- Email: [email protected]
Characterization and optimization of poly(glycidyl methacrylate-co-styrene) synthesized by atom transfer radical polymerization
European Polymer Journal 44 (2008) 4082–4091
Contents lists available at ScienceDirect
European Polymer Journal journal homepage: www.elsevier.com/locate/europolj
Characterization and optimization of poly(glycidyl methacrylate-co-styrene) synthesized by atom transfer radical polymerization A.S. Brar *, Ashok Kumar Goyal Department of Chemistry, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110 016, India
a r t i c l e
i n f o
Article history: Received 27 March 2008 Received in revised form 2 September 2008 Accepted 15 September 2008 Available online 20 September 2008
Keywords: Atom transfer radical polymerization (ATRP) NMR Copolymerization Styrene Glycidyl methacrylate
a b s t r a c t Styrene (S) and glycidyl methacrylate (GMA) copolymers were synthesized by atom transfer radical polymerization (ATRP) under different conditions. The effect of initiators, ligands, solvents, and temperature to the linear first-order kinetics and polydispersity index (PDI) was investigated for bulk polymerization. First-order kinetics was observed between linearly increasing molecular weight versus conversion and low polydispersities (PDI) were achieved for ethyl 2-bromo isobutyrate (EBiB) as an initiator and N,N0 ,N0 ,N00 ,N00 -pentamethyldiethylenetriamine (PMDETA)/CuBr as a catalyst. The copolymers with different compositions were synthesized using different in-feed ratios of monomers. Copolymers composition was calculated from 1H NMR spectra which were further confirmed by quantitative 13C{1H} NMR spectra. The monomer reactivity ratios were obtained with the help of Mayo–Lewis equation using genetic algorithm method. The values of reactivity ratios for glycidyl methacrylate and styrene monomers are rG = 0.73 and rS = 0.42, respectively. Ó 2008 Published by Elsevier Ltd.
1. Introduction The advent of controlled/living radical polymerization (CRP) has gain vast attention of the synthetic polymer scientists [1–2]. Controlled radical polymerization methods [3–9] are frequently used to synthesize polymeric systems with well defined molecular weights, mass distributions, end groups and controlled chain topologies. Among the various methods of controlled/living radical polymerization, atom transfer radical polymerization (ATRP) is an useful polymerization technique for the polymerization of a wide variety of monomers [10–19] along with a number of functional monomers [20–25]. Functionalized copolymers are industrially important because of synthetic potential due to cross linking reactions, chain extensions and preparation of block and graft copolymers. Glycidyl methacrylate (GMA) is a commercially interesting functional monomer because of the presence of epoxy group, * Corresponding author. Tel.: +91 11 26591377; fax: +91 11 25195693. E-mail address: [email protected] (A.S. Brar). 0014-3057/$ - see front matter Ó 2008 Published by Elsevier Ltd. doi:10.1016/j.eurpolymj.2008.09.013
which permits a large number of reactions [26–27]. The copolymers based on GMA have great significance in advanced biotechnology [28–30] by easy conversion of epoxy group in various functional groups. Moreover, homogenous and heterogeneous polymer networks can be prepared by GMA, which are used in coatings, matrix resins and adhesives [31–33]. From last few years, many researchers are trying to optimize ATRP conditions for various monomers. Matyjaszewki et al. [34] shows that polymerization in the presence of multidentate alkyl amine ligands such as N,N,N0 ,N00 ,N00 -pentamethyldiethylenetriamine (PMDETA) were found to proceed at faster rate and low temperature. They also show that copper bromide and chloride complexes with Me6-TREN were highly active toward acrylates and methacrylates [35]. Optimization of catalyst based on PMDETA has recently been described for methacrylates [36] and acrylates [37–38]. Lu et al. [16] have reported the atom transfer radical polymerization of styrene initiated by triphenylmethyl chloride. They investigated the effect of catalyst complex,
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091
solvent, temperature, and concentration of initiating system. Fuente et al. [23] demonstrated that atom transfer radical polymerization of GMA using ethyl bromoisobutyrate, PMDETA and CuCl in toluene and diphenyl ether at 30 and 50 °C proceeded in a controlled manner. FernandezGarcia et al. [24] performed ATRP of GMA/butyl acrylate yielding well defined statistical copolymers. Krishnan and Shrinivasan [25] reported a detailed study of the kinetics and characterization of poly(glycidyl methacrylate) obtained by ATRP. They performed the homopolymerization reactions using CuX/N-alkyl-2-pyridyl methanimine as a catalyst at ambient temperature. They investigated that poly glycidyl methacrylate is particularly sensitive to different components of polymerization, such as an initiator, catalyst, and the solvent. Considering the above-mentioned study and certain limitations found in controlled radical polymerization, the goal of present work is to explore the suitable reaction conditions for controlled copolymerization of GMA and styrene by ATRP, using copper based catalyst system. The effect of various reaction parameters i.e. nature of ligands, initiators, solvents and variation in temperature for controllability of living radical bulk copolymerization of GMA with styrene are investigated.
2. Experimental 2.1. Materials The monomers, glycidyl methacrylate (GMA, 99%, Fluka) and styrene (St, 99%, Merck, Germany) were dried over CaH2 and polymerization inhibitor was removed by vacuum distillation and kept below 5 °C before use. Methyl 2-bromopropionate (MBP, 98%), ethyl 2-bromoisobutyrate (EBiB, 98%), N,N,N0 ,N0 ,N00 -pentamethyldiethylenetriamine (PMDETA, 99%), N,N,N0 ,N0 ,N00 ,N00 -hexamethyltriethylenetetramine (HMTETA, 99%), tris (2-aminoethyl)-amine, (TREN, 96%), CuBr (99%), and 4,40 -dinonyl-2,20 -dipyridyl (dNbpy, 97%) were purchased from Aldrich and used as received. Benzyl chloride (BzCl, 98%) was purchased from CDH India. 2.2. Copolymerization Copolymers of glycidyl methacrylate (GMA) and styrene were synthesized with different in-feed ratios of monomers under ATRP conditions. All copolymerization reactions were performed using copper based catalyst (CuBr/ligand complex) and various initiators under nitrogen atmosphere. For synthesis of copolymers, a stock solution containing the calculated amount of monomer and ligand along with CuBr was prepared and sealed with rubber septum. The solution was degassed by three vacuum-nitrogen cycles and stirred at room temperature. The calculated amount of an initiator was then added to solution with a syringe and the solution was again purged with nitrogen. Finally the flask containing solution was kept in oil bath and maintained at desired temperature. The solution becomes progressively viscous, indicating the onset of polymerization. The solution was then taken
4083
out at different interval of time to observe the change in molecular weight and polydispersity Index (PDI) with conversion. The reaction was quenched by diluting with tetrahydrofuran (THF) and subsequently passed through a neutral alumina column to remove the catalyst. The solution was then concentrated and precipitated in methanol. The precipitated copolymers were further purified by dissolving in chloroform and precipitating in methanol and finally dried under vacuum at 50 °C until constant weight was reached. 2.3. Characterization Total monomer conversion was measured gravimetrically. The molecular weight (Mn) and polydispersity index (PDI, Mw/Mn) of synthesized copolymers were determined using gel permeation chromatography (GPC) equipped with a Hitachi L-2130 pump with Waters column and a Hitachi L-2490 RI detector against polystyrene standards. HPLC grade THF was used as an eluent at the flow rate of 0.5 mL/min at room temperature. Copolymers composition was calculated using 1H and quantitative 13C{1H} NMR spectra. NMR spectra were recorded at 25 °C on Bruker DPX-300 NMR spectrometer in about 10% polymer solutions using CDCl3 as a solvent. The Quantitative 13C{1H} NMR spectra were recorded with 12 s delay time and using tris(acetylacetonato)chromium(III) [Cr(acac)3] as a relaxing agent. The intensities of various NMR signals were measured from the integrated peak areas calculated with an electronic integrator.
