Chemical modification of poly(vinylacetylene) and synthesis of poly(1,2,3-triazole)s

Article abstract of DOI:10.5012/bkcs.2011.32.5.1471

A series of new polymers containing 1,2,3-triazoles were synthesized and their structures and properties were characterized by FT-IR, ¹H NMR, TGA, DSC and GPC. The results showed that the polymers modified by alkyl groups had good solubility, thermal stability and reasonable molecular weights. It was also demonstrated that the properties of fluorine-containing polymers were seriously affected by fluorine atoms with hydrophobic and chemical proof properties.

Full text of DOI:10.5012/bkcs.2011.32.5.1471

Chemical Modification of Poly(vinylacetylene) and Synthesis
Bull. Korean Chem. Soc. 2011, Vol. 32, No. 5 1471
DOI 10.5012/bkcs.2011.32.5.1471
Chemical Modification of Poly(vinylacetylene) and Synthesis of Poly(1,2,3-triazole)s
†,‡,*
‡
Shan Liao, and Le-yong Wang
†
Lian-jun Wang,
†
School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, P. R. China
‡
College of Chemistry and Chemical Engineering, Hunan Institute of Engineering, Hunan 411104, P. R. China
*
E-mail: wangljchem@gmail.com
Received December 22, 2010, Accepted March 2, 2011
A series of new polymers containing 1,2,3-triazoles were synthesized and their structures and properties were
1
characterized by FT-IR, H NMR, TGA, DSC and GPC. The results showed that the polymers modified by
alkyl groups had good solubility, thermal stability and reasonable molecular weights. It was also demonstrated
that the properties of fluorine-containing polymers were seriously affected by fluorine atoms with hydrophobic
and chemical proof properties.
Key Words : Chemical modification, 1,2,3-Triazoles, Fluorinated polymers, Properties
Introduction
characteristics of fluorine atoms, the enhanced appearance
of fluorinated portions on the surfaces of fluorine-containing
polymers is of importance in the potential applications as
anti-thermal, water repellency, chemical proof, lubricant and
In recent years, there has been wide interests in click
chemistry, an appealing concept proposed by Sharpless and
1
co-workers, especially the copper-catalyzed Huisgen 1,3-
12
electric insulation materials.
dipolar cycloaddition of azides and terminal alkynes, the
archetypal example of click chemistry. Since the objective of
click chemistry would be to establish an ideal set of
straightforward and highly selective reactions in synthetic
chemistry, more and more researchers have been engaged in
developing this strategy. In the field of polymer materials,
click chemistry has been used for polymeric synthesis as
well as the modification of surfaces nanometer- and meso-
Experimental Part
Materials. Triethylamine (TEA), tetrahydrofuran (THF),
methanol (MeOH) and acetonitrile (MeCN) were distilled
from CaH2. Chlorotrimethylsilane was distilled from P2O5.
Magnesium turnings were treated with 5% aqueous hydro-
chloric acid for several minutes, washed with water, ethanol
and ether successively, and dried at 120 °C under vacuum
for 4 h. Other reagents were used as supplied. Trimethyl-
silyacetylene (TMSA) 1 was synthesized from commercial
2
scale structures. Click reaction was used for synthesis of
polymers containing 1,2,3-triazoles in the backbones from
the monomers of dialkynes and diazides. For example, a
new kind of glue was obtained with click chemistry by Diaz
13
acetylene using literature procedures.
3
et al. and a series of poly(alkyl aryl) ethers were synthe-
Measurements. Infrared spectra were obtained on Thermo
4
sized with click chemistry reaction in our research group.
Electron Corporation Nicolet 380 FT-IR spectrophotometer.
1
And functional hyperbranched polymers were synthesized
by click reaction from the monomers of triynes and di-
H NMR (400 MHz) was recorded on a Bruker AM-400
1
spectrometer with Me4Si ( H NMR) as an internal standard.
5
azides. When click reaction was applied in the chemical
Relative molecular weights and molecular weight distribu-
tions were measured by gel permeation chromatography
(GPC) system equipped with a Waters 1515 Isocratic HPLC
pump, a Waters 2414 refractive index detector (RI), a Waters
2487 dual-wavelength λ absorbance detector and a set of
Waters Styragel columns (HR3, HR4 and HR5, 7.8 × 300
mm). GPC measurements were carried out at 35 °C using
THF as an eluent with a 1.0 mL/min flow rate. The system
was calibrated with polystyrene standards. Differential
scanning calorimetry (DSC) was conducted on a NetZSch
(German) DSC 204 F1 system under nitrogen calibrated
with indium and zinc standards. Thermogravimetric analysis
(TGA) was performed on NetZSch (German) TGA 209 F1
system on powder samples at a heating rate of 10 °C/min in
N2 atmosphere.
modification of polymers, many novel polymers were also
6 7
obtained such as dendronized polymers, hydrogels, end-
8
functional polymers, and so on..
