Complex of cross-linked polyvinylamine with Cu(II) as catalyst for vinyl polymerization

Applied Catalysis A: General 247 (2003) 163–173

Complex of cross-linked polyvinylamine with Cu(II) as catalyst for vinyl polymerization Jianmei Lu∗ , Zhenqian Zhang, Xuewei Xia, Xiulin Zhu Department of Chemistry and Chemical Engineering, SuZhou University, 1 Shi Zhi Street, Soochow 215006, Jiangsu Province, PR China Received 30 November 2002; received in revised form 21 January 2003; accepted 22 January 2003

Abstract A complex of polyvinylamine (PVAm) and Cu(II) was synthesized and IR, TG and XPS were employed to examine its structure. It has been found that PVAm-Cu(II) complex/sodium sulfite (Na2 SO3 ) system can be used as initiator of methyl methacrylate (MMA) polymerization. The overall polymerization rate can be expressed as Rp = k[MMA]1.4 [Na2 SO3 ]0.5 [PVAm-Cu(II)]0 . The activity of initiator system varies with the composition of PVAm-Cu(II) complex. The polymerization proceeds by a free radical way, and primary radicals are formed by the process of “complexation-hydrogen transfer” between PVAm-Cu(II)/ Na2 SO3 /MMA system. The copolymerization of MMA and styrene (St) with PVAm-Cu(II)/Na2 SO3 system as initiator differs from the conventional radical copolymerization. © 2003 Elsevier Science B.V. All rights reserved. Keywords: Radical polymerization; Polyvinylamine; Copolymerization; Catalyst; Cupric ion

1. Introduction Because of the ease of recovery and separation from the reaction system, polymeric catalyst, as a very important branch of functional polymer and catalyst, has attracted great interest in last few decades. A large amount of polymeric catalysts have been developed, including polymeric catalysts for free radical polymerization [1–5]. Nishimura et al. used Nylon-3-Cu(II)/urea system as initiator of MMA polymerization [6], Krmura et al. used the complex of vinyl alcohol and Cu(II)/CCl4 system as initiator [7,8]. Earlier polymerization with foregoing polymeric catalyst needs rigorous condition and the ∗ Corresponding author. Tel.: +86-512-6511-7345; fax: +86-512-6724-2919. E-mail address: [email protected] (J. Lu).

monomer conversion was low. Yang et al. found that complex of polypropylene-graft polycarboxylate and Cu(II)/sodium sulfite system could be used as initiator for polymerization of MMA, and the reaction condition was mild [9]; in the present study, we chose PVAm-Cu(II)/Na2 SO3 system as initiator of MMA polymerization and copolymerization of MMA and styrene (St). We extensively discuss the rate of polymerization of MMA, the effects of composition of polymer–metal complexes on polymerization and the initiation activities of copolymerization. Compared to the homogeneous system of Cu2+ /Na2 SO3 , the inhomogeneous PVAm-Cu(II) system can be easily separated from the polymer product, which is environmentally valuable because the coordinated Cu(II) would not become pollutant while the hydrophile Cu2+ is harmful to environment. The PVAm-Cu(II) catalyzes the polymerization and copolymerization in

0926-860X/03/$ – see front matter © 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0926-860X(03)00090-5