3. Results and discussion 3.1. Composition and reactivity ratios determination The composition of GMA/St copolymers with different percent conversion were determined with the help of 1H NMR spectra (Fig. 1a). The relative areas of aromatic protons (I1) and aliphatic proton (I2) resonances were calculated and then composition of GMA/St copolymers was calculated. The compositions were further confirmed by quantitative 13C{1H} NMR spectra (Fig. 1b). The variation of copolymers composition (FGMA) as a function of percent conversion for three different in-feed compositions (fGMA) of GMA/St copolymers are shown in Table 1. Monomer reactivity ratios for GMA/St copolymers were optimized using this copolymer composition data. The reactivity ratios for GMA/St comonomers were calculated using non linear genetic algorithm method [39]. The values of reactivity ratios were found to be rGMA = 0.73 and rSt = 0.42, respectively, which are close to the reported values [40]. Theoretical copolymers composition, percent conversion and theoretical molecular weight calculations were done using reactivity ratios by the methodology described previously [41]. 3.2. Optimization of ATRP conditions The copolymerization of GMA with styrene was carried out in molar ratios of 1:1. The effect of various components
4084
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091
Fig. 1. (a) 1H and (b)
13
C{1H} NMR spectra of GMA/St copolymer (FGMA = 0.54) in CDCl3 at 25 °C.
Table 1 GMA molar fraction in-feed (fGMA), conversions and GMA compositions (FGMA,Theo. and FGMA,NMR) for GMA/St copolymers prepared by ATRP at 60 °C in bulk fGMA
Conversion (%)
FGMA,
0.25
8 30 43 57 67
0.37 0.36 0.34 0.33 0.32
0.39 0.36 0.36 0.34 0.32
1140 3725 5237 6847 7982
1250 3825 5375 7000 8150
1.29 1.26 1.28 1.23 1.20
0.50
12 32 46 59 79
0.55 0.55 0.54 0.54 0.53
0.56 0.54 0.54 0.54 0.53
1697 4195 5938 7551 10,015
1800 4325 6100 7725 10,200
1.31 1.26 1.27 1.24 1.22
0.75
17 42 60 71 87
0.73 0.74 0.74 0.74 0.74
0.74 0.74 0.75 0.75 0.75
2440 5745 8128 9587 11,715
2700 5950 8300 9750 12,000
1.35 1.30 1.26 1.27 1.25
Theo.
FGMA,
NMR
Theo. M. Wt.
Mn GPC
PDIMw/Mn
[GMA + St]0/[EBiB]0 = 100:1 and [EBiB]0/[CuBr]0/[PMDETA]0 = 1:0.5:0.5.
of ATRP (ligands, initiators, solvents, and variation in temperature) were examined to achieve controlled copolymerization in bulk.
3.2.1. Effect of ligand The catalyst is of prime importance for the success of ATRP because it determines the position of atom transfer
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091
equilibrium and the dynamics of exchange between active and dormant species. On the basis of literature survey, CuBr/nitrogenous ligands are extensively used as the catalysts. The role of ligand in ATRP is to solubilize the Cu salts and to tune the Cu catalyst activity. The choice of ligand greatly influences the effectiveness of catalyst. To select good ligand for copolymerization of GMA and styrene, the initial copolymerization was performed with a [Monomer]/[Initiator] molar ratio of 100:1 with CuBr/ligand (dNbpy, PMDETA, HMTETA, and TREN) as a catalyst in molar ratio of 0.5/0.5 in bulk at 60 °C. The molecular weight evolution (Mn) and polydispersity index (PDI) as a function of percent conversion for three different ligands (PMDETA, HMTETA, and TREN) are shown in Fig. 2. It was observed that no polymerization takes place with dNbpy even after 48 h. On increasing the polymerization temperature up to 80 °C, percent conversion had reached only 8% in 48 h, while the linear increase in molecular weights with percent conversion was observed in case of PMDETA, HMTETA, and TREN (Fig. 2b). Molecular weights are in good agreement with predicted molecular weights when the polymerization was carried out using PMDETA or HMTETA as ligands, while higher values than the predicted values are found in case of TREN. The straight lines were obtained on plotting ln[M]0/[M] vs. time for PMDETA and HMTETA which follow the first-order kinetics, while a significant curvature was observed in case of TREN (Fig. 2a). This observation indicates that active catalyst was formed when PMDETA or HMTETA were used as ligand while radical coupling and termination reactions takes place in case of TREN, which results in low catalytic efficiency. The low values of polydispersities were also found when PMDETA or HMTETA used as a ligand, while higher PDI was observed in case of TREN (Fig. 2c). The above observation can be explained on the basis of number of nitrogen atom present in the ligands. The Cu complexes formed with multidentate alkyl amine ligands promote ATRP more successfully as compare to mono or bi-dentate ligands. Therefore when bipyridine is used as a ligand the polymerization is not efficient, because of less catalytic efficiency as compare to PMDETA, HMTETA, and TREN. Furthermore in case of TREN, three primary amine groups are present as compare to HMTETA and PMDETA, which reduces the catalytic activity of Cu complex. Therefore the complex formed with CuBr as metal halide and PMDETA or HMTETA as ligands give ATRP significantly. 3.2.2. Effect of Initiator The selection of a good initiator is most important factor for successful ATRP. Matyjaszewski and coworkers [42–43] had outlined ten general guidelines for selection of efficient initiators. They suggested that the initiators should be structurally similar to those of monomers. Keeping this in mind, polymerizations were done by changing initiating systems and maintaining the other conditions constant. No polymerization was observed in the presence of (2-bromoethyl) benzene. The results obtained with 2bromopropionate (MBP), 2-bromoisobutyrate (EBiB), and benzyl chloride (BzCl) as an initiators are shown in Fig. 3. In all cases, molecular weight of copolymers initiated by different initiators increased linearly with percent conver-
4085
sion, which indicates the presence of constant concentration of growing chains through out the reaction. A comparison of semilogarithmic plot between ln[M]0/[M] vs. time show different rate of polymerizations for different initiating systems (Fig. 3a). The polymerization rate is fastest for MBP and slowest for benzyl chloride. The plot shows the linear relation for MBP and EBiB but deviation from linearity was observed in case of benzyl chloride, indicates the presence of termination reactions. On comparing the experimental molecular weight with predicted molecular weight vs. conversion, the results were found in good agreement with EBiB, while in case of MBP, experimental molecular weights are little more than predicted values but a large difference was observed in case of benzyl chloride (Fig. 3b). The low values of polydispersities were also observed for EBiB and MBP (Fig. 3c). The above observations can be explained from the stability of free radicals formed by initiators, i.e. less stable free radicals have more chances to undergo controlled polymerization and vice versa. Free radicals generated from (2-bromoethyl) benzene and benzyl chloride are more stable than generated from MBP and EBiB, due to presence of benzene ring adjacent to radical site. In the case of (2-bromoethyl) benzene, resulting free radical is secondary which is more stable than primary free radical formed in case of benzyl chloride. Therefore no polymerization was observed when initiated by (2-bromoethyl) benzene. Furthermore the free radicals formed with EBiB are structurally more similar to monomer as compare to MBP, so polymerization with EBiB as an initiating system proceeds in a controlled manner. Therefore, controllability of the polymerization can be ranked for initiators as: EBiB > MBP > benzyl chloride > (2-bromoethyl) benzene. 