Macromolecules, Vol. 35, No. 11, 2002
Discotic Liquid Crystals 4329
it clearly will be difficult to distinguish the ColA phase
from the well-established NCol phase, except by optical
microscopy experiments and investigations of the local
dynamics, e.g., by dielectric relaxation spectroscopy.
Mater. Chem. 1998, 8, 47-51. (h) Favre-Nicolin, C. D.; Lub,
J . Macromolecules 1996, 29, 6143-6149. (i) Disch, S.; Finkel-
mann, H.; Ringsdorf, H.; Schuhmacher, P. Macromolecules
1
1
995, 28, 2424-2428. (j) Braun, C. D.; Lub, J . Liq. Cryst.
999, 26, 1501-1509.
(
10) (a) Praefcke, K.; Singer, D. In Handbook of Liquid Crystals;
Demus, D., Goodby, J . W., Gray, G. W., Spiess, H. W., Vill,
V., Eds.; Wiley VCH: New York, 1998; Vol. 2B, pp 945-967.
(b) Ringsdorf, H.; W u¨ stefeld, R. Philos. Trans. R. Soc. London
Ack n ow led gm en t. We thank Vanina Kleiman for
the preparation of D1 and Otto van den Berg for the
preparation of the acceptors A1, (A1)2, and P (A1). Ben
Norder is acknowledged for technical assistance with
the thermal analysis and Enno Klop of the Akzo Nobel
Chemical Research Arnhem, Department of Applied
Physics, for assistance in performing XRD analysis.
1
990, A330, 95-108. (c) Praefcke, K.; Holbrey, J . D. J .
Inclusion Phenom. 1996, 24, 19-41.
(
11) (a) Davidson, P.; Levelut, A. M.; Strzelecka, H.; Gionis, V. J .
Phys. (Paris) 1983, 44, L-823. (b) Weck, M.; Dunn, A. R.;
Matsumoto, K.; Coates, G. W.; Lobkovsky, E. B.; Grubbs, R.
H. Angew. Chem., Int. Ed. 1999, 38, 2741-2745.
Refer en ces a n d Notes
(12) Kouwer, P. H. J .; Berg, O. v. d.; J ager, W. F.; Mijs, W. J .;
Picken, S. J . Macromolecules 2002, 35, 2576-2582.
(
1) Chandrasekhar, S.; Sadashiva, B. K.; Suresh, K. A. Pramana
977, 9, 471.
(
(
(
13) J anietz, D.; Praefcke, K.; Singer, D. Liq. Cryst. 1993, 13, 247-
1
2
53.
(
2) For a review on discotic liquid crystals, read: (a) Cammidge,
A. N.; Bushby, R. J . In Handbook of Liquid Crystals; Demus,
D., Goodby, J . W., Gray, G. W., Spiess, H. W., Vill, V., Eds.;
Wiley VCH: New York, 1998; Vol. 2B, pp 693-748. (b)
Chandrasekhar, S. In Handbook of Liquid Crystals; Demus,
D., Goodby, J . W., Gray, G. W., Spiess, H. W., Vill, V., Eds.;
Wiley VCH: New York, 1998; Vol. 2B, pp 749-780 and
references in both chapters.
14) Rosenblum, M.; Brawn, N.; Papenmeier, J .; Applebaum, M.
J . Organomet. Chem. 1966, 6, 173-180.
15) (a) Sonogashira, K.; Tohda, Y.; Nagihara, N. Tetrahedron Lett.
1
975, 4467. (b) Brandsma, L.; Vasilevsky, S. F.; Verkuijsse,
H. D. In Applications of Transition Metal Catalysis in Organic
Synthesis; Springer-Verlag: Berlin, 1998; pp 198-225.
16) J anietz, D. Chem. Commun. 1996, 713-714.
