Post-functionalization of disubstituted polyacetylenes via click chemistry

Article abstract of DOI:10.1007/s11426-011-4376-x

We report a synthetic design and the experimental exploration of preparation of disubstituted polyacetylenes (PAs, P3) through 1,3-dipolar cycloaddition of azides with precursor PA bearing alkyne pendants. The precursor PA (P2) was derived by desilylation of the pristine PA with trimethylethynylsilane side chains (P1). P1 was obtained by polymerization of a dual-alkyne containing monomer with one of the alkynes end-capping by trimethylsilane (M) under the promotion of WCl₆-Ph₄Sn catalyst. Two synthetic routes, i.e. two-steps (from P1 to P3 via precursor P2) and one-pot (from P1 to P3 without separation and purification of P2) were tried and the results indicated that one-pot strategy is more facile and resultant P3-1 showed higher purity and higher molecular weight than the resultant of P3-2. By using the techniques such as GPC, FTIR and ¹H NMR spectroscopy the polymerization behavior and the structures of the polymers were well characterized.

Full text of DOI:10.1007/s11426-011-4376-x

SCIENCE CHINA
Chemistry
December 2011 Vol.54 No.12: 1948–1954
doi: 10.1007/s11426-011-4376-x
• ARTICLES •
Post-functionalization of disubstituted polyacetylenes via
click chemistry
TONG Li1, QIN AnJun1, ZHANG XiaoA1, MAO Yu1, SUN JingZhi1*& TANG Ben Zhong1,2*
1Institute of Biomedical Macromolecules, MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer
Science and Engineering, Zhejiang University, Hangzhou 310027, China
2Department of Chemistry, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China
Received June 30, 2011; accepted July 21, 2011; published online September 5, 2011
We report a synthetic design and the experimental exploration of preparation of disubstituted polyacetylenes (PAs, P3) through
1,3-dipolar cycloaddition of azides with precursor PA bearing alkyne pendants. The precursor PA (P2) was derived by desi-
lylation of the pristine PA with trimethylethynylsilane side chains (P1). P1 was obtained by polymerization of a dual-alkyne
containing monomer with one of the alkynes end-capping by trimethylsilane (M) under the promotion of WCl6-Ph4Sn catalyst.
Two synthetic routes, i.e. two-steps (from P1 to P3 via precursor P2) and one-pot (from P1 to P3 without separation and puri-
fication of P2) were tried and the results indicated that one-pot strategy is more facile and resultant P3-1 showed higher purity
and higher molecular weight than the resultant of P3-2. By using the techniques such as GPC, FTIR and 1H NMR spectroscopy
the polymerization behavior and the structures of the polymers were well characterized.
disubstituted polyacetylene, click chemistry, one-pot method, selective polymerization
with limited types of functional moieties [15–23] have been
1 Introduction
obtained, and apparently it still remains a daunting chal-
lenge to polymerize disubstituted acetylenes bearing reac-
tive groups with active protons or coordinative ligands
which would readily deactivate the brittle transition-metal
catalysts for acetylene polymerizations. There is no doubt
that new synthetic methods need to be explored for prepar-
ing the functional disubstituted PAs.
Through the efforts of chemists, many effective methods
have been found, and most of them are focused on the syn-
thesis of new monomers or on the exploration of new cata-
lyst systems [3, 24, 25]. But in practice, if the monomers are
different, the reaction conditions are often necessary to be
explored again, which makes the research rather cumber-
some and time-consuming. Alternatively, if we can obtain a
precursor of disubstituted PAs, based on which the expected
functional disubstituted PAs can be indirectly prepared by
post-polymerization modification, the synthesis of function-
al disubstituted PAs will become more facile and a variety
of novel functional disubstituted PAs will come into being.
Polyacetylene (PA) is the prototypic conjugated polymer for
its metallic conductive properties, but its intractability and
instability greatly limited its scope of practical applications.
