Polymerization and characterization of self-assembled β-cyclodextrin- threaded chiral monomers

Article abstract of DOI:10.1002/pola.24070

A helical inclusion complex polymer was fabricated through the polymerization of β-cyclodextrin-threaded chiral monomers. The photo induced polymerization of inclusion complex clusters caused shrinkage of the polymer and decreased the pitches, leading to the disappearance of spring-like construction under TEM. From the results of circular dichroism of the inclusion complex polymer, the helical construction was confirmed, and an entanglement of the polymer chains is proposed. After removal of the β-cyclodextrins from the pendant groups of the inclusion complex polymer, the helical structure was found to be maintained. The highly ordered molecular arrangement of β-cyclodextrins removed from the inclusion complex polymer was confirmed using POM. Here we demonstrate the fabrication of helical polymer fibers composed of entangled polymers through self-assembled β-cyclodextrin- threaded chiral monomers. The helical polymer construction was maintained by the entwisted polymer chains even after the removal of β-cyclodextrins from the pendant groups of the inclusion complex polymer.

Full text of DOI:10.1002/pola.24070

Polymerization and Characterization of Self-Assembled
b-Cyclodextrin-Threaded Chiral Monomers
YI-HONG CHIU, JUI-HSIANG LIU
Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan 70101, Republic of China
Received 16 February 2010; accepted 13 April 2010
DOI: 10.1002/pola.24070
Published online in Wiley InterScience (www.interscience.wiley.com).
ABSTRACT: A helical inclusion complex polymer was fabricated
through the polymerization of b-cyclodextrin-threaded chiral
monomers. The photo induced polymerization of inclusion
complex clusters caused shrinkage of the polymer and
decreased the pitches, leading to the disappearance of spring-
like construction under TEM. From the results of circular
dichroism of the inclusion complex polymer, the helical con-
struction was confirmed, and an entanglement of the polymer
chains is proposed. After removal of the b-cyclodextrins from
the pendant groups of the inclusion complex polymer, the heli-
cal structure was found to be maintained. The highly ordered
molecular arrangement of b-cyclodextrins removed from the
inclusion complex polymer was confirmed using POM. Here
we demonstrate the fabrication of helical polymer fibers com-
posed of entangled polymers through self-assembled b-cyclo-
dextrin-threaded chiral monomers. The helical polymer
construction was maintained by the entwisted polymer
chains even after the removal of b-cyclodextrins from the
C
V
pendant groups of the inclusion complex polymer.
2010
Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48:
2975–2981, 2010
KEYWORDS: chiral; nanocomposites; photopolymerization; self-
assembly; synthesis
INTRODUCTION Cyclodextrins (CDs) are known to form
inclusion complexes (ICs) with various low molecular weight
compounds and polymers.1–4 The complex formation mecha-
nism has been recognized to involve the interaction of the
polymer chain with the CD cavity through van der Waals
interaction as well as the hydrophobic effect.5–8 The inclu-
sion ability of CDs has been studied extensively and has
been applied to many fields including food science, cosmet-
ics, and pharmaceutical industries.9–11 Over the past decade,
polymeric inclusion complexes have attracted much attention
due to their unique supramolecular architectures, such as
molecular tubes or polyrotaxanes, as well as a good model
for macromolecular recognition in biological systems.12–16
ture along an axis perpendicular to their longitudinal axis,
have been reported by solvent evaporation from lyotropic
liquid crystalline phases,28 by crosslinking of the cellulose
derivatives,29 and by self-assembly of diblock copolymers.30
Oligosilane-nanofibers were prepared through the fabrication
of permethyldecasilane within a helical superstructure of
schizophyllan.31 However, helical construction induction by
the self-assembly of optically active cyclodextrin-threaded
inclusion complexes has not been reported. We have previ-
ously shown that helical construction could be induced
through the self-assembly of cyclodextrin-threaded chiral
monomer clusters.32 Theoretically, homopolymers and self-
assembled monomers can be dissolved in proper solvents. In
this investigation, the self-assembled inclusion complex was
found to disappear when the sample powder was dissolved
in pyridine. We now show that the induced helical structure
is maintained due to the entanglement of the polymer chains
even after polymerization of the self-assembled inclusion
complexes and removal of b-cyclodextrins from the pendant
groups of the inclusion complex polymer. From these results,
schematic representations for the formation of helical con-
struction and shrinkage of polymers were constructed.