The preparation of Poly(vinylacetylene) (PVacet) was
9
firstly reported by Kaneko et al. and then a few reports on
10
PVacet were occurrence. To the best of our knowledge,
however, no report on its thermal stability has been yet
available. In fact, it would explode at 210 °C, which was
demonstrated by thermogravimetric analysis in this report.
So the pendent terminal alkynes in PVacet were used to react
with azides via click reaction to get some modified polymers
that we expected. In this paper, the thermal stability of
PVacet and modified PVacet with pendent alkyl or fluoro-
alkyl groups were studied. Meanwhile, the 1,2,3-triazole
rings grafted onto the substrate polymer may increase the
Synthesis of PVacet 4. PVacet was prepared through three
11
antibacterial ability of novel polymers. And due to the
6
steps and the detailed procedures were reported by Helms.

1472 Bull. Korean Chem. Soc. 2011, Vol. 32, No. 5
Lian-jun Wang et al.
−1
Polymer 3: white powder (80%). IR (KBr, cm ): ν 2959,
0.58 mmol) and organic azide (0.58 mmol) dissolved in 8
mL THF. Under vigorously stirring, CuSO4·5H2O (7 mg, 5
mol %) and sodium ascorbate (12 mg, 10 mol %) dissolved
in 8 mL H2O were added, then stirred for 12 h at room
temperature. The reaction mixture was poured into hexane,
and the precipitate was washed with ammonia and water for
several times. Finally, the products were dried at 60 °C under
vacuum for 48 h.
2917, 2899, 2852, 2168, 1944, 1865, 1447, 1407, 1350,
1
1250, 1098, 841, 759, 698, 638; H NMR (400 MHz, CDCl3,
δ): 2.9-2.6 (1H, br), 1.6-1.2 (2H, br), 0.2 (9H, s).
−1
Polymer 4: pale yellow powder (72%). IR (KBr, cm ): ν
3299, 2928, 2856, 2113, 1629, 1448, 1363, 1253, 1098, 848,
1
630; H NMR (400 MHz, CDCl3, δ): 3.2-2.7 (1H, br), 2.12
(1H, s), 1.9-1.4 (2H, br). Mn = 30150, Mw = 69600, PDI =
2.31.
Compound 6a: pale solid powder (64 mg, 73%). IR (KBr,
−1
cm ): ν 3131, 3063, 2958, 2934, 2873, 1637, 1542, 1458,
Synthesis of Alkyl and Fluoroalkyl Azides from Halides
5a-c. To a 50 mL three-necked flask equipped with a
magnetic stirrer, a thermometer and a condenser were added
alkyl bromide or fluoroalkyl iodide (5 mmol), NaN3 (390
mg, 6 mmol) dissolved in 10 mL water and Tetrabutyl-
ammonium bromide (32 mg, 2 mol %). The reaction mixture
was stirred at 90 °C for 24 h and then cooled to room
temperature, and extracted with ether (3 × 10 mL). The
organic phase was dried over MgSO4, filtered, and concen-
trated. The products 5a-c were obtained by flash chromato-
graphy based on gel silca with petroleum ether/ethyl acetate
(10:1 v/v) as the eluent.
1380, 1336, 1247, 1216, 1146, 1095, 1051, 835, 802, 757;
1
H NMR (400 MHz, CDCl3, δ): 6.9-7.2 (1H, br), 1.4-1.1
(2H, br), 4.4-3.9 (2H, br), 2.4-2.1 (1H, br), 1.9-1.5 (4H, br),
1.0-0.8 (3H, br); Mn = 51230, Mw = 135800, PDI = 2.65.
Compound 6b: pale solid powder (76 mg, 64%). IR (KBr,
−1
cm ): ν 3125, 3064, 2927, 2856, 1631, 1538, 1458, 1340,
1
1261, 1216, 1152, 1105, 1045, 906, 858, 803, 726; H NMR
(400 MHz, CDCl3, δ): 7.2-6.8 (1H, br), 4.4-4.0 (2H, br), 2.4-
2.1 (1H, br), 2.0-1.5 (2H, br), 1.5-1.0 (12H, br), 1.0-0.7 (3H,
br); Mn = 63856, Mw = 175600, PDI = 2.75.