If appropriate substituents are attached to the polyene
backbone, the above-mentioned problems could be solved
and meanwhile the substituents might endow it with new
functional properties [1–3]. The substituted PAs have been
found to show photoconductivity, optical nonlinearity,
magnetic susceptibility, photo- and electroluminescence,
liquid crystallinity, biocompatibility, chain helicity, and so
on [1–26], indicating the bright prospect of the substituted
PAs. Generally, disubstituted PAs are superior to their
monosubstituted counterparts in performance [15–23].
However, the molecular functionalization of disubstituted
PAs is difficult [2, 3]. Up to now, disubstituted acetylenes
*Corresponding author (email: sunjz@zju.edu.cn; tangbenz@ust.hk)
© Science China Press and Springer-Verlag Berlin Heidelberg 2011
chem.scichina.com www.springerlink.com

Tong L, et al. Sci China Chem December (2011) Vol.54 No.12
1949
Masuda and coworkers, Tang and coworkers have done
some contribution in this area [15–23, 26]. However, the
exploration has never desisted.
flask was put into a glovebox and 75 mg (11 mmol) of di-
chlorobis(triphenylphosphine)palladium(II), 81 mg (0.4
mmol) of CuI, and 56 mg (0.22 mmol) of triphenylphos-
phine were added. Afterward, 50 mL anhydrous THF, 60
mL dried triethylamine and 1.36 mL (14.3 mmol) of
1-pentyne were injected into the flask by syringes under
stirring respectively. The mixture was stirred at room tem-
perature for 4 h. The formed precipitates were filtered and
washed with diethyl ether. The organic solvent was com-
bined and evaporated by vacuum rotary. The crude product
was purified by silica gel column chromatography using
petroleum ether as eluent. A light yellow liquid was obtained
in 85.5% yield. 1H NMR (500 MHz, CDCl3),  (TMS, ppm):
7.40 (d, 2H), 7.25 (d, 2H), 2.36 (t, 2H), 1.62 (m, 2H), 1.03 (t,
3H) 13C NMR (125 MHz, CDCl3), δ (TMS, ppm): 133.3,
131.6, 123.3, 121.7, 91.8, 79.9, 22.3, 21.6, 13.8.
It is well-known that the 1,3-dipolar cycloaddition of az-
ides with alkynes catalyzed by copper(I) complexes under
mild conditions, coined as “click reaction”, has received
extensive attention as a highly efficient and stereoselective
reaction coupled with excellent functional group compati-
bility [27–34]. The click chemistry strategy has been suc-
cessfully utilized to macromolecular chemistry, affording
polymeric materials varying from block copolymers, den-
drimers, to complex macromolecular structures. It is a ra-
tional consideration that combining the click chemistry with
the precursor route to disubstituted PAs renders a great
chance to prepare functionalized PAs.
Herein, we demonstrate the design and synthesis of a
monomer with two kinds of internal alkynes (trimethyl((4-
(pent-1-ynyl)phenyl)ethynyl)silane), and the polymerization
of such a monomer by selective opening one alkyne and
leaving trimethylsilyl(TMS)-linked alkyne intact. The ob-
tained polymer (P1) bearing TMS-protected alkyne can be
used as a precursor. After de-protection, the free alkyne
group is potentially allowable for the click reaction with
variety of functional blocks with azide group. Thus, a facile
route to functional disubstituted PAs is available. For con-
venience, we have also explored one-pot synthetic route to
the post-functionalized disubstituted PAs.
