Organic Acids Used as New Ligands for Atom Transfer Radical

Chapter 16

Organic Acids Used as New Ligands for Atom Transfer Radical Polymerization Downloaded by UNIV OF GUELPH LIBRARY on August 8, 2012 | http://pubs.acs.org Publication Date: June 26, 2003 | doi: 10.1021/bk-2003-0854.ch016

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Shenmin Zhu , Deyue Yan , and Marcel Van Beylen 1

College of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China Department of Chemistry, Catholic University Leuven, Celestijnenlaan, 200F, B-3001 Heverlee, Leuven, Belgium

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Organic acids have been successfully employed as new ligands in iron-mediated A T R P and reverse A T R P . Their applications in the preparation of block copolymers, graft polymers and graft block copolymers were also investigated. The new ligands, such as isophthalic acid, iminodiacetic acid, acetic acid and succinic acid, are much cheaper than conventional ligands used previously. Furthermore, non-toxic organic acids are safer for health. The controlled radical polymerization was carried out at 25-130 °C resulting in polymers with controlled molecular weight and narrow molecular weight distribution (M /M =1.2-1.5). w

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© 2003 American Chemical Society

In Advances in Controlled/Living Radical Polymerization; Matyjaszewski, K.; ACS Symposium Series; American Chemical Society: Washington, DC, 2003.

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Downloaded by UNIV OF GUELPH LIBRARY on August 8, 2012 | http://pubs.acs.org Publication Date: June 26, 2003 | doi: 10.1021/bk-2003-0854.ch016

Introduction

Atom transfer radical polymerization (ATRP) is among the most promising approaches to controlled radical polymerization. Recent advances aimed at the design of new ligands and new metals that affect the activity and selectivity of the A T R P catalysts. The pioneering work in A T R P was reported by Matyjaszewski (1-4) who used copper as the transition-metal and bipyridine (bpy) or its derivatives as ligands, and by Sawamoto (J) who used ruthenium/organic phosphorus compounds as catalyst systems. Other catalyst systems involving different transition-metals, such as iron (6,7), nickel (8) and palladium (8) have also been reported. Iron-mediated A T R P has been successfully implemented with precise end functionality, predetermined molecular weights and low polydispersity (9). A s far as Fe catalytic system is concerned, various ligands of nitrogen, phosphorus donors and mixed coordinating ligands have been successfully used in the A T R P of styrène (10,11). However organic amines and phosphorus are harmful to human beings and are rather expensive. Recently a new kind of ligands based on organic acids was developed in our laboratory. Various acids such as acetic acid, iminodiacetic acid, succinic acid and isophthalic acid, have been successfully employed as new ligands in the ironmediated atom transfer radical polymerization of vinyl monomers, such as styrene (St) and methyl methacrylate ( M M A ) . The new ligands, i.e., organic acids, are much cheaper than conventional ligands used previously. Furthermore, non-toxic organic acids are safer for health than bpy, its derivatives and organic phosphorus compounds. The systems with different organic acids can react at 25 °C to 130 °C resulting in "living'Vcontrolled radical polymerization with relatively narrow molecular weight distribution of the resulting polymers (M /M„=1.2-1.5). The measured molecular weights are close to the calculated values for the polymerization of M M A and are somewhat lower than the theoretical ones for styrene. 11

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As we know that A T R P has been performed in various solvents (12). Vairon reported that A T R P of styrene was implemented in the presence o f a limited amount of D M F (-10 % v/v) (13). Even though block copolymers with polysulfones have been prepared in 1, 4-dimethoxybenzene (14), it is difficult to carry out A T R P of styrene in copper-mediated system using chloromethylated polysulfone as the macroinitiator which requires D M F as the solvent (>50 % v/v). Most recently, D M F was used as the solvent for A T R P of acrylonitrile (15). In our work, the catalyst of FeCl /isophthalic acid was used for the preparation of novel linear aromatic polyethersulfone (PSF)-based graft copolymers. G P C , DSC, IR, H N M R were performed to characterize the graft polymers. Aromatic polyethersulfone is attractive for the rigid characteristics of die chains and PSFbased graft copolymers are promising to be used as a sort of molecular reinforced materials. 2

