- Email: [email protected]
MAO system
European Polymer Journal 36 (2000) 2055±2058
Short communication
Syndiotactic polymerization of styrene with CpTiCl2(OR)/ MAO system Jianfei Liu 1, Haiyan Ma, Jiling Huang, Yanlong Qian* Laboratory of Organometallic Chemistry, East China University of Science and Technology, Shanghai 200237, People's Republic of China Received 24 May 1999; received in revised form 6 September 1999; accepted 24 September 1999
Abstract CpTiCl2(OR) (R=Cyclohexyl, CH2Ph, C6H4-But-p, nBu, iBu, CH2CH1CH2) are synthesized, characterized and tested as syndiotactic polymerization catalysts of styrene. The structure and nature of the R group has a great eect on the activity of catalysts. Unsaturated groups and the conjugation of unsaturated groups with oxygen result in the drop of activity; while a more hindered R group increases activity. 7 2000 Elsevier Science Ltd. All rights reserved. Keywords: Syndiotactic; Polymerization; Styrene
1. Introduction In the past ten years, syndiotactic polystyrene has attracted much attention due to its excellent performance, which is claimed to be comparable to that of engineering resins like polyesters, PPS and nylon-66 [1,2]. Thus, the synthesis of syndiotactic polystyrene via syndiotactic polymerization remains a research focus in polymer science [3,4]. Most of polymerization catalysts used to catalyze the syndiotactic polymerization of styrene are half-sandwich titanium trichloride compounds. There are also reports on the use of half-sandwich titanium trichloride derivatives, such as CpTi(OR)3, as the catalysts in the syndiotactic polymerization of styrene [5±7]. Ishihara reported that the
* Corresponding author. Fax: +86-21-6470-2573. E-mail address: [email protected] (Y. Qian). 1 Present address: Institute of Medicinal Chemistry, 2nd Military Medical University, Shanghai 200433, People's Republic of China.
catalytic activity of titanium compounds decreased in the order: CpTiCl3>>Ti(OEt)4 > Ti(OMe)4 0 TiCl4 [8]. This makes us meditate that probably the replacement of Cl with an OR group in CpTiCl3 increases the catalytic activity. And indeed it is so Ð we found that CpTiCl2(OR) was more active than CpTiCl3 in the syndiotactic polymerization of styrene [9,10]. In a continuation of our study on the syndiotactic polymerization of styrene by CpTiCl2(OR), a series of new CpTiCl2(OR) complexes is synthesized and tested as a syndiotactic polymerization catalyst of styrene to learn more about the in¯uence of the R group on the polymerization. 2. Experimental CpTiCl2(OR) were prepared according to the literature [11]. Analytical data for the CpTiCl2(OR) complexes are as follows: CpTiCl2(O-cyclohexyl) [12]: yellow crystal, m.p. 72± 738C, yield 90.5%. 1H NMR (CDCl3, d ): 1.20 0 2.00
0014-3057/00/$ - see front matter 7 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 0 1 4 - 3 0 5 7 ( 9 9 ) 0 0 2 4 9 - 9
