Single-handed helical polyethers synthesized via anionic polymerization of optically active 3-(9-alkylfluoren-9-yl)propene oxides

Article abstract of DOI:10.1016/j.polymer.2010.10.017

A series of optically active 3-(9-alkylfluoren-9-yl)propene oxides were synthesized by the reaction of 9-alkylfluoren-9-yllithium with the optically active epichlorohydrin at -70 °C and polymerized using KOH as an initiator. The molecular weight of the po

Full text of DOI:10.1016/j.polymer.2010.10.017

Polymer 51 (2010) 5712e5718
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Polymer
journal homepage: www.elsevier.com/locate/polymer
Single-handed helical polyethers synthesized via anionic polymerization of
optically active 3-(9-alkylfluoren-9-yl)propene oxides
*
Yunkai Sun, Nianfa Yang , Ji Liu, Jing Cao, Hang Gong
Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education, College of Chemistry, Xiangtan University, Hunan 411105, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of optically active 3-(9-alkylfluoren-9-yl)propene oxides were synthesized by the reaction of
9-alkylfluoren-9-yllithium with the optically active epichlorohydrin at ꢀ70 ꢁC and polymerized using
KOH as an initiator. The molecular weight of the poly(3-(9-alkylfluoren-9-yl)propene oxide)s is larger
than that of poly(4,4,4-triphenyl-1-butene oxide), which had been proved to take stable helical
conformation in solution, and their molecular weight distributions were narrower (Mw/Mn ¼ 1.02 to
1.09) than poly(4,4,4-triphenyl-1-butene oxide). By investigating of chiroptical properties of a series of
polymers derived from optically active epoxide, it is suggested that the poly(3-(9-alkylfluoren-9-yl)
propene oxide)s keep one-handed helical conformation in solution.
Received 5 August 2010
Received in revised form
17 September 2010
Accepted 9 October 2010
Available online 16 October 2010
Keywords:
Optical epoxide
Chirality
Ó 2010 Elsevier Ltd. All rights reserved.
Helical polyether
1. Introduction
of the polyepoxide backbone make polyepoxide flexible, and
therefore result in a difficulty for forming helical polyether. Despite
Synthetic polymers with single-handed helical structure have
attracted much attention since it was discovered that the single-
handed helical polymer poly(triphenylmethyl methacrylate) (TrMA)
had chiral recognizing ability [1e7]. So far, huge amounts of synthetic
polymers which keep a single-handed helical conformation in solu-
tion have been synthesized from acrylamides [8e12], styrenes
[13e18], aldehydes [19,20], isocyanates [21e26], isocyanides
[27e30], acetylenes [31e33], N-propargylphosphonamidates [34],
N-propargylureas [35] and so on. However, to our knowledge, there
was no information about the single-handed helical polymer derived
from epoxides until our group prepared successfully optically active
helical polyether recently [36,37].
this difficulty, our group have reported that the polymer of optically
active 4,4,4-triphenyl-1-butene oxide (TPBO) can keep a prevailing
helicity of backbone in solution [36,37]. However, the degree of
polymerization (DP) of poly-TPBO is not high and the molecular
weight distribution is too wide. Here, we report helical polyep-
oxides prepared from the polymerization of optically active 3-(9-
alkylfluoren-9-yl)propene oxides (AFPOs). When the bulky
pendant CPh3 of poly-TPBO was substituted with 9-alkylfluoren-9-
yl group, the polyepoxide not only kept a prevailing helicity of
backbone in solution but also had higher molecular weight and
narrower molecular distribution.
In the polymer of the vinyl compound, there is a common char-
acteristic that the repeated unit of the backbone contains only two
atoms and the atoms bearing a bulky pendantresponsible for forming
helical conformation are isolated from each other only by one atom
(see Fig. 1A).
In the polymer of epoxide, the repeated unit contains three
atoms and the atoms bearing a bulky pendant are isolated from
each other by two atoms. Further more, among the three atoms of
the repeated unit of the backbone, there is an oxygen atom, which
bears no any other substituent (see Fig. 1B). These characteristics
2. Results and discussion
The optical AFPOs were synthesized with good yield (69～80%)
by the reaction of the corresponding 9-alkylfluoren-9-yllithium
with optical epichlorohydrin (ECH) in THF at ꢀ70 ꢁC for 30 min and
then at room temperature for 3 h (see Scheme 1).
It has been proved [36] that the reaction forming epoxide
monomers proceeded in two steps: 1) organolithium attacked CH2
of the oxirane group of ECH at ꢀ70 ꢁC and ring was opened to give
intermediate 2; 2) LiCl was eliminated from intermediate 2 at room
temperature to yield epoxide monomer 1. Therefore, the chiral
atom’s configuration of the epoxide still remained unchanged in all
the processes and the e.e. value of the epoxide monomer was equal
to that of the ECH.
