甲基丙烯酸甲酯的可逆加成断裂链转移（RAFT）的乳液聚合
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摘要
可逆加成断裂链转移(Reversible Addition-Fragmentation Chain Transfer Polymerization—RAFT)聚合是九十年末兴起的“活性”/可控自由基聚合方法之一。相对于其它“活性”自山基聚合,RAFT聚合的主要优点是:ⅰ) 可以直接应用传统自由基聚合的配方和工艺基础;ⅱ) 适用单体范围广;ⅲ) 同时还能保证较高的聚合速率。在过去的十多年中,RAFT聚合在本体、溶液体系中已经取得了很好的发展;由于乳液聚合的众多优点(环保等等)而使乳液聚合成为RAFT聚合工业化的最佳实现方式,因此人们越来越多的开始关注RAFT乳液聚合的研究。但是到目前为止,RAFT在乳液聚合中的应用仍然存在很多困难。早期的研究发现:在RAFT乳液聚合过程中会产生大量的凝聚物,以及严重的分相,并且聚合速率非常慢。本文旨在研究RAFT乳液聚合失稳的机理。
通过理论模拟发现,在乳液聚合与细乳液聚合一样,反应过程中存在乳胶粒的“超级溶胀”现象。据此我们提出乳胶粒的“超级溶胀”是活性自由基乳液聚合失稳的主要原因的假设。根据模拟结果,我们设计并研究了不同反应参数对乳液稳定性的影响。研究发现,加快引发速率,增大乳化剂浓度和增大目标分子量都能改善乳液的稳定性;这个结论与模拟结果相符,并且支持乳胶粒的“超级溶胀”是RAFT乳液聚合失稳的主要原因的假设。当乳化剂含量为10%,引发剂为氧化还原体系以及目标分子量为40000g/mol的实验条件下,可以成功地进行甲基丙烯酸甲酯(methyl methacrylate,简写为MMA)的RAFT乳液聚合,并且乳液稳定,聚合物分子量分布较窄。
另外,通过对RAFT乳液聚合反应过程中RAFT试剂在单体液滴中的浓度的测定,发现RAFT试剂比单体更容易从单体液滴中通过水相迁移到乳胶粒中,否定了质量传递是乳液失稳原因的说法。
最后,本文还对苯乙烯的RAFT乳液聚合稳定性的影响和MMA的半连续聚合进行了初步研究。
Reversible addition-fragmentation chain transfer (RAFT) polymerization is one of the living/controlled free radical polymerization techniques. Compared with other living/controlled free radical polymerization methods, major advantages of the RAFT polymerization are i) very similar recipe and processes to the traditional free radical polymerization, ii) a larger variety of monomers, and iii) higher polymerization rate.In the past decade, RAFT polymerization has been extensively investigated in bulk and solution polymerization. More recently, the research attention of the RAFT processes has been directed to emulsion/miniemulsion polymerization systems, which are commercially viable methods for implementing RAFT polymerization and environmentally benign. However, few successes of RAFT polymerization have been reported for an ab initio emulsion system. The colloidal instability is the major problem. An oily layer or very large particle size were usually observed. Poor control in molecular weigh and polydispersity index were also reported in most cases. The current thesis aims at revealing the mechanism of colloidal instability in an ab initio emulsion RAFT polymerization.Based on the theoretical simulations, we assume the superswelling occurring in Stage I of RAFT emulsion polymerization is the cause for the colloidal instability. Theoretical analysis predicts that stability of the emulsion polymerization could be improved by increasing initiation rate, surfactant level, and targeted molecular weight. The RAFT polymerization of MMA in emulsion was then experimentally investigated in order to check the predictions. The experimental results are in excellent accord with the theoretical predictions. The poor control in molecular weight and polydispersity index were found to be significantly dependent on the colloidal instability. For the first time, we demonstrated that RAFT polymerization can be successfully implemented with little coagulum, well control in molecular weight, and low polydispersity index using the same process as the traditional emulsion polymerization but with higher the surfactant levels and initiation rates.
By measuring the concentration of RAFT agents in the droplets in the early stage of the emulsion polymerization, it is evident that there is no limitation of mass transportation for RAFT agents to cross the water phase from droplets to particles. Mass transportation limitation is less likely to be the reason of the colloidal instability.The RAFT polymerization of styrene in emulsion is still colloidally unstable even with higher initiation rate and surfactant concentration. The semibatch of the RAFT polymerization of MMA in emulsion to decrease the surfactant concentration broadens the molecular weight distribution. Further investigations are needy.
