Mesogenicity of organophosphazenes: The effect of phosphazene rings and side groups on the phase transition

Article abstract of DOI:10.1080/10426500212223

Cyclotriphosphazene and cyclotetraphosphazene derivatives with mesogenic 4-N-(4-alkoxyphenyl)iminomethyl)phenoxy and 4-(4′-alkoxy) biphenoxy moieties were synthesized. Schiff base moiety has higher mesomorphic stability than that in biphenyl moiety both in cyclotriphosphazene and cyclotetraphosphazene. Cyclotriphosphazenes possess higher thermal stability in the mesomorphic phase than the cyclotetraphosphazenes, suggesting the difference in the molecular structure.

Full text of DOI:10.1080/10426500212223

This article was downloaded by: [University of Toronto Libraries]
On: 11 August 2014, At: 08:56
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,
37-41 Mortimer Street, London W1T 3JH, UK
Phosphorus, Sulfur, and Silicon and the Related
Elements
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/gpss20
Mesogenicity of Organophosphazenes: The Effect of
Phosphazene Rings and Side Groups on the Phase
Transition
Keiichi Moriya a , Toshihiro Yamane a , Toshiya Suzuki a , Tsuyoshi Masuda a , Hiroshi Mizusaki
a , Shinichi Yano a & Meisetsu Kajiwara b
a Department of Chemistry, Faculty of Engineering , Gifu University , Yanagido, Gifu, Japan
b School of Dentistry , Aichigakuin University , Chikusa-ku, Nagoya, Japan
Published online: 27 Oct 2010.
To cite this article: Keiichi Moriya , Toshihiro Yamane , Toshiya Suzuki , Tsuyoshi Masuda , Hiroshi Mizusaki , Shinichi Yano &
Meisetsu Kajiwara (2002) Mesogenicity of Organophosphazenes: The Effect of Phosphazene Rings and Side Groups on the Phase
Transition, Phosphorus, Sulfur, and Silicon and the Related Elements, 177:6-7, 1427-1432, DOI: 10.1080/10426500212223
To link to this article: http://dx.doi.org/10.1080/10426500212223
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained
in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the
Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and
are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and
should be independently verified with primary sources of information. Taylor and Francis shall not be liable for
any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever
or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of
the Content.
This article may be used for research, teaching, and private study purposes. Any substantial or systematic
reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any
form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://
www.tandfonline.com/page/terms-and-conditions

Phosphorus, Sulfur and Silicon, 2002, Vol. 177:1427–1432
C
Copyright 2002 Taylor & Francis
1042-6507/02 $12.00 + .00
DOI: 10.1080/10426500290093018
MESOGENICITY OF ORGANOPHOSPHAZENES: THE
EFFECT OF PHOSPHAZENE RINGS AND SIDE
GROUPS ON THE PHASE TRANSITION
Keiichi Moriya,a Toshihiro Yamane,a Toshiya Suzuki,a
Tsuyoshi Masuda,a Hiroshi Mizusaki,a Shinichi Yano,a
and Meisetsu Kajiwarab
Department of Chemistry, Faculty of Engineering, Gifu
University, Yanagido, Gifu, Japana and School of Dentistry,
Aichigakuin University, Chikusa-ku, Nagoya, Japanb
(Received August 2, 2001; accepted December 25, 2001)
Cyclotriphosphazene and cyclotetraphosphazene derivatives with mes-
ogenic 4-N-(4-alkoxyphenyl)iminomethyl)phenoxy and 4-(40-alkoxy)
biphenoxy moieties were synthesized. Schiff base moiety has higher
mesomorphic stability than that in biphenyl moiety both in cy-
clotriphosphazene and cyclotetraphosphazene. Cyclotriphosphazenes
possess higher thermal stability in the mesomorphic phase than the
cyclotetraphosphazenes, suggesting the difference in the molecular
structure.
Keywords: Cyclotetraphosphazene; cyclotriphosphazene; liquid
crystals; organophosphazene; phase transition
INTRODUCTION
In the cyclotriphosphazene derivatives, several mesomorphic phases
5
have been observed and discussed on the phase transition.1
In this study, the cyclotriphosphazenes and cyclotetraphosphazenes
with mesomorphic 4-(N-(4-alkoxyphenyl)iminomethyl)phenoxy and 4-
(40-alkoxy)biphenoxy side groups (see Figure 1) were synthesized. The
effect of the phosphazene nucleus and side groups on the mesomorphic
phase transition in the organophosphazenes was studied based on the
molecular shape and structure.
1427