The important biological functions of proteins, nucleic acids,
and polysaccharides appear to be controlled by not only their
first-order structures but also those of higher-order species, for
example, a double helix of DNA.17–19 The research field study-
ing the precision architecture of synthetic macromolecules with
higher structural order, that is, ‘‘supramolecular chemistry,’’
therefore, has recently been of importance for addressing bio-
logical mechanisms.20–23 In particular, the study of the supra-
molecular chemistry connected with polymerization chemistry
is conceived as a significant research topic to elucidate the bio-
logical mechanisms of naturally occurring macromolecules.24–27
EXPERIMENTAL
Instrumentations
Several studies on solid polymeric films having cholesteric
order, in which the molecules are arranged in a helical struc-
FTIR spectra were recorded on a Jasco VALOR III Fourier
transform infrared spectrophotometer. Nuclear magnetic
Additional Supporting Information can be found in the online version of this article. Correspondence to: J.-H. Liu (E-mail: jhliu@mail.ncku.edu.tw)
C
V
Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 48, 2975–2981 (2010) 2010 Wiley Periodicals, Inc.
SELF-ASSEMBLED CHIRAL MONOMERS, CHIU AND LIU
2975

JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
SCHEME 1 Synthesis of chiral
monomer CAHB.
resonance (NMR) spectra were obtained using a Bruker
AMX-400 high-resolution NMR spectrometer. Differential
scanning calorimetry (DSC) was conducted with a Perkin–
confirmed using FTIR and DSC. Figure 2 shows both heating
and cooling cycles of DSC analysis. The synthesized inclusion
complex reveals completely different thermal properties
from both b-CD and CAHB. Melting point of monomer and
À1
ꢀ
Elmer DSC 7 at a heating and cooling rate of 10 C min in
a nitrogen atmosphere. Scanning electron microscope (SEM)
microphotographs were obtained with a JEOL HR-FESEM
JSM-6700F (Osaka, Japan) instrument. The cross section
morphology of the samples was characterized by transmis-
sion electron microscopy (TEM) using a JEOL JEM-1200CX-II
microscope. The anisotropic properties of the highly ordered
self-assembled polymer fibers were investigated by an Olym-
pus BH-2 polarized light microscope (POM) equipped with
Mettler hot stage FP-82, and the temperature scanning rate
ꢀ
b-cyclodextrin appears at 160 and 305 C, respectively. How-
ever, no significant peaks could be found at the temperatures
by DSC scanning analyses. Evaporation of water at 100 ꢀC
and polymerization of monomers at 195 ꢀC were found. As
seen in Figure 2(a), no significant peaks were found during
cooling cycle. Figure 2(b) shows TEM image of b-cyclodex-
trin threaded monomer clusters. As pointed out in our previ-
ous report, significant helical pitch can be seen.32
Polymerization of the Self-Assembled Monomers
was determined at the rate of 10 C minÀ1. The helical con-
ꢀ
The powdered sample was set on a Petri dish, and Ciba
IRGACURE 184 (1-Hydroxy-cyclohexyl-phenyl-ketone) was
used as a photoinitiator. Ciba-184 photoinitiator dissolved in
methyl ethyl ketone (5 wt %) was dropped onto the pow-
dered inclusion complex. After drying at room temperature,
the sample was exposed to 254 nm UV light for 5 min. The
extent of polymerization was monitored using FTIR by fol-
lowing the unsaturated double bond absorption around
1640 cmÀ1, which disappeared after UV exposure due to po-
lymerization. The polymerized self-assembled inclusion com-
plex was analyzed using SEM, TEM, and POM.
struction of the polymerized inclusion complex was analyzed
using a JASCO J-715 circular dichroism spectrometer.