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J. Liu et al. / European Polymer Journal 36 (2000) 2055±2058
(m, 10H), 4.73 (m, 1H), 6.71 (s, 5H). IR (KBr, cmÿ1): 3107.3, 2934.7, 2854.9, 1444.6, 1359.7, 1075.1, 847.4. MS (m/e): 282 (M+, 56), 246 (MÿHCl, 70), 182 (MÿHOR, 81), 148 (MÿClÿOR, 58), 99 (OR, 30), 82 (C6H10, 58), 43 (C3H7, 69), 29 (C2H5, 44). EA: Calcd. C, 46.63; H, 5.65; Found C, 45.72; H, 5.51. CpTiCl2(OCH2Ph) [12]: yellow crystal, m.p. 78± 808C, yield 96%. 1H NMR (CDCl3,d ): 5.60 (s, 2H), 6.58 (s, 5H), 7.30±7.50 (m, 5H). IR (KBr, cmÿ1): 3097.2, 3062.2, 2902.4, 2848.4, 1494.6, 1359.6, 1070.3, 852.4, 827.3, 732.8, 705.8. MS (m/e): 289 (Mÿ1, 0.62), 254 (MÿClÿ1, 35.3), 220 (Mÿ2Cl, 2.1), 183 (MÿOR, 4.4), 148 (MÿORÿCl, 11.2), 91 (CH2Ph, 100), 65 (Cp, 24.4). EA: Calcd. C, 49.52; H, 4.16; Found C, 49.01; H, 4.24. CpTiCl2(OC6H4-But-p): orange crystal, m.p. 68± 708C, yield 87.3%. 1H NMR (CDCl3, d ): 1.36 (s, 9H), 6.79 (s, 5H), 6.97 (d, 2H, J = 8.79 Hz), 7.35 (d, 2H, J = 8.79). IR (KBr, cmÿ1): 3104.9, 2962.7, 2872, 1594.9, 1503.3, 1460, 1370, 1019.3, 820.6. MS (m/e): 332 (M+, 22), 317 (MÿCH3, 93), 297 (MÿCl, 8), 281 (MÿCH3ÿHCl, 23), 262 (Mÿ2Cl, 2), 183 (MÿOR, 47), 65 (Cp, 100).EA: Calcd. C, 54.09; H, 5.45; Found C, 54.64; H, 5.58. CpTiCl2(OnBu): yellow oil. yield 85.6%. 1H NMR (CDCl3, d ): 0.92 (t, 3H, J = 7.35 Hz), 1.42 (m, 2H), 1.66 (m, 2H), 4.65 (m, 2H, J = 5.60 Hz), 6.69 (s, 5H). IR (KBr, cmÿ1): 3108.7w, 2958.7, 2926.0, 2869.6, 1436.7, 1363.4, 1038.4, 860.3, 823.7. MS (m/e): 256 (M+, 12), 213 (MÿC3H7, 89), 183 (MÿOR, 100), 148 (MÿClÿOR, 39), 65 (Cp, 25). EA: Calcd. C,42.06; H, 5.49; Found C, 41.48; H, 5.21. CpTiCl2(OiBu) [12]: orange oil, yield 90%. 1H NMR (CDCl3, d ): 0.90 (d, 6H, J = 6.65 Hz), 1.9 (m, 1H), 4.40 (d, 2H, J = 6.25), 6.65 (s, 5H). IR (KBr, cmÿ1): 3108.2, 2961.3, 2926.7, 2871.2, 1465.7, 1439.3, 1388.5, 1365.4, 1043.2. MS (m/e): 256 (M+, 19), 221 (MÿCl, 46), 213 (MÿC3H7, 100), 183 (MÿOR, 74), 148 (MÿClÿOR, 30), 65 (Cp, 13), 57 (C4H9,15). EA: Calcd. C, 42.06: H, 5.49; Found C, 42.13; H, 5.52. CpTiCl2(OCH2CH1CH2): yellow oil, yield 86%. 1H NMR (CDCl3, d ): 5.08 (d, 2H, J = 4.2 Hz), 5.23 (d, 1H, J = 9.8 Hz), 5.35 (d, 1H, J = 16.4 Hz), 5.91 (m, 1H), 6.69 (s, 5H). IR (KBr, cmÿ1): 3018.6, 2912.2, 2855.2, 1644.6, 1418.9, 991.6, 850, 830. MS (m/e): 240 (M+, 20), 206 (MÿHCl+2, 35), 205 (MÿCl, 27), 204 (MÿHCl, 88), 185 (MÿOR+2, 51), 183 (MÿOR, 73), 150 (MÿClÿOR+2, 32), 147 (MÿHClÿOR, 100), 64 (CpÿH, 69), 40 (CH0CH1CH2, 46). EA: Calcd. C, 39.87; H, 4.15; Found C, 39.89; H, 4.10. MAO was produced by Witco GmbH. Styrene was puri®ed by washing several times with dilute NaOH solution, dried over anhydrous CaCl2, vacuum distillation from CaH2 and stored at ÿ208C in darkness. Toluene was distilled from sodium and diphenyl ketone under argon just before use.