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a different mechanism from the Cu2+ /Na2 SO3 does and the former’s activity is higher and gives higher monomer conversion. 2. Experimental 2.1. Materials Methyl methacrylate (MMA) was purified before polymerization as described in [10] and subsequently was redistilled under reduced pressure, distillate at 312 K (70 mmHg) collected. Styrene was purified as described in [11] and redistilled under reduced pressure whereafter, distillate at 317 K (20 mmHg) collected. Sodium sulfite and cupric dichloride were both analytically pure grade. 2.2. Preparation of PVAm-Cu(II) Polyacrylamide was synthesized through suspension polymerization of acrylamide in cyclohexane solution. The obtained polyacrylamide was cross-linked by cross-linking agent. Cross-linked polyacrylamide was then used to prepare cross-linked polyvinylamine (PVAm) by the means of Hofmann degradation with sodium hypochlorite and sodium hydroxide [12]. The prepared PVAm was added to a solution of cupric dichloride. The mixture was stirred for 2 h, then filtered-off. The filtrated solid was washed with deionized water to remove cupric ion, and dried under vacuum at 323 K for 24 h. The amount of cupric in the PVAm-Cu(II) was determined by complex metric titration after ignition. EA 1110 element analyzer was employed to measure N, H and C contents in PVAm-Cu(II). PVAm and its cupric complex were taken in KBr pellets and the IR absorption spectra were determined with a Mangna-550 infrared spectrophotometer. TG curve of PVAm and PVAm-Cu(II) was measured with Perkin-Elmer thermal analyzer in Nitrogen. Heating rate is 20 K/min. 2.3. Polymerization procedure and analysis of polymer Appropriate quantities of MMA, cupric sulphate, PVAm-Cu(II) (cupric ion in equal mole) and ketone were placed in the reaction vessel and protected by

pure Nitrogen. The reactants were maintained at the desired temperature by a thermostat. The requisite quantity of sodium sulphite solution was quickly introduced and the polymerization was allowed to continue. After a prescript interval of time, further polymerization was quenched by the addition of an excess of 2,2-diphenyl-1-picrylhydrazyl (DPPH) solution. The polymers were then precipitated, filtered and refined. The polymer obtained was dried to constant weight under vacuum below 313 K. The rate of polymerization (Rp ) was gravimetrically calculated [13]. The structure and tacticity of polymers were analyzed by 1 H INOVA 400 Hz NMR spectrometer at 298 K [14]. Weight-average molecule weights and the molecule weight distribution of obtained polymer were determined by Waters 1515 gel permeation chromatograph GPC. GPC experiments were conducted in tetrahydrofuran (THF) solution at 298 K with polystyrene as reference. The structure of coordination was analyzed through the photoelectron spectroscopy (type: Np -1 Shenyang). 2.4. Copolymerization of MMA and styrene Copolymerizations were carried out at different temperature using PVAm-Cu(II)/Na2 SO3 system as initiator in ketone solution. The copolymer samples at low conversion (below 5%) were precipitated by a large quantity of methanol, repeatedly washed by methanol and dried under vacuum for 24 h. 3. Results and discussion 3.1. Characteristics of polymer–metal complexes cupric complex Fig. 1 shows the absorption peaks of the PVAm (3514, 2021, 1666 (C=O), 1404, 652 cm−1 ), the PVAm-Cu(II) (3514, 2021, 1692, 1397, 876, 602 cm−1 ). The spectrum of PVAm-Cu(II) presents a decrease in the peak intensity of 3514, 2021 cm−1 whereas the absorption peak 1666 cm−1 in PVAm spectrum shifts to 1692 cm−1 . All changes are due to the formation of bond between –NH2 and Cu(II). The TG curves are different between PVAm and PVAm-Cu(II). Fig. 2 shows PVAm loss weight 56.27% in 325–480 K while PVAm-Cu(II) 23.90%. Compared

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165

Fig. 2. TG curves. Fig. 1. IR spectra.

to PVAm curve, weight loss of PVAm-Cu(II) is mild, which indicated that PVAm-Cu(II) is more thermostable than PVAm. XPS spectra of PVAm-Cu(II) and CuCl2 ·2H2 O were showed in Fig. 3 and inner electrons’ binding energy was showed in Table 1. According to the table1, it was indicated that coordination occurred between Cu2+ and the atom of polymers. After

Table 1 Electron binding energy (eV) of XPS PVAm-Cu(II) Sample

PVAm CuCl2 ·2H2 O PVAm-CuCl2

O 1s

Cl 2p

531.6 531.6

N 1s

Cu2+ 2p 2p3/2

2p1/2

934.2 932.6

954.6 953.3

400.4 199.8 198.8

405.1

Fig. 3. XPS spectra of PVAm-Cu(II) and CuCl2 ·2H2 O: (a) CuCl2 ·2H2 O; (b) PVAm-Cu(II).