Synthesis of Chiral Monomer
Scheme 1 shows the synthesis of chiral monomer choles-
teryl-4-(6-acryloyloxyhexyloxy) benzoate (CAHB). Detailed
synthetic processes are described in our previous report.32
Yield: 56%; phase transition temperature: Crystal 101.2 ꢀC
Nematic 160 ꢀC Isotropic. Scheme 2 shows the molecular
structure of the synthesized inclusion complex. The threaded
number of b-cyclodextrin onto the monomer was estimated
using NMR analysis.32
Removal of b-Cyclodextrin from the Inclusion
Complex Polymer
Preparation of Chiral Monomers Threaded
with b-Cyclodextrin
After polymerization of the self-assembled inclusion complex,
the polymerized inclusion complex was dissolved in pyridine,
heated to 70 ꢀC and stirred for 1 day. The sample solution
was then ultrasonically agitated at room temperature for
30 min. After washing thoroughly with water and THF, the
To synthesize the inclusion complex, b-cyclodextrin (b-CD)
was dissolved in water at 60 ꢀC. CAHB in tetrahydrofuran
(THF) was then added, and the resulting reaction mixture
ꢀ
was stirred at 50 C for 24 h. The turbid solution was ultra-
ꢀ
sample powder was dried at 70 C for 10 h.
sonically agitated at room temperature for 15 min, and the
clear solution was allowed to stand at room temperature
Fabrication of b-CD Free Inclusion Complex
Polymer-Embedded Composite Polymer Film
ꢀ
(25 C) for 1 day. The precipitate was collected, washed thor-
oughly with THF and then with water to remove the residual
CAHB and b-CD, and dried at 60 C under vacuum. Figure 1
shows the processes of the synthesis of the inclusion com-
plex b-CD-CAHB. The synthesized inclusion complex was
The synthesized b-CD free fibrous inclusion complex polymer
(30 mmol), methyl methacrylate (30 mmol), trimethylolpro-
pane triacrylate (10 mmol), and Ciba IRGACURE 184
(1-Hydroxy-cyclohexyl-phenyl-ketone) photoinitiator (5 wt %)
ꢀ
2976
INTERSCIENCE.WILEY.COM/JOURNAL/JPOLA

ARTICLE
SCHEME 2 b-Cyclodextrin threaded chiral monomer. The
threaded number of b-cyclodextrin was estimated from NMR
analysis. The calculated value of the CD/CAHB ratio is 1.57.
This means that one or two CD molecules were threaded on
each CAHB monomer. [Color figure can be viewed in the
online issue, which is available at www.interscience.wiley.com.]
were dissolved in methyl ethyl ketone. The sample mixture was
dropped onto a substrate. After drying at room temperature,
the mixture was cured under 254 nm UV exposure.
RESULTS AND DISCUSSION
Solvent Effect on the Self-Assembly of the
Inclusion Complexes
Scheme 2 shows the molecular structure of the synthesized
inclusion complex. As described in our previous report,32
due to molecular interactions and the chirality effect, self-as-
sembly of the inclusion complex occurred leading to the for-
mation of helical construction. The top view and the cross
section of the helical structure of the self-assembled inclu-
sion complex are shown in the Supporting Information. It is
noteworthy that the self-assembled helical structure disap-
peared when the collected sample powder was dissolved
in pyridine. From the pyridine sample solution, a self-
assembled cluster of the inclusion complex could not be
found. This could be due to the occurrence of solvation of
FIGURE 2 (a) DSC analysis of the synthesized inclusion com-
plex. Thermal properties of both free b-CD and monomer are
disappeared. (b) TEM image of self-assembled inclusion com-
plexes. [Color figure can be viewed in the online issue, which
is available at www.interscience.wiley.com.]
pyridine in the sample solution. The molecular interaction
between the inclusion complexes may be displaced by the
solvation forces. The self-assembly of the inclusion com-
plexes is then restricted. The self-assembled inclusion com-
plex cluster was found to dissolve in pyridine. This result
suggests that the interaction between pyridine and the
FIGURE 1 Processes for the synthesis of b-cyclodextrin
threaded monomer. After completion of reaction, residual free
monomers and b-cyclodextrins were completely removed by
washing with THF and water. [Color figure can be viewed in the
online issue, which is available at www.interscience.wiley.com.]