3.2.3. Effect of solvent To optimize the solvent effect, copolymerization was performed in dimethylformamide (DMF) and toluene (monomer:solvent::1:1). It was observed that in presence of DMF as a solvent, initially polymerization started and proceeds up to 13% conversion till 75 h after that no further increase in percentage conversion was observed. In presence of toluene, polymerization proceeds significantly and copolymers with low polydispersity and expected molecular weights were obtained as in bulk polymerization (Fig. 4). The polymerization rate is faster in bulk than toluene as a solvent while polymerization rate is very slow in DMF which becomes stable after 75 h and copolymer with high polydispersity was formed. Therefore copolymerization could not proceed significantly in DMF as in bulk and toluene. It has been suggested that suitable solvent may increase the solubility of catalyst, but in present work, solubility of catalyst should not be crucial, because the polymerization proceeds successfully in bulk and solvents with low polarity but not significantly in DMF and other solvents with high polarity. 3.2.4. Effect of polymerization temperature To investigate the effect of temperature, copolymerization was carried out at different temperatures. The resulted kinetics and the dependence of molecular weight (Mn) and polydispersity index (PDI) on percent conversion are
4086
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091
Fig. 2. (a) Variation of ln([M]0/[M]) with reaction time, (b) Mn,GPC (dotted line indicates the theoretical number-average molecular weight) and (c) polydispersities (Mw/Mn) with percent conversion for ATRP of GMA/St at 60 °C in bulk using different ligands. [GMA + St]0/[EBiB]0 = 100:1 and [EBiB]0/ [CuBr]0/[Ligand]0 = 1:0.5:0.5.
shown in Fig. 5. The plot between ln([M]0/[M]) vs. time at different temperature from 40 to 80 °C shows first-order
linearity, which shows that polymerization is a first-order with respect to monomer and the concentration of growing
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091
4087
Fig. 3. (a) Variation of ln([M]0/[M]) with reaction time, (b) Mn,GPC (dotted line indicates the theoretical number-average molecular weight) and (c) polydispersities (Mw/Mn) with percent conversion for ATRP of GMA/St at 60 °C in bulk using different Initiators. [GMA + St]0/[Initiator]0 = 100:1 and [Initiator]0/[CuBr]0/[PMDETA]0 = 1:0.5:0.5.
4088
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091
Fig. 4. (a) Variation of ln([M]0/[M]) with reaction time, (b) Mn,GPC (dotted line indicates the theoretical number-average molecular weight) and (c) polydispersities (Mw/Mn) with percent conversion for ATRP of GMA/St at 60 °C in different solvents. [GMA + St]0/[EBiB]0 = 100:1, [EBiB]0/[CuBr]0/ [PMDETA]0 = 1:0.5:0.5 and [monomer]/[solvent] = 1:1.
radicals remains constant. The rate of polymerization increases with increase of temperature, indicates that induction period get shortened by increasing temperature.
The molecular weights increase with increase of conversion, but the values are higher than the predicted values at temperature 40 °C and 80 °C which indicates the lower
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091
4089
Fig. 5. (a) Variation of ln([M]0/[M]) with reaction time, (b) Mn,GPC (dotted line indicates the theoretical number-average molecular weight) and (c) polydispersities (Mw/Mn) with percent conversion for ATRP of GMA/St in bulk at different temperatures. [GMA + St]0/[EBiB]0 = 100:1 and [EBiB]0/[CuBr]0/ [PMDETA]0 = 1:0.5:0.5.
initiation efficiencies. On comparing the polydispersities at different temperature, it was observed that at 60 °C, polydispersities are lower than at 40 °C and 80 °C (Fig. 5c). It
was also observed that polydispersity decreases with percent conversion at 60 °C while there is no order of PDI at 40 °C and 80 °C. This observation may imply the participa-
4090
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091
tion of side reactions (chain transfer or termination reactions) with increasing temperature and low initiation efficiency at low temperature. 4. Conclusion The Atom transfer radical copolymerization of glycidyl methacrylate and styrene was performed successfully using EBiB as an initiator and CuBr/PMDETA as a catalyst in bulk and toluene as a solvent at 60 °C. The reaction followed a first-order kinetic with respect to monomer concentration, indicating a constant concentration of the propagating radical, low polydispersities (Mw/Mn < 1.3), and efficient control over Mn. The investigation about the effect of various ATRP components show that ligand, initiator and the solvent are crucial parameters for the polymerization. The increase of temperature not only increases the rate of polymerization, but also shortens the induction period. Acknowledgment The author (Ashok Kumar Goyal) thanks to the Department of Science and Technology (DST), New Delhi, India, for providing financial support to carry out this work. References [1] Matyjaszewski, K. Controlled radical polymerization; ACS Symposium series 685. Washington DC: Am Chem Soc; 1998. [2] Matyjaszewski K. Controlled/living radical polymerization: progress in ATRP, NMP and RAFT; ACS Symposium series 768. Washington DC: Am Chem Soc; 2000. [3] Matyjaszewski K, Xia J. Atom transfer radical polymerization. Chem Rev 2001;101:2921–90. [4] Kamigaito M, Ando T, Sawamoto M. Metal-catalyzed living radical polymerization. Chem Rev 2001;101:3689–746. [5] Hawker CJ, Bosman AW, Harth E. New polymer synthesis by nitroxide mediated living radical polymerizations. Chem Rev 2001;101:3661–88. [6] Chiefari J, Chong YK, Ercole F, Krstina J, Jeffery J, Le TPT, et al. Living free-radical polymerization by reversible addition-fragmentation chain transfer: the RAFT process. Macromolecules 1998;31: 5559–62. [7] Mayadunne RTA, Rizzardo E, Chiefari J, Chong YK, Moad G, Thang SH. Living radical polymerization with reversible addition-fragmentation chain transfer (RAFT polymerization) using dithiocarbamates as chain transfer agents. Macromolecules 1999;32:6977–80. [8] Moineau G, Dubois Ph, Jerome R, Senninger T, Teyssie Ph. Alternative atom transfer radical polymerization for MMA using FeCl3 and AIBN in the presence of triphenylphosphine: an easy way to wellcontrolled PMMA. Macromolecules 1998;31:545–7. [9] Wang JS, Matyjaszewski K. Living/controlled radical polymerization. Transition-metal-catalyzed atom transfer radical polymerization in the presence of a conventional radical initiator. Macromolecules 1995;28:7572–3. [10] Miura Y, Satoh T, Narumi A, Nishizawa O, Okamoto Y, Kakuchi T. Atom transfer radical polymerization of methyl methacrylate in fluoroalcohol: simultaneous control of molecular weight and tacticity. Macromolecules 2005;38:1041–3. [11] Munoz-Bonilla A, Madruga EL, Fernandez-Garcia M. Atom transfer radical polymerization of cyclohexyl methacrylate at a low temperature. J Polym Sci Part A: Polym Chem 2005;43:71–7. [12] Demirelli K, Coskun M, Kaya E. Polymers based on benzyl methacrylate: synthesis via atom transfer radical polymerization, characterization, and thermal stabilities. J Polym Sci Part A: Polym Chem 2004;42:5964–73. [13] Brar AS, Kaur S. Tetramethylguanidino-tris(2-aminoethyl)amine: a novel ligand for copper-based atom transfer radical polymerization. J Polym Sci Part A: Polym Chem 2005;43:5906–22.