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Results and Discussion A T R P of Styrene Catalyzed by FeCl /Iminodiacetic A c i d (IDA) Iminodiacetic acid (IDA) is an effective ligand for A T R P of both St and M M A with Fe as the transition metal under heterogeneous conditions. Fig. 1 shows that the measured molecular weight linearly increases with increasing monomer conversion; however the measured molecular weight is lower than the theoretical value. As shown in Fig. 1, the increase of polydispersity index with conversion is observed especially at high monomer conversion. In order to explain the reason, the polymerization of styrene with CC1 as the initiator was performed. The results are compared in Fig. 1. Although the system with a chlorine containing initiator gives polymers with higher polydispersity indices than in the system with a bromine containing initiator, M / M decreases slightly with the conversion and falls in with what is predicted for a living polymerization. It has been reported by Matyjaszewski (16) that most of chain ends of the polymer obtained are chlorinated (i.e., %R-C1: 80-90 %). Decomposition may occur more easily in R-Br system than in R - C l system due to the weaker C - X bond in the former during a long reaction time. The dehaiogenation of the minority bromine on the active chain ends may result in the minor increase of M / M with conversion. A first-order kinetic plot of the polymerization is shown in Fig. 2. The plot is almost linear, although a short induction period is observed. The short induction period may be caused by the limited solubility of the catalyst in the reaction medium. No induction period is observed in the chlorine-based system at the reaction temperature of 110 °C (Fig. 2). As it is known, usually high temperature is used to initiate the reaction employing CC1 as the initiator (17), which may sometimes result in side reactions. Therefore, M W D is broader at the beginning of the chloride-based system. The linear semilogarithmic plot of Ln([M]o/[M]) versus time indicates that the polymerization of styrene in bulk is first order with respect to the monomer and the concentration of active centers remains constant throughout the polymerization. This infers that no termination reactions occurred during the polymerization process. 2


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The end group of the resulting polystyrene with the number-average molecular weight equal to 4,100 was investigated using H N M R . The signals of the triplets at 4.4 ppm are attributed to the methine proton geminal to the halide end group. From the ratio of the peak intensity of the end group at 4.4 ppm to that of the phenyl group at 6.4-7.2 ppm, the M is calculated to be 4,500 (Fig. 3). The resulting PS with an α-halogen in the chain end can be used as a macroinitiator for block copolymerization. From the halogen terminated PS macroinitiator ( M „ P Q = 3,320, M /M„ = 1.26), PS-b-PMMA copolymer, M = 32,510, M / M = 1.51, was prepared in D M F catalyzed by FeCl /IDA. In the FT-IR spectrum of the PS-b-PMMA block copolymer, the characteristic peaks at !

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1000080006000e S


4000^ 2000* 0.0

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0.4 0.6 Conversion %

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Figure 1. Dependence of molecular weight and polydispersity on monomer conversion for ATRP of styrene in bulk, [FeClJo = [NH(CH COOH)J30 %) or temperature (>80 °C) led to significant termination. G P C traces in Fig. 10 show that the molecular weight of the copolymer increased with increasing monomer conversion. The monomodal shape of the G P C traces of the products suggests the absence of the homopolymerization. The result indicated that side reactions especially radical-radical termination were negligible even at such high temperature (100 °C) and conversion (66 %). Graft copolymerization catalyzed by FeCl /isophthalic acid in D M F was successfully performed. Downloaded by UNIV OF GUELPH LIBRARY on August 8, 2012 | http://pubs.acs.org Publication Date: June 26, 2003 | doi: 10.1021/bk-2003-0854.ch016

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Elution Volume, ml Figure 10. GPC traces ofPSF-Cl and PSF-g-PMMA graft copolymers, a. PSFCl (MKQPC = 28,440, MJM = 2.17); b. PSF-g-PMMA (M„ c = 64,900, MJM = 2.18, conversion = 23 %), c. PSF-g-PMMA (M = 96,600, MJMn =2.17, conversion = 66 %). n

