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Synthesis of conjugated spirocyclic polymers: Cyclopolymerization of 1,1-dipropargyl-1-silacycloalkanes by transition metal catalysts
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Journal of Industrial and Engineering Chemistry 14 (2008) 720–725 www.elsevier.com/locate/jiec
Synthesis of conjugated spirocyclic polymers: Cyclopolymerization of 1,1-dipropargyl-1-silacycloalkanes by transition metal catalysts In-Sook Lee a, Young-Woo Kwak a,*, Hak-Dong Lee a, Yeong-Soon Gal b b
a Department of Chemistry, Kyungpook National University, Daegu 702-701, Republic of Korea Polymer Chemistry Laboratory, College of Engineering, Kyungil University, Hayang 712-701, Kyungsangbuk-Do, Republic of Korea
Received 27 September 2007; accepted 5 June 2008
Abstract Cyclopolymerization of 1,1-dipropargyl-1-silacyclobutane and 1,1-dipropargyl-1-silacyclopentane was examined by various transition metal catalysts. WCl6 was found to be very effective for this cyclopolymerization to give high yields of polymers. The polymer structures were characterized to have the conjugated polymer backbone with silacycloalkane moieties. The resulting poly(1,1-dipropargyl-1-silacyclobutane) was insoluble in any organic solvents, whereas the poly(1,1-dipropargyl-1-silacyclopentane) was partially soluble. The conjugated spirocyclic polymers were mostly yellow or light-brown powders, depending on the catalyst systems used. The thermal and oxidative stabilities of the polymer were also studied and discussed. # 2008 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. Keywords: Cyclopolymerization; Catalysts; Conjugated spirocyclic polymer; Polyacetylenes; Silacycloalkanes
1. Introduction The polymers having a conjugated backbone are expected to show unique properties such as electrical conductivity, paramagnetism, migration and transfer of energy, color, and chemical reactivity and complex formation ability [1–7]. Polyacetylene (PA), the simplest prototypical conjugated polymer, consists of a backbone of carbon atoms, each bonded to one hydrogen atom and connected together by alternating single and double bonds, and it can be made free-standing thin film by using Shirakawa catalysts [8]. However, this carbonrich material is oxidatively unstable and insoluble, making it unsuitable for applications as a specialty material. More manageable conjugated polymers have been prepared by the introduction of functional substituents into the polyacetylene. The substituents caused important changes in the properties of polymer, such as solubility, stability, melting, chemical, optical, electrical, and other properties [1,2,9–16]. Cyclopolymerization offers access to conjugated polymers with cyclic recurring units via an alternating intramolecular– intermolecular chain propagation [17]. A large variety of a,v-
* Corresponding author. Tel.: +82 53 950 5339. E-mail address: [email protected] (Y.-W. Kwak).
alkadiynes with different functionalities can be subject to the cyclopolymerization to yield a new type of conjugated polymer system [1,18–24]. The resulting polyacetylenes with cyclic recurring units along the backbone display good long-term stability towards oxidation and good solubility in common organic solvents such as chlorobenzene, benzene, chloroform, and DMF [12,25–30]. In our previous study [31], we reported the synthesis of a spirocyclic conjugated polymer with six-membered ring by the polymerization of 1,1-dipropargyl-1-silacyclohexane in the presence of various transition metal catalysts. Now we report the synthesis of poly(1,1-dipropargyl-1-silacycloalkane)s, the spirocyclic conjugated polymers with four- or five-membered rings and the comparisons with the properties of the polymer with six-membered ring. 2. Experimental 2.1. Materials 1,4-Dibromobutane (Aldrich Chemicals, 99%), silicon tetrachloride (Aldrich Chemicals, 99%), and 1,1-dichloro-1silacycloobutane (Gelest) were used as received. Propargyl bromide (Aldrich Chemicals, 80 wt% solution of toluene) was dried with CaH2 and distilled under reduced pressure.
1226-086X/$ – see front matter # 2008 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.jiec.2008.06.002
I.-S. Lee et al. / Journal of Industrial and Engineering Chemistry 14 (2008) 720–725
MoCl5 (Aldrich Chemicals, 99.9+%), WCl6 (Aldrich Chemicals, 99.9+%), and HgCl2 (Aldrich Chemicals, 99.9+%) were used without further purification. Et3SiH (Aldrich Chemicals, 99%) and EtAlCl2 [Aldrich Chemicals, 25 wt% (1.8 M) solution in toluene] and Me4Sn (Aldrich Chemicals, 95%) were used as received. Ph4Sn (Aldrich Chemicals, 97%) was purified by recrystallizing twice from carbon tetrachloride. PdCl2 (Aldrich Chemicals, 99.9+%) was used as received. The solvents were analytical grade materials. They were dried with an appropriate drying agent and distilled. 2.2. General procedures GC analyses were performed on a Hewlett-Packard 5890 FID chromatograph, using a HP-5 (cross-linked methylphenyl silicon) capillary column (30 m). NMR (1H- and 13C-) spectra were recorded on a Varian Mecury 300 MHz and Bruker AM 400 MHz NMR spectrometer in CDCl3 and the chemical shifts were reported in ppm units with tetramethylsilane (TMS) as an internal standard. Magic angle spinning, cross-polarization 13 C NMR spectrum of insoluble polymer was recorded on a Varian Infinity Plus 200 spectrometer (3-s repetition time, 5ms cross-polarization mixing time, and 6-kHz spinning). Infrared spectra were obtained with Mattson Galaxy 7020A FT-IR spectrophotometer using a KBr pellet, and frequencies are given in reciprocal centimeters. UV–vis spectra were taken in THF on a Shimadzu UV-2100 PC spectrophotometer. Molecular weights were determined by a gel permeation chromatography (Waters 254) equipped with m-Styragel columns using CH2Cl2 as an eluent. Monodisperse polystyrene standard samples were used for molecular weight calibration. Thermal properties of polymer were performed with SSC 5200H TG/DTA 320 under a nitrogen atmosphere at a heating rate of 10 8C/min. 2.3. Synthesis of 1,1-dichloro-1-silacycloalkanes 1,1-Dichloro-1-silacyclopentane was prepared as described previously in the literatures [31,32]. MS m/z (relative intensity): 158 (M+ + 4, 0.5), 156 (M+ + 2, 3.7), 154 (M+, 4.8). 1,1Dichloro-1-silacyclobutane was obtained from Gelest Company and used without further purification. 2.4. Synthesis of 1,1-dipropargyl-1-silacyclobutane (DPSCB) A 250-mL three-neck flask equipped with a mechanical stirrer and reflux condenser was charged with 125 mL of ethyl ether and 7.9 g (0.32 mol) of magnesium turnings under ice-bath. A Grignard reagent was prepared by adding 25 mL (0.28 mol) of propargyl bromide and 0.28 g (1.03 mmol) of HgCl2 dissolved in 25 mL of anhydrous ethyl ether to the reaction mixture at ice-water temperature under nitrogen atmosphere. After completion of the addition, the reaction mixture was stirred for 3 h at room temperature, the resulting solution was transferred to a dropping funnel under a