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coordination, 2p electron’s binding energy of Cu(II) (2p3/2 = 932.6 eV and 2p1/2 = 953.3 eV) was less than electron’s binding energy before coordination (2p3/2 = 934.2 eV and 2p1/2 = 954.6 eV). After coordination, electron’s binding energy of N 1s (405.10 eV) was greater than the one before coordination (400.4 eV). Based on this test result and the valence-bond theory [15], it can be considered that Cu(II) accepted lone electron pair of N on the chain of PVAm and during the coordination electric charge transferred as N → Cu. According to table1, the Cl− electron’s binding energy of Cl 2p of coordination was less than that of CuCl2 ·2H2 O by 1 eV, because coordination between Cu2+ and N of polymer caused electron of N partly transfer to Cu2+ , which increased electric charge of Cl atom and decreased electron’s binding energy of Cl 2p of the coordination. According to the test and analysis of XPS, the surrounding space of Cu2+ was partly occupied by Cl− , which was a action of electrostatic attraction. So we could confer that structure (the described structure just relatively indicated the way N atoms bond to Cu2+ , not intended to show a planar structure of four N atoms) of the coordination may be as follows:

Fig. 4. Difference of electric conductivity between CuCl2 aqueous solution and corresponding PVAm-Cu(II) solution.

was showed in Table 2 and Fig. 4. When Cu2+ concentration is about 32.3 mmol/l and the corresponding ratio of N/Cu is about 3.5, the difference of electric conductivities varied slightly with Cu2+ concentration increasing. Since the curl and intertwist of macromolecule, Cu(II) cannot completely coordination with N atom of PVAm unit chain. So it could be roughly inferred that in complex of PVAm-Cu(II), the ratio of N/Cu is about 4 [16]. 3.2. Kinetic study of the polymerization of MMA by using the PVAm-Cu(II)/Na2 SO3 catalytic system

The ratio of coordination of Cu2+ and N on PVAm is roughly measured, through electric conductivity comparison between a series of CuCl2 aqueous solutions and corresponding PVAm–Cu(II) solutions. The result

The polymerization of MMA with PVAm-Cu(II)/ Na2 SO3 system has been kinetically investigated in ketone solution. Fig. 5 shows the rate of polymerization

Table 2 Difference of electric conductivity of CuCl2 aqueous solution and PVAm-Cu(II) solution Group A

Ka − Kb (10 ms)

Group B

Sample

CuCl2 (mmol/l)

Ka (10 ms)

Mass of PVAm (g)

Ratio of Cu2+ /N

Kb (10 ms)

1 2 3 4 5 6

18.3 22.6 28.3 32.3 37.7 56.5

31.4 36.4 44.2 50.6 54.9 84.3

1 1 1 1 1 1

1/6 1/5 1/4 1/3.5 1/3.0 1/2

31.0 35.7 43.4 49.0 53.3 82.6

Ka , electric conductivity of CuCl2 aqueous solution; Kb , electric conductivity of PVAm-Cu(II) solution.

0.4 0.7 0.8 1.6 1.6 1.7

J. Lu et al. / Applied Catalysis A: General 247 (2003) 163–173

Fig. 5. The effect of reactive temperature on rate of polymerization MMA.

167

Fig. 7. The effect of concentration of Na2 SO3 on rate of polymerization.

versus 1/T was calculated. The Rp values were put in Arrhenius equation and overall activation energies (Ea ) were estimated, Ea = 61.3 kJ/mol. Compared with the overall activation energy (Ea = 101.6 kJ/mol) which estimated under the condition of polymerization of MMA initiated by cupric ion/sodium sulfite [17], the result shows PVAm-Cu(II)/Na2 SO3 system decreases the overall activation energy. Fig. 6 shows the relationship between Rp and the MMA concentration at 303 K when the concentration of sodium sulfite was fixed at 4.74 mmol/l. Rp is proportional to the 1.4 power of the monomer concentration, suggesting that the monomer participates in the initiation process.