1428
K. Moriya et al.
FIGURE 1 Chemical formulas of hexakis(4-(40-alkoxy)biphenoxy)cyclotri-
phosphazene (HBCTP-n)(a-1), hexakis(4-(N-(4-alkoxyphenyl)iminomethyl)
phenoxy)cyclotriphosphazene (HSCTP-n)(a-2), octakis(4-(40-alkoxy)biphenoxy)
cyclotetraphosphazene (OBCTP-n)(b-1), and octakis(4-N-(4-alkoxyphenyl)
iminomethyl)phenoxy)cyclotetraphosphazene(OSCTP-n)(b-2).
EXPERIMENTAL
Preparation of Cyclotriphosphazene and
Cyclotetraphosphazene with
4-(40-Alkoxy)biphenoxy Groups
4-Alkoxy-40-biphenols were prepared from 4,40-dihydroxybiphenyl,
n-alkylbromide and KOH in ethanol under reflux for 8 h. The crude
crystals were recrystallized from toluene once and chloroform twice.
Cyclotriphosphazene and cyclotetraphosphazene were prepared from
4-alkoxy-40-biphenols, sodium hydride and hexachlorocyclotriphos-
phazene or octachlorocyclotetraphosphazene in the presence of
n-butylammonium bromide. The crude products were purified using
column chromatography (CHCl3, SiO2) and recrystallized from THF-
cyclohexane(1:1) mixed solution. The purified crystals were checked by
TLC(CHCl3:hexane 7:3), IR, 1H, and 31P NMR and elemental analyses.
Preparation of Cyclotriphosphazene and
Cyclotetraphosphazene with
4-(N-(4-alkoxyphenyl)iminomethyl)phenoxy Groups
4-Alkoxyacetanilide was prepared from n-alkylbromide and KOH in
ethanol under reflux for 6 h. 4-alkoxyaniline was prepared from
4-alkoxyacetanilide and KOH in ethanol under reflux for 12 h. Hexakis-
(4-formylphenoxy)cyclotriphosphazene or octakis(4-formylphenoxy)-
cyclotetraphosphazene was prepared from 4-hydroxybenzaldehyde,
sodium hydride and hexachlorocyclotriphosphazene or octachloro-
cyclotetraphosphazene in THF at ambient temperature for 6 h.
Crude products were recrystallized from a hexane-THF(10:1) solution.
Cyclotriphosphazene and cyclotetraphosphazene were prepared by the
reaction of hexakis(4-formylphenoxy)cyclotriphosphazene or octakis(4-
formylphenoxy)cyclotetraphosphazene and 4-alkoxyaniline in benzene

Mesogenicity of Organophosphazenes
1429
under reflux for 6 h. The crystals purified were checked by IR, 1H, and
31P NMR and elemental analyses.
Analytical Techniques and Instruments
Phase transitions were studied using a differential scanning calorime-
ter (Seiko Instruments DSC 210) in the temperature range from room
temperature to over the melting point at heating/cooling rates of
5 K min 1. The apparatus was calibrated using the melting of indium
(Tm; 429.6 K, 1H; 28.5 Jg 1) and tin (Tm; 505.1 K, 1H; 59.5 Jg 1).
The textures of the mesophase were observed using a polarizing mi-
croscope (Nikon, Optiphot-pol XTP-11) with a temperature-controlled
1
hot stage (Mettler, FP-82) at the heating/cooling rates of 5 K min
under crossed polarizers. Powder X-ray measurements were done with
a Rigaku, Rint 2000, and a homemade cell using CuK beams. 1H NMR
(solvent CDCl3) and 31P NMR (solvent CDCl3) spectra were recorded on
a JEOL JNM-A400 spectrometer using TMS as the internal standard
for the former and 85% H3PO4 as the external standard for the latter.
IR spectra were measured with KBr disks using a Perkin-Elmer FT-IR
1640.
RESULTS AND DISCUSSION
The phase transitions of cyclotriphosphazenes and cyclotetraphos-
phazenes with biphenyl and Schiff base moities with an end carbon
number of 12 were compared.
In the first cooling process of HSCTP-12 DSC thermograms, 5 ex-
opthermic peaks were observed at 499, 485, 446, 429, and 365 K,
respectively. On the polarizing microscope observation, SmA fan and
SmC schlieren textures were observed between 499 and 485 K and 485
and 446 K. A mosaic texture was observed between 446 and 426 K,
suggesting the presence of a higher ordered smectic phase(Sm1), but
this has not been identified at present. At 446 K, HSCTP-12 froze to a
crystal(Cr), and the exothermic peak at 365 K corresponds to a crystal-
crystal phase transition. In the second heating process, five endother-
mic peaks were observed at 378, 435, 453, 486, and 500 K, respec-
tively. From the polarizing microscope observation these temperatures
correspond to a Cr-Cr, Cr-Sm1, Sm1-SmC, SmC-SmA, and SmA-I phase
transitions. Thus, an enantiotropic Cr-Sm1-SmC-SmA-I phase transi-
tion was observed in HSCTP-12.
In the first cooling process of OSCTP-12 DSC thermograms, four
exothermic peaks were observed at 431, 403, 384, and 320 K. On the