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nitrogen atmosphere. The dropping funnel was then attached to one neck of 500-mL three-neck flask equipped with reflux condenser and mechanical stirrer. The Grignard solution was then added dropwise with stirring under nitrogen to 10.2 g (72 mmol) of 1,1-dichloro-1-silacyclobutane in 25 mL of anhydrous ethyl ether at dry ice/acetone bath. After completion of the addition, the reaction mixture was stirred at room temperature for additional 7 h. Then the reaction mixture was quenched with saturated NH4Cl solution and extracted with ethyl ether. The concentrated crude product was purified by fractional distillation (22 mmol, yield: 30%). IR (wavenumbers, cm1, KBr pellet): 3304 (C–H), 2972, 2928, 2876, 2116 (CBBC). 1H NMR (d, ppm, CDCl3): 1.17– 1.22 (m, 4H, silacyclobutyl protons), 1.79 (d, 4H, 2CH2– CBBC, J = 3.0 Hz), 1.84 (t, 2H, 2CBBC–H, J = 3.0 Hz), 2.04– 2.10 (m, 2H, silacyclobuyl protons), 13C NMR (d, ppm, CDCl3): 4.69, 12.45, 17.73, 67.86, 79.96. MS (m/z, relative intensity): 148 (M+, 0.22), 120 (21.0), 109 (16.7), 81 (15.9), 67 (100.0). 2.5. Synthesis of 1,1-dipropargyl-1-silacyclopentane (DPSCP) 1,1-Dipropargyl-1-silacyclopentane was prepared from the Grignard reaction by the same procedure described in the synthesis of DPSCB. IR (wavenumbers, cm1, KBr pellet): 3304 (BBC–H), 2933, 2859, 2116 (CBBC). 1H NMR (d, ppm, CDCl3): 0.76–0.83 (m, 4H, silacyclopentyl protons), 1.61–1.69 (m, 4H, silacyclopentyl protons), 1.72 (d, 4H, 2CH2–CBBC, J = 3.0 Hz), 1.85 (t, 2H, 2CBBC–H, J = 3.0 Hz). 13C NMR (d, ppm, CDCl3): 3.38, 9.92, 27.46, 68.10, 81.26. MS (m/z, relative intensity): 162 (M+, 6.8), 134 (12.1), 123 (60.5), 95 (66.8), 67 (100.0). 2.6. Polymerization procedures All procedures for the preparation of catalyst system and polymerization were carried out under dry nitrogen atmosphere because the active species are sensitive to moisture or oxygen [12]. Typical polymerization procedures are as follows. 2.7. Polymerization of DPSCB by WCl6 In a magnetic-stirred 20-mL reaction vessel equipped with rubber septum, chlorobenzene (1.2 mL), 1.7 mL (0.17 mmol, M/C = 20) of 0.1 M WCl6 solution, and 0.5 mL (3.4 mmol, [M]o = 1.0 M) of DPSCB were added in that order given. The polymerization was carried out at 60 8C oil bath for 24 h under nitrogen atmosphere. Then, 10 mL of chloroform was added to the polymerization solution. The polymer solution was precipitated into an large excess of methanol, filtered from the solution, and then dried under vacuum at 40 8C for 24 h. The polymer yield was 75%. IR (wavenumbers, cm1, KBr pellet): 2928, 2872, 1603 (C C). The resulting poly(1,1dipropargyl-1-silacyclobutane) was insoluble in any organic solvents.
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2.8. Polymerization of DPSCP by WCl6–EtAlCl2 In a magnetic-stirred 20-mL reaction vessel equipped with rubber septum, 0.55 mL (3.40 mmol, [M]o = 1.0 M) of DPSCP and chlorobenzene (0.72 mL) were added. Then the catalyst mixture of 1.70 mL (0.17 mmol, M/C = 20) of 0.1 M WCl6 solution and 0.43 mL (0.17 mmol) of 0.4 M EtAlCl2 solution was injected into the polymerization reaction vessel. After 24 h at 60 8C oil bath, 10 mL of chloroform was added to the polymerization solution. The polymer solution was poured into a large excess of methanol, filtered from the solution, and then dried under vacuum at 40 8C for 24 h. The yield of polymer was 43%. IR (wavenumbers, cm1, KBr pellet): 2930, 2853, 1603 (C C). 1H NMR (d, ppm, CDCl3): 0.51–0.85 (m, 4H, 2SiCH2C), 1.58–2.10 (m, 8H, 2SiCH2C and 2SiCCH2), 6.50–7.11 (m, 2H, vinyl protons). 13C NMR (d, ppm, CDCl3): 11.48, 24.80, 25.90, 27.14, 125.82, 128.89, 133.25, 137.71, 142.13. 3. Results and discussion The ring-forming polymerization of 1,1-dipropargyl-1silacycloalkanes having four- and five-membered rings was carried out by the tungsten- and molybdenum-based catalysts as follows (Scheme 1). We used the Mo- and W-based catalysts for the present cyclopolymerization, which have been found effective for the polymerization of some monosubstituted acetylenes and the cyclopolymerization of nonconjugated diynes [1,10]. The polymerization proceeded well to give a moderate yield of polymer. Table 1 shows the temperature effect for the polymerization of 1,1-dipropargyl-1-silacycloalkanes by WCl6 in chlorobenzene (M/C = 20). As shown in Table 1, the polymer yield was generally increased as the polymerization temperature is increased. Table 2 shows the effect of catalysts for the cyclopolymerization of 1,1-dipropargyl-1-silacycloalkanes. WCl6 alone polymerize DPSCB monomer in chlorobenzene solvent to give the polymer in 75% yield, whereas MoCl5 in toluene solvent gives 74% yield of the polymer. MoCl5 also polymerized DPSCP monomer in tolune solvent to give the corresponding polymer in 59% yields. The catalytic activity of WCl6 was found to be similar with that of MoCl5. The similar high catalytic activities of WCl6 and MoCl5 had also been observed for the polymerization of 1-ethynylcyclohexene [33],
Table 1 Temperature effect for the polymerization of 1,1-dipropargyl-1-silacycloalkanes by WCl6a. Ring size [polymer]
Catalyst
Temperature (8C)
Yield (%) b
Four-ring [poly(DPSCB)]
WCl6
40 60 80
46 75 84
Five-ring [poly(DPSCP)]
WCl6
40 60 80
31 59 73
a Polymerization was carried out in chlorobenzene for 24 h. Monomer-to catalyst mole ratio (M/C) and initial monomer concentration were 20 and 1.0 M, respectively. b Methanol-insoluble polymer.
Table 2 Polymerization of 1,1-dipropargyl-1-silacycloalkanes by transition metal catalystsa. Ring size [polymer]
Catalyst
M/Cb
Solvent
Yield (%)c
Four-ring [poly(DPSCB)]
WCl6 MoCl5 PdCl2
20 20 20
Chlorobenzene Toluene DMF
75 74 15
Five-ring [poly(DPSCP)]
WCl6 MoCl5 PdCl2
20 20 20
Chlorobenzene Toluene DMF
59 59 10
a b c
triethyl a-propargylphosphonoacetate [34], 2-ethynyl-N-pargylpyridinium tetraphenylborate [24], and 1,1-dipropargyl-1silacyclohexane [31]. This polymerization was also tested by PdCl2 in DMF solvent. However, the polymerization of DPSCB and DPSCP monomers by PdCl2 proceeded in somewhat mild manner to give the polymers in 15% and 10% yields, respectively. Table 3 shows the results for the cyclopolymerization of 1,1dipropargyl-1-silacycloalkanes by WCl6-based catalysts. The various organotin, organosilicon, and organoaluminium Table 3 Polymerization of 1,1-dipropargyl-1-silacycloalkanes by WCl6-based catalystsa. Exp. Catalyst no systemb (mole ratio)
Yield (%)c
Mw/Mnd
Four-ring Five-ring Four-ring Five-ring 1 2 3 4 5 6
WCl6 WCl6–Ph4Sn (1:1) WCl6–(n-Bu)4Sn (1:1) WCl6–Me4Sn (1:1) WCl6–EtAlCl2 (1:1) WCl6–Et3SiH (1:1) a
Scheme 1. Cyclopolymerization of 1,1-dipropargyl-1-silacycloalkanes by transition metal catalysts.