1-Iodo-4-(pent-1-ynyl)benzene (3)
A two-necked rounded bottom flask equipped with a rubber
plug and a stirring bar was evacuated under vacuum and
flushed with nitrogen three times. Then 2 g (8.97 mmol) of
2 in 100 mL THF was injected into the flask. The flask was
put into acetone bath immediately, stired, and then poured
liquid nitrogen was put into the acetone in order to get low
temperature of 78 °C. Under this temperature, 6.17 mL
(9.87 mmol) of n-BuLi was injected dropwise into the solu-
tion and reacted for 1 h. Afterwards, with strong nitrogen
flow, the rubber plug was opened to add 3 g (8.97 mmol) of
I2 as fast as possible and reacted for another 0.5 h. Then it
was admitted to rise to room temperature and continued to
react for 1 h or about so. Deionized water was added to end
the reaction and was extracted with DCM for 3 times with
the followed step that washing the organic solution with
Na2S2O3 (aq.) and deionized water respectively. The organic
phase was dried over magnesium sulfate and the crude
product was condensed under vacuum rotary without further
purified. A brown liquid (2 g) was obtained in 83.3% yield.
1H NMR (500 MHz, CDCl3),  (TMS, ppm): 7.62 (d, 2H),
7.13 (d, 2H), 2.37 (t, 2H), 1.63 (m, 2H), 1.06 (t, 3H).
2 Experimental
2.1 General experimental section
All the chemicals used in this study were purchased from
Acros or Alfa without otherwise stating. Tetrahedrofuran
(THF) was distilled from sodium benzophenone ketyl under
nitrogen before used. Other solvents were purified by
standard methods.
1H and 13C NMR spectra were recorded on a Bruker
ADVANCE DMX 500 MHz spectrometer with tetrame-
thylsilane as the internal standard. FTIR spectra were rec-
orded on a Bruker Vector 22 spectrometer. Average molec-
ular weights (Mw) and polydispersity indices (PDI) of the
polymers were estimated by a Waters PL-GPC-50 gel per-
meation chromatography (GPC) system equipped with a
Refractive Index (RI) detector, using a set of monodisperse
polystyrenes as calibration standards. High-resolution mass
spectra (HRMS) were taken on a GCT Premier CAB 048
mass spectrometer operating in MALDI-TOF model.
Trimethyl((4-(pent-1-ynyl)phenyl)ethynyl)silane (M)
The procedure was the similar to synthesis of compound 2.
A yellow liquid was obtained in 58.8%. The synthesis of M
would be shown in Scheme 1. 1H NMR (500 MHz, CDCl3),
 (TMS, ppm): 7.36 (d, 2H), 7.30 (d, 2H), 2.38 (t, 2H), 1.63
2.2 Synthesis of the monomer
1-Bromo-4-(pent-1-ynyl)benzene (2)
Into a rounded bottom flask equipped with a stirring bar was
placed 3 g (11 mmol) of 1-bromo-4-iodobenzene (1). The
Scheme 1 Synthetic route to the monomer with two alkynes.

1950
Tong L, et al. Sci China Chem December (2011) Vol.54 No.12
(m, 2H), 1.04 (t, 3H), 0.24 (s, 9H) 13C NMR (125 MHz,
CDCl3),  (TMS, ppm): 131.9, 131.5, 124.5, 122.3, 105.0,
95.8, 92.7, 80.7, 22.4, 21.7, 13.8, 0.18. HRMS (MALDI-TOF,
m/z): (M+) calcd for C16H20Si, 240.1334; found, 240.1336.
The polymer which was dried in an open atmosphere to a
constant weight was isolated as a green-yellow solid. IR
1
(thin film),  (cm1): 2157(C C), 1658(C==C). H NMR
(500 MHz, CDCl3),  (TMS, ppm): 7.4–6.9 (aromatic pro-
tons), 2.38, 1.62, 1.04 (pentyne), 0.26 (protons in TMS
groups) 13C NMR (125 MHz, CDCl3),  (TMS, ppm): 142.0
(C=C), 133.2, 131.2, 121.2 (aromatic carbons), 105.7, 94.62
(internal alkyne linking to protection TMS group), 37.9,
22.4, 14.6 (carbons belonging to pentyne), 0.27 (carbons in
TMS groups).
2.3 Polymerization
All the polymer reactions shown in Scheme 2 were carried
out under dry nitrogen in a vacuum-line system except for
the purification of the polymers, which was done in an open
atmosphere. Typical procedures for polymerization are
given below.