Polymerization was conducted in small ampoules baked under vacuum and ¯ushed with argon several times. Styrene (2 ml), an appropriate amount of MAO in 10 ml toluene, and titanium compounds in toluene were sequentially injected. The mixtures were kept at 508C for a certain time, then terminated with 100 ml 10% HCl in EtOH, and dried under vacuum at 508C to constant weight. The melting point of polystyrene was recorded on DSC 2910 Modulated DSC Universal V1.10B TA Instruments.
3. Results and discussion Table 1 summarizes the in¯uence of the R structure on polymerization. Generally, the change of [Ti] and [Al] in the given range has little in¯uence on the syndiotacticity and the melting point of the polymer, which are in the range of 94±99.5% and 255±2608C respectively. However, the considerable decrease of the activity is observed for all the complexes tested when [Ti] is decreased from 0.42 to 0.21 mM. In all the complexes, the catalysts containing the secondary alkoxy group are apparently more active than those containing the primary alkoxy group, as can be seen from the comparison of CpTiCl2(OBun) with CpTiCl2(OBui). As aluminum is an electron-de®cient atom while oxygen is an electron-donating atom, capable of coordinating with aluminum in MAO, the oxygen in primary alkoxides coordinate much more easily to aluminum in MAO than the oxygen in the secondary alkoxides due to the steric eect. This results in a decrease of activity. Therefore, the catalysts containing more hindered alkoxy group have higher activity. When R contains an aryl, the catalyst is less active than that of its aliphatic analogs as can be seen from the comparison of CpTiCl2(OC6H4-But-p) with CpTiCl2(O-cyclohexyl). It is well-known [13±15] that TiIII cation is the active species in the syndiotactic polymerization of styrene catalyzed by half-sandwich titanocene catalysts. There is also a report that aromatic ring can coordinate to TiIII cation [16]. We believe that this coordination, which competes with the monomer, leads to the drop of activity. Also, considerable activity decrease is observed when aryl is directly linked to oxygen (Runs 5,6 and 3,4). This may be due to the electron-donating eect of aryl, which reduces the positivity of TiIII (active species) and thus is unfavorable to the coordination of monomer, and the steric eect as discussed above. Of all the complexes, CpTiCl2(O-cyclohexyl) is the most active one. Thus the in¯uence of temperature on the polymerization was studied, and the results were summarized in Table 2. It is obvious that a higher pol-
J. Liu et al. / European Polymer Journal 36 (2000) 2055±2058
2057
Table 1 Syndiotactic polymerization of styrene catalyzed by CpTiCl2 X
a b
gPS/(molTimolSh). g of 2-butanone insoluble polymer/g of bulk polymer.
ymerization temperature is unfavorable for the syndiotactic polymerization of styrene. The higher the temperature, the lower the syndiotacticity of the polystyrene. However, it is worth noting that polymer yields increase with the increase in tem-
perature although a long polymerization time is needed. At 70 and 908C, the syndiotactic polystyrene precipitates very slowly from the mixtures. It seems that syndiotactic polymerization is a fast process prohibited by high temperature, which increases the possi-
Table 2 Polymerization of styrene catalyzed by CpTiCl2(O-cyclohexyl)/MAOa under dierent temperaturesb Run
[Ti] (mM)
[Al] (M)
Al/Ti (103)
Time (h)
Temp. (8C)
Yield (g)
Ac (106)
Sd (%)
13 14 15 16
0.42 0.42 0.42 0.42
0.83 0.83 0.83 0.83
2.0 2.0 2.0 2.0
1 1 17 25
25 50 70 90
0.1504 0.2614 0.7479 0.9511
1.73 3.00 0.51 0.43
96.5 95.1 92.9 72.6
a
MAO used in this experiment is not the same batch as that in Table 1. Polymerization conditions: styrene 2 ml, [S]=1.45. c gPS/(molTimolSh). d g of 2-butanone insoluble polymer/g of bulk polymer. b
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bility of atactic polymerization. The catalytic activity also decreases with the increase of temperature in the range of 50±908C due to the low polymerization rates.