通过理论模拟发现,在乳液聚合与细乳液聚合一样,反应过程中存在乳胶粒的“超级溶胀”现象。据此我们提出乳胶粒的“超级溶胀”是活性自由基乳液聚合失稳的主要原因的假设。根据模拟结果,我们设计并研究了不同反应参数对乳液稳定性的影响。研究发现,加快引发速率,增大乳化剂浓度和增大目标分子量都能改善乳液的稳定性;这个结论与模拟结果相符,并且支持乳胶粒的“超级溶胀”是RAFT乳液聚合失稳的主要原因的假设。当乳化剂含量为10%,引发剂为氧化还原体系以及目标分子量为40000g/mol的实验条件下,可以成功地进行甲基丙烯酸甲酯(methyl methacrylate,简写为MMA)的RAFT乳液聚合,并且乳液稳定,聚合物分子量分布较窄。
另外,通过对RAFT乳液聚合反应过程中RAFT试剂在单体液滴中的浓度的测定,发现RAFT试剂比单体更容易从单体液滴中通过水相迁移到乳胶粒中,否定了质量传递是乳液失稳原因的说法。
最后,本文还对苯乙烯的RAFT乳液聚合稳定性的影响和MMA的半连续聚合进行了初步研究。
Reversible addition-fragmentation chain transfer (RAFT) polymerization is one of the living/controlled free radical polymerization techniques. Compared with other living/controlled free radical polymerization methods, major advantages of the RAFT polymerization are i) very similar recipe and processes to the traditional free radical polymerization, ii) a larger variety of monomers, and iii) higher polymerization rate.In the past decade, RAFT polymerization has been extensively investigated in bulk and solution polymerization. More recently, the research attention of the RAFT processes has been directed to emulsion/miniemulsion polymerization systems, which are commercially viable methods for implementing RAFT polymerization and environmentally benign. However, few successes of RAFT polymerization have been reported for an ab initio emulsion system. The colloidal instability is the major problem. An oily layer or very large particle size were usually observed. Poor control in molecular weigh and polydispersity index were also reported in most cases. The current thesis aims at revealing the mechanism of colloidal instability in an ab initio emulsion RAFT polymerization.Based on the theoretical simulations, we assume the superswelling occurring in Stage I of RAFT emulsion polymerization is the cause for the colloidal instability. Theoretical analysis predicts that stability of the emulsion polymerization could be improved by increasing initiation rate, surfactant level, and targeted molecular weight. The RAFT polymerization of MMA in emulsion was then experimentally investigated in order to check the predictions. The experimental results are in excellent accord with the theoretical predictions. The poor control in molecular weight and polydispersity index were found to be significantly dependent on the colloidal instability. For the first time, we demonstrated that RAFT polymerization can be successfully implemented with little coagulum, well control in molecular weight, and low polydispersity index using the same process as the traditional emulsion polymerization but with higher the surfactant levels and initiation rates.
By measuring the concentration of RAFT agents in the droplets in the early stage of the emulsion polymerization, it is evident that there is no limitation of mass transportation for RAFT agents to cross the water phase from droplets to particles. Mass transportation limitation is less likely to be the reason of the colloidal instability.The RAFT polymerization of styrene in emulsion is still colloidally unstable even with higher initiation rate and surfactant concentration. The semibatch of the RAFT polymerization of MMA in emulsion to decrease the surfactant concentration broadens the molecular weight distribution. Further investigations are needy.
引文
1 Grimaldi, S.; Finet J. P.; Zeghdaoui, A.; Tordo, P.; Benoit, D.; Gnanou, Y.; Fontanille, M.; Nicol, E; Pierson, J. E Polym Prepr 1997, 38, 651-654.
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4 Chiefari, J.; Chong, Y. K.; Ercole, E; Krstina, J. Macromolecules 1998, 31, 5559-5562.
5 Chong, Y. K.; Le TPT; Moad, G.; Rizzardo, E.; Thang, S. H. Macromolecules 1999, 32, 2071-2074.
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9 Monteiro, M. J.; Sjoberg, M.; van tier Vlist, J.; Gottgens, C. M. J Polym Sci Part A: Polym Chem 2000, 38, 4206-4217.
10 Otsu, T.; Yoshida, M. Macromol Chem Rapid Commun 1982, 3, 127.
11 Otsu, T.; Matsunaga, T.; Kuriyama, A. Eur Polym J 1989, 25(7&8): 643-650.
12 Georges, M. K.; Veregin, R.; Kazmaier, P. M.; Hamer, G. K. Macromolecules 1993, 26, 2987-2988.
13 Hawker, C. J. Trend in Polymer Science 1996, 4, 183-188.
14 Wayland, B. B.; Poszmilk, G.; Mukerjec, S. L. J Am Chem Soc 1994, 116, 7943-7944.
15 Wang, J. S.; Matyjaszewski, K. J Am Chem Soc 1995, 117(20): 5614-5615.
16 Percec, V.; Barboiu, B. Macromolecules 1995, 28(23): 7970-7972.
17 Moad, G.; Chiefari, J.; Chong, Y. K.; Krstina, J.; Mayadunne, R. T. A., Postma, A..; Rizzardo, E.; Thang, S. H. Polym. Int., 2000, 49: 993-1001.