* Corresponding author. Tel.: þ86 0731 58293833.
E-mail address: nfyang@xtu.edu.cn (N. Yang).
0032-3861/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.polymer.2010.10.017

Y. Sun et al. / Polymer 51 (2010) 5712e5718
5713
CH CH2 CH CH2 CH CH2
A
B
R
R
R
KOH
O
CH CH2
R
O
CH CH2 O CH CH2
O
R
R
R
R
(
)
n
(R)-1
O
O
Fig. 1. A: the backbone of the vinyl polymer; B: the backbone of the polyepoxide; R:
bulky pendant.
R= CH3, C2H5, n-C3H7, or n-C4H9,
Scheme 2. The polymerization of 3-(9-alkylfluoren-9-yl)propene oxides.
In most case, the polymerization of optical AFPOs was carried out
in bulk using KOH as an initiator. (see Scheme 2). In order to obtain
higher molecular weight, the solution polymerization of (R)-3-(9-
ethylfluoren-9-yl)propylene oxide was also conducted in xylene.
The polymerization results are shown in Table 1.
The molecular weight of poly-AFPOs depends on the polymer-
ization conditions and the monomer type. Fig. 2 shows the the GPC
trace of poly((R)-3-(9-methylfluoren-9-yl)propylene oxide) (poly-
(R)-MFPO) (run 1), poly((R)-3-(9-ethylfluoren-9-yl)propylene
oxide) (poly-(R)-EFPO) (run 3), poly((R)-3-(9-propylfluoren-9-yl)
propylene oxide) (poly-(R)-PFPO) (run 5), poly((R)-3-(9-butyl-
fluoren-9-yl)propylene oxide) (poly-(R)-BFPO) (run 7) and poly-
(R)-EFPO yieded by solution polymerization (run 11).
The bulk polymerization rates of AFPOs are much faster than
that of TPBO and the DP of poly-AFPOs are much higher than that of
poly-TPBO. For the bulk polymerization of AFPOs at 130 ꢁC, it just
took 4 h for the polymeriztion system to solidify with the DPs being
17 while, for that of TPBO at 150 ꢁC, it expended 7 days for the
system to solidify [36,37] with its DP being only 7. The molecular
weight distribution (Mw/Mn) of poly-TPBO is 1.8. However, that of
poly-AFPOs are 1.02e1.09.
The molecular weight of poly-AFPO produced in solution poly-
merization was larger than that produced in bulk polymerization.
The molecular weight of poly-(R)-EFPO produced in bulk poly-
merization was 4300 (see run 3 and Fig. 2b) while that produced by
solution polymerization in xylene under the similar polymerization
condition was 5100 (see run 11 and Fig. 2e).
the optical rotation sign of poly-AFPOs, which is opposite to their
monomers’, is the same as that of poly-TPBO whose monomer have
the same configuration as the corresponding AFPO. This property of
optical rotation sign is another evidence for polyepoxides to form
helical conformation.
The absolute value of the poly-AFPOs’ specific rotation ([
times as large as that of the corresponding monomer and this
enhance of the [ ] from monomer to polymer supports powerfully
a]) is 44
a
that poly-AFPOs keep a stable helical conformation.
The CD spectrum properties of poly-AFPO system and poly-
TPBO system are similar to their specific rotation properties (see
Fig. 4). The Cotton effects of poly-(R)-AFPOs, whose monomers have
a negative Cotton effect, are positive, and are the same as that of
poly-(R)-TPBO, whose monomer have a positive Cotton effect.
Cotton effects of the S-isomer of AFPOs, TPBO and their polymers
are opposite to that of the corresponding R-isomer. These proper-
ties of the Cotton effect also support intensively that poly-AFPOs
keep prevailing helical conformation in solution.
The absolute value of the maximum molar ellipticity ([
q
]
,
max
referred to one monomeric unit for polymer) of poly-AFPOs is about
40 times as high as that of the corresponding monomers (see Fig. 4).
This larger amplification of the maximum molar ellipticity from
monomer to polymer are also consistent with the conclusion that
poly-AFPOs keep a stable helical conformation.
The amplification times of the [q]max from AFPOs to poly-AFPOs is
more than 40, which indicates that the helicity poly-AFPOs.is excellent.
The epoxy ring of AFPOs was opened after polymerization and
the opening of the epoxy ring should have an impact on the chi-
roptical properties of poly-AFPOs. However, the experiment data
indicated this impact was not much. When the epoxy ring of (R)-3-
The reason why AFPOs have higher polymerization activity than
TPBO is that 9-alkylfluoren-9-yls are smaller than triphenylmethyl
and make less hindrance for polymerization.