Compound 6c: yellow solid powder (186 mg, 60%). IR
−1
(KBr, cm ): ν 3124, 3060, 2945, 2855, 1635, 1457, 1212,
Compound 5a: colorless liquid (450 mg, 91%). IR (KBr,
−1
cm ): n 2962, 2925, 2854, 2103, 1629, 1458, 1412, 1260,
1151, 992, 841, 808, 737.
1
1094, 1019, 863, 800; H NMR (400 MHz, CDCl3, δ): 3.47
Compound 6d: yellow solid powder (62 mg, 80%). IR
−1
(KBr, cm ): ν 3125, 3061, 2933, 2855, 2109, 1636, 1457,
(2H, m, J = 7.01 Hz), 1.55 (2H, m, J = 6.72 Hz, J = 7.54 Hz),
1.38 (2H, m, J = 7.01 Hz, J = 7.54 Hz), 0.93 (3H, m, J = 6.68
Hz).
1396, 1336, 1266, 1170, 1096, 1046, 930, 838, 798.
Compound 5b: colorless liquid (713 mg, 92%). IR (KBr,
Results and Discussion
−1
cm ): ν 2926, 2857, 2096, 1555, 1459, 1374, 1260, 1104,
1
1023, 804; H NMR (400 MHz, CDCl3, δ): 3.25 (2H, m, J =
Synthesis and Characterization of PVacet. PVacet was
6
7.01 Hz), 1.58 (2H, m, J = 7.01 Hz, J = 7.53 Hz), 1.35 (10H,
m), 0.89 (3H, t, J = 7.01 Hz) .
prepared according to the literature procedures (Scheme 1).
First, compound 2 was synthesized by the Sonogashira
−1
Compound 5c: white solid (2.32 g, 95%). IR (KBr, cm ):
15
coupling reaction between vinyl bromide and trimethyl-
ν 2960, 2922, 2856, 2109, 1629, 1444, 1343, 1206, 1151,
silylacetylene (TMSA) in which 5 mol % Pd(PPh3)2Cl2 was
used as a typical palladium catalyst, 10 mol % CuI as a
cocatalyst, and triethylamine as a solvent with a yield of
60%. Then, the monomer 2 was polymerized in bulk at 60 °C
with AIBN. No fraction of the TMS-protected polymer 3
was performed in this procedure, which resulted in broader
polydispersity than that described in the literature. Finally,
the polymer 3 was dissolved in THF and deprotected under
aqueous KOH to produce polymer 4 containing pendent
alkynes.
1
1079, 1066, 986, 921, 882, 711; H NMR (400 MHz, CDCl3,
δ): 3.62 (2H, m, J = 7.01 Hz), 2.55 (2H, m, J = 7.01 Hz).
Synthesis of 2,2,2-trifluoroethyl Azide 5d. Methane-
sulfonyl chloride (228 mg, 2 mmol) was slowly dropped,
under a nitrogen atmosphere, to a dichloride methane solu-
tion (30 mL) of trifluoroethanol (200 mg, 2 mmol) and
triethylamine (10 mg, 5 mol %) at −5 °C. After complete
methanesulfonation (4 h), the solvent was removed by rotary
evaporation. Then, to this system, NaN3 (143 mg, 2.2 mmol),
DMSO (30 mL) and 18-crown-6 (27 mg, 5 mol %) were
added, and stirred at 110 °C for 20 h. The reaction mixture
was diluted with ether (50 mL) and washed with brine (3 ×
10 mL) followed by water (3 × 10 mL). The organic phase
was dried over MgSO4, filtered, and concentrated. The pro-
duct 5d was obtained by flash chromatography based on gel
silca with petroleum ether/ethyl acetate (10:1 v/v) as the
14
eluent.
Compound 5d: pale brown liquid (208 mg, 85%). IR
−1
(KBr, cm ): ν 2960, 2922, 2856, 2109, 1629, 1444, 1343,
1
1206, 1151, 1079, 1066, 986, 921, 882, 711; H NMR (400
MHz, CDCl3, δ): 3.85 (2H, dd).
Chemical Modification of Polymers. To a 25 mL flask
equipped with a magnetic stirrer were added PVacet (30 mg,
Scheme 1. Synthesis of PVacet.