Acknowledgements This project was supported by China Postdoctoral Science Foundation, National Natural Science Foundation of China (29734145 and 29871010), State Key Laboratory of Coordination Chemistry, Nanjing University.
References [1] Sinclair KB, Wilson RB. Chem Ind 1994:857. [2] Moore S. Modern Plastic International 1992:22. [3] Foster P, Chien JCW, Rausch MD. Organometallics 1996;15:2404.
[4] Kaminsky W, Lenk S, Scholz V, Roesky HW, Herzog A. Macromolecules 1997;30(25):7646. [5] Chien JCW, Salajka Z. J Polym Sci Part A: Polym Chem 1991;29(9):1243, 1253. [6] Chien JCW, Salajka Z, Dong S. Macromolecules 1992;25:3199. [7] Kucht A, Kucht H, Barry S, Chien JCW, Rausch MD. Organometallics 1993;12:3075. [8] Ishihara N, Kuramoto M, Uoi M. Macromolecules 1988;21:3356. [9] Liu J, Huang J, Qian Y, Wang F, Chan ASC. Polym Bull 1996;37:719. [10] Liu J, Huang J, Qian Y, Wang F, Chan ASC. Polym J 1997;29(2):182. [11] Fussing IMM, Plecher D, Whitby RJ. J Organomet Chem 1994;470:109. [12] Fraurenkron M, Tzavellas N, Klouras N, Raptopoulou CP. Monatsh Chem 1996;127(11):1137. [13] Grassi A, Lamberti C, Zambelli A, Mingozzi. Macromolecules 1997;30:1884. [14] Xu G, Lin S. Macromolecules 1997;30:685. [15] Grassi A, Zambelli A. Polym Prep 1996;37(2):533. [16] Scollard JC, McConville DH, Payne NC, Vittal JT. Macromolecules 1996;29:5241.
Short communication
Syndiotactic polymerization of styrene with CpTiCl2(OR)/ MAO system Jianfei Liu 1, Haiyan Ma, Jiling Huang, Yanlong Qian* Laboratory of Organometallic Chemistry, East China University of Science and Technology, Shanghai 200237, People's Republic of China Received 24 May 1999; received in revised form 6 September 1999; accepted 24 September 1999
Abstract CpTiCl2(OR) (R=Cyclohexyl, CH2Ph, C6H4-But-p, nBu, iBu, CH2CH1CH2) are synthesized, characterized and tested as syndiotactic polymerization catalysts of styrene. The structure and nature of the R group has a great eect on the activity of catalysts. Unsaturated groups and the conjugation of unsaturated groups with oxygen result in the drop of activity; while a more hindered R group increases activity. 7 2000 Elsevier Science Ltd. All rights reserved. Keywords: Syndiotactic; Polymerization; Styrene
1. Introduction In the past ten years, syndiotactic polystyrene has attracted much attention due to its excellent performance, which is claimed to be comparable to that of engineering resins like polyesters, PPS and nylon-66 [1,2]. Thus, the synthesis of syndiotactic polystyrene via syndiotactic polymerization remains a research focus in polymer science [3,4]. Most of polymerization catalysts used to catalyze the syndiotactic polymerization of styrene are half-sandwich titanium trichloride compounds. There are also reports on the use of half-sandwich titanium trichloride derivatives, such as CpTi(OR)3, as the catalysts in the syndiotactic polymerization of styrene [5±7]. Ishihara reported that the
* Corresponding author. Fax: +86-21-6470-2573. E-mail address: [email protected] (Y. Qian). 1 Present address: Institute of Medicinal Chemistry, 2nd Military Medical University, Shanghai 200433, People's Republic of China.