Fig. 7 presents the dependence of Rp on the concentration of sodium sulfite at 303 K at a fixed MMA concentration (0.2 mol/l). Rp increases in proportion to the 0.50 power of concentration of sodium sulfite, indicating that the polymerization involves the usual bimolecular termination between polymer radicals. This result suggests that sodium sulfite and PVAm-Cu(II) form a complex with a high stability constant that can produce initiating radicals. Fig. 8 presents the relationship between conversion of polymerization of MMA and the weight of PVAm-Cu(II) when the concentration of sodium sulfite was fixed at 4.74 mmol/l and the MMA concentration was fixed at 0.2 mol/l at 303 K. The weight of

Fig. 6. The effect of concentration on rate of polymerization.

Fig. 8. The effect of amount of PVAm-Cu(II) on conversion of PMMA: (filled circles) 30 mg; (filled squares) 25 mg; (downward triangles) 20 mg; (upward triangles) 10 mg; (shaded circles) 5 mg.

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PVAm-Cu(II) has no effect on conversion of polymerization of MMA. Therefore, Rp is proportional to the 0 power of the weight of PVAm-Cu(II). From the aforementioned results, the following kinetic expression is obtained for the present polymerization: Rp = k[MMA]1.4 [Na2 SO3 ]0.5 [PVAm–Cu(II)]0 3.3. Effect of the constitution of PVAm-Cu(II) on the catalytic activity In order to disclose the relationship between the constitution and the catalytic activity of PVAm-Cu(II), three different cross-linking level of PVAm were synthesized. It is clear from the results in Table 3 that no matter how cross-linking level, the catalyst activity was optimum as long as the –NH2 /Cu(II) was about 5.1. This may indicate environment of cupric ion in PVAm-Cu(II) is favorable for the formation of active centers. Among the group, no. 4 shows the conversion of PMMA reached 70.7% and Mw of polymerization of MMA is 555 000. From Table 1, it is clear the function of –NH2 /Cu(II) plays an important role in the initiation. The polydispersity (Mw /Mn ) of PMMA which initiated either by PVAm-Cu(II)/Na2 SO3 system or Cu2+ /Na2 SO3 system values of 3.0 are similar to those of conventional radical polymerization of MMA [18]. The tacticity of PMMA prepared with PVAm-Cu(II)/Na2 SO3 system at 303 K were determined by 1 H NMR spec-

troscopy. The result is mm = 3–4%, mr = 31–34%, and rr = 63–65%. Similar results have been reported for conventional radical polymerization of MMA [19]. 3.4. Proposed initiation mechanism for polymerization of MMA It is proposed that PVAm-Cu(II) system catalyzes MMA polymerization in a complexation-hydrogen transfer mechanism, different from the reduction– oxidation mechanism of Cu2+ /Na2 SO3 does. To verify the mechanism, we conducted following experiments in contrast. 1. Cu2+ /Na2 SO3 is a reduction–oxidation system, able to catalyze the MMA polymerization in highest monomer conversion of 41.1%. While PVAm-Cu(II) system can effectively catalyze MMA polymerization in higher monomer conversion of 65.3% with sound repeatability. 2. PVAm-Cu(II)/Na2 SO3 catalyzed MMA and other monomers polymerization in varied pH. The result indicated that the reactivity of catalyst varied with different pH. In the catalysis system, Na2 SO3 acts as initiator and the source of primary free radicals. The pH value of Na2 SO3 ’s water solution (0.1 g Na2 SO3 solved in 350 g water) is 7, which implies existence of secondary hydrolysis equilibrium of Na2 SO3 in water solution.