Chemical Modification of Poly(vinylacetylene) and Synthesis
Bull. Korean Chem. Soc. 2011, Vol. 32, No. 5 1473
Table 1. Solubility of PVacet and the modified polymers
Polymers Acetone THF CHCl
NMP DMSO DMF
4
+
+
+
–
–
+
+
+
–
–
+
+
+
–
–
+
+
+
s
+
+
+
s
+
+
+
s
6a
6b
6c
6d
Scheme 2. Synthesis of organic azides.
–
–
–
Note: (+), soluble; (s), swell; (–), insoluble.
Table 2. Physical properties of PVacet and the modified polymers
Polymers
Mn
Mw
(Mw/Mn)
T
(°C)
52
T
(°C)
210
4
30150
69600
2.31
2.65
2.75
–
6a
6b
6c
6d
51230 135800
63860 175600
86
–
314
287
336
439
Scheme 3. Synthesis of azido trifluoroethane.
–
–
65
–
–
–
–
Synthesis of Organic Azides. Organic azides can be pre-
16
pared from halides, alcohols, amines or hydrazines. Here,
GPC in THF (0.1 wt %) vs. polystyrene at 35 °C. DSC and TGA at 10
°C/min in N atmosphere.
the azides 5a-c were synthesized through modification of
17
literature procedures in 85-95% yields by halides (Scheme
2). In the reactions performed in our lab, rather than organic
solvent, only water was added and tetrabutylammonium
bromide was used as a kind of phase transfer catalyst (PTC),
which resulted in a little higher yields and easy purification.
As for the preparation of compound 5d, two steps were
required with 2,2,2-trifluoro- ethanol as the original material
(Scheme 3). At first, the intermediate, methylsulfonyl rami-
fication was formed, and then the resulting ramification
Solubility of Polymers: From the solubility tests of
polymers (Table 1), we can see that polymers 6a and 6b
possessed good solubility which might be the result of
grafting flexible pendent groups onto substrate polymer, but
polymers 6c and 6d containing fluorine atoms were not able
to be dissolved in most organic solvents such as acetone,
THF, CHCl3, DMF, and so on. Polymer 6c only could be
swollen in the polar solvents, and 6d could be dispersed
homogenously in the polar solvents, but it would subside
after keeping immobile for a period of time. The chemical
proof property of modified polymers 6c and 6d might be
illustrated that the pendent fluorinated groups, like a sheath,
protected the backbones of polymers from the attack of
organic solvents.
18
reacted with NaN3 without further purification.
Chemical Modification of PVacet. The chemical modifi-
cation of PVacet were carried out in a 1:1 solvent ratio of
water to THF using 5 mol % CuSO4·5H2O and 10 mol %
sodium ascorbate (Scheme 4). Usually, the click reactions
were performed smoothly at room temperature. When we
raised the temperature to 60 °C, the reaction would be
completed in an hour, but the resultant molecular weight
distribution was not as good as what we had got at room
temperature. The difference of the isolated yields of polymers
6a-d might be attributed to the bulk effect of azides: the
larger the volume of organic azide was, the lower the yield
could be. The change of the color of the solution, from
orange yellow to blue green, was a simple signal for the
completion of the reaction.
Molecular Weights and Their Distributions of Polymers:
The molecular weights and their distributions of PVacet and
modified polymers were listed in the Table 2. It can be seen
that the molecular weights of modified polymers 6a and 6b,
determined by GPC, became larger and the molecular
weight distributions became a little broader. Furthermore,
the molecular weights of polymers became heavier with the
increase of the molecular weights of pendent chains, which
7
was similar to what was described by Helms. However,
Properties of Polymers.
fluorinated polymers 6c and 6d couldn’t be characterized by
GPC because of their insolubility in organic solvents such as
acetone, THF, DMF, and so on.
Thermal Stability of Polymers: The thermal stability of
each polymer were examined with dynamic thermogravi-
metric analysis (TGA) at a heating rate of 10 °C/min (Fig. 1).
Corresponding decomposed temperatures (Td) were listed in
the Table 2. It should be noted that the substrate polymer,
PVacet showed a volatile weight loss at about 210 °C. To
demonstrate this exploding case, a small block of PVacet
was placed in a Bunsen burner flame and it blew up with a
“pu” sound. However, all the modified polymers displayed
good thermal stability. The fluorinated polymers 6c-d ex-
Scheme 4. Modification of polymers by click chemistry.

1474 Bull. Korean Chem. Soc. 2011, Vol. 32, No. 5
Lian-jun Wang et al.
curves of polymers 6b and 6d from 150 °C to 230 °C, and
this might be attributed to the cooling crystallization of the
long pendant units.