FIGURE 3 (a) POM texture, and (b) SEM image of the polymer-
ized inclusion complex. Bright texture shows highly ordered
molecule arrangement. [Color figure can be viewed in the online
issue, which is available at www.interscience.wiley.com.]
SELF-ASSEMBLED CHIRAL MONOMERS, CHIU AND LIU
2977

JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
FIGURE 4 (a) TEM images, (b) perpendicular cross section, and (c) tipped cross section of the polymerized inclusion complex.
Solid black texture shows shrinkage of polymers.
inclusion complex is strong enough to replace the forces
between the self-assembled inclusion complexes. As pointed
out in our previous report, the threaded CD numbers onto
monomer were analyzed and confirmed using 1H NMR with
pyridine as solvent.32
Characterization of Polymerized Self-Assembled
Inclusion Complexes
The sample powder was characterized after UV-induced
polymerization of the inclusion complex. Figure 3(a,b) show
the POM texture and SEM images of the polymerized inclu-
sion complex, respectively. As seen in Figure 3(a), a bright fi-
brous texture indicates the existence of polymerized highly
ordered inclusion complexes. A fibrous appearance under
SEM could be seen in Figure 3(b). Interestingly, as seen in
Figure 4, the spring-like structure disappeared under TEM.
Instead of a spring-like structure, Figure 4(a) shows only solid
black fibrous structures. Figure 4(b,c) show the cross section
of the polymerized self-assembled inclusion complex. A solid
black spot is observed. As will be described later, this spot is
likely due to polymer shrinkage. Figure 4(c) shows the cross
section of a tipped fiber. The appearance is similar to the image
shown in our previous report32; however, in this case, the pitch
was obviously shortened. Because of the closed arrangement,
the spring-like structure could no longer be seen.
To describe the phenomena observed, we propose a sche-
matic representation for the formation and the polymeriza-
tion of the self-assembled inclusion complex. Figure 5(a)
shows the arrangement of the self-assembled inclusion com-
plex. The helical construction is formed by the aggregated
inclusion clusters due to chirality. This construction is sup-
ported by the molecular interaction between the inclusion
complexes. The inset cross section of the helical construction
shows the existence of the inclusion complex clusters. The
real appearance of the self-assembled inclusion complex
clusters is shown in the Supporting Information. Over time,
dissolving the helical sample powder in pyridine destroys
the helical construction due to solvation.
FIGURE 5 Schematic representation of the (a) self-assembled
Theoretically, polymerization of the monomers forms chemi-
cal bonds between the monomers and usually causes volume
shrinkage. We believe that this is the main reason for the
inclusion complex cluster, and (b) polymerized inclusion com-
plex. These figures do not show the exact relative size. Entangle-
ment of polymer chains fixes the self-assembled construction.
2978
INTERSCIENCE.WILEY.COM/JOURNAL/JPOLA

ARTICLE
cause shrinkage of helical construction. After polymerization,
the relationship between the monomers will change from an
external to an internal relationship. The monomers should
then be connected to each other by chemical bonds. As seen
in Figure 5(b), due to the decrease of molecular distance,
both the diameter and the pitch of the fibrous structure
decreased, leading to the formation of rod-like (an almost
solid-helix with a smaller pitch) construction. This results in
the solid spot seen in Figure 4(b,c). In this investigation, var-
ious fibrous constructions were obtained. The SEM and TEM
images of fibrous constructions before and after polymeriza-
tion could not be compared directly. Furthermore, Figure
5(a,b) do not reveal the exact relative size. From the images
shown in Supporting Information, few tens inclusion com-
plexes were aggregated forming the spring-like construction.
As seen in Figure 5(b), after polymerization, entwisted poly-
mer chain may fix the fibrous structure leading to the
increase of solvent resistance.