Table 3 The effect of –NH2 /Cu2+ ratio on catalysis of MMA Run number

Cross-linking level (%)

–NH2 /–CONH2 (mmol/mmol)

–NH2 (mmol/g)

Bound metal (mmol/g)

–NH2 /Cu2+ (mmol/mmol)

Conversion (%)

Mw (×104 )

1 2 3

2

68/32

6.325 8.453 9.432

1.965 1.654 1.342

3.2 5.1 7.0

53.8 62.1 56.8

35.7 45.6 33.9

4 5 6 7 8 9

5

47/53

8.837 9.872 10.540 10.350 11.654 12.342

1.732 1.432 1.034 1.543 1.153 0.878

5.1 6.9 10.2 6.7 10.1 14.1

70.7 65.3 54.6 63.2 56.3 45.6

55.5 35.9 28.6 34.6 26.4 23.2

10 11

10

8.437 10.432

1.668 1.346

5.0 7.7

65.7 60.1

48.2 32.7

34/66

44/56

J. Lu et al. / Applied Catalysis A: General 247 (2003) 163–173

Fig. 9. The effect of amount of coordinated Cu and Cu2+ on monomer conversion.

SO3 3− + H2 O
HSO3 − + OH− , K1 = 1.59E − 7 HSO3 − + H2 O
H2 SO3 + OH− , K1 = 7.69E − 13 SO3 2− + 2H2 O
H2 SO3 + 2OH− , K1 = 1.22E − 19 Calculation indicates, when Na2 SO3 ’s hydrolysis is one-stage, the solution’s pH value is about 9.3, while when the hydrolysis is mainly in the secondary way the pH value is about 6.9. Based on the pH value, the ion concentration could be calculated. [H2 SO3 ] = 4.11E−5 mmol/l, [SO3 2− ] = 2.27 mmol/l, [HSO3 − ] = 4.38 mmol/l. That is to say, Na2 SO3 mainly exists as HSO3 − , secondly as SO3 2− , in the initiation process shown in Fig. 9, a equilibrium is maintained with varied pH value.

When the pH is approximately 7, SO3 2− coordinates with PVAm-Cu(II) as (II), by which primary radicals come into being. The oxygen ion and the carbonyl oxygen both have lone-pair electrons, which enable them coordi-

169

nate with the empty orbit of Cu(II) in PVAm-Cu(II). MMA and HSO3 − can be activated on the surface of PVAm-Cu(II). H free radical is dissociated from the activated HSO3 − , initiating the polymerization of MMA, which has been diffusing from oil phase to water phase and activated on the PVAm-Cu(II) surface. Therefore, PVAm-Cu(II) catalyzes MMA polymerization in a coordination way. Since the primary free radical is from HSO3 − , initiation effect of the system as well as the PMMA yield varies greatly with the pH value of Na2 SO3 (Fig. 10). When pH value of solution was adjusted by hydrochloric acid to about 3 or lower, MMA could not be catalyzed to polymerization since in acid solution Na2 SO3 is turned into H2 SO3 or SO2 and the concentration of HSO3 − is very low, which decreased even cut off the primary free radical source. While the solution pH value is adjusted to 8 by NaOH, according to the calculation, [H2 SO3 ] = 2.77 mmol/l, [SO3 2− ] = 2.27 mmol/l, [HSO3 − ] = 0.36 mmol/l and the system could catalyze the MMA polymerization with MMA yield lower than 50%. Only when Na2 SO3 solution pH value is 7, the yield of PMMA could be the highest. When Na2 SO3 water solution at higher or lower pH value, PMMA yield may considerably decrease. 3. Besides MMA, other monomers such as styrene, butyl methacrylate, butyl acrylate, were also tested. Styrene cannot be catalyzed to polymerization even when water solution’s pH value is 7, because styrene does not have unbonding lone-pair electron and cannot coordinate with PVAm-Cu(II). Other acrylate monomers cannot be polymerized because there is lack of donor methyl on double bond and the double bond could not be

polarized, although there are carbonyl oxygen, which disable them to coordinate with Cu(II). In all, the PVAm-Cu(II)/Na2 SO3 system catalyzes the MMA polymerization in a complexation-hydrogen

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transformation mechanism.