1H NMR spectrum of poly-TPBO showed two obvious olefin-
proton signals at 5.27 ppm and 6.21 ppm (see Fig. 3), indicating that
there was a severe chain transfer[37] in the bulk plymerization. It
was this chain transfer that resulted in the wide molecular weight
distribution. In 1H NMR spectra of poly-AFPOs, there was no such
an olefin-proton signal, indicating that no chain transfer took place
in the plymerization. Therefore, the molecular weight distribution
of poly-AFPOs was very narrow and the molecular weight of poly-
AFPOs was higher than that of poly-TPBO.
(9-ethylfluoren-9-yl)propene oxide [(R)-EFPO] was opened by OHꢀ
20
or t-BuOꢀ, the [
a
]
365 of the ring-opening product 3a (ꢀ81.2) or 3b
(ꢀ106) was not much enough (Scheme 3). Therefore, the change of
chiroptical properties after polymerization does not result from the
opening of the epoxy ring.
It is possible that the large optical rotation and the large CD
intensity of poly-AFPOs may arise from the chiral carbons in the
polymer main chain. To rule out this posiblity, (R)-4-(9-propyl-
fluoren-9-yl)-1-butene oxide [(R)-PFBO] (see Fig. 5) was synthesized
By analysing the chiroptical properties of a series of polyep-
oxides, poly-TPBO was proved to exist in the form of prevailing
helicity in solution [36]. In the same way, poly-AFPOs was also
proved to exist in the form of prevailing helicity in solution.
The optical rotation sign of AFPOs is opposite to that of TPBO
whose configuration is the same as the correpongding AFPO. But
20
and polymerized. The [
a
]
of (R)-PFBO is þ14.6 and that of its
365
polymer þ27.0. Fig. 3 shows that CD intensity of (R)-PFBO and that of
its polymer is almost the same. This small chiroptical property
differences between (R)-PFBO and its polymer implies that the large
optical rotation and the large CD intensity of poly-AFPOs by no
means arise from the chiral carbons in the polymer main chain.
The chiroptical property differences also depend on the distance
between the chromophore and the backbone which contains chiral
atom. But, the study on the chiroptical properties of (R)-4,4-
diphenyl-1-hexene oxide [(R)-DPHO] (see Fig. 5) and its polymer
negated that the large optical rotation and the large CD intensity of
poly-AFPOs result from the right distance between the chromo-
phore and the backbone. Although this distance in (R)-DPHO is the
O
n-BuLi
Cl
O
R
R
Li
R
H
(R)-1
OLi
H
O
O
Cl
Cl
Y
Li
H
-70oC
r.t.
Y
Y
H
same as that in (R)-AFPOs, the chiroptical property differences
2
20
between (R)-DPHO and its polymer are not much. [
a]
of (R)-
365
R= CH3, C2H5, n-C3H7, or n-C4H9, Y=9-Alkylfluoreneyl
DPHO is þ108 and that of its polymer þ229. The CD intensity of (R)-
DPHO is also close to its polymer’s (see Fig. 6).
Scheme 1. The synthesis of optical 3-(9-alkylfluoren-9-yl)propene oxide.

5714
Y. Sun et al. / Polymer 51 (2010) 5712e5718
Table 1
The polymerization of AFPOsa.
monomer
polymer
Cnf.b
[
a
]
365
Yd/%
[a]
365
Mne/ꢂ103
DPe
Mw/Mn
20
c
20
c
e
run
R
1f
2f
3
4
5
6
7
8
CH3
CH3
C2H5
C2H5
n-C3H7
n-C3H7
n-C4H9
n-C4H9
C2H5
R
S
R
S
R
S
R
S
ꢀ14.2 ꢃ 0.2
þ14.1 ꢃ 0.2
ꢀ21.2 ꢃ 0.3
þ21.0 ꢃ 0.3
ꢀ21.6 ꢃ 0.3
þ21.6 ꢃ 0.3
ꢀ16.0 ꢃ 0.2
þ16.0 ꢃ 0.2
ꢀ21.2 ꢃ 0.3
ꢀ21.2 ꢃ 0.3
ꢀ21.2 ꢃ 0.3
71.7
72.6
84.4
83.1
77.9
78.6
81.4
81.0
53.8
67.3
61.7
þ786 ꢃ 10
ꢀ793 ꢃ 10
þ934 ꢃ 14
ꢀ970 ꢃ 14
3.7
3.7
4.3
4.3
4.8
4.8
4.7
4.7
2.3
3.8
5.1
16
16
17
17
18
18
17
17
9
1.04
1.04
1.02
1.03
1.06
1.04
1.05
1.05
1.12
1.03
1.09
þ1346 ꢃ 18
ꢀ1361 ꢃ 18
þ734 ꢃ 10
ꢀ758 ꢃ 10
þ424 ꢃ 8
9g
10h
11i
R
R
R
C2H5
C2H5
þ836 ꢃ 12
þ994 ꢃ 14
15
20
a
Conducted in bulk, initiator: KOH, the molar ratio of monomer to initiator (M0/Int): 25, polymerization temperature (T): 130 ꢁC, polymerization time (t): 4 h
b
c
d
e
f
the configuration of monomers.
measured in THF (c ¼ 10.00 g/L).