18 Matyjaszewski, K.; Davis, T. P., Handbook of radical polymerization, John Wiley and Sons, Inc., 2002;
19 Pan, G. F.; Sudol, E. D.; Dimonie V. L; El-Aasser M. S. Macromolecules 2001, 34, 481-488
20 de Brouwer, H.; Tsavalas, J. G.; Schork, F. J.; Monteiro, M. J. Macromolecules 2000, 33, 9239-9246.
21 Lansalot, M.; Davis, T. P.; Heuts, J. P. A. Macromolecules 2002, 35, 7582-7591
22 Bon, S. A. F., Bosveld, M., Klumperman, B., German, A. L., Controlled radical polymerization in emulsion, Macromolecules, 1997, 30: 324-326;
23 Apostolovie, B.; Quattrini, E.; Butte, A.; Storti, G.; Morbidelli, M. DECHEMA Monographs 2004, 138, 115-121
24 Monteiro, M. J.; Adamy, M. M.; Leeuwen, B. J.; van Herk, A. M.; Destarac, M. Macromolecules 2005, 38, 1538-1541
25 Mcleary, J. B.; Tonge, M. P.; Roos, D. D.; Sanderson, R. D.; Klumperman, B. J Polym Sci Part A: Polym Chem 2004, 42, 960-974.
26 Prescott, S. W.; Ballard, M. J.; Rizzardo, E.; Gilbert, R. G. Macromolecules 2002, 35, 5417-5425
27 Ferguson, C. J.; Hughes, R. J.; Nguyen, D.; Pham, B. T. T.; Gilbert, R. G.; Serelis, A. K.; Such, C. H.; Hawkett, B. S. Macromolecules 2005, 38, 2191-2204
28 Matyjaszewski, K.; Qui, J.; Shipp, D. A.; Gaynor, S. G. Macromol Symp 2000, 155, 15-29
29 Luo, Y. W.; Tsavalas, J.; Schork, F. J. Macromolecules 2001, 34, 5501-5507
30 Yang, L.; Luo, Y. W.; Li, B. G. Acta Polym Sinica 2004, 3, 462-464.
31 Yang L.; Luo Y. W.; Li B.G. J Polym Sci Part A: Polym Chem 2005, 43, 4972-4979
32 Luo Y. W.; Liu X. Z.; J Polym Sci Polym Chem 2004 42, 6248-6258
33 Morton, M.; Kaizerman, S.; Altier, M. W. J Colloid Sci 1954, 9, 300-312
34 Ugelstad, J.; Mork, P. C.; Kaggerud, K. H.; Ellingsen, T.; Berge, A. Adv Col Int Sci 1980, 13, 101
35 Landfester, K.; Bechthold, N.; Tiarks, F.; Antonietti, M. Macromolecules 1999, 32, 5222-5228
36 Fontenot, K. phD Dissertation, Georgia Institute of Technology, 1991
37 Odian, G. In Principles of Polymerization, 4th Ed.; Wiley: New York, 2004; p 362.
38 Odian, G. In Principles of Polymerization, 4th Ed.; Wiley: New York, 2004; p 329.
39 Chong, Y. K.; Krstina, J.;Tam, P. T. Le; Moad, G.; Postma, A.; Rizzardo, E., Thang, S. H. Macromolecules 2003, 36: 2256-2272;