2.4 Desilylation of the polymer
Into a 10 mL Schlenk tube with a side arm was added
294 mg (1.2 mmol) of the monomer (M). The tube was
evacuated under vacuum and flushed with dry nitrogen
three times before injecting 2 mL of toluene. The catalyst
solution was prepared in another tube by dissolving 24 mg
(0.06 mmol) of tungsten chloride (WCl6) and 26 mg (0.06
mmol) of tetraphenyltin (Ph4Sn) in 2 mL of toluene. After
aging for 15 min at room temperature, the monomer solu-
tion was transferred to this tube using a hypodermic syringe.
The reaction mixture was stirred at 80 °C for 24 h. Diluted
with 4 mL CHCl3, the crude product was added dropwise to
300 mL methanol through a cotton filter under stirring. The
precipitate was allowed to stand over night and then filtered
with a Gooch crucible, washing with methanol for 3 times.
Into a 10 mL Schlenk tube was added 87 mg (0.36 mmol) of
polymer P1. After the tube being evacuated under vacuum
and flushed with dry nitrogen for 3 times, 3.5 mL of fresh
distilled THF was injected. When the polymer P1 was dis-
solved completely, the tube was put into ice-salt (NaCl)
bath to reach 10 °C, and 0.9 mL of 1 M TBAF (tetrabu-
tylammonium fluoride) solution in THF was added drop-
wise, stirring. Then the mixture was allowed to warm up to
ambient temperature and reacted overnight. The following
step was the same as shown in the polymerization part.
IR (thin film),  (cm1): 3312 (HC), 2104(C C), 1605
(C==C).
2.5 Click reaction
1-(Azidomethyl)-4-bromobenzene (N3-R)
A rounded bottom flask was equipped with a stirring bar,
2 g (8 mmol) of 1-bromo-4-(bromomethyl)benzene and 0.63
g (9.6 mmol) of NaN3 was placed. Then, 50 mL DMSO was
added and the mixture was stirred at 30 °C overnight. Fol-
lowed by ending the reaction with deionized water was ex-
tracting the mixture with diethyl ether for 6 times or more.
All the organic solvent was condensed and purified by a
silica gel column chromatography using petroleum ether as
1
eluent. A transparent liquid was obtained in 60% yield. H
NMR (500 MHz, CDCl3),  (TMS, ppm): 7.50 (m, 2H),
7.18 (d, 2H), 4.30 (s, 2H). 13C NMR (125 MHz, CDCl3), 
(TMS, ppm): 134.6, 132.2, 130.0, 122.5, 54.3.
General procedures of P2’s click reaction
24 mg (0.14 mmol) of P2 and 3 mg (0.0029 mmol) of
Cu(PPh3)3Br were added into a 10 mL Schlenk tube, which
was evacuated and flushed with dry nitrogen for three times
then 2 mL of fresh distilled THF being injected. N3-R then
was injected and the mixture was stirred at 60 °C for 12 h.
The successive procedures were similar to the procedures as
shown before. The product P3 was isolated as a black solid
1
in yield of 59.1%. H NMR (500 MHz, CDCl3),  (TMS,
ppm): 8.1–6.7 (aromatic protons), 5.5 (protons attached to
phenyl and triazole), 2.34, 1.67, 1.02 (pentyne).
Scheme 2 Two post-function methods for the preparation of disubstituted
PAs via click reaction.

Tong L, et al. Sci China Chem December (2011) Vol.54 No.12
1951
Procedures of one-pot method
Into a 10 mL Schlenk tube was added stirring bar and 69 mg
(0.29 mmol) of P1. The tube was put in glove box and 11
mg (0.058 mmol) CuI was added. Then 3.5 mL fresh dis-
tilled THF, 0.24 mL (1.45 mmol) DIPEA was injected be-
fore 0.12 mL 1 M TBAF in THF being injected dropwise.