>GP

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Thermal analysis reveals that there is only one glass transition temperature Tg=122 °C for the copolymer of PSF-g-PMMA (the glass-transition temperatures of P M M A and PSF are 100 and 180 °C, respectively), indicating there is no macroscopic phase separation. The H N M R spectra of the chloromethylated macroinitiator and typical graft copolymer are shown in Figure 11. In the analysis of *H N M R of the graft copolymer, the disappearance of the signals around 4.5 ppm corresponding to -CH C1 shows the complete initiation (Fig. l i b ) . Resonances at 0.8-1.1 ppm (-CH ), 3.6 ppm (-OCH ) represent the existence of M M A in the graft copolymer. So the successful formation of graft copolymers was supported by the results of *H N M R analysis. The effect of the macroinitiator concentration on the graft copolymerization catalyzed by FeCl /isophthalic acid is compiled in Table I . The polymerization was implemented as mentioned above. After 16.5 h, the reaction was stopped. When [PSF-C1] = 2.25x1ο* mol-, the graft product with M = 96,650 and M /M„ = 1.78 is obtained (see entry no. 1, in table 1). When the concentration of PSF-C1 decreases from l . B x l O " mol to 3.52xl0" mol, the molecular weight increases to 167,000 from 99,000. The various molecular weights of PSF-g!

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233 P M M A samples resulting from different macroinitiator concentrations at 110 °C are prepared. The entire peaks are monomodal, and the polydispersity index (M /M„) changes from 2.17 (macroinitiator) to 1.78, 1.83, 1.71, 1.85, respectively. It can be concluded that high temperature facilitates the graft copolymerization. w


Table I . Graft Copolymerization of M M A from PSF-C1 Catalyzed by FeCU/Isophthalic Acid with Various Concentrations of Macroinitiator* MJM [Initiator]/mol (PSF-Cl) Conversion (%) 1.78 96,650 38.5 2.25X10" 1.83 99,000 34.8 1.13x1ο 1.71 115,800 33.5 5.65xl0' 1.85 167,000 33.5 3.52xl0*[MMA] = 2.69 mole-I/', [FeCl ] = [isophthalic acid]/2 =0.0297 molel/ , at 110 °C in 71% (v/v) DMF; reaction time = 16.5 h. N

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Figure 11. H NMR spectra of chloromethylated aromatic polyethersulfone(a) and PSF-graft-PMMA φ) initiated by PSF-Cl/FeCl /isophthalic acid, MMA conversion = 66 %. 2


234 PSF-g-PBA and PSF-g-PMA Graft copolymers with elastic and glassy segments are expected to exhibit thermoplastic elastomer behavior. It is the goal of this work to synthesize graft copolymers with elastic and glassy segments such as PSF-g-PMA and PSF-g-PBA by A T R P of M A and B A using a rigid polymer (PSF-C1) as the macroinitiator. The results of GPC, H N M R , FT-IR, D S C tests illustrated the sucessful synthesis of PSF-g-PBA and PSF-g-PMA. !


Experimental Materials: Methyl methacrylate and styrene were vacuum distilled over C a H just before polymerization. Ligands were recrystallized prior to use. F e C l was washed with acetone and dried at 60 °C under vacuum before use. The initiators, 1-phenylethyl bromide and ethyl 2-bromopropionate, were used as received from Aldrich; CCI4 was distilled before polymerization. Polymerization Procedures: The general procedure of the polymerization was as follows: the catalyst, the ligand and the monomer were added to a flask with stirring; three cycles of vacuum-nitrogen are applied in order to remove oxygen; after the mixture was stirred at 25 °C for one hour, the initiator was added. Then the flask was immersed in an oil bath at the required temperature. After a given time, the flask was opened and a certain amount of tetrahydrofuran (THF) was added into the reaction system to dissolve the resulting polymer. Measurements: The monomer conversion was determined by gravimetry. Molecular weight (M„) and molecular weight distribution (MWD) were obtained by gel permeation chromatography (GPC) that was carried out with a PE200 instrument equipped with a mixed 5μ PS columns (refractive index detector). A l l samples were run in T H F at 25 °C with a flow rate of l.Ornl/min and calibrated with polystyrene standards. H N M R spectrum was recorded on a B R U K E R A V A N C E 5 0 0 500MHz N M R at room temperature in CDC1 . 2