Conclusions
PVacet was prepared through three steps from TMSA, and
then it was modified via click reaction with the introduction
of alkyl or fluoroalkyl groups to the pendent alkynes of the
polymer. The solubility of alkyl-modified polymers was the
same as PVacet, but the thermal stability was greatly
improved. Fluoroalkyl-modified polymers, with excellent
thermal stability and solvent- repelling, could have potential
applications as anti-thermal, water repellency and chemical
proof materials.
Figure 1. TG curves of polymers.
References
1. Kolb, H. C.; Finn, M. G.; Sharpless, K. B. Angew. Chem. Int. Edit.
2001, 40, 2004.
2. For reviews see: (a) Lutz, J. F. Angew. Chem. Int. Edit. 2007, 46,
1018. (b) Binder, W. H.; Sachsenhofer, R. Macromol. Rapid
Comm. 2007, 28, 15. (c) Nandivada, H.; Jiang, X.; Lahann, J. Adv.
Mater. 2007, 19, 2197. (d) Fournier, D.; Hoogenboom, R.;
Schubert, U. S. Chem. Soc. Rev. 2007, 36, 1369.
3. Diaz, D. D.; Punna, S.; Holzer, P.; Mcpherson, A. K.; Sharpless,
K. B.; Fokin, V. V.; Finn, M. G. J. Polym. Sci. Pol. Chem. 2004,
42, 4392.
4. Zhu, Y. Q.; Huang, Y. G.; Meng, W. D.; Li, H. Q.; Qing, F. L.
Polymer 2006, 47, 6272.
5. Haussler, M.; Qin, A. J.; Tang, B. Z. Polymer 2007, 48, 6181.
6. Chang, Z. J.; Xu, Y.; Zhao, X.; Zhang, Q. H.; Chem, D. J. Appl.
Mater. Interfaces 2009, 12, 2804.
7. Ossipov, D. A.; Hilborn, J. Macromolecules 2006, 39, 1709.
8. Lutz, J. F.; Borner, H. G.; Han, K. Macromol. Rapid Comm. 2005,
26, 514.
Figure 2. DSC curves of polymers with endo direction.
9. Kaneko, I.; Hagihara, N. Polym. Lett. 1971, 9, 275.
10. (a) Mavinkurve, A.; Visser, S.; VandenBroek, W.; TerBrugge, F.;
Pennings, A. J. Eur. Polym. J. 1997, 33, 719. (b) Mavinkurve, A.;
Visser, S.; VandenBroek, W.; Pennings, A. J. J. Polym. Sci. Pol.
Chem. 1996, 34, 985.
hibited higher Td value than those of the polymers 6a-b
because of the stronger interchain interactions of the -CF3
groups. The polymer 6d exhibited much higher Td value
than that of the polymer 6c, and this was attributed to the
longer fluorine-containing pendant chains in the polymer 6d.
The series of polymers were subjected to different scann-
ing calorimetry (DSC), and the results of these experiments
are shown in Figure 2 and Table 2. The polymers showed
weak glass transitions, some of which could not be assigned
unambiguously. Because of the instability of the substrate
polymer 4, the terminal measurement temperature was stopp-
ed at 180 °C, before which there was no occurrence of
crystallization peak or melting peak in DSC curve. The Tg’s
values of polymers 6a and 6c were higher than that of the
precursor 4, which was attributable to the rigid properties of
1,2,3-triazole rings. Exothermic peaks were observed on the
11. Holla, B. S.; Mahalinga, M.; Karthikeyan, M. S.; Poojary, B.;
Akberali, P. M.; Kumari, N. S. Eur. J. Med. Chem. 2005, 40, 1173.
12. (a) Reisinger, J. J.; Hillmyer, M. A. Prog. Polym. Sci. 2002, 27,
971. (b) Imae, T. Curr. Opin. Colloid In. 2003, 8, 307.
13. Holmes, A. B.; Sporikou, C. N. Org. Synth. 1987, 65, 61.
14. Wu, Y. M.; Deng, J.; Fang, X.; Chen, Q. Y. J. Fluorine Chem. 2004,
125, 1415.
15. Sonogashira, K.; Tohda, Y.; Hafihara, N. Tetrahedron Lett. 1975,
16, 4467.
16. Scriven, E. F. V.; Turnbull, K. Chem. Rev. 1988, 88, 297.
17. Boyer, J. H.; Hammer, J. J. Am. Chem. Soc. 1955, 77, 951.
18. Caution: Be careful in the operation of organic azides which were
facile to explode. Don’t evaporate to dryness in the process of
rotary evaporation!