In the process of hydrogen transfer, by which the radicals come into being, the carbon bonding to fewer H is the prior destination of H transfer [20].

Terminal SO3 group was determined in polymer structure by dye-partition [21], which manifested that SO3 − was one of the reactive species.

Fig. 10. Suggested mechanism of initiation.

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Fig. 11. 1 H NMR spectrum of no. 29 copolymer in CDCl3 at 298 K.

Table 4 Composition of MMA and St in the feeds, copolymer and parameters of Fineman–Ross T (K)

Number

Monomer

Copolymer

MMA

St

MMA

St

Conversion (%)

G

H

293

1 2 3 4 5 6 7

10 15 20 25 30 35 40

90 85 80 75 70 65 60

73.2 75.6 82.6 85.3 87.6 89.9 92.3

26.8 24.4 17.4 14.7 12.4 10.1 7.7

2.2 2.5 2.9 3.0 3.1 3.5 3.6

0.07043 0.11951 0.19734 0.27589 0.36791 0.47797 0.61105

0.00452 0.01005 0.01317 0.01915 0.02600 0.03257 0.03708

303

8 9 10 11 12 13 14

10 15 20 25 30 35 40

90 85 80 75 70 65 60

67.2 74.9 81.3 84.2 87.0 89.3 91.4

32.8 25.1 18.7 15.8 13.0 10.7 8.6

2.5 2.9 3.1 3.1 3.8 4.1 4.3

0.05688 0.11733 0.19250 0.27078 0.36453 0.47394 0.60394

0.00603 0.01044 0.14376 0.02083 0.02745 0.03474 0.04182

313

15 16 17 18 19 20 21

10 15 20 25 30 35 40

90 85 80 75 70 65 60

63.5 73.2 77.2 81.7 84.9 88.1 90.4

36.5 26.8 22.8 18.3 15.1 11.9 9.6

2.7 3.3 3.1 3.7 3.9 4.5 4.4

0.04724 0.11186 0.17617 0.25867 0.35235 0.46573 0.59587

0.00710 0.01140 0.01846 0.02489 0.32667 0.03916 0.04720

323

22 23 24 25 26 27 28

10 15 20 25 30 35 40

90 85 80 75 70 65 60

61.1 70.4 76.1 81.3 84.1 87.0 89.1

38.9 29.6 23.9 18.7 15.9 13.0 10.9

2.9 3.3 3.1 3.6 4.0 4.1 4.9

0.04037 0.10227 0.17149 0.25666 0.34755 0.45800 0.58511

0.00786 0.01310 0.01963 0.02556 0.03473 0.04332 0.05437

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Table 4 (Continued) T (K)

Number

333

Monomer

29 30 31 32 33 34 35

Copolymer

MMA

St

MMA

St

10 15 20 25 30 35 40

90 85 80 75 70 65 60

57.1 66.4 74.1 79.0 82.6 85.4 88.4

42.9 33.6 25.9 21.0 17.4 14.6 11.6

Conversion (%)

G

H

3.1 3.5 3.4 3.9 4.3 4.6 5.2

0.02763 0.08717 0.16262 0.24473 0.33829 0.44641 0.57919

0.00927 0.01576 0.02184 0.02954 0.03869 0.04957 0.05832

G = R(ρ − 1)/ρ; H = R2 /ρ where ρ = d[MMMA ]/d[MSt ] and R = [MMMA ]/[MSt ].