[14] Hua D, Bai R, Lu W, Pan C. Dithiocarbamate mediated controlled/ living free radical polymerization of methyl acrylate under 60Co cray irradiation: conjugation effect of N-group. J Polym Sci Part A: PolymChem 2004;42:5670–7. [15] Venkatesh R, Vergouwen F, Klumperman B. Atom transfer radical copolymerization of a-olefins with methyl acrylate: determination of activation rate parameters. Macromol Chem Phys 2005;206:547–52. [16] Xu Y, Lu J, Xu Q, Wang L. Atom transfer radical polymerization of styrene initiated by triphenylmethyl chloride. Eur Polym J 2005;41:2422–7. [17] Denizli BK, Lutz JF, Okrasa L, Pakula T, Guner A, Matyjaszewski K. Properties of well-defined alternating and random copolymers of methacrylates and styrene prepared by controlled/living radical polymerization. J Polym Sci Part A: Polym Chem 2005;43:3440–6. [18] Lutz JF, Matyjaszewski K. Kinetic modeling of the chain-end functionality in atom transfer radical polymerization. Macromol Chem Phys 2002;203:1385–95. [19] Lazzari M, Chiantore O, Mendichi R, Lopez-Quintela MA. Synthesis of polyacrylonitrile-block-polystyrene copolymers by atom transfer radical polymerization. Macromol Chem Phys 2005;206:1382–8. [20] Robinson KL, Khan MA, de Banez MV, Wang XS, Armes SP. Controlled polymerization of 2-hydroxyethyl methacrylate by ATRP at ambient temperature. Macromolecules 2001;34:3155–8. [21] Beers KL, Boo S, Gaynor SG, Matyjaszewski K. Atom transfer radical polymerization of 2-hydroxyethyl methacrylate. Macromolecules 1999;32:5772–6. [22] Kickelbick G, Paik HJ, Matyjaszewski K. Immobilization of the copper catalyst in atom transfer radical polymerization. Macromolecules 1999;32:2941–7. [23] Canamero PF, Fuente JL, Madruga EL, Fernandez-Garcia M. Atom transfer radical polymerization of glycidyl methacrylate: a functional monomer. Macromol Chem Phys 2004;205:2221–8. [24] Fuente JL, Canamero PF, Fernandez-Garcia M. Synthesis and characterization of glycidyl methacrylate/butyl acrylate copolymers obtained at a low temperature by atom transfer radical polymerization. J Polym Sci Part A: Polym Chem 2006;44: 1807–16. [25] Krishnan R, Srinivasan KSV. Controlled/living radical polymerization of glycidyl methacrylate at ambient temperature. Macromolucules 2003;36:1769–71. [26] May CA. Epoxy resins chemistry and technology. New York: Marcel Dekker; 1988. [27] Chen Z, Bao H, Liu J. Synthesis of a well-defined epoxy copolymer by atom transfer radical polymerization. J Polym Sci Part A: Polym Chem 2001;39:3726–32. [28] Kalal J. Epoxy and aldehyde polymers as reagents. J Polym Sci Polym Symp 1978;62:251–70. [29] Kovar J, Navratilova M, Skursky L. Immobilization of horse liver alcohol dehydrogenase on copolymers of glycidyl methacrylate and ethylene dimethacry late. Biotechnol Bioeng 1982;24:837–45. [30] Jones RG, Yoon S, Nagasaki Y. Facile synthesis of epoxystyrene and its copolymerisations with styrene by living free radical and atom transfer radical strategies. Polymer 1999;40:2411–8. [31] Vijayaraghavan PG, Reddy BSR. 4-Chlorophenyl acrylate and glycidyl methacrylate copolymers: Synthesis, characterization, reactivity ratios, and application. J Macromol Sci Pure Appl Chem 1999;36: 1181–95. [32] Godwin GG, Selvamalar CSJ, Penlidis A, Nanjundan S. Homopolymer of 4-propanoylphenyl methacrylate and its copolymers with glycidyl methacrylate: synthesis, characterization, reactivity ratios and application as adhesives. React Funct Polym 2004;59:197–209. [33] Zhang X, Tanaka H. Copolymerization of glycidyl methacrylate with styrene and applications of the copolymer as paper-strength additive. J Appl Polym Sci 2001;80:334–9. [34] Xia J, Matyjaszewski K. Controlled/living radical polymerization. Atom transfer radical polymerization using multidentate amine ligands. Macromolecules 1997;30:7697–700. [35] Xia J, Gaynor SG, Matyjaszewski K. Controlled/living radical polymerization. Atom transfer radical polymerization of acrylates at ambient temperature. Macromolecules 1998;31:5958–9. [36] Davis KA, Matyjaszewski K. Investigation of the ATRP of n-butyl methacrylate using the Cu(I)/N, N, N0 , N00 , N00 -pentamethyldiethylenetriamine catalyst system. Chinese J Polym Sci 2004;22: 195–204. [37] Nanda AK, Matyjaszewski K. Effect of [PMDETA]/[Cu(I)] ratio, monomer, solvent, counterion, ligand, and alkyl bromide on the activation rate constants in atom transfer radical polymerization. Macromolecules 2003;36:1487–93.
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091 [38] Hung J, Pintauer T, Matyzajaszewski K. Effect of variation of [PMDETA]0/[Cu(I)Br]0 ratio on atom transfer radical polymerization of n-butyl acrylate. J Polym Sci Part A: Polym Chem 2004;42:3285–92. [39] Brar AS, Singh G, Shankar R. Analysis of quaternary carbon resonances of vinylidene chloride/methyl acrylate copolymers. Eur Polym J 2004;40:2679–88. [40] Brar AS, Yadav A, Hooda S. Characterization of glycidyl methacrylate/ styrene copolymers by one- and two-dimensional NMR spectroscopy. Eur Polym J 2002;38:1683–90.
4091
[41] Brar AS, Saini T. Atom transfer radical copolymerization of acrylonitrile and ethyl methacrylate at ambient temperature. J Polym Sci Part A: Polym Chem 2006;44:1975–84. [42] Wang JL, Grimaud T, Shipp DA, Matyjaszewski K. Controlled/ living atom transfer radical polymerization of methyl methacrylate using various initiation systems. Macromolecules 1998;31: 1527–34. [43] Ambade AV, Kumar A. Controlling the degree of branching in vinyl polymerization. Prog Polym Sci 2000;25:1141–70.