The mixture was stirred at 50 °C for 12 h. The successive
procedures were the same as before. A black solid P3 was
1
obtained in yield of 83.3%. H NMR (500 MHz, CDCl3), 
(TMS, ppm): 9.0–5.9 (aromatic protons), 5.5 (protons on
phenyl and triazole), 2.32, 1.59, 1.01 (protons of pentyne).
3 Results and discussion
The synthesis of monomer containing two alkyne moieties
is a key step to the target polymer. In principle, M can be
obtained by direct substitution of the bromide of compound
2 by trimethylethynylsilane. But in experiment, the separa-
tion of 2 and M was unexpectedly difficult. Fortunately, this
problem was solved by introducing one more step, as shown
in the Scheme 1 [4, 34]. We finally got the monomer in high
purity by transformation of 2 to 3, which was confirmed by
the 1H and 13C NMR spectra as well as HR-MS analysis.
The experimental results of the disubstituted PA (P1)
were summarized in Table 1. In previous studies, the yield
and Mw of disubstituted polyacetylenes could not meet de-
mands simultaneously [3, 26]. But our present results are
different, the yield can be over 30% and the Mw has reached
104 Da with relatively narrow polydispersity. Besides, the
solubility of the disubstituted polymer P1 was also checked
and to our delight, P1 could dissolve well in CHCl3 (at least
120 mg/mL), THF, CH2Cl2 and acetone.
Figure 1 13C NMR spectra of the monomer (a) and its polymer P1 (b) in
CDCl3. The solvent peak is marked with an asterisk.
In addition, successful selective consumption of alkyne
group was confirmed by 13C (Figure 1) and FTIR measure-
ment (Figures 1 and 2). For example, in Figure 1(a), the
resonance peaks at  = 92 and 81 ppm (denoted as peaks e
and f) are corresponding to the penta-1-ynyl. They disap-
peared after polymerization (Figure 1(b)); while, the peaks
for g and h are still in presence. The characteristic signal at
 = 140 ppm in Figure 1(b) can be assigned to the carbons
in PAs’ backbone. These data validate that the selective
polymerization of internal alkyne has been achieved.
FTIR spectra give more information. As shown in Figure
2, Figure 2(a) displays the IR absorption features of M, the
Figure 2 IR spectra of the monomer M (a), its polymer P1 (b), P2 (c),
P3-2 (d) and P3-1 (e).
Table 1 Results of polymerization for P1a)
Temperature (°C)
No.
1
Yield (%)
33.2
Mw
PDI
2.00
3.17
80
80–95 b)
17000
38000
stretching band of C C is clearly shown at wavenumber of
2157 and 1520 cm1, indicating the existence of pristine
CC bonds. After the polymerization reaction catalyzed by
WCl6-Ph4Sn system, these two bands are still in presence,
suggesting that only partial alkynes have been consumed. In
2
24.1
a) Catalyzed by WCl6-Ph4Sn in toluene under nitrogen for 24 h; [M]o =
1 M, [WCl6] = [Ph4Sn] = 0.05 M. Determined by GPC in THF on the basis
of a linear polystyrene calibration; b) the temperature was kept at 95 °C for
about 2 h then cooled to 80 °C.

1952
Tong L, et al. Sci China Chem December (2011) Vol.54 No.12
other words, the WCl6-Ph4Sn catalyst system can only
polymerize one of the two kinds of internal alkyne groups.
The selective polymerization of alkyne is attributed to the
steric and electronic effect of the protected groups (TMS)
[33].
It’s well known that 1,3-dipolar cycloadditions between
terminal alkynes and azides proceeds efficiently in mild
condition. To make use of this facile synthetic strategy, the
desilylation of P1 was firstly carried out (Scheme 2). The
characterization data of the resultant polymer (P2) are list
in Table 2; and the FTIR spectrum is shown in Figure 2.