Polymerization was carried out at 60 8C for 24 h. Mole ratio of monomer and catalyst. Methanol-insoluble polymer.
75 32 33 51 20 38
59 46 20 26 43 35
– – – – – –
3100/1500 4000/1600 3300/1600 500/400 5000/2100 4900/2000
Polymerization was carried out in chlorobenzene at 60 8C for 24 h. The M/C of monomer to catalyst and initial monomer concentration ([M]0) were 20 and 1.0 M, respectively. b The mixture of WCl6 and cocatalyst was aged for 15 min at room temperature before use. c Methanol-insoluble polymer. d The molecular weight were measured with GPC.
I.-S. Lee et al. / Journal of Industrial and Engineering Chemistry 14 (2008) 720–725 Table 4 Solvent effect for the polymerization of 1,1-dipropargyl-1-silacycloalkanes by WCl6a. Solvent
1,2-Dichloroethane Chlorobenzene Tetralin 1,4-Dioxane Cyclohexane THF Toluene Chloroform Cyclohexene
Yield (%)b
Table 5 Solubility behaviors of poly(1,1-dipropargyl-1-silacycloalkane)sa. Solvent
Mw/Mnc
Four-ring
Five-ring
Four-ring
Five-ring
36 75 66 51 46 5 23 64 41
20 59 77 11 64 25 65 31 13
– – – – – – – – –
6900/2000 3100/1500 – – – – – 14000/3500 –
a Polymerization was carried out by WCl6 at 60 8C for 24 h. The M/C of monomer to catalyst and initial monomer concentration ([M]o) were 20 and 1.0 M, respectively. b Methanol-insoluble polymer. c The molecular weights of soluble polymers were measured with GPC.
Toluene Benzene Chlorobenzene Cyclohexene Chloroform Triethylamine Dichloromethane 1,2-Dichloroethane THF Carbon tetrachloride 1,4-Dioxane Ethyl ether DMF n-Hexane Methanol Acetone a
compounds have been used as an effective cocatalysts [1,10]. However, in this case, these cocatalysts rather decreased the polymer yields slightly, although the reason is not clear in the present state. Table 4 shows the solvent effect for the polymerization of 1,1-dipropargyl-1-silacycloalkanes. WCl6 alone polymerize DPSCB monomer in chlorobenzene solvent to give the polymer in 75% yield, whereas in toluene solvent gives 23% yield of polymer. This catalyst also polymerized DPSCP in chlorobenzene solvent to give the corresponding polymer in 59% yield. The 1,1-dipropargyl-1-silacycloalkanes were easily polymerized in aromatic hydrocarbons and haloalkanes such as toluene, tetralin, chlorobenzene, chloroform. The high yields of polymer were obtained in the solvents of chlorobenzene and tetralin for the both polymerization of DPSCB and DPSCP. They are good solvents for not only the catalyst but also the resulting polymers. The resulting poly(1,1-dipropargyl-1-silacycloalkane)s by Mo- and W-based catalysts were yellow or light-brown powders, whereas the same samples prepared by PdCl2 were mostly black powder. The solubility test was performed for powdery samples in excess solvent. Table 5 shows the solubility behaviors of poly(1,1-dipropargyl-1-silacycloalkane)s. The resulting poly(DPSCB) having four-membered ring was found to be insoluble in any organic solvents, regardless of the reaction conditions. On the other hand, the poly(DPSCP) having five-membered ring was partially soluble in aromatic and halogenated hydrocarbon solvents such as toluene, chlorobenzene, chloroform, carbon tetrachloride, etc. The soluble portion of poly(DPSCP) was about 50%. It was found that the polymerization of DPSCB seems to proceeded in semi-heterogeneous manner in some cases, whereas the polymerization of DPSCP proceed in homogeneous manner. The insolubility of the resulting poly(1,1dipropargyl-1-silacycloalkane)s may be originated by the cross-linking of conjugated cyclopolymers during the polymerization and/or the work-up process. The weight-average molecular weights of the soluble poly(DPSCP) were in the range of 3100–14000.
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b
Solubilityb Four-ring
Five-ring
+ + + + + + + + + + + +
The solubility test was performed for powdery samples in excess solvent. Solubility, ++: soluble; +: partially soluble; : insoluble.
The polymer structures of poly(1,1-dipropargyl-1-silacycloalkane)s were characterized by NMR (1H- and 13C-), infrared, and UV–vis spectroscopies. Fig. 1 shows the FT-IR spectra of poly(DPSCB) and poly(PDPSCP) in KBr pellet. The IR spectra of polymers did not show any acetylenic CC bond stretching (2116 cm1 for DPSCB and DPSCP monomers) and C–H bond stretching (3304 cm1 for DPSCB and DPSCP monomers) frequencies. Instead, the C C stretching frequency peak of conjugated spirocyclic polymers, poly(DPSCB) and ploy(DPSCP), was newly observed at around 1603 cm1. The aliphatic C–H stretching peaks were observed at 2853 and 2930 cm1. A strong peak of Si–C linkages of polymer was observed at 814 cm1. The 1H NMR spectra of soluble poly(DPSCP) was measured in CDCl3. It did not show the acetylenic proton peak (1.85 ppm) of DPSCP monomer. Instead, the new vinyl protons of
Fig. 1. FT-IR spectra of poly(DPSCB) (A) and poly(DPSCP) (B) in KBr pellet.
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Fig. 2. Solid-state
I.-S. Lee et al. / Journal of Industrial and Engineering Chemistry 14 (2008) 720–725
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Fig. 3. UV–vis spectrum of the soluble poly(DPSCP) in THF.