Isolated yields
Determined by GPC (polystyrene as standard, THF as solvent).
T: 120 ꢁC.
g
h
i
M0/Int: 30, T: 90 ꢁC, t: 24 h
M0/Int: 30, T: 120 ꢁC, t: 10 h
M0/Int: 30, T: 125 ꢁC, t: 48 h, xylene (50% wt) was added.
Since the opening of the epoxy ring, the chiral carbons in the
the helical pipe. There are four groups of p-stacked structure which
main chain of the polymer and the distance from the backbone to
the bulky group in pendant do not result in the large optical rota-
tion and the large CD intensity of poly-AFPOs, there must be
another factor which is responsible for this chiroptical properties,
and this factor should be the one-handed helical backbone.
The reason why the optical rotation and the maximum molar
ellipticity of poly-(R)-PFBO are not large is that the bulky 9-alkyl-
fluoren-9-yl group is far from the polymer backbone, which makes
the backbone too flexible to form a stable helical conformation.
Nakano reported that the polymer of dibenzofulvene (DBF)
consist of three fluorene rings in the helical column. At each end of
helial column, there are three fluorene rings, with tow of fluorene
rings forming
(R)-DPHO (n ¼ 18) cannot form helical conformation and also have
not such a -stacked structure.
p-stacked structure. In the“Chem3D Ultra 8.0”, Poly-
p
To exclude further the possibility that the change of chiroptical
properties resulted from the chiral carbons in the main chain of the
polymer, the relation between chiroptical properties of poly-(R)-
EFPO and its degree of polymerizations (DP) was studied. The poly-
(R)-EFPO with different DP were obtained by changing polymeri-
zation condition. DP of 3a is 1. The relation between chiroptical
possess a novel “
the side chain are stacked on top of each other [38] and
structure consisting of three or more fluorene units lead to a helical
structure [39]. Perhaps there are -stacked structure in poly-AFPO
and, besides bulkiness of the side-chain groups, these -stacked
p-stacked structure” inwhich the aromatic groups in
p-stacked
properties of poly-(R)-EFPO and its DP are shown in Fig. 8.
20
As being shown in Fig. 8, the [
a
]
and the [
q
]
of poly-(R)-
365
max
p
EFPO increase with the increase of DP linearly when DP is less than
17, and their come to maximum and become constant when DP is
more than 19. This relation between the chiroptical property
p
fluorene groups are the driving force that lead to helical conforma-
tion. In order to confirm this guess, poly-(R)-EFPO (n ¼ 18) was drawn
in “ChemDraw Ultra 8.0” software, then the poly-(R)-EFPO drawn in
“ChemDraw Ultra 8.0” was pasted in “Chem3D Ultra 8.0” software,
and a beautiful helical conformation figure came out (see Fig. 7).
From the 3D helical figure, one can find that three monomeric
units form one turn with all of oxygen atoms locating in the inner of
characteristic of poly-(R)-EFPO and its DP indicates that the
20
tremendous [
a
]
and the [
q
]
of the polymer does not come
365
max
from the chiral carbons in the main chain of the polymer but from
the stable helical conformation.
3. Conclusion
In summary, a series of optical active AFPO was synthesized and
anionically polymerized. The molecular weight of poly-AFPOs is higher
than that of poly-TPBO, and molecular weight distribution of poly-
AFPOs is narrower than that of poly-TPBO, which has been proved to
keep a stable one-handed helical conformation in solution. The specific
20
optical rotation ([
a
]
365) and the maximum molar ellipticity ([
q]max) of
poly-AFPOs is 44 times as large as that of the corresponding monomer.
This enhance of the [ ] and the [ ] from monomer to polymer results
a
q
from the formation of a stable helical conformation.
4. Experimental
4.1. Synthesis of 9-alkylfluorene
Fig. 2. The GPC trace evolution of the polyethers. GPC was measured with polystyrene
as a standard and THF as eluent. The elution time “tr” was used to express the peak
position: a, run 1 in Table 1, tr ¼ 15.406 min; b, run 3, tr ¼ 15.211 min; c, run 5,
tr ¼ 15.103 min; d, run 7, tr ¼ 15.274 min; e, run 11, tr ¼ 14.925 min.