Figure 2(c) displays the IR absorption features of P2, the
absorption band at a wavenumber of 2144 cm1 is assigned
to the stretching mood of C C. In addition, a new band at
a wavenumber of 3312 cm1 emerges (in comparison with
Figure 2(b)). This band is associated with C–– H stretching
mood of the C C–– H entity. These two bands at 2144
and 3312 cm1 indicate the releasing of external alkyne in
P2.
The existence of free external alkyne group allows us to
implement the post-modification of P2 by clicking alkyne
with azide compounds bearing functionalities. To validate
this idea, we conducted a click reaction of P2 with 1-(azi-
domethyl)-4-bromobenzene. Delightfully, the reaction went
on smoothly, and P3 was obtained in a mild condition, i.e.
just stirring at 60 °C for 12–18 h in the presence of Cu(I)
catalyst. To characterize the structure of the resulted poly-
mer, both FTIR and 1H NMR spectroscopic techniques were
used. As shown by Figure 2D, the IR absorption bands at
2144 and 3312 cm1 both disappeared completely, indicat-
ing that the CC–– H moieties had been consumed thor-
oughly. Meanwhile, in the finger-print region, the bands at
around 1050–1100 cm1 can be assigned to the bending
mood of polar C==N bonds. The emergence of these bands
implies the formation of triazole moieties in the click reac-
tion process.
Figure 3 1H NMR spectra of P1 (a), click reaction product P3-2 (b) and
P3-1 in CDCl3 (c). The solvent peaks are marked with asterisks.
peak for TMS vanished totally, suggesting that the desilyla-
tion was well proceeded. The resonance peaks for propanyl
groups shifted to low field slightly and became broader. The
resonance peaks at field lower than 7.0 ppm show some
new features in Figure 3(b). On one hand, they are split,
which is reasonable because the click reaction has intro-
duced a bromophenyl group into the resulted polymer. On
the other hand, the chemical shifts appear in lower field;
this is also reasonable because both bromo- and triazol-
yl-moieties are electron withdrawing functionalities. More
significantly, a new peak at around  = 5.46 ppm is ob-
served in Figure 3(b), which is assigned to the protons on
the methyl group linking the end phenyl with triazole
moiety. These observations evidently confirm the successful
transformation of P2 to expected functional disubstituted
PA, or P3 through the click chemistry strategy. Moreover,
the peak attributed to the C C–– H proton at around  = 3
ppm could hardly be seen in Figure 3(b). It implies that the
efficiency of the grafting is higher than the upper limitation
of NMR spectroscopy (97%).
1H NMR spectra disclose further information about the
post-polymerization reaction (see Figure 3). In Figure 3(a),
the resonance peaks showing in the high-field region ( < 3)
are assigned to the chemical shifts of the propanyl attaching
to polymer backbone and the methyls in TMS, and the
broad band showing around 7.2 ppm are caused by the pro-
tons on the phenyl group. After click reaction, the resonance
In our experiment, we encountered the difficulty of low
throughput due the low solubility of P2 in the solvents that
suitable for click reaction of P2 with azides. The data in
Table 2 reveal that the final polymer (P3-2) has an evident
lower molecular weight than its precursor polymer P2, alt-
hough the molecular weight of the repeat unit of P3 is high-
er than that of P2. Besides the systematic error in molecular
weight measurement caused by different experimental batch-
es, this observation can be explained as following. After
purification and drying in vacuum, the collected P2 can be
Table 2 Experimental results of P2, P3-1 and P3-2a)
Polymer
P2
Yield (%)
54.5
Solubility
Lb)
Mw
PDI
1.9
1.9
1.7
30000
27000
12000
P3-1
P3-2
83.3
Ac)
59.1
Ac)
a) P3-1 and P3-2 stand for the target polymer P3 obtained by one-pot
and two-step methods, respectively; b) the solubility was very low in or-
ganic solvents; c) the solubility in some organic solvents is acceptable.
Molecular weight was determined by GPC in THF on the basis of a linear
polystyrene calibration.