1430
K. Moriya et al.
polarizing microscope observation, between 431 and 403 K, the SmA
fan texture was observed. OSCTP froze to a crystal at 403 K and the
exothermic peaks at 431 and 403 K correspond to crystal-crystal phase
transitions. In the second heating process, four endothermic peaks were
observed at 320, 384, 403, and 431 K. The crystal melted at 403 K
and a similar SmA fan texture was observed between 403 and 431 K.
Therefore an enantiotropic Cr-SmA-I phase transition was observed in
OSCTP-12.
In the first cooling process of HBCTP-12, three exothermic peaks
were observed at 425, 418, and 378 K. Between 425 and 418 K, a SmC
schlieren texture was observed. At 418 K, HBCTP-12 froze and the peak
at 378 K corresponds to a Cr-Cr phase transition. In the second heat-
ing process, three endothermic peaks corresponding to Cr-Cr, Cr-SmC,
and SmC-I phase transitions were observed at 392, 425, and 453 K.
Thus an enantiotropic Cr-SmC-I phase transition was observed in
HBCTP-12.
In the cooling process of OBCTP-12, exothermic peaks were observed
at 394 and 387 K. Between these temperatures, a SmA fan texture was
observed. In the second heating process, only one endothermic peak,
which corresponds to melting, was observed at 398 K. Only a monotropic
SmA phase was observed at OBCTP-12.
Comparing these results, the biphenyl circumstances are very low
mesogenicity compared to that in Schiff base moiety. In these com-
pounds, the tetrameric nucleus is much less mesomorphic stability than
that in trimeric nucleus. These results suggest that the molecular struc-
ture in cyclotriphosphazene stabilizes the mesomorphic structure com-
pared to that in cyclotetraphosphazene.
In Figure 2, the alkyl spacer dependence of the phase transition
in the series of HSCTP-n(closed circles) and OSCTP-n(open circles)
was shown. In the series of the tetramer with an increase in the end
alkoxy carbon number, the clearing points increased and the melting
points decrease with an increase in the carbon number. As a result,
the mesomorphic temperature region in OSCTP-n increased with the
increasing carbon number. In the cyclotriphosphazenes with similar
mesomorphic side chains, this tendency in which the mesomorphic
temperature region increased with the increasing carbon number
was also shown. However, the difference between cyclotriphosphazene
and cyclotetraphosphazene is that the mesomorphic phase in cyclote-
traphosphazene is much less thermally stable than those of the cyclo-
break triphosphazenes because both the melting and clearing points in
the cyclotetraphosphazenes are lower than those in the cyclotriphos-
phazenes.

Mesogenicity of Organophosphazenes
1431
FIGURE 2 Alkoxy carbon number dependence of phase transition tempera-
ture in the series of HSCTP-n and OSCTP-n.
In Figure 3, the alkyl spacer dependence of the phase transition in
the series of HBCTP-n(closed circles) and OBCTP-n(open circles) was
shown. In the series of the trimer with an increase in the end alkoxy
carbon number, the clearing points increased and the melting points
decrease with an increase in the carbon number. As a result, the meso-
morphic temperature region in HBCTP-n increased with the increasing
carbon number. In the OBCTP-n series, only monotropic SmA phase
was observed at n= 11 and n= 12 in the cooling process. Therefore
for biphenoxy moieties cyclotriphosphazene has higher mesomorphic
FIGURE 3 Alkoxy carbon number dependence of phase transition tempera-
ture in the series of HBCTP-n and OBCTP-n.

1432
K. Moriya et al.
stability than that in cyclotetraphosphazene. This is probably caused
by the difference in the molecular structure of the cyclotriphosphazenes
and cyclotetraphosphazenes.
REFERENCES
[1] K. Moriya, S. Yano, and M. Kajiwara, Chem. Lett., 1039–1042 (1990).
[2] K. Moriya, H. Mizusaki, M. Kato, T. Suzuki, S. Yano, M. Kajiwara, and K. Tashiro,
Chem. Mater., 9, 255–263 (1997).
[3] K. Moriya, T. Suzuki, H. Mizusaki, S. Yano, and M. Kajiwara, Chem. Lett., 1001–1002
(1997).
[4] K. Moriya, T. Suzuki, Y. Kawanishi, T. Masuda, H. Mizusaki, S. Nakagawa,
H. Ikematsu, K. Mizuno, S. Yano, and M. Kajiwara, Appl. Organometal. Chem., 12,
771–779 (1998).
[5] K. Moriya, Y. Kawanishi, S. Yano, and M. Kajiwara, J. Chem. Soc. Chem. Commun.,
1111–1112 (2000).