9-Alkylfluorene (alkyl ¼ methyl, ethyl, n-propyl and n-butyl)
were prepared using the method proposed by Kurt L. Schoen and
E. I. Becker [40].

Y. Sun et al. / Polymer 51 (2010) 5712e5718
5715
Fig. 3. 1H NMR spectra of polymers: A, poly-TPBO; B, poly-PFPO.
4.2. Synthesis of (R)- or (S)-3-(9-alkylfluoren-9-yl)propylene oxide
CH2), 2.11e2.13(m, 1H, CHH), 1.97e2.02 (m, 1H, CHH), 1.55 (s, 3H,
Me). 13C NMR (CDCl3, 100 MHz)
: 151.18, 150.92, 139.94, 139.79,
d
To a solution of 9-methylfluorene (9.00g, 0.05 mol) in THF
(40 mL), was dropped n-BuLi solution in hexane (20.0 mL, 2.5 M) at
0 ꢁC with stirring under nitrogen atmosphere. The reaction mixture
was stirred at room temperature for 2 h to give a dark red solution
of 9-methylfluoren-9-yllithium. A solution of (R)-(ꢀ)-epichlorohy-
drin (ECH) (2.4 mL) in dried THF (10 mL) was added dropwise at
ꢀ70 ꢁC with stirring within 30 min. The mixture was warmed to
room temperature after the addition of ECH and stirred at room
temperature for 3 h before distilled water (10 mL) was added. The
mixture was extracted with diethyl ether (3 ꢂ 15 mL) and the
combined extract was washed with water and dried over anhy-
drous Na2SO4. The solvent was evaporated in vacuo and the residue
was recrystallized from ethanol to obtain 9.23g of (R)-3-(9-meth-
127.39, 127.38, 127.35, 127.27, 123.20, 122.90, 120.11, 120.09, 49.46,
49.17, 47.09, 43.36, 26.34.
(S)-3-(9-methylfluoren-9-yl)propylene oxide [(S)-MFPO] was
synthesized as (R)-MFPO except that (R)-(ꢀ)-ECH was replaced by
20
(S)-(þ)-ECH. (S)-MFPO, yield, 77.6%, [
a
]
365
¼ þ14.1ꢁ(c ¼ 0.0100 g/
mL, THF), e.e.: 98.7% (t(S) ¼ 13.900 min). The m.p., element analysis
and the NMR spectrum data was the same as (R)-MFPO.
When 9-methylfluorene was replaced by 9-ethylfluorene, 9-
propylfluorene and 9-butylfluorene, respectively, to react with (R)-
(ꢀ)-ECH or (S)-(þ)-ECH, the corresponding monomers had been
obtained.
(R)-3-(9-ethylfluoren-9-yl)propylene oxide [(R)-EFPO]: yield
20
80.2%, white crystal, m.p.: 76e77 ꢁC. [
a
]
¼ ꢀ21.2ꢁ (c ¼ 10.0 g/L,
365
ylfluoren-9-yl)propylene oxide [(R)-MFPO]. Yield 78.3%, white
THF), e.e.: 98.8% (t(R) ¼ 13.275 min); (S)-EFPO: yield, 79.8%,
20
20
crystal, m.p.: 41e42 ꢁC. [
a
]
¼ ꢀ14.2ꢁ(c ¼ 0.0100 g/mL, THF), e.e.:
[a
]
¼ þ21.0ꢁ (c ¼ 10.0 g/L, THF), e.e.: 98.7% (t(S) ¼ 11.667 min).
365
365
98.8% (t(R) ¼ 13.817 min); Anal. Calcd for C17H16O: C, 86.40; H, 6.82;
Anal. Calcd for C18H18O: C, 86.36; H, 7.25; Found C, 86.34; H, 7.27. 1H
O, 6.77; Found C, 86.34; H, 6.85. 1H NMR(CDCl3, 400 MHz)
d
(ppm):
NMR(CDCl3, 400 MHz)
d
(ppm): 7.73 (d, J ¼ 5.6 Hz, 2H, Ar), 7.44 (d,
7.73 (d, J ¼ 6.8 Hz, 2H, AreH), 7.48 (d, J ¼ 6.2 Hz, 1H, AreH),
J ¼ 7.2, 1H, AreH), 7.29e7.39 (m, 5H, AreH), 2.41e2.45 (m, 1H, CH),
2.25e2.28 (m, 2H, CH2), 1.99e2.12 (m, 4H, 2CH2), 0.33 (t, J ¼ 7.4 Hz,
7.32e7.40 (m, 5H, AreH), 2.38e2.41 (m, 1H, CH), 2.30e2.33 (m, 2H,
3H, Me). 13C NMR (CDCl3, 100 MHz)
d(ppm): 149.20, 148.96, 141.12,
140.94, 127.30, 127.26, 127.17, 127.12, 123.29, 123.00, 119.93, 119.90,
54.05, 49.01, 47.21, 42.87, 32.60, 8.02.