17) From a fast OPM measurement on a (slowly degrading)
polymer sample, a clearing temperature of the order of 230
(
(
(
3) Applications of discotic liquid crystals: (a) Kamada, K.;
Watanabe, J .; Arakawa, K.; Kozono, H. Fuji Photo Film Co.,
Ltd. Eur. Pat. Appl. EP 646829 A1, 1995. (b) Mori, H.; Itoh,
Y.; Nishiura, Y.; Nakamura, T.; Shinagawa, Y. J pn. J . Appl.
Phys. 1997, 36, 143-147. (c) Adam, D.; Schuhmacher, P.;
Simmerer, J .; Haussling, L.; Siemensmeyer, K.; Etzbach, K.
H.; Ringsdorf, H.; Haarer, D. Nature (London) 1994, 371,
°
C could be determined.
(18) The broad melting temperatures of A1 and (A1)2
are due to
the presence of E/Z-isomers of A1 and hence three isomers
for (A1)2.
(19) Gl u¨ sen, B.; Kettner, A.; Wendorff, J . H. Mol. Cryst. Liq. Cryst.
1997, 303, 115-120.
(20) Unpublished results from investigations in our own labora-
tories.
1
41-143. (d) Boden, N.; Movaghar, B. In Handbook of Liquid
Crystals; Demus, D., Goodby, J . W., Gray, G. W., Spiess, H.
W., Vill, V., Eds.; Wiley VCH: New York, 1998; Vol. 2B, pp
7
81-798 and references therein.
4) Tinh, N. H.; Destrade, C.; Gasparoux, H. Phys. Lett. 1979,
2A, 25.
(21) Qualitatively discussed XRD results use the terms lateral for
the [h00] or [0k0] direction and columnar for the [001]
direction. Also, when no columns are present, like in the
nematic discotic (ND) phase.
(
(
(
(
7
5) Ringsdorf, H.; W u¨ stefeld, R.; Zerta, E.; Ebert, M.; Wendorff,
J . H. Angew. Chem., Int. Ed. Engl. 1989, 28, 914-918.
6) Praefcke, K.; Singer, D.; Kohne, B.; Ebert, M.; Liebmann, A.;
Wendorff, J . H. Liq. Cryst. 1991, 10, 147-159.
7) (a) Kouwer, P. H. J .; J ager, W. F.; Mijs, W. J .; Picken, S. J .
Macromolecules 2001, 34, 7582-7584. (b) A comprehensive
discussion on the NL phase is given in ref 7a. For the sake of
clarity, we give here some further experimental character-
istics of the NL phase. The NL phase showed all the features
required to unambiguously identify it as a nematic me-
sophase, even after extensive annealing. For example, a clear
(22) Usually, two spacing are not sufficient to calculate the
parameters of a monoclinic unit cell (three variables: a, b,
and R). Estimation of the volume of the unit cell, assuming
that it consists of one donor and one acceptor disk, offered
us a third known quantity to calculate the lattice parameters
a, b, and R. For example, a unit cell consisting of 1 D1 and
1
1
/2 (A1)2 has a unit cell mass of M ) MD1 + /2M(A1)2 ) 1428
3.
-
1
g mol and a unit cell volume of V ) M/(FNA) ) 2.1 nm
Fitting the spacings with a monoclinic cell with a fixed
volume gives the presented results.
1
schlieren texture with ( /2 and (1 disclinations, occasional
(23) Kouwer, P. H. J .; J ager, W. F.; Berg, O. v. d.; Mijs, W. J .;
Picken, S. J . Polym. Mater. Sci. Eng. 2001, 85, 303-304.
(24) (a) Bengs, H.; Karthaus, O.; Ringsdorf, H.; Baehr, C.; Ebert,
M.; Wendorff, J . H. Liq. Cryst. 1991, 10, 161-168. (b) Ebert,
M.; Frick, G.; Baehr, C.; Wendorff, J . H.; W u¨ stefeld, R.;
Ringsdorf, H. Liq. Cryst. 1992, 11, 293-309. (c) M o¨ ller, M.;
Tsukruk, V. V.; Wendorff, J . H.; Bengs, H.; Ringsdorf, H. Liq.
