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Laser-initiated catalytic polymerization of vinyl monomer by metal carbonyls
Journal of Molecular Cata&&,
64 (1991) 277-282
277
Laser-initiated catalytic polymerization of vinyl monomer by metal carbonyls Jie Zhang, Pei Jin, Kejian Fu* Institute of Physics, Chinese Academy of Sciences, Be@ing 100080 (China)
and Yihua Zhou National Center for Certified Reference Materials, Beving (China) (Received June 4, 1990; accepted July 16, 1990)
Abstract Under the activation of pulsed UV laser, a highly efficient catalyst was formed from W(CO),-CCl,. The polystyrene obtained was characterized by IR spectroscopy and its molecular weight was measured to be 2.5x 104. The influences of irradiation time, polymerization time and catalyst lifetime were studied. Comparisons of catalysts from W(CO)G-CC14, Mo(CO)~-CC~~ and Cr(CO)e-CC14 are made. The comparison between catalytic polymerizations of phenylacetylene and of styrene is also discussed.
Introduction
Metal carbonyl complexes are well known to undergo light-induced loss of CO ligands in solution to give coordinatively unsaturated organometallic species which are potent catalysts (1). The coordinatively unsaturated metal carbonyl is used not only in the selective catalytic reactions of hydrogenation, isomerization and hydrosilation in mild conditions [2-41 but also in the catalytic polymerization of acetylene and its derivatives under the irradiation of UV light [5-71. Recently Fu et al. [8, 91 for the first time have reported photocatalytic polymerization by metal carbonyl using a pulsed UV laser. Moreover, these methods can provide fundamental information on the effect of laser-operating parameters on the polymerization of monomer. In a recent paper, Jin et al. [lo] have reported photocatalytic polymerization of one type of aryne monomer using a pulsed UV laser with W(CO)6-CC11 and W(CO)6-TiC1,-CC1, catalysts. In order to compare different reactive monomers, we report here the catalytic polymerization of another type of aryl olefin monomer under the same experimental conditions. Styrene, the most simple aryl olefln, is chosen as the reactive monomer. The general photocatalytic polymerization of styrene has been carried out using azobisisobutyronitrile (AIBN) under the irradiation of a high pressure Hg lamp; the quantum yield and yield of polystyrene was low [ 111. In this paper, we *Author to whom correspondence should be addressed.
0304-5102KllR3.50
0 Elsevier Sequoia/Printed in The Netherlands
278
investigate the influence of laser energy, irradiation time and lifetime of the catalyst on the polymerization of styrene and also compare the effects of the different catalysts W(CO)G-CC1,, Mo(CO),CCl, and Cr(CO),-Ccl,.
Experimental
Styrene (AR) was washed four times with NaOH solution, and then washed four times with distilled water and dried one week over CaCla before use. Metal carbonyls were purchased from Aldrich Chemical Inc. and used without further purification. CCl,(GR) was distilled twice before use. UV pulsed laser experiments were performed with a frequency triplet Nd”‘: YAG Laser (Spectra Physics Inc.) operating at 355 nm, with a pulse duration of 7-8 ns and cycles of 10 Hz. The polymerization process was as follows: a solution (10 ml) of W(CO), (0.1 mmol) was first irradiated with UV laser (355 run, 10 Hz) at 19 “C, and the irradiated solution was poured into styrene monomer and kept in the dark at room temperature and in air for 24 h. Polymerization was then terminated with alcohol. The polymer formed was precipitated in alcohol, filtered and dried to a constant weight. The polymer obtained was a white powder identified on an IR spectrometer (Perkin Elmer 1600 Series Fl’ IR) of resolution 2 cm- ‘. The weight average molecular weight of the polymer was measured by light scattering method from a Zimm plot using a Photal DLS-700 spectrophotometer. Results and discussion Figure 1 shows the UV absorption spectrum of a W(CO)G-CCld solution, showing that laser light of 355 nm can be absorbed effectively by W(CO),. The W(CO), was immediately decomposed in CCll solvent to form a kind of catalyst for the polymerization of styrene. The polymer obtained was
I 200
300
400
500
wavelength
600
700
800
(nm>
Fig. 1. Absorption of W(CO)6 in Ccl4 solvent. [W(CO),] = 10d2 M.