(R)-3-(9-propylfluoren-9-yl)propylene oxide [(R)-PFPO]: yield
20
77.3%; white crystal, m.p.: 87e88 ꢁC; [
a]
¼ ꢀ21.6ꢁ (c ¼ 10.0 g/L,
365
THF); e.e.: 98.6% (t(R) ¼ 12.408 min); (S)-PFPO: yield 78.1%,
20
[a
]
¼ þ21.6ꢁ(c ¼ 10.0 g/L, THF); e.e.: 98.7%, (t(S) ¼ 11.183 min);
365
Anal. Calcd for C19H20O: C, 86.32; H, 7.63; O, 6.05; Found C, 86.27; H,
7.65. 1H NMR(CDCl3, 400 MHz)
d
(ppm): 7.72 (d, J ¼ 7.2 Hz, 2H,
AreH), 7.45 (d, J ¼ 6.8 Hz, 1H, AreH), 7.30e7.37 (m, 5H, AreH),
2.40e2.45 (m, 1H, CH), 2.25e2.27 (m, 2H, CH2), 1.97e2.10 (m, 4H,
2CH2), 0.65e0.67 (m, 5H, Et). 13C NMR (CDCl3)
d(ppm, 100 MHz):
149.62, 149.38, 140.90, 140.72, 127.26, 127.25, 127.22, 127.11, 123.28,
122.98, 119.93, 119.90, 53.68, 48.94, 47.19, 43.10, 42.25, 16.89, 14.32.
1) KOH or t-BuOK
O
OH
2) H3O+
OX
20
365
20
Fig. 4. The CD spectra of chiral epoxides and their polymer (molar ellipticity [q]
3a X = H,
[α]
= -81.2o
= - 106o
(R)-EFPO
referred to one monomeric unit for polymers). a: 3-(9-meth-ylfluoren-9-yl)propylene
oxide; b: 3-(9-ethylfluoren-9-yl)propylene oxide; c: 3-(9-n-propylfluoren-9-yl)
propylene oxide; d: 3-(9-n-butyl-fluoren-9-yl)propylene oxide; e: 4,4,4-triphenyl-1-
butene oxide.
3b X = t-Bu,
[
α]
365
Scheme 3. Opening of the epoxy ring of (R)-EFPO.

5716
Y. Sun et al. / Polymer 51 (2010) 5712e5718
O
O
(R)-PFBO
(R)-DPHO
Fig. 5. The structure of (R)-PFBO and (R)-DPHO.
(R)-3-(9-butylfluoren-9-yl)propylene oxide [(R)-BFPO]: yield
20
69.4%, white crystal, m.p.: 46e47 ꢁC; [
a
]
365
¼ ꢀ16.0ꢁ(c ¼ 10.0 g/L,
THF); e.e: 98.3%, (t(R) ¼ 11.858 min); (S)-BFPO: yield 68.7%,
20
[
a]
¼ þ16.0ꢁ(c ¼ 10.0 g/L, THF); e.e: 98.3%, (t(S) ¼ 10.717 min);
365
Anal. Calcd for C20H22O: C, 86.29; H, 7.97; O, 5.75; Found C, 86.29; H,
7.99. 1H NMR(CDCl3, 400 MHz)
d
(ppm): 7.73 (d, J ¼ 6.4 Hz, 2H,
AreH), 7.45 (d, J ¼ 6.8 Hz, 1H, AreH), 7.30e7.37 (m, 5H, AreH),
2.39e2.44 (m, 1H, CH), 2.24e2.26 (m, 2H, CH2), 2.01e2.09 (m, 4H,
CH2CH2), 1.04e1.12 (m, 2H, CH2), 0.59e0.69 (m, 5H, Et). 13C NMR
Fig. 7. Poly-(R)-EFPO was simulated in “Chem3D Ultra 8.0” software.