40 Quinn, J. F.; Rizzardo, E.; Davis, T. P. Chem Commun 2001, 11, 1044-1045.
2 Wang, J.S.; Matyjaszwski, K. Macromolecules 1995, 28, 7901-7910.
3 Kato, M.; Kamigaito, M.; Sawamoto, M.; Higashimura, T. Macromolecules 1995, 28, 172 1-1723.
4 Chiefari, J.; Chong, Y. K.; Ercole, E; Krstina, J. Macromolecules 1998, 31, 5559-5562.
5 Chong, Y. K.; Le TPT; Moad, G.; Rizzardo, E.; Thang, S. H. Macromolecules 1999, 32, 2071-2074.
6 Uzulina, I.; Kanagasabapathy, S.; Claverie, J. Macromol Syrup 2000, 150, 33-38.
7 Monteiro, M. J.; Hodgson, M.; de Brouwer, H. J. Polym Sci Part A: Polym Chem 2000, 38, 3864-3874
8 Monteiro, M. J.; de Barbeyrac, J. Macromolecules 2001, 34, 4416-4423.
9 Monteiro, M. J.; Sjoberg, M.; van tier Vlist, J.; Gottgens, C. M. J Polym Sci Part A: Polym Chem 2000, 38, 4206-4217.
10 Otsu, T.; Yoshida, M. Macromol Chem Rapid Commun 1982, 3, 127.
11 Otsu, T.; Matsunaga, T.; Kuriyama, A. Eur Polym J 1989, 25(7&8): 643-650.
12 Georges, M. K.; Veregin, R.; Kazmaier, P. M.; Hamer, G. K. Macromolecules 1993, 26, 2987-2988.
13 Hawker, C. J. Trend in Polymer Science 1996, 4, 183-188.
14 Wayland, B. B.; Poszmilk, G.; Mukerjec, S. L. J Am Chem Soc 1994, 116, 7943-7944.
15 Wang, J. S.; Matyjaszewski, K. J Am Chem Soc 1995, 117(20): 5614-5615.
16 Percec, V.; Barboiu, B. Macromolecules 1995, 28(23): 7970-7972.
17 Moad, G.; Chiefari, J.; Chong, Y. K.; Krstina, J.; Mayadunne, R. T. A., Postma, A..; Rizzardo, E.; Thang, S. H. Polym. Int., 2000, 49: 993-1001.
18 Matyjaszewski, K.; Davis, T. P., Handbook of radical polymerization, John Wiley and Sons, Inc., 2002;
19 Pan, G. F.; Sudol, E. D.; Dimonie V. L; El-Aasser M. S. Macromolecules 2001, 34, 481-488
20 de Brouwer, H.; Tsavalas, J. G.; Schork, F. J.; Monteiro, M. J. Macromolecules 2000, 33, 9239-9246.
21 Lansalot, M.; Davis, T. P.; Heuts, J. P. A. Macromolecules 2002, 35, 7582-7591
22 Bon, S. A. F., Bosveld, M., Klumperman, B., German, A. L., Controlled radical polymerization in emulsion, Macromolecules, 1997, 30: 324-326;
23 Apostolovie, B.; Quattrini, E.; Butte, A.; Storti, G.; Morbidelli, M. DECHEMA Monographs 2004, 138, 115-121
24 Monteiro, M. J.; Adamy, M. M.; Leeuwen, B. J.; van Herk, A. M.; Destarac, M. Macromolecules 2005, 38, 1538-1541
25 Mcleary, J. B.; Tonge, M. P.; Roos, D. D.; Sanderson, R. D.; Klumperman, B. J Polym Sci Part A: Polym Chem 2004, 42, 960-974.
26 Prescott, S. W.; Ballard, M. J.; Rizzardo, E.; Gilbert, R. G. Macromolecules 2002, 35, 5417-5425
27 Ferguson, C. J.; Hughes, R. J.; Nguyen, D.; Pham, B. T. T.; Gilbert, R. G.; Serelis, A. K.; Such, C. H.; Hawkett, B. S. Macromolecules 2005, 38, 2191-2204
28 Matyjaszewski, K.; Qui, J.; Shipp, D. A.; Gaynor, S. G. Macromol Symp 2000, 155, 15-29
29 Luo, Y. W.; Tsavalas, J.; Schork, F. J. Macromolecules 2001, 34, 5501-5507
30 Yang, L.; Luo, Y. W.; Li, B. G. Acta Polym Sinica 2004, 3, 462-464.
31 Yang L.; Luo Y. W.; Li B.G. J Polym Sci Part A: Polym Chem 2005, 43, 4972-4979
32 Luo Y. W.; Liu X. Z.; J Polym Sci Polym Chem 2004 42, 6248-6258
33 Morton, M.; Kaizerman, S.; Altier, M. W. J Colloid Sci 1954, 9, 300-312
34 Ugelstad, J.; Mork, P. C.; Kaggerud, K. H.; Ellingsen, T.; Berge, A. Adv Col Int Sci 1980, 13, 101
35 Landfester, K.; Bechthold, N.; Tiarks, F.; Antonietti, M. Macromolecules 1999, 32, 5222-5228
36 Fontenot, K. phD Dissertation, Georgia Institute of Technology, 1991
37 Odian, G. In Principles of Polymerization, 4th Ed.; Wiley: New York, 2004; p 362.
38 Odian, G. In Principles of Polymerization, 4th Ed.; Wiley: New York, 2004; p 329.
39 Chong, Y. K.; Krstina, J.;Tam, P. T. Le; Moad, G.; Postma, A.; Rizzardo, E., Thang, S. H. Macromolecules 2003, 36: 2256-2272;
40 Quinn, J. F.; Rizzardo, E.; Davis, T. P. Chem Commun 2001, 11, 1044-1045.