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Conclusions Organic acids, such as isophthalic acid, iminodiacetic acid, acetic acid and succinic acid, have been successfully used as a new kind of ligands in ironmediated A T R P . They are much cheaper than conventional ligands used previously. Furthermore, organic acids of very low toxicity are safer for health. The controlled radical polymerization reactions were carried out at 25-130 °C resulting in polymers with controlled molecular weight and narrow molecular weight distribution. Commercially available PSF was modified into an A T R P macroinitiator by chloromethylation. The FeCl /isophthalic acid catalyst system can be used to 2


235 prepare the molecular reinforced materials such as PSF-g-PMMA, PSF-g-PMA and PSF-g-PBA from PSF-C1 in D M F .

References


1. 2. 3. 4. 5. 6. 7. 8.

9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23.

Wang, J. S.; Matyjaszewski, K . , J. Am. Chem. Soc. 1995, 117, 5614. Wang, J. S.; Matyjaszewski, K . , Macromolecules 1995, 28, 7901. Patten, T. E.; Xia, J.; Abernathy, T.; Matyjaszewski, K . , Science 1996, 272, 866. Xia, J.; Gaynor, S. G.; Matyjaszewski, K., Macromolecules 1997, 30, 7697. Kato, M . ; Kamigaito, M . ; Sawamoto, M . ; Higashimura, T., Macromolecules 1995, 28, 1721. Matyjaszewski, K . ; Wei, M.; X i a , J.; McDermott, Ν. E., Macromolecules 1997, 30, 8161. Teodorescu, M.; Gaynor, S. G.; Matyjaszewski, K . , Macromolecules 2000, 33, 2335. Granel, C.; Dubois, Ph.; Jérôme, R.; Teyssié, Ph., Macromolecules 1996, 29, 8576; Lecomte, P.; Drapier, I.; Dubois, Ph.; Jérôme, R.; Teyssié, Ph., Macromolecules 1997, 30, 7631. Wei, M. L.; Xia, J. H . ; Matyjaszewski, K . , Polym. Prep. 1997, 38(2), 233. Ando, T.; Kamigaito, M.; Sawamoto, M., Macromolecules 1997, 30, 4507. Moineau, G.; Granel, C.; Dubois, Ph.; Jérôme, R.; Teyssié, Ph., Macromolecules 1998, 31, 542. Matyjaszewski, K . ; Nakagawa, K . ; Jasieczek, C. G., Macromolecules 1998, 31, 1535. Pascual, S.; Coutin, B . ; Tardi, M . ; Polton, Α.; Vairon, J.-P., Macromolecules 1999, 32, 1432. Gaynor, S.; Matyjaszewski, K., Macromolecules 1997, 30, 4241. Kowalewski, T.; Tsarevsky, Ν. V.; Matyjaszewski, K . , J. Am. Chem. Soc. 2002, 124, 10632. Matyjaszewski, K . ; Shipp, D . Α.; Wang, J.; Grimaud, T.; Patten, T. E., Macromolecules 1998, 31, 6836. Matyjaszewski, K . , Macromolecules 1998, 31, 4710. Qiu, J.; Matyjaszewski, K . , Macromolecules 1997, 30, 5643. Cheng, G.; Hu, Ch.; Ying, Sh., Macromol. Rapid Commun. 1999, 20, 303. Ahmad, N. M.; Heatley, F.; Lovell, P. Α., Macromolecules 1998, 31, 2822. Wang, J.-L.; Grimaud, T.; Shipp, D., Macromolecules 1998, 31, 1527. Ziegler, M. J.; Paik, H . ; Davis, Κ. Α.; Gaynor, S. G.; Matyjaszewski, K . , Polym. Prep. 1999, 40, 432. Beers, K . L . ; Gaynor, S. G.; Matyjaszewski, K . , Macromolecules 1998, 31, 9413.


Organic Acids Used as New Ligands for Atom Transfer Radical

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