279
characterized by IR spectroscopy. The IR spectra of the polymer in KBr pellet form were taken, and a typical spectrum is shown in Fig. 2. The polymer has two strong absorption peaks at 700 and 760 cm-’ and has four typical absorption peaks at 2870, 2920, 3025 and 3074 cm-‘. All these clearly indicate the specificity of polystyrene. The weight average molecular weight of polystyrene is 2.5 X 104, measured by the light scattering method. The polymerization depends on laser energy, irradiation time and catalyst lifetime. Figure 3 illustrates the dependence of polymer yield on laser energy. The W(CO)G-CC14 solution was irradiated for ten minutes, with polymerization times of styrene of 24 h. With increasing laser energy, the polymer yield increases sharply and then saturates rapidly. The influence of laser irradiation time on polymer yield is shown in Fig. 4. The laser energy is 4.0 mJ per pulse, and the polymerization time of styrene is also 24 h. Polymer yield increases rapidly with laser irradiation time and saturates after 30 min. Because of the high power density, a large number of photons are absorbed in a short time to form a highly efficient catalyst. 65.00XT
3500
4000
3000
2500
1600
2000
1000
cm-’ 500
Fig. 2. IR spectra of polystyrene. 100
I
0 0
80 _
$
I
I
0
0
80_
1
d 4020 -
0 I
0
10
I
20
I
30
40
0
20
40
60
a0
Lamer Energy (mJ/pulse) Irradiation Time (minute) Fig. 3. Dependence of yield of polymer on laser energy; laser irradiation time 10 min, wavelength 355 run, [W(CO),] = lo-’ M. Fig. 4. Dependence of yield of polymer on laser irradiation time; laser energy 4.0 mJ per pulse, wavelength 355 nm, [W(CO),] = lo-’ M.
280
In the present experiment, polymerization is carried out by the catalyst in only mild conditions, so the effect of catalyst lifetime on the polymerization process is significant. UV laser energy of 4.0 mJ per pulse was used to irradiate the W(CO),-Ccl, system, and after 30 mm the catalyst produced was stored for different times in air. It wss then poured into styrene monomer and, the polymerization terminated with alcohol after 24 h. The results are shown in Fig. 5. The halflife of the catalyst was -3 h. The catalysts produced from W(CO)G-CC1.,, Mo(CO)&C& and Cr(CO)6-CC14 under the irradiation of UV laser were also compared. The experimental conditions for MOM and Cr(C0)4 are same as those of W(CO),. The results are shown in Table 1; the MO-based catalyst is less active and the Cr-based catalyst is ineffective. The catalyst decomposed from W(CO),--CC& not only can catalyze the pol~er~ation of aryne, but also can catalyze the pol~e~zation of aryl olefin. Table 2 presents the comparison between the polymerizations of styrene and of phenylacetylene under the same experimental conditions. The yield and quantum yield of polystyrene are larger than that of polyphenylacetylene.
00 0
60 -
0 400
20 _
0
0 /
I
I
0 t
I
3
e
B
12
15
Jdfetime.of
0
t
10
,
n
24
Catalyst(hour)
Fig. 5. Dependence of yield of polymer on llfethne of catalyst; laser energy 4.0 mJ per Puke, wavelength 355 run, laser irradiation time 10 mln, [W(CO)~j=10-2 M.
TABLE 1. Comparisons of W-based, MO-based and Cr-based catalysts (concentrations M(CO)B= 10T2 M) in catalyzing polymerization of styrene. The polymerization time of styrene monomer ls 24 h Catalyst
W(CO)gCC14 Mo(CO)~-CC& Cr(CO)+X19
Laser parameters Wavelength (nm)
Cycle
Energy w/P)
355 355 355
10 10 10
20 20 20
Irradiation time (min>
Yield (%)
10 10 10
8% 3.5 0
281
TABLE 2 Comparison between the pol~e~ation of styrene and that of phenyl~e~lene experimental conditions. Irradiation time 30 mm, fW(CO),] = lo-’ M Monomer
Laser parameters
(nm)
Cycle (Ha)
Energy (mJlP)
355 355
10 10
4.0 4.0
‘Wavelength Ph-C=CH, Ph-C-CH
under the same
Cataiyst
Yield (%)
Quantum yield
Molecular weight
w(co)(I-ccI, W(CO)s-CCl~
81.4 34
66 16
2.5 x lo4 2.6 x lo4
Conclusion By studying the influences of laser energy, irradiation time and catalyst lifetime on pol~e~zation and by calculating the qu~tum yield of polymer, it has been determined that the product decomposed from We-CCl* under the irradiation of pulsed UV laser is a highly efficient catalyst, especially for the polymerization of aryl 6lefin monomer (high yield and quantum yield of polymer were obtained). The polymer was characterized by IR spectroscopy. By comparison of three kinds of catalysts decomposed from W(CO)B-CC14, Mo(CO)~--CC~~ and Cr(CO)6-CC1,, the W-based catalyst was determined to be the most suitable for the polymerization of aryl olefin monomer. The primary process of decomposition of M(CO)6 (M=Mo, W) in CCL solvent irradiated by W laser is being studied by transient IR spectroscopy. The structure of the catalyst is also being characterized.
