid State Ionics 141–142 (2001) 231–236
Fig. 3. Structure of wLiAl 2 ŽOH. 6 xw m-NH 2 C 6 H 4 COOx P nH 2 O Ža., wLiAl 2 ŽOH. 6 xw m-NH 2 C 6 H 4 COOx P nH 2 O heated in air Žb..
tion compound can be described by the formula
wLiAl 2 ŽOH. 6 xw m-NH 2 C 6 H 4 COOx P 2H 2 O.
3.2. InÕestigation of the polymerization of the anions
of aminobenzoic acids in the interlayer space of
intercalation compounds
To perform polymerization of the anions in the
interlayer space, the samples of synthesized compounds were heated in air at 908C. It was stated
preliminarily that polymerization is substantially dependent on water vapour partial pressure over the
samples. Heating in dry air does not lead to any
change in the sample color. Because of this, the
samples of synthesized compounds were heated for
100 h at 908C and relative humidity 75%. Under
these conditions, gray-pink color of LDHŽ mNH 2 C 6 H 4 COO. is changed for dark violet close to
black, while white LDHŽ p-NH 2 C 6 H 4 COO. is
changed for pale blue and beige LDH Ž oNH 2 C 6 H 4 COO. is changed for dark beige. These
changes in color are the evidence of the formation of
polyconjugated system ŽPCS. that occurs with the
intercalate containing the anion m-aminobenzoic
acid. The formation of PCS is confirmed by ESR
data ŽFig. 4.. The concentration of paramagnetic
centres in initial intercalation compound is approximately 10 16 –10 17 spinrg. Heating of the initial compound in air causes a sharp Žthree orders of magnitude. increase of the intensity of ESR signals. ESR
spectra of vacuum samples at 77 and 300 K contain
isotropic signals 7.3–7.5 G wide, with g s 2.000
and Gauss line shape. Air adsorption of these sample
does not change the signal width; however, peak
intensity increases. The number of paramagnetic centres is 10 19 –10 20 spinrg. It should be noted that a
similar increase of peak intensity of ESR spectra in
the presence of oxygen and independence of signal
width on temperature in vacuum and in air were
earlier observed for asphalthenes and are explained
as the appearance of non-degenerated two-dimensional electron gas in PCS with odd number of
V.P. IsupoÕ et al.r Solid State Ionics 141–142 (2001) 231–236
235
insignificant changes in the IR spectra of the samples.
3.3. The possible mechanism of polymerization
Fig. 4. ESR spectra of wLiAl 2 ŽOH. 6 xw m-NH 2 C 6 H 4 COOxPnH 2 O
heated in air at 908C. Conditions of measurements: 1—vacuum, 2
—air, T —300 K.
carbon atoms w19x. Because of this, it can be assumed that the heating of intercalation compound in
air leads to the appearance of polyconjugated aromatic system with two-dimensional electron gas. The
formation of PCS is also confirmed by the data of IR
and Raman spectroscopy. The comparison of IR
spectra of the initial LDHŽ m-NH 2 C 6 H 4 COO. and
the products of its oxidation reveals a sharp decrease
of the band at 1250 cmy1 , which points to a substantial decrease of the number of amino groups –NH 2 .
Besides, intensive background in lower frequencies
of Raman spectrum of the product is the evidence of
the formation of well-ordered and rather long PCS in
the interlayer space of intercalate ŽFig. 5.. Relatively
small changes of X-ray diffraction patterns of
LDHŽ m-NH 2 C 6 H 4 COO. at the formation of PCS
are the evidence that the layered character of the
structure of initial compound is conserved ŽFig. 2..
In the case of LDHŽ p-NH 2 C 6 H 4 COO. and
LDHŽ o-NH 2 C 6 H 4 COO., less substantial changes of
color were observed during heating. This is the
evidence that the formation of polyconjugated system occurs to a lesser extent, which is confirmed by
The experimental data on aminobenzoate anions
polymerization can be interpreted as follows. Oxygen atoms of anions are in molecular contact with
the surface of positively charged layers wLiAl 2ŽOH. 6 xq. In the case of perpendicular orientation of
the benzene rings with respect to these layers, one of
most probable versions of the packing of m-aminobenzoate anions will be that shown in Fig. 3. One
can see that every NH 2 group of one anion should
be in molecular contact with the benzene ring of
another anion. Oxygen molecules have the possibility to get into the anion contact zone through the
voids and to take part in the oxidative polymerization of anions with the formation of PCS and water
molecules ŽFig. 3.. As one can see, at this orientation
of anions, the formation of the new bond should
most probably take place between nitrogen atom of
the amino group and the fourth carbon atom of the
benzene ring of the neighbouring molecule. In this
case, the repetition period along the polymer chain
˚ w2x. is close to the parameter a
Žwhich is about 10 A
Fig. 5. Raman-spectra: NaŽ m-NH 2 C 6 H 4 COO. Ž1., wLiAl 2ŽOH . 6 xw m-NH 2 C 6 H 4 COO x P nH 2 O Ž2 ., wLiAl 2 ŽOH . 6 xw mNH 2 C 6 H 4 COOxPnH 2 O heated in air 908C Ž3..