FIGURE 6 FTIR spectrum of the b-cyclodextrin-removed inclu-
sion complex polymer. The collected inclusion complex poly-
mer is considered as free of residual of b-CD and monomer.
The circular dichroism spectrum of the polymerized inclu-
sion complex is offered in our previous report.32 A signifi-
cant Cotton effect is seen in the spectrum. This result sug-
gests that the helical structure is maintained after
polymerization. Shrinkage of the polymer volume may signif-
icantly decrease the pitch of the helical construction leading
to the disappearance of the spring-like structure, as seen in
Figure 4(a–c).
disappearance of the spring-like structure after polymeriza-
tion. Figure 5(b) shows the entanglement of the polymer
chain after polymerization. The entwisted side chain poly-
mers are expected to fix the helical construction. The helical
construction formed in this investigation is very different
from that of single chain helical polymers, for example, RNA,
and single helix DNA. To confirm the existence of helical
structure, the circular dichroism spectrum was measured. As
seen in Figure 5(a,b), polymerization of the monomers
should reduce the distance between the monomers and
Removal of the Threaded b-Cyclodextrin From the
Pendant Groups of the Polymers
To investigate the effect of b-cyclodextrin on helical construc-
tion, b-cyclodextrins were removed from the pendant groups
of the inclusion complex polymer. After heat ꢀtreatment of the
inclusion complex polymer in pyridine at 70 C for 1 day, the
sample solution was further ultrasonically agitated at room
temperature for 30 min. The collected sample powder was
washed with water and THF thoroughly. Figure 6 shows the
FTIR spectrum of the sample powder. As compared with the
spectra shown in Supporting Information, the characteristic
FIGURE 7 (a) TEM image, (b) cross section, and (c) POM tex-
ture of the b-cyclodextrin-removed inclusion complex polymer,
and the (d) b-cyclodextrin-removed inclusion complex polymer
fiber embedded polymer nanocomposite film. [Color figure can be
viewed in the online issue, which is available at www.interscience.
wiley.com.]
FIGURE 8 CD spectrum of the b-cyclodextrin-removed inclusion
complex polymer. Appeared negative Cotton effect is the same
as the spectrum reported in our previous article.32 [Color figure
can be viewed in the online issue, which is available at
www.interscience.wiley.com.]
SELF-ASSEMBLED CHIRAL MONOMERS, CHIU AND LIU
2979

JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
absorption from b-cyclodextrin disappeared. The result sug-
gests that the threaded b-cyclodextrins were removed from the
pendant groups of the inclusion complex polymer.
assembled inclusion complex cluster was found to cause vol-
ume shrinkage leading to the disappearance of spring-like
construction under TEM. The entanglement of the polymer
chain fixes the helical construction of the polymer, even af-
ter the removal of the threaded b-cyclodextrin from the
pendant groups of the inclusion complex polymers. The hel-
ical construction was confirmed using circular dichroism
microscopy.
As seen in Figure 7(a,b), after removal of the b-cyclodextrin
from the inclusion complex polymer, a solid black columnar
construction was obtained. This is similar to the TEM images
obtained before removal of b-cyclodextrin. As described in
Figure 5(b), the entangled polymer chains may fix the helical
construction. Figure 7(c) shows the highly ordered molecular
arrangement of the b-cyclodextrin removed polymer fiber. The
results are consistent with the proposed schematic represen-
tation shown in Figure 5(a,b). The b-cyclodextrin-removed
polymer fiber was further mixed with methyl methacrylate,
trimethylolpropane triacrylate, and Ciba IRGACURE 184 (1-
Hydroxy-cyclohexyl-phenyl-ketone) photoinitiator (5 wt %)
in methyl ethyl ketone. Figure 7(d) shows the POM texture of
the fabricated polymer composite with the b-cyclodextrin-
removed polymer nano-fibers after 254 nm UV curing. The
highly ordered molecular arrangement was fixed in a polymer
composite and appeared as bright fibrous textures under
POM. In our previous report, polymer composite with the b-
cyclodextrin-threaded polymer fibers was synthesized.32
The authors thank the National Science Council of the Republic
of China (Taiwan) for financially supporting this research under
contract No. NSC 97-2221-E-006-026.