catalytic activity of titanium compounds decreased in the order: CpTiCl3>>Ti(OEt)4 > Ti(OMe)4 0 TiCl4 [8]. This makes us meditate that probably the replacement of Cl with an OR group in CpTiCl3 increases the catalytic activity. And indeed it is so Ð we found that CpTiCl2(OR) was more active than CpTiCl3 in the syndiotactic polymerization of styrene [9,10]. In a continuation of our study on the syndiotactic polymerization of styrene by CpTiCl2(OR), a series of new CpTiCl2(OR) complexes is synthesized and tested as a syndiotactic polymerization catalyst of styrene to learn more about the in¯uence of the R group on the polymerization. 2. Experimental CpTiCl2(OR) were prepared according to the literature [11]. Analytical data for the CpTiCl2(OR) complexes are as follows: CpTiCl2(O-cyclohexyl) [12]: yellow crystal, m.p. 72± 738C, yield 90.5%. 1H NMR (CDCl3, d ): 1.20 0 2.00
0014-3057/00/$ - see front matter 7 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 0 1 4 - 3 0 5 7 ( 9 9 ) 0 0 2 4 9 - 9
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J. Liu et al. / European Polymer Journal 36 (2000) 2055±2058
(m, 10H), 4.73 (m, 1H), 6.71 (s, 5H). IR (KBr, cmÿ1): 3107.3, 2934.7, 2854.9, 1444.6, 1359.7, 1075.1, 847.4. MS (m/e): 282 (M+, 56), 246 (MÿHCl, 70), 182 (MÿHOR, 81), 148 (MÿClÿOR, 58), 99 (OR, 30), 82 (C6H10, 58), 43 (C3H7, 69), 29 (C2H5, 44). EA: Calcd. C, 46.63; H, 5.65; Found C, 45.72; H, 5.51. CpTiCl2(OCH2Ph) [12]: yellow crystal, m.p. 78± 808C, yield 96%. 1H NMR (CDCl3,d ): 5.60 (s, 2H), 6.58 (s, 5H), 7.30±7.50 (m, 5H). IR (KBr, cmÿ1): 3097.2, 3062.2, 2902.4, 2848.4, 1494.6, 1359.6, 1070.3, 852.4, 827.3, 732.8, 705.8. MS (m/e): 289 (Mÿ1, 0.62), 254 (MÿClÿ1, 35.3), 220 (Mÿ2Cl, 2.1), 183 (MÿOR, 4.4), 148 (MÿORÿCl, 11.2), 91 (CH2Ph, 100), 65 (Cp, 24.4). EA: Calcd. C, 49.52; H, 4.16; Found C, 49.01; H, 4.24. CpTiCl2(OC6H4-But-p): orange crystal, m.p. 68± 708C, yield 87.3%. 1H NMR (CDCl3, d ): 1.36 (s, 9H), 6.79 (s, 5H), 6.97 (d, 2H, J = 8.79 Hz), 7.35 (d, 2H, J = 8.79). IR (KBr, cmÿ1): 3104.9, 2962.7, 2872, 1594.9, 1503.3, 1460, 1370, 1019.3, 820.6. MS (m/e): 332 (M+, 22), 317 (MÿCH3, 93), 297 (MÿCl, 8), 281 (MÿCH3ÿHCl, 23), 262 (Mÿ2Cl, 2), 183 (MÿOR, 47), 65 (Cp, 100).EA: Calcd. C, 54.09; H, 5.45; Found C, 54.64; H, 5.58. CpTiCl2(OnBu): yellow oil. yield 85.6%. 1H NMR (CDCl3, d ): 0.92 (t, 3H, J = 7.35 Hz), 1.42 (m, 2H), 1.66 (m, 2H), 4.65 (m, 2H, J = 5.60 Hz), 6.69 (s, 5H). IR (KBr, cmÿ1): 3108.7w, 2958.7, 2926.0, 2869.6, 1436.7, 1363.4, 1038.4, 860.3, 823.7. MS (m/e): 256 (M+, 12), 213 (MÿC3H7, 89), 183 (MÿOR, 100), 148 (MÿClÿOR, 39), 65 (Cp, 25). EA: Calcd. C,42.06; H, 5.49; Found C, 41.48; H, 5.21. CpTiCl2(OiBu) [12]: orange oil, yield 90%. 1H NMR (CDCl3, d ): 0.90 (d, 6H, J = 6.65 Hz), 1.9 (m, 1H), 4.40 (d, 2H, J = 6.25), 6.65 (s, 5H). IR (KBr, cmÿ1): 3108.2, 2961.3, 2926.7, 2871.2, 1465.7, 1439.3, 1388.5, 1365.4, 1043.2. MS (m/e): 256 (M+, 19), 221 (MÿCl, 46), 213 (MÿC3H7, 100), 183 (MÿOR, 74), 148 (MÿClÿOR, 30), 65 (Cp, 13), 57 (C4H9,15). EA: Calcd. C, 42.06: H, 5.49; Found C, 42.13; H, 5.52. CpTiCl2(OCH2CH1CH2): yellow oil, yield 86%. 