236
V.P. IsupoÕ et al.r Solid State Ionics 141–142 (2001) 231–236
4. Conclusion
The use of intercalation compounds of aluminium
hydroxide makes possible to control the character of
molecular contacts between the anions of aminobenzoic acids in interlayer space. This allows to
control the possibility of the formation of polyconjugated chains during oxidative polymerization of intercalated organic anions.
References
Fig. 6. Project of p-NH 2 C 6 H 5 COOy anions in wLiAl 2 ŽOH. 6 xw pNH 2 C 6 H 4 COOxPnH 2 O on the plane Ž001..
for the initial intercalation compound which should
˚ At this orientation of the formed chains
be 10.2 A.
with respect to the hydroxide layer, the change of the
position of carboxylic groups with respect to the
positively charged layer is small.
In the case of LDHŽ p-NH 2 C 6 H 4 COO., molecular contact between NH 2 group of one anion and
benzene ring of another ring is absent ŽFig. 6.. For
such a contact to appear between the neighbouring
anions, it is necessary to change substantially the
orientation of acid anion with respect to positively
charged layer. This change of orientation is not
profitable for two reasons. There would be rather
tight packing of the anions in the interlayer space,
and the weakening of the Coulomb interaction between anions and positively charged layer would
occur. Thus, the absence of molecular contact of the
required type may be one of the major reasons for
large differences in the rates of PCS formation in the
interlayer space of these intercalation compounds.
For LDHŽ o-NH 2 C 6 H 4 COO., like for LDHŽ m-NH 2C 6 H 4 COO., the contact between NH 2 group of one
anion with benzene ring of another anion is also
possible. Qualitative differences observed in the behaviour of these substances during polycondensation
require additional investigation. It would be interesting to investigate polymerization of organic molecules into layered double hydroxides with planar
type of packing of organic anions w20x.
w1x M.G. Kanatzidis, L.M. Tonge, J. Am. Chem. Soc. 109
Ž1987. 3797.
w2x C.G. Wu, D.C. Degroot, H.O. Marcy, J.L. Schindler, C.R.
Kannewurf, T. Bakas, V. Papaefthymiou, W. Hirpo, J.P.
Yesinowski, Y.J. Liu, M.G. Kanatzidis, J. Am. Chem. Soc.
117 Ž1995. 9229.
w3x H. Nakajima, G. Matsubayashi, Chem. Lett. 3 Ž1993. 423.
w4x A. Destefanis, S. Foglia, A.A.G. Tomlinson, J. Mater. Chem.
5 Ž1995. 475.
w5x N. Kinomura, T. Toyama, N. Kumada, Solid State Ionics 78
Ž1995. 281.
w6x K.J. Chao, T.C. Chang, S.Y. Ho, J. Mater. Chem. 3 Ž1993.
427.
w7x H. Tagaya, S. Sato, N. Kuramoto, J.I. Kadokawa, M. Karasu,
K. Chiba, J. Inclusion Phenom. Mol. Recognit. Chem. 18
Ž1994. 193.
w8x P. Colomban, A. Efremova, A. Gruger, A. Novak, Solid
State Ionics 78 Ž1995. 19.
w9x T.C. Chang, W.Y. Shen, S.Y. Ho, Microporous Mater. 4
Ž1995. 335.
w10x S. Uma, J. Gopalakrishnan, Mater. Sci. Eng., B 34 Ž1995.
175.
w11x T.A. Kerr, H. Wu, L.F. Nazar, Chem. Mater. 8 Ž1996. 2005.
w12x B.E. Koene, L.F. Nazar, Solid State Ionics 89 Ž1996. 147.
w13x N.S.P. Bhuvanesh, J. Gopalakrishnan, Mater. Sci. Eng., B 53
Ž1998. 267.
w14x H.J. Nam, H. Kim, S.H. Chang, S.G. Kang, S.H. Byeon,
Solid State Ionics 120 Ž1999. 189.
w15x V.P. Isupov, L.E. Chupakhina, Russ. J. Inorg. Chem. 43
Ž1998. 51.
w16x A.P. Nemurdy, V.P. Isupov, N.P. Kotsupalo, V.V. Boldyrev,
React. Solids 1 Ž1986. 221.
w17x Y. Furukawa, F. Ueda, Y. Hyodo, I. Harada, T. Nakajima, T.
Kawagoe, Macromolecules 21 Ž1988. 1297.
w18x A.V. Besserguenev, A.M. Fogg, R.J. Francis, S.J. Price, D.
O’Hare, V.P. Isupov, B.P. Tolochko, Chem. Mater. 9 Ž1997.
241.
w19x V.A. Poluboyarov, O.V. Andryushkova, M.Yu. Bulinnikova,
Sib. Khim. Zh. 5 Ž1992. 5, Žin Russian..
´ Fudala, I. Palinko,
w20x A.
´ ´ I. Kiricsi, Inorg. Chem. 38 Ž1999.
4653.