C NMR spectrum of the insoluble poly(DPSCP).
conjugated polymer backbone were also seen at the region of 6.50–7.11 ppm, which had not been observed in the 1H NMR spectrum of monomer. The peaks of the two methylene protons of silacyclopentane adjacent to the silicon atom were observed at 0.51–0.85 ppm. And the peaks of the two methylene protons of silacyclopentane and the two methylene protons adjacent to the vinylic carbons were observed at 1.58–2.10 ppm. The 13C NMR spectrum of soluble poly(DPSCP) did not show any acetylenic carbon peaks (68.10 and 81.26 ppm) of DPSCP. Instead, the 13C NMR spectrum of poly(DPSCP) exhibited newly the olefinic carbon peaks of the conjugated polymer backbone at the region of 125.82–142.13 ppm. The peaks of various methylene carbons of poly(DPSCP) were observed at the region of 11.48–27.14 ppm. Fig. 2 shows the solid-state 13C NMR spectrum of insoluble poly(DPSCP). This spectrum exhibited the broad carbon peaks of conjugated polymer backbone of poly(DPSCP) at 110–160 ppm, which are corresponded to the vinyl carbons of conjugated polymer backbone, and it also showed broad methylene carbon peaks at 10–80 ppm. The peak at around 225 ppm may be due to the carbonyl carbons, which may be originated from air oxidation of conjugated polymer backbone of poly(DPSCP). Fig. 3 shows the typical UV–vis spectrum of poly(DPSCP) in THF. It showed a characteristic broad absorption band at the visible region, which is originated from the p ! p* transition of the conjugated polyene main chain. These spectral data indicated that the present poly(DPSCP) have a conjugated backbone system having spirocyclic recurring units. The TGA thermograms of poly(1,1-dipropargyl-1-silacycloalkane)s in Fig. 4 showed that these polymers start to decompose after 200 8C. Poly(DPSCB) retains 98% of its original weight at 200 8C, 95% at 300 8C, 66% at 500 8C, 51% at 800 8C, whereas poly(DPSCP) retains 99% of its original weight at 200 8C, 95% at 300 8C, 66% at 500 8C, 45% at 800 8C. These polymers showed characteristic two stepwise weight losses [200–575 8C, 800–1130 8C for poly(DPSCB), 200–570 8C, 640–960 8C for poly(DPSCP)]. It may be
explainable that the first weight loss is originated by the decomposition of organic conjugated cyclopolymers and the the second weight loss is by the further degradation of the residual semi-inorganic components. The high contents of residual weight even after 1400 8C may be deduced to be due to the formation of Si–C matrices. Polyacetylene and poly(1,6-heptadiyne) itself were easily oxidized in air at room temperature [35–37]. Thus we measured the IR spectrum for checking the oxidative stability of these two conjugated cyclopolymers. The IR spectrum of poly(DPSCB) and poly(DPSCP), which had been exposed for 10 days to air at room temperature, showed a small new carbonyl absorption band at 1700 cm1. These polymers were found to be more stable to air oxidation than those of PA and poly(1,6heptadiyne) itself. As the exposing time was increased, the carbonyl peak intensities were gradually increased. This phenomenon was caused by air oxidation of conjugated polymer backbone.
Fig. 4. TGA thermograms of poly(DPSCB) (solid line) and poly(DPSCP) (dotted line) measured under nitrogen atmosphere at a heating rate of 10 8C/ min.
I.-S. Lee et al. / Journal of Industrial and Engineering Chemistry 14 (2008) 720–725
4. Conclusion New conjugated spirocyclic polymers, poly(1,1-dipropargyl-1-silacycloalkane)s, were prepared by the ring-forming polymerization of the corresponding nonconjugated dipropargyl monomers by using Mo- and W-based catalysts. WCl6 and MoCl5 itself were found to be effective for the polymerization of 1,1-dipropargyl-1-silacycloalkanes and showed similar catalytic activity. The resulting polymers were yellow or light-brown powders, whereas the same sample prepared by PdCl2 was mostly black powder. The poly(DPSCB) was found to be insoluble in organic solvents, whereas the poly(DPSCP) was partially soluble in common organic solvents. The chemical structure of poly(1,1-dipropargyl-1-silacycloalkane)s was characterized by various instrumental methods to have the conjugated polymer backbone system having the designed spirocyclic recurring units. These cojugated cyclopolymers were thermally stable up to 200 8C. Acknowledgement The work has been supported by Regional Industrial Engineering Development Foundation Grant (100273472006-01). References [1] S.K. Choi, Y.S. Gal, S.H. Jin, H.K. Kim, Chem. Rev. 100 (2000) 1645. [2] K. Nagai, T. Masuda, T. Nakagawa, B.D. Freeman, I. Finnau, Prog. Polym. Sci. 26 (2001) 721. [3] J.W.Y. Lam, B.Z. Tang, J. Polym. Sci.: Part A: Polym. Chem. 41 (2003) 2607. [4] M.R. Buchmeiser, Adv. Polym. Sci. 176 (2005) 89. [5] Y.S. Gal, S.H. Jin, K.T. Lim, W.C. Lee, J. Ind. Eng. Chem. 11 (2005) 603. [6] Y.S. Gal, S.H. Jin, S.H. Kim, J. Ind. Eng. Chem. 12 (2006) 235. [7] A. Maity, M. Biswas, J. Ind. Eng. Chem. 12 (2006) 626. [8] T. Ito, H. Shirakawa, S. Ikeda, J. Polym. Sci.: Part A: Polym. Chem. 12 (1974) 11. [9] Y.S. Gal, W.C. Lee, S.Y. Kim, J.W. Park, S.H. Jin, K.N. Koh, S.H. Kim, J. Polym. Sci.: Part A: Polym. Chem. 39 (2001) 3151. [10] Y.S. Gal, S.H. Jin, S.K. Choi, J. Mol. Catal. A: Chem. 213 (2004) 115. [11] J.W.Y. Lam, B.Z. Tang, Acc. Chem. Res. 38 (2005) 745.