So PVAm-Cu(II) supplies the reactive species, catalyzes MMA polymerization in a different way and decreases the polymerization activity energy. 3.5. Monomer reactivity of MMA (rMMA ) and styrene (rSt ) Fig. 11 is a typical 1 H NMR spectrum if a MMA and Styrene copolymer. The protons of the phenyl group appeared around chemical shift δ = 7 ppm. The styrene composition in a copolymer was calculated from the peak area of the protons due to the phenyl group (Ap ) and the total area of all protons (At ); that is the mole fraction of styrene in a copolymer is FSt = 8Ap /5At [22,23]. The feed and calculated compositions of MMA and styrene in the copolymers at different temperature are summarized in Table 4. The monomer reactivity ratios for rMMA and rSt were evaluated using the Fineman–Ross method. Table 5 shows the monomer reactivity ratios at different temperature. It was found that rMMA = 10.51 and rSt = 0.068 (333 K). These monomer reactivity ratios of MMA and styrene initiated by PVAm-Cu(II)/Na2 SO3 system are obviously different from those obtained by homogenous (bulk or solution) copolymerization (that rMMA = 0.52 and Table 5 Monomer reactivity ratios for rMMA and rSt

4. Conclusions 1. The inhomogeneous PVAm-Cu(II)/Na2 SO3 system could catalyze MMA polymerization and MMA and styrene copolymerization in a complexationhydrogen transformation mechanism, different from the oxidation-reduction mechanism of Cu2+ / Na2 SO3 . PVAm-Cu(II)/Na2 SO3 system has higher catalysis activity, the monomer conversion could reach 65.3%, while, if catalyzed by Cu2+ / Na2 SO3 in same condition, the monomer conversion can only reach 41.9%. Catalyzed by PVAm-Cu(II)/Na2 SO3 , the MMA polymerization’s overall activation energy is 61.3 kJ/mol, and overall polymerization rate can been expressed as Rp = k[MMA]1.4 [Na2 SO3 ]0.5 [PVAm–Cu(II)]0

T (K)

rMMA rSt

rSt = 0.46, 333 K) [24,25]. In heterogeneous reaction system, the velocity of monomer’s transfer is an important factor to composition of copolymer, so the composition of MMA–St copolymer did not conform to that prepared from common system. The value of rMMA decreases with reactive temperature increases while rSt increases. These results are of great interest because they may provide some information of MMA and styrene initiated by PVAm-Cu(II)/Na2 SO3 system.

293

303

313

323

333

16.10 0.025

14.88 0.035

12.72 0.042

11.61 0.054

10.51 0.068

2. MMA conversion varies with ratio of –NH2 /Cu(II) in the PVAm-Cu(II). The optimum ratio of –NH2 /Cu(II) is about 5.1. 3. These monomer reactivity ratios of MMA and styrene initiated by PVAm-Cu(II)/Na2 SO3 system

J. Lu et al. / Applied Catalysis A: General 247 (2003) 163–173

(rMMA = 10.51 and rSt = 0.068) are obviously different from those obtained by homogenous (bulk or solution) copolymerization. This show polymer–metal complexes catalyst has effect on monomer reactivity ratios. Acknowledgements This work was financially supported by the National Science Foundation of China (No. 2007603) and Jiangsu Province National Science Foundation BK 2002042. References [1] D.C. Sherrington, J. Polym. Sci. Part A: Polym. Chem. 39 (2001) 2364. [2] S.M. Howdle, K. Jeraberk, V. Leocarbo, P.C. Marr, D.C. Sherrington, Polym. Commun. 41 (2000) 7273. [3] P.V. Prabhakaran, S. Venkatachalam, S. Ninan, Eur. Polym. J. 35 (1999) 1743. [4] R. Wang, C. Chai, Y. He, Y. Wang, S. Li, Eur. Polym. J. 35 (1999) 2051. [5] Y. Li, G. Liu, G. Yu, J. Macromol. Sci. Chem. A 26 (1989) 405. [6] T. Nishimura, T. Ouchi, M. Inato, Makromol. Chem. 177 (1976) 1895. [7] K. Kimura, Y. Inaki, K.T. Die, Makromol. Chem. 176 (1975) 2241. [8] K. Kimura, Y. Inaki, K. Takemoto, Makromol. Chem. 178 (1977) 317.

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