Contents lists available at ScienceDirect
European Polymer Journal journal homepage: www.elsevier.com/locate/europolj
Characterization and optimization of poly(glycidyl methacrylate-co-styrene) synthesized by atom transfer radical polymerization A.S. Brar *, Ashok Kumar Goyal Department of Chemistry, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110 016, India
a r t i c l e
i n f o
Article history: Received 27 March 2008 Received in revised form 2 September 2008 Accepted 15 September 2008 Available online 20 September 2008
Keywords: Atom transfer radical polymerization (ATRP) NMR Copolymerization Styrene Glycidyl methacrylate
a b s t r a c t Styrene (S) and glycidyl methacrylate (GMA) copolymers were synthesized by atom transfer radical polymerization (ATRP) under different conditions. The effect of initiators, ligands, solvents, and temperature to the linear first-order kinetics and polydispersity index (PDI) was investigated for bulk polymerization. First-order kinetics was observed between linearly increasing molecular weight versus conversion and low polydispersities (PDI) were achieved for ethyl 2-bromo isobutyrate (EBiB) as an initiator and N,N0 ,N0 ,N00 ,N00 -pentamethyldiethylenetriamine (PMDETA)/CuBr as a catalyst. The copolymers with different compositions were synthesized using different in-feed ratios of monomers. Copolymers composition was calculated from 1H NMR spectra which were further confirmed by quantitative 13C{1H} NMR spectra. The monomer reactivity ratios were obtained with the help of Mayo–Lewis equation using genetic algorithm method. The values of reactivity ratios for glycidyl methacrylate and styrene monomers are rG = 0.73 and rS = 0.42, respectively. Ó 2008 Published by Elsevier Ltd.
1. Introduction The advent of controlled/living radical polymerization (CRP) has gain vast attention of the synthetic polymer scientists [1–2]. Controlled radical polymerization methods [3–9] are frequently used to synthesize polymeric systems with well defined molecular weights, mass distributions, end groups and controlled chain topologies. Among the various methods of controlled/living radical polymerization, atom transfer radical polymerization (ATRP) is an useful polymerization technique for the polymerization of a wide variety of monomers [10–19] along with a number of functional monomers [20–25]. Functionalized copolymers are industrially important because of synthetic potential due to cross linking reactions, chain extensions and preparation of block and graft copolymers. Glycidyl methacrylate (GMA) is a commercially interesting functional monomer because of the presence of epoxy group, * Corresponding author. Tel.: +91 11 26591377; fax: +91 11 25195693. E-mail address: [email protected] (A.S. Brar). 0014-3057/$ - see front matter Ó 2008 Published by Elsevier Ltd. doi:10.1016/j.eurpolymj.2008.09.013
which permits a large number of reactions [26–27]. The copolymers based on GMA have great significance in advanced biotechnology [28–30] by easy conversion of epoxy group in various functional groups. Moreover, homogenous and heterogeneous polymer networks can be prepared by GMA, which are used in coatings, matrix resins and adhesives [31–33]. From last few years, many researchers are trying to optimize ATRP conditions for various monomers. Matyjaszewki et al. [34] shows that polymerization in the presence of multidentate alkyl amine ligands such as N,N,N0 ,N00 ,N00 -pentamethyldiethylenetriamine (PMDETA) were found to proceed at faster rate and low temperature. They also show that copper bromide and chloride complexes with Me6-TREN were highly active toward acrylates and methacrylates [35]. Optimization of catalyst based on PMDETA has recently been described for methacrylates [36] and acrylates [37–38]. Lu et al. [16] have reported the atom transfer radical polymerization of styrene initiated by triphenylmethyl chloride. They investigated the effect of catalyst complex,
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091
solvent, temperature, and concentration of initiating system. Fuente et al. [23] demonstrated that atom transfer radical polymerization of GMA using ethyl bromoisobutyrate, PMDETA and CuCl in toluene and diphenyl ether at 30 and 50 °C proceeded in a controlled manner. FernandezGarcia et al. [24] performed ATRP of GMA/butyl acrylate yielding well defined statistical copolymers. Krishnan and Shrinivasan [25] reported a detailed study of the kinetics and characterization of poly(glycidyl methacrylate) obtained by ATRP. They performed the homopolymerization reactions using CuX/N-alkyl-2-pyridyl methanimine as a catalyst at ambient temperature. They investigated that poly glycidyl methacrylate is particularly sensitive to different components of polymerization, such as an initiator, catalyst, and the solvent. Considering the above-mentioned study and certain limitations found in controlled radical polymerization, the goal of present work is to explore the suitable reaction conditions for controlled copolymerization of GMA and styrene by ATRP, using copper based catalyst system. The effect of various reaction parameters i.e. nature of ligands, initiators, solvents and variation in temperature for controllability of living radical bulk copolymerization of GMA with styrene are investigated.
2. Experimental 2.1. Materials The monomers, glycidyl methacrylate (GMA, 99%, Fluka) and styrene (St, 99%, Merck, Germany) were dried over CaH2 and polymerization inhibitor was removed by vacuum distillation and kept below 5 °C before use. Methyl 2-bromopropionate (MBP, 98%), ethyl 2-bromoisobutyrate (EBiB, 98%), N,N,N0 ,N0 ,N00 -pentamethyldiethylenetriamine (PMDETA, 99%), N,N,N0 ,N0 ,N00 ,N00 -hexamethyltriethylenetetramine (HMTETA, 99%), tris (2-aminoethyl)-amine, (TREN, 96%), CuBr (99%), and 4,40 -dinonyl-2,20 -dipyridyl (dNbpy, 97%) were purchased from Aldrich and used as received. Benzyl chloride (BzCl, 98%) was purchased from CDH India. 2.2. Copolymerization Copolymers of glycidyl methacrylate (GMA) and styrene were synthesized with different in-feed ratios of monomers under ATRP conditions. All copolymerization reactions were performed using copper based catalyst (CuBr/ligand complex) and various initiators under nitrogen atmosphere. For synthesis of copolymers, a stock solution containing the calculated amount of monomer and ligand along with CuBr was prepared and sealed with rubber septum. The solution was degassed by three vacuum-nitrogen cycles and stirred at room temperature. The calculated amount of an initiator was then added to solution with a syringe and the solution was again purged with nitrogen. Finally the flask containing solution was kept in oil bath and maintained at desired temperature. The solution becomes progressively viscous, indicating the onset of polymerization. The solution was then taken
4083
out at different interval of time to observe the change in molecular weight and polydispersity Index (PDI) with conversion. The reaction was quenched by diluting with tetrahydrofuran (THF) and subsequently passed through a neutral alumina column to remove the catalyst. The solution was then concentrated and precipitated in methanol. The precipitated copolymers were further purified by dissolving in chloroform and precipitating in methanol and finally dried under vacuum at 50 °C until constant weight was reached. 2.3. Characterization Total monomer conversion was measured gravimetrically. The molecular weight (Mn) and polydispersity index (PDI, Mw/Mn) of synthesized copolymers were determined using gel permeation chromatography (GPC) equipped with a Hitachi L-2130 pump with Waters column and a Hitachi L-2490 RI detector against polystyrene standards. HPLC grade THF was used as an eluent at the flow rate of 0.5 mL/min at room temperature. Copolymers composition was calculated using 1H and quantitative 13C{1H} NMR spectra. NMR spectra were recorded at 25 °C on Bruker DPX-300 NMR spectrometer in about 10% polymer solutions using CDCl3 as a solvent. The Quantitative 13C{1H} NMR spectra were recorded with 12 s delay time and using tris(acetylacetonato)chromium(III) [Cr(acac)3] as a relaxing agent. The intensities of various NMR signals were measured from the integrated peak areas calculated with an electronic integrator.