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[12] B.V. Naidu, B.H. Oh, D.H. Nam, C.K. Hwang, S.H. Jin, K.T. Lim, H.S. Hwang, J.W. Lee, Y.S. Gal, J. Polym. Sci.: Part A: Polym. Chem. 44 (2006) 1555. [13] T.L. Gui, J.H. Yin, D.X. Wang, S.H. Jin, H.J. Lee, K.T. Lim, W.S. Lyoo, Y.S. Gal, Mol. Cryst. Liq. Cryst. 459 (2006) 19. [14] L.M. Lai, J.W.Y. Lam, B.Z. Tang, J. Polym. Sci.: Part A: Polym. Chem. 44 (2006) 2117. [15] Y.S. Gal, W.C. Lee, S.H. Jin, K.T. Lim, S.H. Jang, W.S. Lyoo, E. Han, S.Y. Kim, Macromol. Res. 15 (2007) 267. [16] Y.S. Gal, S.H. Jin, J.W. Park, J. Polym. Sci.: Part A: Polym. Chem. 45 (2007) 5679. [17] G.B. Butler, Acc. Chem. Res. 15 (1982) 370. [18] Y.S. Gal, S.K. Choi, Polymer (Korea) 11 (1987) 563. [19] Y.S. Gal, S.K. Choi, J. Polym. Sci.: Part C: Polym. Lett. 26 (1988) 115. [20] Y.H. Kim, Y.S. Gal, U.Y. Kim, S.K. Choi, Macromolecules 21 (1988) 1991. [21] Y.S. Gal, S.K. Choi, J. Polym. Sci.: Part A: Polym. Chem. 31 (1993) 345. [22] H.J. Lee, Y.S. Gal, W.C. Lee, J.M. Oh, S.H. Jin, S.K. Choi, Macromolecules 28 (1995) 1208. [23] Y.S. Gal, W.C. Lee, H.J. Lee, S.H. Jang, S.K. Choi, J. Macromol. Sci. Pure Appl. Chem. A 31 (1997) 2251. [24] Y.S. Gal, S.H. jin, T.L. Gui, W.C. Lee, N.G. Yun, S.H. Park, S.S. Lee, J.S. Bae, J. Ind. Eng. Chem. 11 (2005) 432. [25] C. Halvorson, A. Hays, B. Kraabel, R. Wu, F. Wudl, A.J. Heeger, Science 265 (1994) 1215. [26] D.W. Samuel, I. Ledoux, C. Dhenaut, J. Zyss, H.H. Fox, R.R. Schrock, R.J. Silbey, Science 265 (1994) 1070. [27] H.J. Lee, S.J. Kang, H.K. Kim, H.N. Cho, J.T. Park, S.K. Choi, Macromolecules 28 (1995) 4638. [28] D.C. Choi, S.H. Kim, J.H. Lee, H.N. Cho, S.K. Choi, Macromolecules 30 (1997) 176. [29] C. Sivakumar, T. Vasudevan, A. Gopalan, T.C. Wen, Polymer 43 (2002) 1781. [30] J.O. Krause, D. Wang, U. Anders, R. Weberskirch, M.T. Zarka, O. Nuyken, C. Jager, D. Haarer, M.R. Buchmeiser, Macromol. Symp. 217 (2004) 179. [31] Y.S. Gal, I.-S. Lee, E.-H. Chang, Y.-W. Kwak, Bull. Kor. Chem. Soc. 28 (2007) 1305. [32] R. West, J. Am. Chem. Soc. 76 (1954) 6012. [33] Y.S. Gal, B. Jung, J.H. Kim, W.C. Lee, S.K. Choi, J. Polym. Sci.: Part A: Polym. Chem. 33 (1995) 307. [34] Y.S. Gal, B. Jung, W.C. Lee, H.J. Lee, S.K. Choi, Macromolecules 28 (1995) 2086. [35] H. Shirakawa, Angew. Chem. Int. Ed. 40 (2001) 2574. [36] H.W. Gibson, F.C. Bailey, A.J. Epstein, R. Rommelmann, S. Kaplan, J. Harbour, X.Q. Yang, D.B. Tanner, J.M. Pochan, J. Am. Chem. Soc. 105 (1983) 4417. [37] Y.S. Gal, W.C. Lee, T.L. Gui, S.H. Jin, K. Koh, S.H. Kim, D.W. Kim, J.M. Ko, J.H. Chun, Kor. Polym. J. 9 (2001) 220.
Journal of Industrial and Engineering Chemistry 14 (2008) 720–725 www.elsevier.com/locate/jiec
Synthesis of conjugated spirocyclic polymers: Cyclopolymerization of 1,1-dipropargyl-1-silacycloalkanes by transition metal catalysts In-Sook Lee a, Young-Woo Kwak a,*, Hak-Dong Lee a, Yeong-Soon Gal b b
a Department of Chemistry, Kyungpook National University, Daegu 702-701, Republic of Korea Polymer Chemistry Laboratory, College of Engineering, Kyungil University, Hayang 712-701, Kyungsangbuk-Do, Republic of Korea
Received 27 September 2007; accepted 5 June 2008
Abstract Cyclopolymerization of 1,1-dipropargyl-1-silacyclobutane and 1,1-dipropargyl-1-silacyclopentane was examined by various transition metal catalysts. WCl6 was found to be very effective for this cyclopolymerization to give high yields of polymers. The polymer structures were characterized to have the conjugated polymer backbone with silacycloalkane moieties. The resulting poly(1,1-dipropargyl-1-silacyclobutane) was insoluble in any organic solvents, whereas the poly(1,1-dipropargyl-1-silacyclopentane) was partially soluble. The conjugated spirocyclic polymers were mostly yellow or light-brown powders, depending on the catalyst systems used. The thermal and oxidative stabilities of the polymer were also studied and discussed. # 2008 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. Keywords: Cyclopolymerization; Catalysts; Conjugated spirocyclic polymer; Polyacetylenes; Silacycloalkanes
1. Introduction The polymers having a conjugated backbone are expected to show unique properties such as electrical conductivity, paramagnetism, migration and transfer of energy, color, and chemical reactivity and complex formation ability [1–7]. Polyacetylene (PA), the simplest prototypical conjugated polymer, consists of a backbone of carbon atoms, each bonded to one hydrogen atom and connected together by alternating single and double bonds, and it can be made free-standing thin film by using Shirakawa catalysts [8]. However, this carbonrich material is oxidatively unstable and insoluble, making it unsuitable for applications as a specialty material. More manageable conjugated polymers have been prepared by the introduction of functional substituents into the polyacetylene. The substituents caused important changes in the properties of polymer, such as solubility, stability, melting, chemical, optical, electrical, and other properties [1,2,9–16]. Cyclopolymerization offers access to conjugated polymers with cyclic recurring units via an alternating intramolecular– intermolecular chain propagation [17]. A large variety of a,v-
* Corresponding author. Tel.: +82 53 950 5339. E-mail address: [email protected] (Y.-W. Kwak).
alkadiynes with different functionalities can be subject to the cyclopolymerization to yield a new type of conjugated polymer system [1,18–24]. The resulting polyacetylenes with cyclic recurring units along the backbone display good long-term stability towards oxidation and good solubility in common organic solvents such as chlorobenzene, benzene, chloroform, and DMF [12,25–30]. In our previous study [31], we reported the synthesis of a spirocyclic conjugated polymer with six-membered ring by the polymerization of 1,1-dipropargyl-1-silacyclohexane in the presence of various transition metal catalysts. Now we report the synthesis of poly(1,1-dipropargyl-1-silacycloalkane)s, the spirocyclic conjugated polymers with four- or five-membered rings and the comparisons with the properties of the polymer with six-membered ring. 2. Experimental 2.1. Materials 1,4-Dibromobutane (Aldrich Chemicals, 99%), silicon tetrachloride (Aldrich Chemicals, 99%), and 1,1-dichloro-1silacycloobutane (Gelest) were used as received. Propargyl bromide (Aldrich Chemicals, 80 wt% solution of toluene) was dried with CaH2 and distilled under reduced pressure.