1H NMR (CDCl3, d ): 5.08 (d, 2H, J = 4.2 Hz), 5.23 (d, 1H, J = 9.8 Hz), 5.35 (d, 1H, J = 16.4 Hz), 5.91 (m, 1H), 6.69 (s, 5H). IR (KBr, cmÿ1): 3018.6, 2912.2, 2855.2, 1644.6, 1418.9, 991.6, 850, 830. MS (m/e): 240 (M+, 20), 206 (MÿHCl+2, 35), 205 (MÿCl, 27), 204 (MÿHCl, 88), 185 (MÿOR+2, 51), 183 (MÿOR, 73), 150 (MÿClÿOR+2, 32), 147 (MÿHClÿOR, 100), 64 (CpÿH, 69), 40 (CH0CH1CH2, 46). EA: Calcd. C, 39.87; H, 4.15; Found C, 39.89; H, 4.10. MAO was produced by Witco GmbH. Styrene was puri®ed by washing several times with dilute NaOH solution, dried over anhydrous CaCl2, vacuum distillation from CaH2 and stored at ÿ208C in darkness. Toluene was distilled from sodium and diphenyl ketone under argon just before use.
Polymerization was conducted in small ampoules baked under vacuum and ¯ushed with argon several times. Styrene (2 ml), an appropriate amount of MAO in 10 ml toluene, and titanium compounds in toluene were sequentially injected. The mixtures were kept at 508C for a certain time, then terminated with 100 ml 10% HCl in EtOH, and dried under vacuum at 508C to constant weight. The melting point of polystyrene was recorded on DSC 2910 Modulated DSC Universal V1.10B TA Instruments.
3. Results and discussion Table 1 summarizes the in¯uence of the R structure on polymerization. Generally, the change of [Ti] and [Al] in the given range has little in¯uence on the syndiotacticity and the melting point of the polymer, which are in the range of 94±99.5% and 255±2608C respectively. However, the considerable decrease of the activity is observed for all the complexes tested when [Ti] is decreased from 0.42 to 0.21 mM. In all the complexes, the catalysts containing the secondary alkoxy group are apparently more active than those containing the primary alkoxy group, as can be seen from the comparison of CpTiCl2(OBun) with CpTiCl2(OBui). As aluminum is an electron-de®cient atom while oxygen is an electron-donating atom, capable of coordinating with aluminum in MAO, the oxygen in primary alkoxides coordinate much more easily to aluminum in MAO than the oxygen in the secondary alkoxides due to the steric eect. This results in a decrease of activity. Therefore, the catalysts containing more hindered alkoxy group have higher activity. When R contains an aryl, the catalyst is less active than that of its aliphatic analogs as can be seen from the comparison of CpTiCl2(OC6H4-But-p) with CpTiCl2(O-cyclohexyl). It is well-known [13±15] that TiIII cation is the active species in the syndiotactic polymerization of styrene catalyzed by half-sandwich titanocene catalysts. There is also a report that aromatic ring can coordinate to TiIII cation [16]. We believe that this coordination, which competes with the monomer, leads to the drop of activity. Also, considerable activity decrease is observed when aryl is directly linked to oxygen (Runs 5,6 and 3,4). This may be due to the electron-donating eect of aryl, which reduces the positivity of TiIII (active species) and thus is unfavorable to the coordination of monomer, and the steric eect as discussed above. Of all the complexes, CpTiCl2(O-cyclohexyl) is the most active one. Thus the in¯uence of temperature on the polymerization was studied, and the results were summarized in Table 2. It is obvious that a higher pol-
J. Liu et al. / European Polymer Journal 36 (2000) 2055±2058
2057
Table 1 Syndiotactic polymerization of styrene catalyzed by CpTiCl2 X
a b
gPS/(molTimolSh). g of 2-butanone insoluble polymer/g of bulk polymer.