Tong L, et al. Sci China Chem December (2011) Vol.54 No.12
1953
dissolved partially in proper solvents. It means that only the
fraction with low molecular weight has gone through with
the click reaction. Consequently, the finally obtained poly-
mer has a lower molecular weight. Considering that the
click reaction is highly efficient, we tried to prepare P3
through a one-pot scheme (see Scheme 2). Fortunately, re-
sultant showing the same aspect as P3-2 was obtained and it
was denoted as P3-1. To make it doubtless that the resultant
has the same intrinsic structure as P3-1 rather than the un-
touched precursor P2, both FTIR and 1H NMR characteriza-
tions were carried out on the resultant, and the recorded data
are demonstrated in Figure 2 (curve (e)) and (curve (c)),
respectively.
It is obvious that spectral features of curve E seems iden-
tical to that of D. Specifically, the disappearance of the ab-
sorption band at 2144 and 3312 cm1 indicates the CC
bonds have been transformed, and the appearance of the
bands at around 1000–1100 cm1 indicates the formation of
triazole group. Moreover, curve (c) in Figure 3 shows simi-
lar characteristics of curve (b). The most significant one is
the emergence of a  at around 5.54 ppm, which is an indi-
cation of the triazole moiety. Therefore, both FTIR and
NMR spectra clearly validate that the obtained polymer is
the expected resultant.
There are two noteworthy essences in the one-pot route.
One is revealed by the comparison between curve (b) and (c)
in Figure 3. The resonance peaks at 0.88 and 1.26 ppm in
curve (b) are assigned to the hexane, which was used for
precipitation of the resultant mixture and encapsulated in
polymer matrix. Both of them are invisible in curve (c) due
to the saving of the middle separation and purification steps.
The other is that the molecular weight of P3-1 (27000) is
evidently higher than that of P3-2 (12000). These data sug-
gest that the one-pot strategy can give rise to expected di-
substituted functional PAs with higher purity and higher
molecular weight.
that one-pot method gave rise to resultant polymer with
higher purity and higher molecular weight. All these re-
marks have been supported by experimental and spectral
data.
This work was partially supported by the National Natural Science Foun-
dation of China (21074113, 20634020 & 20974028), the National Basic
Research Program of China (973 Program, 2009CB623605), the Research
Grants Council of Hong Kong (603509 & HKUST2/CRF/10), and the
University Grants Committee of Hong Kong (AoE/P-03/08). B.Z.T. thanks
the support from the CAO GuangBiao Foundation of Zhejiang University.
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4 Conclusions
12 Goto H, Zhang HQ, Yashima E. Chiral stimuli-responsive gels: He-
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13 Dong YP, Lam JWY, Peng H, Cheuk KKL, Kwok HS, Tang BZ.
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14 Lam JWY, Dong YP, Cheuk KKL, Law CCW, Lai LM, Tang BZ.
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properties of poly(alkyl phenylpropiolate)s bearing stereogenic pen-
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In summary, we have demonstrated that functional disub-
stituted PAs can be successfully prepared by click chemistry
strategy. By rational design, a dual-alkyne containing
monomer with one of the alkynes end-capping by trime-
thylsilane (TMS) was synthesized. This monomer can be
selectively polymerized and P1 has been derived by using
WCl6-Ph4Sn catalyst, leaving the TMS end-capped alkyne
group untouched and the other completely consumed in
polymerization reaction. After desilylation of P1, the pre-
cursor polymer P2 was derived, the presence of free external
alkynes was confirmed by FTIR, and 1H NMR spectroscopy.
The click reaction between P2 and functional azides was tried
and expected polymer P3 was obtained. To find a more fac-
ile synthetic route, both one-pot and two-steps methods
have been explored, and the experimental results revealed
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34 Liu JZ, Zheng RH, Tang YH, Lam JWY, Qin AJ, Ye MX, Hong YN,
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25 Xu K, Peng H, Lam WY, Dong Y, Sun Q, Salhi F, Tang BZ. Transi-