1226-086X/$ – see front matter # 2008 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.jiec.2008.06.002
I.-S. Lee et al. / Journal of Industrial and Engineering Chemistry 14 (2008) 720–725
MoCl5 (Aldrich Chemicals, 99.9+%), WCl6 (Aldrich Chemicals, 99.9+%), and HgCl2 (Aldrich Chemicals, 99.9+%) were used without further purification. Et3SiH (Aldrich Chemicals, 99%) and EtAlCl2 [Aldrich Chemicals, 25 wt% (1.8 M) solution in toluene] and Me4Sn (Aldrich Chemicals, 95%) were used as received. Ph4Sn (Aldrich Chemicals, 97%) was purified by recrystallizing twice from carbon tetrachloride. PdCl2 (Aldrich Chemicals, 99.9+%) was used as received. The solvents were analytical grade materials. They were dried with an appropriate drying agent and distilled. 2.2. General procedures GC analyses were performed on a Hewlett-Packard 5890 FID chromatograph, using a HP-5 (cross-linked methylphenyl silicon) capillary column (30 m). NMR (1H- and 13C-) spectra were recorded on a Varian Mecury 300 MHz and Bruker AM 400 MHz NMR spectrometer in CDCl3 and the chemical shifts were reported in ppm units with tetramethylsilane (TMS) as an internal standard. Magic angle spinning, cross-polarization 13 C NMR spectrum of insoluble polymer was recorded on a Varian Infinity Plus 200 spectrometer (3-s repetition time, 5ms cross-polarization mixing time, and 6-kHz spinning). Infrared spectra were obtained with Mattson Galaxy 7020A FT-IR spectrophotometer using a KBr pellet, and frequencies are given in reciprocal centimeters. UV–vis spectra were taken in THF on a Shimadzu UV-2100 PC spectrophotometer. Molecular weights were determined by a gel permeation chromatography (Waters 254) equipped with m-Styragel columns using CH2Cl2 as an eluent. Monodisperse polystyrene standard samples were used for molecular weight calibration. Thermal properties of polymer were performed with SSC 5200H TG/DTA 320 under a nitrogen atmosphere at a heating rate of 10 8C/min. 2.3. Synthesis of 1,1-dichloro-1-silacycloalkanes 1,1-Dichloro-1-silacyclopentane was prepared as described previously in the literatures [31,32]. MS m/z (relative intensity): 158 (M+ + 4, 0.5), 156 (M+ + 2, 3.7), 154 (M+, 4.8). 1,1Dichloro-1-silacyclobutane was obtained from Gelest Company and used without further purification. 2.4. Synthesis of 1,1-dipropargyl-1-silacyclobutane (DPSCB) A 250-mL three-neck flask equipped with a mechanical stirrer and reflux condenser was charged with 125 mL of ethyl ether and 7.9 g (0.32 mol) of magnesium turnings under ice-bath. A Grignard reagent was prepared by adding 25 mL (0.28 mol) of propargyl bromide and 0.28 g (1.03 mmol) of HgCl2 dissolved in 25 mL of anhydrous ethyl ether to the reaction mixture at ice-water temperature under nitrogen atmosphere. After completion of the addition, the reaction mixture was stirred for 3 h at room temperature, the resulting solution was transferred to a dropping funnel under a
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nitrogen atmosphere. The dropping funnel was then attached to one neck of 500-mL three-neck flask equipped with reflux condenser and mechanical stirrer. The Grignard solution was then added dropwise with stirring under nitrogen to 10.2 g (72 mmol) of 1,1-dichloro-1-silacyclobutane in 25 mL of anhydrous ethyl ether at dry ice/acetone bath. After completion of the addition, the reaction mixture was stirred at room temperature for additional 7 h. Then the reaction mixture was quenched with saturated NH4Cl solution and extracted with ethyl ether. The concentrated crude product was purified by fractional distillation (22 mmol, yield: 30%). IR (wavenumbers, cm1, KBr pellet): 3304 (C–H), 2972, 2928, 2876, 2116 (CBBC). 1H NMR (d, ppm, CDCl3): 1.17– 1.22 (m, 4H, silacyclobutyl protons), 1.79 (d, 4H, 2CH2– CBBC, J = 3.0 Hz), 1.84 (t, 2H, 2CBBC–H, J = 3.0 Hz), 2.04– 2.10 (m, 2H, silacyclobuyl protons), 13C NMR (d, ppm, CDCl3): 4.69, 12.45, 17.73, 67.86, 79.96. MS (m/z, relative intensity): 148 (M+, 0.22), 120 (21.0), 109 (16.7), 81 (15.9), 67 (100.0). 2.5. Synthesis of 1,1-dipropargyl-1-silacyclopentane (DPSCP) 1,1-Dipropargyl-1-silacyclopentane was prepared from the Grignard reaction by the same procedure described in the synthesis of DPSCB. IR (wavenumbers, cm1, KBr pellet): 3304 (BBC–H), 2933, 2859, 2116 (CBBC). 1H NMR (d, ppm, CDCl3): 0.76–0.83 (m, 4H, silacyclopentyl protons), 1.61–1.69 (m, 4H, silacyclopentyl protons), 1.72 (d, 4H, 2CH2–CBBC, J = 3.0 Hz), 1.85 (t, 2H, 2CBBC–H, J = 3.0 Hz). 13C NMR (d, ppm, CDCl3): 3.38, 9.92, 27.46, 68.10, 81.26. MS (m/z, relative intensity): 162 (M+, 6.8), 134 (12.1), 123 (60.5), 95 (66.8), 67 (100.0). 2.6. Polymerization procedures All procedures for the preparation of catalyst system and polymerization were carried out under dry nitrogen atmosphere because the active species are sensitive to moisture or oxygen [12]. Typical polymerization procedures are as follows. 2.7. Polymerization of DPSCB by WCl6 In a magnetic-stirred 20-mL reaction vessel equipped with rubber septum, chlorobenzene (1.2 mL), 1.7 mL (0.17 mmol, M/C = 20) of 0.1 M WCl6 solution, and 0.5 mL (3.4 mmol, [M]o = 1.0 M) of DPSCB were added in that order given. The polymerization was carried out at 60 8C oil bath for 24 h under nitrogen atmosphere. Then, 10 mL of chloroform was added to the polymerization solution. The polymer solution was precipitated into an large excess of methanol, filtered from the solution, and then dried under vacuum at 40 8C for 24 h. The polymer yield was 75%. IR (wavenumbers, cm1, KBr pellet): 2928, 2872, 1603 (C C). The resulting poly(1,1dipropargyl-1-silacyclobutane) was insoluble in any organic solvents.
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2.8. Polymerization of DPSCP by WCl6–EtAlCl2 In a magnetic-stirred 20-mL reaction vessel equipped with rubber septum, 0.55 mL (3.40 mmol, [M]o = 1.0 M) of DPSCP and chlorobenzene (0.72 mL) were added. Then the catalyst mixture of 1.70 mL (0.17 mmol, M/C = 20) of 0.1 M WCl6 solution and 0.43 mL (0.17 mmol) of 0.4 M EtAlCl2 solution was injected into the polymerization reaction vessel. After 24 h at 60 8C oil bath, 10 mL of chloroform was added to the polymerization solution. The polymer solution was poured into a large excess of methanol, filtered from the solution, and then dried under vacuum at 40 8C for 24 h. The yield of polymer was 43%. IR (wavenumbers, cm1, KBr pellet): 2930, 2853, 1603 (C C). 1H NMR (d, ppm, CDCl3): 0.51–0.85 (m, 4H, 2SiCH2C), 1.58–2.10 (m, 8H, 2SiCH2C and 2SiCCH2), 6.50–7.11 (m, 2H, vinyl protons). 13C NMR (d, ppm, CDCl3): 11.48, 24.80, 25.90, 27.14, 125.82, 128.89, 133.25, 137.71, 142.13. 3. Results and discussion The ring-forming polymerization of 1,1-dipropargyl-1silacycloalkanes having four- and five-membered rings was carried out by the tungsten- and molybdenum-based catalysts as follows (Scheme 1). We used the Mo- and W-based catalysts for the present cyclopolymerization, which have been found effective for the polymerization of some monosubstituted acetylenes and the cyclopolymerization of nonconjugated diynes [1,10]. The polymerization proceeded well to give a moderate yield of polymer. Table 1 shows the temperature effect for the polymerization of 1,1-dipropargyl-1-silacycloalkanes by WCl6 in chlorobenzene (M/C = 20). As shown in Table 1, the polymer yield was generally increased as the polymerization temperature is increased. Table 2 shows the effect of catalysts for the cyclopolymerization of 1,1-dipropargyl-1-silacycloalkanes. WCl6 alone polymerize DPSCB monomer in chlorobenzene solvent to give the polymer in 75% yield, whereas MoCl5 in toluene solvent gives 74% yield of the polymer. MoCl5 also polymerized DPSCP monomer in tolune solvent to give the corresponding polymer in 59% yields. The catalytic activity of WCl6 was found to be similar with that of MoCl5. The similar high catalytic activities of WCl6 and MoCl5 had also been observed for the polymerization of 1-ethynylcyclohexene [33],
Table 1 Temperature effect for the polymerization of 1,1-dipropargyl-1-silacycloalkanes by WCl6a. Ring size [polymer]
Catalyst
Temperature (8C)
Yield (%) b
Four-ring [poly(DPSCB)]
WCl6
40 60 80
46 75 84
Five-ring [poly(DPSCP)]
WCl6
40 60 80
31 59 73
a Polymerization was carried out in chlorobenzene for 24 h. Monomer-to catalyst mole ratio (M/C) and initial monomer concentration were 20 and 1.0 M, respectively. b Methanol-insoluble polymer.