REFERENCES AND NOTES
1 Nielsen, A. L.; Andersen, M. B. O.; Bugge, T. V.; Nielsen, C.
F.; Nielsen, T. B.; Wimmer, R.; Yu, D.; Larsen, K. L. J Polym Sci
Part A: Polym Chem 2009, 47, 6619–6629.
2 Xue, J.; Jia, Z.; Jiang, X.; Wang, Y.; Chen, L.; Zhou, L.; He, P.;
Zhu, X.; Yan, D. Macromolecules 2006, 39, 8905–8907.
3 Choi, S. J.; K. E. Geckeler, K. E. Polymer 2007, 48, 1445–1449.
4 Gotsev, M. G.; Ivanov, P. M.; Jaime, C. Chirality 2007, 19,
There are many articles that use circular dichroism spectra as
evidence of the existence of helical structure of self-assembled
bulk supramolecules.33,34 In our case, the synthesized self-
assembled inclusion complexes are supramolecules. The helical
structure should be able to be detected through circular dichro-
ism analysis. As described earlier, if entanglement of the poly-
mer chains occurred, the helical structure should be maintained
even after the removal of the b-cyclodextrin from the inclusion
complex polymer. Figure 8 shows the results of the circular
dichroism spectrum of the b-cyclodextrin-removed inclusion
complex polymer. A significant Cotton effect is seen in the spec-
trum. The Cotton effect is called ‘‘positive’’ if the optical rotation
first increases as the wavelength decreases (as first observed
by Cotton), and ‘‘negative’’ if the rotation first decreases. In this
investigation, the synthesized chiral polymers before and after
the removal of b-cyclodextrin should be considered as different
polymers. Their UV-vis spectra and circular dichroism analysis
(CD spectra) are different. As seen in Figure 8 and the CD spec-
trum in our previous report,32 both polymers reveal the same
negative cotton effect before and after the removal of b-cyclo-
dextrin. The results suggest that the helical structure should be
maintained. The CD spectrum shown in Figure 8 is not so per-
fect; it could be due to the complicated helical construction
formed through the entanglement of the polymer chains.
203–213.
5 Ohya, Y.; Takamido, S.; Nagahama, K.; Ouchi, T.; Ooya,
T.; Katoono, R.; Yui, N. Macromolecules 2007, 40, 6441–
6444.
6 Uyar, T.; Rusa, C. C.; Hunt, M. A.; Aslan, E.; Hacaloglu, J.;
Tonelli, A. E. Polymer 2005, 46, 4762–4775.
7 Satav, S. S.; Karmalkar, R. N.; Kulkarni, M. G.; Mulpuri, N.;
Sastry, G. N. Macromolecules 2007, 40, 1824–1830.
8 Wenz, G.; Krauter, I.; Sackmann, E. J Polym Sci Part A: Polym
¨
Chem 2009, 47, 6223–6230.
9 Yuan, W.; Ren, J. J Polym Sci Part A: Polym Chem 2009, 47,
2754–2762.
10 Gamsiz, E. D.; Miller, L.; Thombre, A. G.; Ahmed, I.; Carrier,
R. L. Biotech Bioeng 2010, 105, 409–420.
11 Horvath, G.; Premkumar, T.; Boztas, A.; Lee, E.; Jon, S.;
Geckeler, K. E. Mol Pharmaceutics 2008, 5, 358–363.
12 Yang, G. F.; Wang, H. B.; Yang, W. C.; Gao, D.; Zhan, C. G.
J Phys Chem B 2006, 110, 7044–7048.
13 Liu, Y.; Yu, L.; Chen, Y.; Zhao, Y. L.; Yang, H. J Am Chem
Soc 2007, 129, 10656–10657.
14 Sald´ıas, C.; Gargallo, L.; Sandoval, C.; Leiva, A.; Radic, D.;
Caballero, J.; Saavedra, M.; Gonza´lez-Nilo, F. D. Polymer 2009,
50, 2926–2932.