(CDCl3, 100 MHz) d(ppm): 149.62, 149.37, 140.92, 140.74, 127.26,
127.25, 127.21, 127.11, 123.27, 122.97, 119.93, 119.90, 53.56, 48.94,
47.18, 43.21, 39.58, 25.62, 22.92, 13.75.
under nitrogen atmosphere. The mixture was refluxed for 5 h and
extracted with diethyl ether (3 ꢂ 5 mL) after cooling to room
temperature. The extract was washed with water and dried over
anhydrous MgSO4. The solvent was evaporated in vacuo and the
4.3. Synthesis of 3a and 3b
residue was separated by column chromatography (hexane/
20
4.3.1. Synthesis of 3a
CH2Cl2 ¼ 5/1) to obtain 3b, yield 32.5%. (R)-3b: [
a]
¼ ꢀ108
365
To a solution of (R)-PFPO (0.50 g, 0.002 mol) in THF 15 mL, was
added aqueous solution of KOH (1 mL, 50% wt) with stirring. The
mixture was refluxed for 24 h and extracted with diethyl ether
(3 ꢂ 5 mL) after cooling to room temperature. The extract was
washed with water, dried over anhydrous MgSO4 and evaporated in
vacuo. The residue was separated by column chromatography
(c ¼ 10.0 g/L, THF).; 1H NMR(CDCl3, 400 MHz)
d(ppm): 7.70 (d,
J ¼ 6.4 Hz, 2H, Ar), 7.28e7.47 (m, 6H, Ar), 3.02 (s,1H, OH), 2.69e2.73
(m, 1H, CH), 2.60e2.64 (m, 1H, CHH), 2.31e2.34 (m, 1H, CH),
2.02e2.19 (m, 4H, 2CH2), 0.94 (s, 9H, 3CH3), 0.28 (t, J ¼ 7.2 Hz, 3H,
CH3). 13C NMR (CDCl3, 100 MHz)
d/ppm: 149.69, 149.27, 141.20,
140.98, 127.21, 127.13, 127.03, 126.92, 123.55, 123.14, 119.83, 119.81,
72.86, 68.20, 66.15, 53.79, 43.27, 33.78, 27.31, 7.97. Anal. Calcd for
C22H28O2: C, 81.44; H, 8.70; O, 9.86; found C, 81.40; H, 8.75; O, 9.91.
(hexane/CH2Cl2
¼
4/1) to obtain 3a, yield 44.8%. (R)-3a:
20
[
a]
¼ ꢀ81.2; (c ¼ 10.0 g/L, THF). 1H NMR(CDCl3, 400 MHz)
d
365
(ppm): 7.68 (d, J ¼ 6.2 Hz, 2H, Ar), 7.20e7.41 (m, 6H, Ar), 3.64 (s, 1H,
CH), 3.09e3.13 (m, 1H, CHH), 2.90e3.04 (m, 1H, CHH), 2.83e2.87
(m, 1H, CHH), 2.57e2.62 (m, 1H, CHH), 1.94 (q J ¼ 5.8, 2H, CH2), 0.53
4.4. Synthesis of (R)-4-(9-ethylfluoren-9-yl)butylene oxide
(t, J ¼ 6.2 Hz, 3H, CH3). 13C NMR (CDCl3, 100 MHz)
d(ppm): 149.61,
To a solution of 9-ethylfluorene [40] (9.70 g, 0.05 mol) in THF
(50 mL), was dropped n-BuLi solution in hexane (20.0 mL, 2.5 M) at
0 ꢁC with stirring under nitrogen atmosphere. The reaction mixture
was stirred at room temperature for 2 h to give a dark red solution
149.22, 141.16, 140.91, 127.13, 127.05, 127.01, 126.87, 123.48, 123.06,
119.74, 119.71, 67.74, 64.45, 51.33, 41.27, 32.06, 9.41. Anal. Calcd for
C18H20O2: C, 80.56; H, 7.51; O, 11.92; found C, 80.49; H, 7.55; O,
11.95.
of 9-ethylfluoren-9-yllithium.
A solution of dibromomethane
(0.05 mol) in dried THF (5 mL) was added dropwise at ꢀ10 ꢁC with
stirring within 20 min. The mixture was warmed to room
temperature with stir for 3 h before distilled water (10 mL) was
4.3.2. Synthesis of 3b
To a solution of (R)-PFPO (0.50 g, 0.002 mol) in THF 15 mL, was
dropped t-BuOK solution in THF (1.7 mL, 1.2 M) at r.t. with stirring
Fig. 6. The CD spectra of (R)-PFBO, (R)-DPHO and their polymers.
Fig. 8. The function of the ½
aꢄ23065 and the [
q]
of poly-(R)-EFPO vs DP.