ymerization temperature is unfavorable for the syndiotactic polymerization of styrene. The higher the temperature, the lower the syndiotacticity of the polystyrene. However, it is worth noting that polymer yields increase with the increase in tem-
perature although a long polymerization time is needed. At 70 and 908C, the syndiotactic polystyrene precipitates very slowly from the mixtures. It seems that syndiotactic polymerization is a fast process prohibited by high temperature, which increases the possi-
Table 2 Polymerization of styrene catalyzed by CpTiCl2(O-cyclohexyl)/MAOa under dierent temperaturesb Run
[Ti] (mM)
[Al] (M)
Al/Ti (103)
Time (h)
Temp. (8C)
Yield (g)
Ac (106)
Sd (%)
13 14 15 16
0.42 0.42 0.42 0.42
0.83 0.83 0.83 0.83
2.0 2.0 2.0 2.0
1 1 17 25
25 50 70 90
0.1504 0.2614 0.7479 0.9511
1.73 3.00 0.51 0.43
96.5 95.1 92.9 72.6
a
MAO used in this experiment is not the same batch as that in Table 1. Polymerization conditions: styrene 2 ml, [S]=1.45. c gPS/(molTimolSh). d g of 2-butanone insoluble polymer/g of bulk polymer. b
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J. Liu et al. / European Polymer Journal 36 (2000) 2055±2058
bility of atactic polymerization. The catalytic activity also decreases with the increase of temperature in the range of 50±908C due to the low polymerization rates.
Acknowledgements This project was supported by China Postdoctoral Science Foundation, National Natural Science Foundation of China (29734145 and 29871010), State Key Laboratory of Coordination Chemistry, Nanjing University.
References [1] Sinclair KB, Wilson RB. Chem Ind 1994:857. [2] Moore S. Modern Plastic International 1992:22. [3] Foster P, Chien JCW, Rausch MD. Organometallics 1996;15:2404.
[4] Kaminsky W, Lenk S, Scholz V, Roesky HW, Herzog A. Macromolecules 1997;30(25):7646. [5] Chien JCW, Salajka Z. J Polym Sci Part A: Polym Chem 1991;29(9):1243, 1253. [6] Chien JCW, Salajka Z, Dong S. Macromolecules 1992;25:3199. [7] Kucht A, Kucht H, Barry S, Chien JCW, Rausch MD. Organometallics 1993;12:3075. [8] Ishihara N, Kuramoto M, Uoi M. Macromolecules 1988;21:3356. [9] Liu J, Huang J, Qian Y, Wang F, Chan ASC. Polym Bull 1996;37:719. [10] Liu J, Huang J, Qian Y, Wang F, Chan ASC. Polym J 1997;29(2):182. [11] Fussing IMM, Plecher D, Whitby RJ. J Organomet Chem 1994;470:109. [12] Fraurenkron M, Tzavellas N, Klouras N, Raptopoulou CP. Monatsh Chem 1996;127(11):1137. [13] Grassi A, Lamberti C, Zambelli A, Mingozzi. Macromolecules 1997;30:1884. [14] Xu G, Lin S. Macromolecules 1997;30:685. [15] Grassi A, Zambelli A. Polym Prep 1996;37(2):533. [16] Scollard JC, McConville DH, Payne NC, Vittal JT. Macromolecules 1996;29:5241.