Table 2 Polymerization of 1,1-dipropargyl-1-silacycloalkanes by transition metal catalystsa. Ring size [polymer]
Catalyst
M/Cb
Solvent
Yield (%)c
Four-ring [poly(DPSCB)]
WCl6 MoCl5 PdCl2
20 20 20
Chlorobenzene Toluene DMF
75 74 15
Five-ring [poly(DPSCP)]
WCl6 MoCl5 PdCl2
20 20 20
Chlorobenzene Toluene DMF
59 59 10
a b c
triethyl a-propargylphosphonoacetate [34], 2-ethynyl-N-pargylpyridinium tetraphenylborate [24], and 1,1-dipropargyl-1silacyclohexane [31]. This polymerization was also tested by PdCl2 in DMF solvent. However, the polymerization of DPSCB and DPSCP monomers by PdCl2 proceeded in somewhat mild manner to give the polymers in 15% and 10% yields, respectively. Table 3 shows the results for the cyclopolymerization of 1,1dipropargyl-1-silacycloalkanes by WCl6-based catalysts. The various organotin, organosilicon, and organoaluminium Table 3 Polymerization of 1,1-dipropargyl-1-silacycloalkanes by WCl6-based catalystsa. Exp. Catalyst no systemb (mole ratio)
Yield (%)c
Mw/Mnd
Four-ring Five-ring Four-ring Five-ring 1 2 3 4 5 6
WCl6 WCl6–Ph4Sn (1:1) WCl6–(n-Bu)4Sn (1:1) WCl6–Me4Sn (1:1) WCl6–EtAlCl2 (1:1) WCl6–Et3SiH (1:1) a
Scheme 1. Cyclopolymerization of 1,1-dipropargyl-1-silacycloalkanes by transition metal catalysts.
Polymerization was carried out at 60 8C for 24 h. Mole ratio of monomer and catalyst. Methanol-insoluble polymer.
75 32 33 51 20 38
59 46 20 26 43 35
– – – – – –
3100/1500 4000/1600 3300/1600 500/400 5000/2100 4900/2000
Polymerization was carried out in chlorobenzene at 60 8C for 24 h. The M/C of monomer to catalyst and initial monomer concentration ([M]0) were 20 and 1.0 M, respectively. b The mixture of WCl6 and cocatalyst was aged for 15 min at room temperature before use. c Methanol-insoluble polymer. d The molecular weight were measured with GPC.
I.-S. Lee et al. / Journal of Industrial and Engineering Chemistry 14 (2008) 720–725 Table 4 Solvent effect for the polymerization of 1,1-dipropargyl-1-silacycloalkanes by WCl6a. Solvent
1,2-Dichloroethane Chlorobenzene Tetralin 1,4-Dioxane Cyclohexane THF Toluene Chloroform Cyclohexene
Yield (%)b
Table 5 Solubility behaviors of poly(1,1-dipropargyl-1-silacycloalkane)sa. Solvent
Mw/Mnc
Four-ring
Five-ring
Four-ring
Five-ring
36 75 66 51 46 5 23 64 41
20 59 77 11 64 25 65 31 13
– – – – – – – – –
6900/2000 3100/1500 – – – – – 14000/3500 –
a Polymerization was carried out by WCl6 at 60 8C for 24 h. The M/C of monomer to catalyst and initial monomer concentration ([M]o) were 20 and 1.0 M, respectively. b Methanol-insoluble polymer. c The molecular weights of soluble polymers were measured with GPC.
Toluene Benzene Chlorobenzene Cyclohexene Chloroform Triethylamine Dichloromethane 1,2-Dichloroethane THF Carbon tetrachloride 1,4-Dioxane Ethyl ether DMF n-Hexane Methanol Acetone a
compounds have been used as an effective cocatalysts [1,10]. However, in this case, these cocatalysts rather decreased the polymer yields slightly, although the reason is not clear in the present state. Table 4 shows the solvent effect for the polymerization of 1,1-dipropargyl-1-silacycloalkanes. WCl6 alone polymerize DPSCB monomer in chlorobenzene solvent to give the polymer in 75% yield, whereas in toluene solvent gives 23% yield of polymer. This catalyst also polymerized DPSCP in chlorobenzene solvent to give the corresponding polymer in 59% yield. The 1,1-dipropargyl-1-silacycloalkanes were easily polymerized in aromatic hydrocarbons and haloalkanes such as toluene, tetralin, chlorobenzene, chloroform. The high yields of polymer were obtained in the solvents of chlorobenzene and tetralin for the both polymerization of DPSCB and DPSCP. They are good solvents for not only the catalyst but also the resulting polymers. The resulting poly(1,1-dipropargyl-1-silacycloalkane)s by Mo- and W-based catalysts were yellow or light-brown powders, whereas the same samples prepared by PdCl2 were mostly black powder. The solubility test was performed for powdery samples in excess solvent. Table 5 shows the solubility behaviors of poly(1,1-dipropargyl-1-silacycloalkane)s. The resulting poly(DPSCB) having four-membered ring was found to be insoluble in any organic solvents, regardless of the reaction conditions. On the other hand, the poly(DPSCP) having five-membered ring was partially soluble in aromatic and halogenated hydrocarbon solvents such as toluene, chlorobenzene, chloroform, carbon tetrachloride, etc. The soluble portion of poly(DPSCP) was about 50%. It was found that the polymerization of DPSCB seems to proceeded in semi-heterogeneous manner in some cases, whereas the polymerization of DPSCP proceed in homogeneous manner. The insolubility of the resulting poly(1,1dipropargyl-1-silacycloalkane)s may be originated by the cross-linking of conjugated cyclopolymers during the polymerization and/or the work-up process. The weight-average molecular weights of the soluble poly(DPSCP) were in the range of 3100–14000.
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b
Solubilityb Four-ring
Five-ring
+ + + + + + + + + + + +
The solubility test was performed for powdery samples in excess solvent. Solubility, ++: soluble; +: partially soluble; : insoluble.