3. Results and discussion 3.1. Composition and reactivity ratios determination The composition of GMA/St copolymers with different percent conversion were determined with the help of 1H NMR spectra (Fig. 1a). The relative areas of aromatic protons (I1) and aliphatic proton (I2) resonances were calculated and then composition of GMA/St copolymers was calculated. The compositions were further confirmed by quantitative 13C{1H} NMR spectra (Fig. 1b). The variation of copolymers composition (FGMA) as a function of percent conversion for three different in-feed compositions (fGMA) of GMA/St copolymers are shown in Table 1. Monomer reactivity ratios for GMA/St copolymers were optimized using this copolymer composition data. The reactivity ratios for GMA/St comonomers were calculated using non linear genetic algorithm method [39]. The values of reactivity ratios were found to be rGMA = 0.73 and rSt = 0.42, respectively, which are close to the reported values [40]. Theoretical copolymers composition, percent conversion and theoretical molecular weight calculations were done using reactivity ratios by the methodology described previously [41]. 3.2. Optimization of ATRP conditions The copolymerization of GMA with styrene was carried out in molar ratios of 1:1. The effect of various components
4084
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091
Fig. 1. (a) 1H and (b)
13
C{1H} NMR spectra of GMA/St copolymer (FGMA = 0.54) in CDCl3 at 25 °C.
Table 1 GMA molar fraction in-feed (fGMA), conversions and GMA compositions (FGMA,Theo. and FGMA,NMR) for GMA/St copolymers prepared by ATRP at 60 °C in bulk fGMA
Conversion (%)
FGMA,
0.25
8 30 43 57 67
0.37 0.36 0.34 0.33 0.32
0.39 0.36 0.36 0.34 0.32
1140 3725 5237 6847 7982
1250 3825 5375 7000 8150
1.29 1.26 1.28 1.23 1.20
0.50
12 32 46 59 79
0.55 0.55 0.54 0.54 0.53
0.56 0.54 0.54 0.54 0.53
1697 4195 5938 7551 10,015
1800 4325 6100 7725 10,200
1.31 1.26 1.27 1.24 1.22
0.75
17 42 60 71 87
0.73 0.74 0.74 0.74 0.74
0.74 0.74 0.75 0.75 0.75
2440 5745 8128 9587 11,715
2700 5950 8300 9750 12,000
1.35 1.30 1.26 1.27 1.25
Theo.
FGMA,
NMR
Theo. M. Wt.
Mn GPC
PDIMw/Mn
[GMA + St]0/[EBiB]0 = 100:1 and [EBiB]0/[CuBr]0/[PMDETA]0 = 1:0.5:0.5.
of ATRP (ligands, initiators, solvents, and variation in temperature) were examined to achieve controlled copolymerization in bulk.
3.2.1. Effect of ligand The catalyst is of prime importance for the success of ATRP because it determines the position of atom transfer
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091
equilibrium and the dynamics of exchange between active and dormant species. On the basis of literature survey, CuBr/nitrogenous ligands are extensively used as the catalysts. The role of ligand in ATRP is to solubilize the Cu salts and to tune the Cu catalyst activity. The choice of ligand greatly influences the effectiveness of catalyst. To select good ligand for copolymerization of GMA and styrene, the initial copolymerization was performed with a [Monomer]/[Initiator] molar ratio of 100:1 with CuBr/ligand (dNbpy, PMDETA, HMTETA, and TREN) as a catalyst in molar ratio of 0.5/0.5 in bulk at 60 °C. The molecular weight evolution (Mn) and polydispersity index (PDI) as a function of percent conversion for three different ligands (PMDETA, HMTETA, and TREN) are shown in Fig. 2. It was observed that no polymerization takes place with dNbpy even after 48 h. On increasing the polymerization temperature up to 80 °C, percent conversion had reached only 8% in 48 h, while the linear increase in molecular weights with percent conversion was observed in case of PMDETA, HMTETA, and TREN (Fig. 2b). Molecular weights are in good agreement with predicted molecular weights when the polymerization was carried out using PMDETA or HMTETA as ligands, while higher values than the predicted values are found in case of TREN. The straight lines were obtained on plotting ln[M]0/[M] vs. time for PMDETA and HMTETA which follow the first-order kinetics, while a significant curvature was observed in case of TREN (Fig. 2a). This observation indicates that active catalyst was formed when PMDETA or HMTETA were used as ligand while radical coupling and termination reactions takes place in case of TREN, which results in low catalytic efficiency. The low values of polydispersities were also found when PMDETA or HMTETA used as a ligand, while higher PDI was observed in case of TREN (Fig. 2c). The above observation can be explained on the basis of number of nitrogen atom present in the ligands. The Cu complexes formed with multidentate alkyl amine ligands promote ATRP more successfully as compare to mono or bi-dentate ligands. Therefore when bipyridine is used as a ligand the polymerization is not efficient, because of less catalytic efficiency as compare to PMDETA, HMTETA, and TREN. Furthermore in case of TREN, three primary amine groups are present as compare to HMTETA and PMDETA, which reduces the catalytic activity of Cu complex. Therefore the complex formed with CuBr as metal halide and PMDETA or HMTETA as ligands give ATRP significantly. 3.2.2. Effect of Initiator The selection of a good initiator is most important factor for successful ATRP. Matyjaszewski and coworkers [42–43] had outlined ten general guidelines for selection of efficient initiators. They suggested that the initiators should be structurally similar to those of monomers. Keeping this in mind, polymerizations were done by changing initiating systems and maintaining the other conditions constant. No polymerization was observed in the presence of (2-bromoethyl) benzene. The results obtained with 2bromopropionate (MBP), 2-bromoisobutyrate (EBiB), and benzyl chloride (BzCl) as an initiators are shown in Fig. 3. In all cases, molecular weight of copolymers initiated by different initiators increased linearly with percent conver-
4085
sion, which indicates the presence of constant concentration of growing chains through out the reaction. A comparison of semilogarithmic plot between ln[M]0/[M] vs. time show different rate of polymerizations for different initiating systems (Fig. 3a). The polymerization rate is fastest for MBP and slowest for benzyl chloride. The plot shows the linear relation for MBP and EBiB but deviation from linearity was observed in case of benzyl chloride, indicates the presence of termination reactions. On comparing the experimental molecular weight with predicted molecular weight vs. conversion, the results were found in good agreement with EBiB, while in case of MBP, experimental molecular weights are little more than predicted values but a large difference was observed in case of benzyl chloride (Fig. 3b). The low values of polydispersities were also observed for EBiB and MBP (Fig. 3c). The above observations can be explained from the stability of free radicals formed by initiators, i.e. less stable free radicals have more chances to undergo controlled polymerization and vice versa. Free radicals generated from (2-bromoethyl) benzene and benzyl chloride are more stable than generated from MBP and EBiB, due to presence of benzene ring adjacent to radical site. In the case of (2-bromoethyl) benzene, resulting free radical is secondary which is more stable than primary free radical formed in case of benzyl chloride. Therefore no polymerization was observed when initiated by (2-bromoethyl) benzene. Furthermore the free radicals formed with EBiB are structurally more similar to monomer as compare to MBP, so polymerization with EBiB as an initiating system proceeds in a controlled manner. Therefore, controllability of the polymerization can be ranked for initiators as: EBiB > MBP > benzyl chloride > (2-bromoethyl) benzene. 