Paper
Journal of Materials Chemistry C
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temperatures of 1b and 1c on heating are comparable. If
dendrimers 1a and 1b are compared with each other, the polar
effect can be more significantly observed; the clearing tempera-
ture of 1b (B144.4 1C) is higher than that of 1a (B118.0 1C) and
the solidifying temperature of 1b (B68.0 1C) is lower than that
of 1a (B82.3 1C). Thus, the strong CN polar group significantly
broadens the mesogenic range of 1b (B70-degrees). The reason
that the CN moieties result in the increasing disc-to-disc
distances is probably that the void space between G3 moieties
may not balance the polar repulsion and enlarging the dendri-
tic disc-to-disc distance is thus necessary. The corresponding
effect in small disc molecules to broaden the mesogenic phases
has been investigated by Williams20 and is in agreement with
our study result.
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Conclusions
In summary, dendrimers 1a and 1b were successfully prepared
and observed to exhibit columnar mesophases on thermal
treatment. Compared with 1c, 1a has a lower clearing tempera-
ture on heating due to the isomeric effect but a comparable
mesogenic range on cooling because of its closer stacking.
Dendrimer 1b enters the columnar mesophase at a significantly
lower temperature and becomes isotropic at a similar tempera-
ture on heating to 1c due to the CN polarity. The Iso-to-Colh
transition temperature of 1b is considerably higher than those
of 1a and 1c on cooling, and the subsequent solidifying
temperature of 1b is lower than those of 1a and 1c. Therefore,
the polar CN groups in dendrimers, significantly reducing the
stacking efficiency, lowering the solidifying temperature and
expanding considerably the mesogenic range, are interesting
and have not been reported so far. This should be applicable to
other types of dendrimers with semi-rigid linkers for preparing
dendrimers with valuable applications.
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and W.-D. Jang, Angew. Chem., Int. Ed., 2014, 53, 6925;
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Conflicts of interest
¨
J. P. F. Werner, G. Mariani and F. Grohn, Macromolecules,
2017, 50, 3464; (d) A. Arrigo, F. Puntoriero, G. L. Ganga,
S. Campagna, M. Burian, S. Bernstorff and H. Amenitsch,
Chem, 2017, 3, 494.
There are no conflicts of interest to declare.
7 (a) Y. Wang, Y. Lu, B. Gao, S. Wang, J. Ding, L. Wang, X. Jing
and F. Wang, Chem. Commun., 2016, 52, 11508; (b) L. Zhao,
S. Wang., J. Lu¨, J. Ding and L. Wang, J. Mater. Chem. C, 2017,
5, 9753; (c) X. Ban, W. Jiang, K. Sun, B. Lin and Y. Sun, ACS
Appl. Mater. Interfaces, 2017, 9, 7339; (d) J. A. McEwan,
A. J. Clulow, A. Nelson, R. D. Jansen-vanVuuren, P. L. Burn
and I. R. Gentle, ACS Appl. Mater. Interfaces, 2018, 10, 3848.
8 (a) B. Soberats, M. Yoshio, T. Ichikawa, X. Zeng, H. Ohno,
G. Ungar and T. Kato, J. Am. Chem. Soc., 2015, 137, 13212;
Acknowledgements
We thank the National Chi Nan University and the Ministry
of Science and Technology, Taiwan for financial support
(105-2119-M-260-006-MY3).
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