Acknowledgements The authors would like to thank Sun Shu-Qing of Qing Hua Universi~ for help in measuring the IR spectra and thank Zhang Xiou-Lan, Zhang DongXiang of the Laser Laboratory, Institute of Physics for help with the laser experiments. The project was supported by the National Natural Science Foundation of China and the Grant Term Fund for ‘Interaction Between Laser and Matter’ from the Chinese Academy of Science.
References Academic Press, New 1 G. L. Geoffroy and M. S. Wrighten, Urganoms tall& Photoc~titry, York, 1979. 2 R. L. Whetten, K. J. Fu and E. R. Grant, J. CM. Phgs., 77 (1982) 3769. 3 K. J. Fu, R. L. Whetten and E. R. Grant, ind Eng. Ckm. Prod. Res. Dev., 23 (1984) 33. 4 J. C. Mitchener and M. S. Wrighten, J. Am C&en. Sot., IO3 (1981) 975.
282 5 T. Masuda, K. Yamaoto
and T. Higashimura, PO&~., 23 (1982) 1663. 6 J. S. Park, S. Sermon, A. Langer and P. Ehrlich, J. PO&~. SC%, Part A, 27 (1989) 4281. 7 T. Masuda and T. Higsshiiura, Ada Polyp Sci., 81 (1987) 121. 8 Ckiraese Pat. Appl. 88 I 0240.6 (1988) to K. 3. Fu, J. H. Yang, J. B. Qiu, W. H. Wang, J. Shan and J. G. Lin. 9 Chinese Put. Appii 89 I 02160.4 (1989) to J. H. Yang, K. J. Fu, J. B. Qiu, Y. Shu and J. F. Gong. 10 P. Jm, J. Shari,, C. X. Lu, Y. H. Zhou and K. J. Fu, PO&m. BULL, 24 (1990) 135. 11 1‘. Kodaira, K. Hayashi and T. Ohnishi, PO&~. J., 4 (1973) 1.
64 (1991) 277-282
277
Laser-initiated catalytic polymerization of vinyl monomer by metal carbonyls Jie Zhang, Pei Jin, Kejian Fu* Institute of Physics, Chinese Academy of Sciences, Be@ing 100080 (China)
and Yihua Zhou National Center for Certified Reference Materials, Beving (China) (Received June 4, 1990; accepted July 16, 1990)
Abstract Under the activation of pulsed UV laser, a highly efficient catalyst was formed from W(CO),-CCl,. The polystyrene obtained was characterized by IR spectroscopy and its molecular weight was measured to be 2.5x 104. The influences of irradiation time, polymerization time and catalyst lifetime were studied. Comparisons of catalysts from W(CO)G-CC14, Mo(CO)~-CC~~ and Cr(CO)e-CC14 are made. The comparison between catalytic polymerizations of phenylacetylene and of styrene is also discussed.
Introduction
Metal carbonyl complexes are well known to undergo light-induced loss of CO ligands in solution to give coordinatively unsaturated organometallic species which are potent catalysts (1). The coordinatively unsaturated metal carbonyl is used not only in the selective catalytic reactions of hydrogenation, isomerization and hydrosilation in mild conditions [2-41 but also in the catalytic polymerization of acetylene and its derivatives under the irradiation of UV light [5-71. Recently Fu et al. [8, 91 for the first time have reported photocatalytic polymerization by metal carbonyl using a pulsed UV laser. Moreover, these methods can provide fundamental information on the effect of laser-operating parameters on the polymerization of monomer. In a recent paper, Jin et al. [lo] have reported photocatalytic polymerization of one type of aryne monomer using a pulsed UV laser with W(CO)6-CC11 and W(CO)6-TiC1,-CC1, catalysts. In order to compare different reactive monomers, we report here the catalytic polymerization of another type of aryl olefin monomer under the same experimental conditions. Styrene, the most simple aryl olefln, is chosen as the reactive monomer. The general photocatalytic polymerization of styrene has been carried out using azobisisobutyronitrile (AIBN) under the irradiation of a high pressure Hg lamp; the quantum yield and yield of polystyrene was low [ 111. In this paper, we *Author to whom correspondence should be addressed.