3.2.3. Effect of solvent To optimize the solvent effect, copolymerization was performed in dimethylformamide (DMF) and toluene (monomer:solvent::1:1). It was observed that in presence of DMF as a solvent, initially polymerization started and proceeds up to 13% conversion till 75 h after that no further increase in percentage conversion was observed. In presence of toluene, polymerization proceeds significantly and copolymers with low polydispersity and expected molecular weights were obtained as in bulk polymerization (Fig. 4). The polymerization rate is faster in bulk than toluene as a solvent while polymerization rate is very slow in DMF which becomes stable after 75 h and copolymer with high polydispersity was formed. Therefore copolymerization could not proceed significantly in DMF as in bulk and toluene. It has been suggested that suitable solvent may increase the solubility of catalyst, but in present work, solubility of catalyst should not be crucial, because the polymerization proceeds successfully in bulk and solvents with low polarity but not significantly in DMF and other solvents with high polarity. 3.2.4. Effect of polymerization temperature To investigate the effect of temperature, copolymerization was carried out at different temperatures. The resulted kinetics and the dependence of molecular weight (Mn) and polydispersity index (PDI) on percent conversion are
4086
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091
Fig. 2. (a) Variation of ln([M]0/[M]) with reaction time, (b) Mn,GPC (dotted line indicates the theoretical number-average molecular weight) and (c) polydispersities (Mw/Mn) with percent conversion for ATRP of GMA/St at 60 °C in bulk using different ligands. [GMA + St]0/[EBiB]0 = 100:1 and [EBiB]0/ [CuBr]0/[Ligand]0 = 1:0.5:0.5.
shown in Fig. 5. The plot between ln([M]0/[M]) vs. time at different temperature from 40 to 80 °C shows first-order
linearity, which shows that polymerization is a first-order with respect to monomer and the concentration of growing
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091
4087
Fig. 3. (a) Variation of ln([M]0/[M]) with reaction time, (b) Mn,GPC (dotted line indicates the theoretical number-average molecular weight) and (c) polydispersities (Mw/Mn) with percent conversion for ATRP of GMA/St at 60 °C in bulk using different Initiators. [GMA + St]0/[Initiator]0 = 100:1 and [Initiator]0/[CuBr]0/[PMDETA]0 = 1:0.5:0.5.
4088
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091
Fig. 4. (a) Variation of ln([M]0/[M]) with reaction time, (b) Mn,GPC (dotted line indicates the theoretical number-average molecular weight) and (c) polydispersities (Mw/Mn) with percent conversion for ATRP of GMA/St at 60 °C in different solvents. [GMA + St]0/[EBiB]0 = 100:1, [EBiB]0/[CuBr]0/ [PMDETA]0 = 1:0.5:0.5 and [monomer]/[solvent] = 1:1.
radicals remains constant. The rate of polymerization increases with increase of temperature, indicates that induction period get shortened by increasing temperature.
The molecular weights increase with increase of conversion, but the values are higher than the predicted values at temperature 40 °C and 80 °C which indicates the lower
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091
4089
Fig. 5. (a) Variation of ln([M]0/[M]) with reaction time, (b) Mn,GPC (dotted line indicates the theoretical number-average molecular weight) and (c) polydispersities (Mw/Mn) with percent conversion for ATRP of GMA/St in bulk at different temperatures. [GMA + St]0/[EBiB]0 = 100:1 and [EBiB]0/[CuBr]0/ [PMDETA]0 = 1:0.5:0.5.
initiation efficiencies. On comparing the polydispersities at different temperature, it was observed that at 60 °C, polydispersities are lower than at 40 °C and 80 °C (Fig. 5c). It
was also observed that polydispersity decreases with percent conversion at 60 °C while there is no order of PDI at 40 °C and 80 °C. This observation may imply the participa-
4090
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091
tion of side reactions (chain transfer or termination reactions) with increasing temperature and low initiation efficiency at low temperature. 4. Conclusion The Atom transfer radical copolymerization of glycidyl methacrylate and styrene was performed successfully using EBiB as an initiator and CuBr/PMDETA as a catalyst in bulk and toluene as a solvent at 60 °C. The reaction followed a first-order kinetic with respect to monomer concentration, indicating a constant concentration of the propagating radical, low polydispersities (Mw/Mn < 1.3), and efficient control over Mn. The investigation about the effect of various ATRP components show that ligand, initiator and the solvent are crucial parameters for the polymerization. The increase of temperature not only increases the rate of polymerization, but also shortens the induction period. Acknowledgment The author (Ashok Kumar Goyal) thanks to the Department of Science and Technology (DST), New Delhi, India, for providing financial support to carry out this work. References [1] Matyjaszewski, K. Controlled radical polymerization; ACS Symposium series 685. Washington DC: Am Chem Soc; 1998. [2] Matyjaszewski K. Controlled/living radical polymerization: progress in ATRP, NMP and RAFT; ACS Symposium series 768. Washington DC: Am Chem Soc; 2000. [3] Matyjaszewski K, Xia J. Atom transfer radical polymerization. Chem Rev 2001;101:2921–90. [4] Kamigaito M, Ando T, Sawamoto M. Metal-catalyzed living radical polymerization. Chem Rev 2001;101:3689–746. [5] Hawker CJ, Bosman AW, Harth E. New polymer synthesis by nitroxide mediated living radical polymerizations. Chem Rev 2001;101:3661–88. [6] Chiefari J, Chong YK, Ercole F, Krstina J, Jeffery J, Le TPT, et al. Living free-radical polymerization by reversible addition-fragmentation chain transfer: the RAFT process. Macromolecules 1998;31: 5559–62. [7] Mayadunne RTA, Rizzardo E, Chiefari J, Chong YK, Moad G, Thang SH. Living radical polymerization with reversible addition-fragmentation chain transfer (RAFT polymerization) using dithiocarbamates as chain transfer agents. Macromolecules 1999;32:6977–80. [8] Moineau G, Dubois Ph, Jerome R, Senninger T, Teyssie Ph. Alternative atom transfer radical polymerization for MMA using FeCl3 and AIBN in the presence of triphenylphosphine: an easy way to wellcontrolled PMMA. Macromolecules 1998;31:545–7. [9] Wang JS, Matyjaszewski K. Living/controlled radical polymerization. Transition-metal-catalyzed atom transfer radical polymerization in the presence of a conventional radical initiator. Macromolecules 1995;28:7572–3. [10] Miura Y, Satoh T, Narumi A, Nishizawa O, Okamoto Y, Kakuchi T. Atom transfer radical polymerization of methyl methacrylate in fluoroalcohol: simultaneous control of molecular weight and tacticity. Macromolecules 2005;38:1041–3. [11] Munoz-Bonilla A, Madruga EL, Fernandez-Garcia M. Atom transfer radical polymerization of cyclohexyl methacrylate at a low temperature. J Polym Sci Part A: Polym Chem 2005;43:71–7. [12] Demirelli K, Coskun M, Kaya E. Polymers based on benzyl methacrylate: synthesis via atom transfer radical polymerization, characterization, and thermal stabilities. J Polym Sci Part A: Polym Chem 2004;42:5964–73. [13] Brar AS, Kaur S. Tetramethylguanidino-tris(2-aminoethyl)amine: a novel ligand for copper-based atom transfer radical polymerization. J Polym Sci Part A: Polym Chem 2005;43:5906–22.