Cryst. 1992, 12, 17-36.
disclination lines, and a smooth appearance were observed
in microscopy experiments. Long-range smectic or columnar
order is not compatible with a schlieren texture due to the
incompressibility of the lamellae or two-dimensional stacks.
Defects in these materials result in typical focal conical
textures (for lamellae) and “oak-leaf” or mosaic textures (for
columns). A SmC phase, also exhibiting a schlieren texture
in a homeotropic alignment, can be excluded due to the
(25) (a) Contact samples of the complex D1:A2 with discotic liquid
crystals with a well-known mesophase are difficult to prepare.
The electron acceptor A2 also complexes the other mesogen
and hence gives rise of a range of different mesophases,
dependent on the exact local composition. Despite the effort,
no conclusions could be drawn from these experiments. (b) A
change in symmetry of the columnar organization (like the
formation of a Col or Col phase) would have resulted in,
1
presence of clear ( /2 disclinations in our texture. Moreover,
after deformation, the schlieren texture reappeared quickly.
(
c) If we would have been looking at a mesophase with long-
range positional order, like a columnar phase, it would
certainly have led to the formation of an (physically bonded)
elastic network due to the presence of the polymer backbone,
which is in strong contrast to the low viscosity that we
observed in the material.
r
ob
at least, an observable change in the small-angle region of
the XRD pattern. Tilting of the disks in the columns would
have resulted in a rectangular or oblique columnar arrange-
ment and in an increase in the d001 spacing.
(
8) (a) Kouwer, P. H. J .; Mijs, W. J .; J ager, W. F.; Picken, S. J .
Macromolecules 2000, 33, 4336-4342. (b) Kouwer, P. H. J .;
Gast, J .; J ager, W. F.; Mijs, W. J .; Picken, S. J . Mol. Cryst.
Liq. Cryst. 2001, 364, 225-234. (c) Kouwer, P. H. J .; Mijs,
W. J .; J ager, W. F.; Picken, S. J . J . Am. Chem. Soc. 2001,
(26) Fontes, E.; Heiney, P. A.; de J eu, W. H. Phys. Rev. Lett. 1988,
61, 1202-1205.
1
23, 4645-4646.
(
27) (a) Maier, W.; Saupe, A. Z. Naturforsch. 1958, 13A, 564. (b)
Maier, W.; Saupe, A. Z. Naturforsch. 1959, 14A, 882. (c)
Maier, W.; Saupe, A. Z. Naturforsch. 1960, 15A, 287.
(
9) (a) Boden, N.; Bushby, R. J .; Cammidge, A. N.; Headdock,
G. J . Mater. Chem. 1995, 5, 2275-2281. (b) Wenz, G.
Makrom. Chem., Rapid Commun. 1985, 6, 577-584. (c)
Herrmann-Sch o¨ nherr, O.; Wendorff, J . H.; Kreuder, W.;
Ringsdorf, H. Makrom. Chem., Rapid Commun. 1986, 7, 97-
(
28) (a) Obviously, for the ND phase TN should coincide with the
clearing temperature: TN ) Ti ) 419 K. (b) The mean-field
potential U of the extended Maier-Saupe theory is defined
1
01. (d) Kreuder, W.; Ringsdorf, H. Makrom. Chem., Rapid
1-c2
as U ) -ꢀ(T)〈P2〉P2(cos θ), where ꢀ(T) ∝ T
. A value of c2 *
Commun. 1983, 4, 807-815. (e) Boden, N.; Bushby, R. J .; Lu,
Z. B. Liq. Cryst. 1998, 25, 47-58. (f) Weck, M.; Mohr, B.;
Maughon, B. R.; Grubbs, R. H. Macromolecules 1997, 30,
1
corresponds to an extra temperature dependence of the
strength ꢀ of the mean-field potential.
6
430-6437. (g) Stewart, D.; McHattie, G. S.; Imrie, C. T. J .
MA0118567