0304-5102KllR3.50
0 Elsevier Sequoia/Printed in The Netherlands
278
investigate the influence of laser energy, irradiation time and lifetime of the catalyst on the polymerization of styrene and also compare the effects of the different catalysts W(CO)G-CC1,, Mo(CO),CCl, and Cr(CO),-Ccl,.
Experimental
Styrene (AR) was washed four times with NaOH solution, and then washed four times with distilled water and dried one week over CaCla before use. Metal carbonyls were purchased from Aldrich Chemical Inc. and used without further purification. CCl,(GR) was distilled twice before use. UV pulsed laser experiments were performed with a frequency triplet Nd”‘: YAG Laser (Spectra Physics Inc.) operating at 355 nm, with a pulse duration of 7-8 ns and cycles of 10 Hz. The polymerization process was as follows: a solution (10 ml) of W(CO), (0.1 mmol) was first irradiated with UV laser (355 run, 10 Hz) at 19 “C, and the irradiated solution was poured into styrene monomer and kept in the dark at room temperature and in air for 24 h. Polymerization was then terminated with alcohol. The polymer formed was precipitated in alcohol, filtered and dried to a constant weight. The polymer obtained was a white powder identified on an IR spectrometer (Perkin Elmer 1600 Series Fl’ IR) of resolution 2 cm- ‘. The weight average molecular weight of the polymer was measured by light scattering method from a Zimm plot using a Photal DLS-700 spectrophotometer. Results and discussion Figure 1 shows the UV absorption spectrum of a W(CO)G-CCld solution, showing that laser light of 355 nm can be absorbed effectively by W(CO),. The W(CO), was immediately decomposed in CCll solvent to form a kind of catalyst for the polymerization of styrene. The polymer obtained was
I 200
300
400
500
wavelength
600
700
800
(nm>
Fig. 1. Absorption of W(CO)6 in Ccl4 solvent. [W(CO),] = 10d2 M.
279
characterized by IR spectroscopy. The IR spectra of the polymer in KBr pellet form were taken, and a typical spectrum is shown in Fig. 2. The polymer has two strong absorption peaks at 700 and 760 cm-’ and has four typical absorption peaks at 2870, 2920, 3025 and 3074 cm-‘. All these clearly indicate the specificity of polystyrene. The weight average molecular weight of polystyrene is 2.5 X 104, measured by the light scattering method. The polymerization depends on laser energy, irradiation time and catalyst lifetime. Figure 3 illustrates the dependence of polymer yield on laser energy. The W(CO)G-CC14 solution was irradiated for ten minutes, with polymerization times of styrene of 24 h. With increasing laser energy, the polymer yield increases sharply and then saturates rapidly. The influence of laser irradiation time on polymer yield is shown in Fig. 4. The laser energy is 4.0 mJ per pulse, and the polymerization time of styrene is also 24 h. Polymer yield increases rapidly with laser irradiation time and saturates after 30 min. Because of the high power density, a large number of photons are absorbed in a short time to form a highly efficient catalyst. 65.00XT
3500
4000
3000
2500
1600
2000
1000
cm-’ 500
Fig. 2. IR spectra of polystyrene. 100
I
0 0
80 _
$
I
I
0
0
80_
1
d 4020 -
0 I
0
10
I
20
I
30
40
0
20
40
60
a0
Lamer Energy (mJ/pulse) Irradiation Time (minute) Fig. 3. Dependence of yield of polymer on laser energy; laser irradiation time 10 min, wavelength 355 run, [W(CO),] = lo-’ M. Fig. 4. Dependence of yield of polymer on laser irradiation time; laser energy 4.0 mJ per pulse, wavelength 355 nm, [W(CO),] = lo-’ M.
280
In the present experiment, polymerization is carried out by the catalyst in only mild conditions, so the effect of catalyst lifetime on the polymerization process is significant. UV laser energy of 4.0 mJ per pulse was used to irradiate the W(CO),-Ccl, system, and after 30 mm the catalyst produced was stored for different times in air. It wss then poured into styrene monomer and, the polymerization terminated with alcohol after 24 h. The results are shown in Fig. 5. The halflife of the catalyst was -3 h. The catalysts produced from W(CO)G-CC1.,, Mo(CO)&C& and Cr(CO)6-CC14 under the irradiation of UV laser were also compared. The experimental conditions for MOM and Cr(C0)4 are same as those of W(CO),. The results are shown in Table 1; the MO-based catalyst is less active and the Cr-based catalyst is ineffective. The catalyst decomposed from W(CO),--CC& not only can catalyze the pol~er~ation of aryne, but also can catalyze the pol~e~zation of aryl olefin. Table 2 presents the comparison between the polymerizations of styrene and of phenylacetylene under the same experimental conditions. The yield and quantum yield of polystyrene are larger than that of polyphenylacetylene.