In this investigation, the existence of b-cyclodextrin threaded
on the monomer is considered to induce helical structure.
After polymerization, the helical structure was fixed through
the entanglement of polymers. Accordingly, after the removal
of b-cyclodextrin from polymer pendant group, the helical
structure was maintained.
15 Yang, C.; Wang, X.; Li, H.; Goh, S. H.; Li, J. Biomacromole-
cules 2007, 8, 3365–3374.
16 Ikeda, T.; Hirota, E.; Ooya, T.; Yui, N. Langmuir 2001, 17,
234–238.
17 Yu, G. H.; He, P. J.; Shao, L. M.; He, P. P. Environ Sci Tech-
CONCLUSIONS
nol 2008, 42, 7944–7949.
Threaded b-cyclodextrin is a necessary factor for the fabrica-
18 Boddohi, S.; Killingsworth, C. E.; Kipper, M. J Biomacromol
tion of helical construction. Polymerization of the self-
2008, 9, 2021–2028.
2980
INTERSCIENCE.WILEY.COM/JOURNAL/JPOLA

ARTICLE
19 Rudd, T. R.; Nichols, R. J.; Yates, E. A. J Am Chem Soc
27 Kim, S. A.; Jung, D. H.; Kim, Y. H.; Kang, M. A.; Jung, H. T.
2008, 130, 2138–2139.
Macromolecules 2006, 39, 6186–6190.
20 Zhao, L.; Northrop, B. H.; Stang, P. J. J Am Chem Soc 2008,
28 Nagai, K.; Sakajiri, K.; Maeda, K.; Okoshi, K.; Sato, T.;
130, 11886–11888.
Yashima, E. Macromolecules 2006, 39, 5371–5380.
21 Sessler, J. L.; Jayawickramarajah, J.; Sathiosatham, M.;
29 Caruso, U.; Panunzi, B.; Roviello, A.; Sirigu, A. Macromole-
Sherman, C. L.; Brodbelt, J. S. Org Lett 2003, 5, 2627–2630.
cules 1994, 27, 3513–3519.
22 Alonso, M. C.; Can˜ ada, F. J.; Barbero, J. J.; Cuevas, G J Am
30 Valkama, S.; Ruotsalainen, T.; Nyka¨nen, A.; Laiho, A.; Koso-
nen, H.; Brinke, G.; Ikkala, O.; Ruokolainen, J. Macromolecules
2006, 39, 9327–9336.
Chem Soc 2005, 127, 7379–7386.
23 Lutz, J. F.; Thunemann, A. F.; Rurack, K. Macromolecules
¨
2005, 38, 8124–8126.
31 Haraguchi, S.; Hasegawa, T.; Numata, M.; Fujiki, M.; Uezu,
K.; Sakurai, K.; Shinkai, S. Org Lett 2005, 7, 5605–5608.
24 Percec, V.; Holerca, M. N.; Magonov, S. N.; Yeardley, D. J.;
Ungar, G.; Duan, H.; Hudson, S. D. Biomacromolecules 2001, 2,
706–728.
32 Liu, J. H.; Chiu, Y. H.; Chiu, T. H. Macromolecules 2009, 42,
3715–3720.
25 Ruokolainen, J.; Eerikainen, H.; Torkkeli, M.; Serimaa, R.;
33 Lin, J.; Zhu, G.; Zhu, X.; Lin, S.; Nose, T.; Ding, W. Polymer
¨
Jussila, M.; Ikkala, O. Macromolecules 2000, 33, 9272–9276.
2008, 49, 1132–1136.
26 Matsuzaki, K.; Mitani, Y.; Akada, K.; Murase, O.; Yoneyama,
34 Zhao, H.; Sanda, F.; Masuda, T. Polymer 2005, 46,
S.; Zasloff, M.; Miyajima, K. Biochemistry 1998, 37, 15144–15153.
2841–2846.
SELF-ASSEMBLED CHIRAL MONOMERS, CHIU AND LIU
2981