max

Y. Sun et al. / Polymer 51 (2010) 5712e5718
5717
added. The mixture was extracted with diethyl ether (3 ꢂ 10 mL)
and the combined extract was washed with water and dried over
anhydrous CaCl2. The solvent was evaporated in vacuo and the
residue was recrystallized from ethanol to obtain 12.10 g of 9-
ethylfluoren-9-yl bromomethane. Yield 84.2%, white crystal, m.p.:
69e70 ꢁC. Anal. Calcd for C16H15Br: C, 66.91; H, 5.26; Br, 27.82;
KOH under argon atmosphere, and then sealed with flame of
Bunsen burner. The test tube was put into an oil bath thermostated
at the desired temperature (such as 130 ꢁC). The reaction mixture
was stirred for 4 h. During this time, the mixture turned to auburn
and got more and more viscous until the magnetic bar could not
move. The reaction mixture was cooled to room temperature and
the tube was opened. THF (10 mL) was added to give a homogenous
solution. The THF solution was poured into methanol (100 mL). The
formed precipitation was filtered and washed with methanol. The
above-mentioned process, solving and precipitating, was repeated,
then the obtained precipitation was dried in vacuo at 50 ꢁC to
obtain polymer, yield 71.7e84.4%.
found C, 66.87; H, 5.32. 1H NMR(CDCl3, 400 MHz)
d(ppm): 7.76 (d,
J ¼ 7.4 Hz, 2H, Ar), 7.52 (d, J ¼ 7.3 Hz, 2H, Ar), 7.34e7.44 (m, 6H, Ar),
3.76 (s, 2H, CH2Br), 2.23 (q, J ¼ 7.3 Hz, 2H, CH2), 0.43 (t, J ¼ 7.3 Hz,
3H, Me). 13C NMR (CDCl3, 100 MHz)
d(ppm): 147.43, 141.08, 127.93,
127.20, 123.55, 119.96, 55.05, 41.86, 29.86, 8.57.
9-ethylfluoren-9-yl bromomethane (2.86g, 10 mmol) was dis-
solved in THF (30 mL) and reacted with Mg (0.48 g, 20 mmol) under
N2 to give a solution of corresponding Grignard reagent. The excess
of unreacted Mg was removed by filtration. Then, CuI (15 mg) was
added to the solution and the reaction mixture was cooled to
ꢀ15 ꢁC. A solution of (R)-ECH (0.12 mmol) in THF (5 ml) was
dropped into the reaction mixture. 30 min later, the reaction
mixture was warmed to r.t. and stirred for another 2 h. KOH
aqueous solution (4 mL, 50% wt) was added with stirring. The
reaction was monitored by TLC and stopped when no further
reaction progress was observed. The organic layer was separated
and water layer was exacted with diethyl ether (3 ꢂ 5 mL). The
organic phase was dried over anhydrous MgSO4. The solvent was
removed under reduce pressure and the residue was separated by
column chromatography (elution hexane/CH2Cl2 ¼ 5/1) to obtain
4.6.2. Solution anionic polymerization
A test tube with stir bar was charged with 10.00 mmol of (R)-
EFPO, a desired amount (0.34 mmol for example) of KOH and
1.25 mL xylene under argon atmosphere and then sealed with
flame of Bunsen burner. The test tube was put into an oil bath
thermostated at the desired temperature (such as 125 ꢁC). The
reaction mixture was stirred for 48 h. During this time, the mixture
turned to auburn and got more and more viscous. The treatment
was the same as that in bulk anionic polymerization and polymer
was obtained, yield 61.7%.
Acknowledgements
(R)-4-(9-ethylfluoren-9-yl) butylene oxide. yield 47.6%, white
We thank National Science Foundation of China (20972131) and
Science Foundation of Hunan (08JJ3013) for financial support of this
work.
20
crystal, m.p. 76～77 ꢁC e.e.: 98.1 (8.103 min), [
a
]
365
¼ þ14.6; Anal.
Calcd for C19H20O: C, 86.32; H, 7.63; O, 6.05; found C, 86.27; H, 7.65;
O, 6.08. 1H NMR(CDCl3, 400 MHz)
d
(ppm): 7.71 (d, J ¼ 6.8 Hz, 2H,
Ar), 7.30e7.35 (m, 6H, Ar), 2.60e2.62 (m, 1H, CHHO), 2.50e2.52 (m,
1H, CHHO), 2.21e2.28 (m, 2H, CH2), 2.13e2.14 (m, 1H, CH),
2.03e2.08 (m, 2H, CH2), 0.83e0.89 (m, 2H, CH2), 0.34 (t, J ¼ 7.2 Hz,
Appendix. Supporting information
3H, CH3). 13C NMR (CDCl3, 100 MHz)
d(ppm): 149.51, 149.33, 141.44,
The supplementary data associated with this article can be
found in the on-line version at doi:10.1016/j.polymer.2010.10.017.
141.34, 127.26, 127.19, 127.08, 127.06, 122.93, 122.82, 119.77, 119.73,
55.08, 52.29, 46.89, 35.83, 33.17, 27.24, 8.32.
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20
[
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¼ þ108; Anal. Calcd for C18H20O: C, 85.67; H, 7.99; O, 6.34;
365
Found C, 85.63; H, 8.03. 1H NMR (CDCl3, 400 MHz)
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