00 0
60 -
0 400
20 _
0
0 /
I
I
0 t
I
3
e
B
12
15
Jdfetime.of
0
t
10
,
n
24
Catalyst(hour)
Fig. 5. Dependence of yield of polymer on llfethne of catalyst; laser energy 4.0 mJ per Puke, wavelength 355 run, laser irradiation time 10 mln, [W(CO)~j=10-2 M.
TABLE 1. Comparisons of W-based, MO-based and Cr-based catalysts (concentrations M(CO)B= 10T2 M) in catalyzing polymerization of styrene. The polymerization time of styrene monomer ls 24 h Catalyst
W(CO)gCC14 Mo(CO)~-CC& Cr(CO)+X19
Laser parameters Wavelength (nm)
Cycle
Energy w/P)
355 355 355
10 10 10
20 20 20
Irradiation time (min>
Yield (%)
10 10 10
8% 3.5 0
281
TABLE 2 Comparison between the pol~e~ation of styrene and that of phenyl~e~lene experimental conditions. Irradiation time 30 mm, fW(CO),] = lo-’ M Monomer
Laser parameters
(nm)
Cycle (Ha)
Energy (mJlP)
355 355
10 10
4.0 4.0
‘Wavelength Ph-C=CH, Ph-C-CH
under the same
Cataiyst
Yield (%)
Quantum yield
Molecular weight
w(co)(I-ccI, W(CO)s-CCl~
81.4 34
66 16
2.5 x lo4 2.6 x lo4
Conclusion By studying the influences of laser energy, irradiation time and catalyst lifetime on pol~e~zation and by calculating the qu~tum yield of polymer, it has been determined that the product decomposed from We-CCl* under the irradiation of pulsed UV laser is a highly efficient catalyst, especially for the polymerization of aryl 6lefin monomer (high yield and quantum yield of polymer were obtained). The polymer was characterized by IR spectroscopy. By comparison of three kinds of catalysts decomposed from W(CO)B-CC14, Mo(CO)~--CC~~ and Cr(CO)6-CC1,, the W-based catalyst was determined to be the most suitable for the polymerization of aryl olefin monomer. The primary process of decomposition of M(CO)6 (M=Mo, W) in CCL solvent irradiated by W laser is being studied by transient IR spectroscopy. The structure of the catalyst is also being characterized.
Acknowledgements The authors would like to thank Sun Shu-Qing of Qing Hua Universi~ for help in measuring the IR spectra and thank Zhang Xiou-Lan, Zhang DongXiang of the Laser Laboratory, Institute of Physics for help with the laser experiments. The project was supported by the National Natural Science Foundation of China and the Grant Term Fund for ‘Interaction Between Laser and Matter’ from the Chinese Academy of Science.
References Academic Press, New 1 G. L. Geoffroy and M. S. Wrighten, Urganoms tall& Photoc~titry, York, 1979. 2 R. L. Whetten, K. J. Fu and E. R. Grant, J. CM. Phgs., 77 (1982) 3769. 3 K. J. Fu, R. L. Whetten and E. R. Grant, ind Eng. Ckm. Prod. Res. Dev., 23 (1984) 33. 4 J. C. Mitchener and M. S. Wrighten, J. Am C&en. Sot., IO3 (1981) 975.
282 5 T. Masuda, K. Yamaoto
and T. Higashimura, PO&~., 23 (1982) 1663. 6 J. S. Park, S. Sermon, A. Langer and P. Ehrlich, J. PO&~. SC%, Part A, 27 (1989) 4281. 7 T. Masuda and T. Higsshiiura, Ada Polyp Sci., 81 (1987) 121. 8 Ckiraese Pat. Appl. 88 I 0240.6 (1988) to K. 3. Fu, J. H. Yang, J. B. Qiu, W. H. Wang, J. Shan and J. G. Lin. 9 Chinese Put. Appii 89 I 02160.4 (1989) to J. H. Yang, K. J. Fu, J. B. Qiu, Y. Shu and J. F. Gong. 10 P. Jm, J. Shari,, C. X. Lu, Y. H. Zhou and K. J. Fu, PO&m. BULL, 24 (1990) 135. 11 1‘. Kodaira, K. Hayashi and T. Ohnishi, PO&~. J., 4 (1973) 1.