The polymer structures of poly(1,1-dipropargyl-1-silacycloalkane)s were characterized by NMR (1H- and 13C-), infrared, and UV–vis spectroscopies. Fig. 1 shows the FT-IR spectra of poly(DPSCB) and poly(PDPSCP) in KBr pellet. The IR spectra of polymers did not show any acetylenic CC bond stretching (2116 cm1 for DPSCB and DPSCP monomers) and C–H bond stretching (3304 cm1 for DPSCB and DPSCP monomers) frequencies. Instead, the C C stretching frequency peak of conjugated spirocyclic polymers, poly(DPSCB) and ploy(DPSCP), was newly observed at around 1603 cm1. The aliphatic C–H stretching peaks were observed at 2853 and 2930 cm1. A strong peak of Si–C linkages of polymer was observed at 814 cm1. The 1H NMR spectra of soluble poly(DPSCP) was measured in CDCl3. It did not show the acetylenic proton peak (1.85 ppm) of DPSCP monomer. Instead, the new vinyl protons of
Fig. 1. FT-IR spectra of poly(DPSCB) (A) and poly(DPSCP) (B) in KBr pellet.
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Fig. 2. Solid-state
I.-S. Lee et al. / Journal of Industrial and Engineering Chemistry 14 (2008) 720–725
13
Fig. 3. UV–vis spectrum of the soluble poly(DPSCP) in THF.
C NMR spectrum of the insoluble poly(DPSCP).
conjugated polymer backbone were also seen at the region of 6.50–7.11 ppm, which had not been observed in the 1H NMR spectrum of monomer. The peaks of the two methylene protons of silacyclopentane adjacent to the silicon atom were observed at 0.51–0.85 ppm. And the peaks of the two methylene protons of silacyclopentane and the two methylene protons adjacent to the vinylic carbons were observed at 1.58–2.10 ppm. The 13C NMR spectrum of soluble poly(DPSCP) did not show any acetylenic carbon peaks (68.10 and 81.26 ppm) of DPSCP. Instead, the 13C NMR spectrum of poly(DPSCP) exhibited newly the olefinic carbon peaks of the conjugated polymer backbone at the region of 125.82–142.13 ppm. The peaks of various methylene carbons of poly(DPSCP) were observed at the region of 11.48–27.14 ppm. Fig. 2 shows the solid-state 13C NMR spectrum of insoluble poly(DPSCP). This spectrum exhibited the broad carbon peaks of conjugated polymer backbone of poly(DPSCP) at 110–160 ppm, which are corresponded to the vinyl carbons of conjugated polymer backbone, and it also showed broad methylene carbon peaks at 10–80 ppm. The peak at around 225 ppm may be due to the carbonyl carbons, which may be originated from air oxidation of conjugated polymer backbone of poly(DPSCP). Fig. 3 shows the typical UV–vis spectrum of poly(DPSCP) in THF. It showed a characteristic broad absorption band at the visible region, which is originated from the p ! p* transition of the conjugated polyene main chain. These spectral data indicated that the present poly(DPSCP) have a conjugated backbone system having spirocyclic recurring units. The TGA thermograms of poly(1,1-dipropargyl-1-silacycloalkane)s in Fig. 4 showed that these polymers start to decompose after 200 8C. Poly(DPSCB) retains 98% of its original weight at 200 8C, 95% at 300 8C, 66% at 500 8C, 51% at 800 8C, whereas poly(DPSCP) retains 99% of its original weight at 200 8C, 95% at 300 8C, 66% at 500 8C, 45% at 800 8C. These polymers showed characteristic two stepwise weight losses [200–575 8C, 800–1130 8C for poly(DPSCB), 200–570 8C, 640–960 8C for poly(DPSCP)]. It may be
explainable that the first weight loss is originated by the decomposition of organic conjugated cyclopolymers and the the second weight loss is by the further degradation of the residual semi-inorganic components. The high contents of residual weight even after 1400 8C may be deduced to be due to the formation of Si–C matrices. Polyacetylene and poly(1,6-heptadiyne) itself were easily oxidized in air at room temperature [35–37]. Thus we measured the IR spectrum for checking the oxidative stability of these two conjugated cyclopolymers. The IR spectrum of poly(DPSCB) and poly(DPSCP), which had been exposed for 10 days to air at room temperature, showed a small new carbonyl absorption band at 1700 cm1. These polymers were found to be more stable to air oxidation than those of PA and poly(1,6heptadiyne) itself. As the exposing time was increased, the carbonyl peak intensities were gradually increased. This phenomenon was caused by air oxidation of conjugated polymer backbone.
Fig. 4. TGA thermograms of poly(DPSCB) (solid line) and poly(DPSCP) (dotted line) measured under nitrogen atmosphere at a heating rate of 10 8C/ min.
I.-S. Lee et al. / Journal of Industrial and Engineering Chemistry 14 (2008) 720–725
4. Conclusion New conjugated spirocyclic polymers, poly(1,1-dipropargyl-1-silacycloalkane)s, were prepared by the ring-forming polymerization of the corresponding nonconjugated dipropargyl monomers by using Mo- and W-based catalysts. WCl6 and MoCl5 itself were found to be effective for the polymerization of 1,1-dipropargyl-1-silacycloalkanes and showed similar catalytic activity. The resulting polymers were yellow or light-brown powders, whereas the same sample prepared by PdCl2 was mostly black powder. The poly(DPSCB) was found to be insoluble in organic solvents, whereas the poly(DPSCP) was partially soluble in common organic solvents. The chemical structure of poly(1,1-dipropargyl-1-silacycloalkane)s was characterized by various instrumental methods to have the conjugated polymer backbone system having the designed spirocyclic recurring units. These cojugated cyclopolymers were thermally stable up to 200 8C. Acknowledgement The work has been supported by Regional Industrial Engineering Development Foundation Grant (100273472006-01). References [1] S.K. Choi, Y.S. Gal, S.H. Jin, H.K. Kim, Chem. Rev. 100 (2000) 1645. [2] K. Nagai, T. Masuda, T. Nakagawa, B.D. Freeman, I. Finnau, Prog. Polym. Sci. 26 (2001) 721. [3] J.W.Y. Lam, B.Z. Tang, J. Polym. Sci.: Part A: Polym. Chem. 41 (2003) 2607. [4] M.R. Buchmeiser, Adv. Polym. Sci. 176 (2005) 89. [5] Y.S. Gal, S.H. Jin, K.T. Lim, W.C. Lee, J. Ind. Eng. Chem. 11 (2005) 603. [6] Y.S. Gal, S.H. Jin, S.H. Kim, J. Ind. Eng. Chem. 12 (2006) 235. [7] A. Maity, M. Biswas, J. Ind. Eng. Chem. 12 (2006) 626. [8] T. Ito, H. Shirakawa, S. Ikeda, J. Polym. Sci.: Part A: Polym. Chem. 12 (1974) 11. [9] Y.S. Gal, W.C. Lee, S.Y. Kim, J.W. Park, S.H. Jin, K.N. Koh, S.H. Kim, J. Polym. Sci.: Part A: Polym. Chem. 39 (2001) 3151. [10] Y.S. Gal, S.H. Jin, S.K. Choi, J. Mol. Catal. A: Chem. 213 (2004) 115. [11] J.W.Y. Lam, B.Z. Tang, Acc. Chem. Res. 38 (2005) 745.
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