[14] Hua D, Bai R, Lu W, Pan C. Dithiocarbamate mediated controlled/ living free radical polymerization of methyl acrylate under 60Co cray irradiation: conjugation effect of N-group. J Polym Sci Part A: PolymChem 2004;42:5670–7. [15] Venkatesh R, Vergouwen F, Klumperman B. Atom transfer radical copolymerization of a-olefins with methyl acrylate: determination of activation rate parameters. Macromol Chem Phys 2005;206:547–52. [16] Xu Y, Lu J, Xu Q, Wang L. Atom transfer radical polymerization of styrene initiated by triphenylmethyl chloride. Eur Polym J 2005;41:2422–7. [17] Denizli BK, Lutz JF, Okrasa L, Pakula T, Guner A, Matyjaszewski K. Properties of well-defined alternating and random copolymers of methacrylates and styrene prepared by controlled/living radical polymerization. J Polym Sci Part A: Polym Chem 2005;43:3440–6. [18] Lutz JF, Matyjaszewski K. Kinetic modeling of the chain-end functionality in atom transfer radical polymerization. Macromol Chem Phys 2002;203:1385–95. [19] Lazzari M, Chiantore O, Mendichi R, Lopez-Quintela MA. Synthesis of polyacrylonitrile-block-polystyrene copolymers by atom transfer radical polymerization. Macromol Chem Phys 2005;206:1382–8. [20] Robinson KL, Khan MA, de Banez MV, Wang XS, Armes SP. Controlled polymerization of 2-hydroxyethyl methacrylate by ATRP at ambient temperature. Macromolecules 2001;34:3155–8. [21] Beers KL, Boo S, Gaynor SG, Matyjaszewski K. Atom transfer radical polymerization of 2-hydroxyethyl methacrylate. Macromolecules 1999;32:5772–6. [22] Kickelbick G, Paik HJ, Matyjaszewski K. Immobilization of the copper catalyst in atom transfer radical polymerization. Macromolecules 1999;32:2941–7. [23] Canamero PF, Fuente JL, Madruga EL, Fernandez-Garcia M. Atom transfer radical polymerization of glycidyl methacrylate: a functional monomer. Macromol Chem Phys 2004;205:2221–8. [24] Fuente JL, Canamero PF, Fernandez-Garcia M. Synthesis and characterization of glycidyl methacrylate/butyl acrylate copolymers obtained at a low temperature by atom transfer radical polymerization. J Polym Sci Part A: Polym Chem 2006;44: 1807–16. [25] Krishnan R, Srinivasan KSV. Controlled/living radical polymerization of glycidyl methacrylate at ambient temperature. Macromolucules 2003;36:1769–71. [26] May CA. Epoxy resins chemistry and technology. New York: Marcel Dekker; 1988. [27] Chen Z, Bao H, Liu J. Synthesis of a well-defined epoxy copolymer by atom transfer radical polymerization. J Polym Sci Part A: Polym Chem 2001;39:3726–32. [28] Kalal J. Epoxy and aldehyde polymers as reagents. J Polym Sci Polym Symp 1978;62:251–70. [29] Kovar J, Navratilova M, Skursky L. Immobilization of horse liver alcohol dehydrogenase on copolymers of glycidyl methacrylate and ethylene dimethacry late. Biotechnol Bioeng 1982;24:837–45. [30] Jones RG, Yoon S, Nagasaki Y. Facile synthesis of epoxystyrene and its copolymerisations with styrene by living free radical and atom transfer radical strategies. Polymer 1999;40:2411–8. [31] Vijayaraghavan PG, Reddy BSR. 4-Chlorophenyl acrylate and glycidyl methacrylate copolymers: Synthesis, characterization, reactivity ratios, and application. J Macromol Sci Pure Appl Chem 1999;36: 1181–95. [32] Godwin GG, Selvamalar CSJ, Penlidis A, Nanjundan S. Homopolymer of 4-propanoylphenyl methacrylate and its copolymers with glycidyl methacrylate: synthesis, characterization, reactivity ratios and application as adhesives. React Funct Polym 2004;59:197–209. [33] Zhang X, Tanaka H. Copolymerization of glycidyl methacrylate with styrene and applications of the copolymer as paper-strength additive. J Appl Polym Sci 2001;80:334–9. [34] Xia J, Matyjaszewski K. Controlled/living radical polymerization. Atom transfer radical polymerization using multidentate amine ligands. Macromolecules 1997;30:7697–700. [35] Xia J, Gaynor SG, Matyjaszewski K. Controlled/living radical polymerization. Atom transfer radical polymerization of acrylates at ambient temperature. Macromolecules 1998;31:5958–9. [36] Davis KA, Matyjaszewski K. Investigation of the ATRP of n-butyl methacrylate using the Cu(I)/N, N, N0 , N00 , N00 -pentamethyldiethylenetriamine catalyst system. Chinese J Polym Sci 2004;22: 195–204. [37] Nanda AK, Matyjaszewski K. Effect of [PMDETA]/[Cu(I)] ratio, monomer, solvent, counterion, ligand, and alkyl bromide on the activation rate constants in atom transfer radical polymerization. Macromolecules 2003;36:1487–93.
A.S. Brar, A.K. Goyal / European Polymer Journal 44 (2008) 4082–4091 [38] Hung J, Pintauer T, Matyzajaszewski K. Effect of variation of [PMDETA]0/[Cu(I)Br]0 ratio on atom transfer radical polymerization of n-butyl acrylate. J Polym Sci Part A: Polym Chem 2004;42:3285–92. [39] Brar AS, Singh G, Shankar R. Analysis of quaternary carbon resonances of vinylidene chloride/methyl acrylate copolymers. Eur Polym J 2004;40:2679–88. [40] Brar AS, Yadav A, Hooda S. Characterization of glycidyl methacrylate/ styrene copolymers by one- and two-dimensional NMR spectroscopy. Eur Polym J 2002;38:1683–90.
4091
[41] Brar AS, Saini T. Atom transfer radical copolymerization of acrylonitrile and ethyl methacrylate at ambient temperature. J Polym Sci Part A: Polym Chem 2006;44:1975–84. [42] Wang JL, Grimaud T, Shipp DA, Matyjaszewski K. Controlled/ living atom transfer radical polymerization of methyl methacrylate using various initiation systems. Macromolecules 1998;31: 1527–34. [43] Ambade AV, Kumar A. Controlling the degree of branching in vinyl polymerization. Prog Polym Sci 2000;25:1141–70.