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Copolymerization of 3-methoxy-4-methacryloyloxybenzal phenylimine with methyl methacrylate
PERGAMON
European Polymer Journal 35 (1999) 1133±1138
Copolymerization of 3-methoxy-4-methacryloyloxybenzal phenylimine with methyl methacrylate R. Balaji, S. Nanjundan * Department of Chemistry, College of Engineering, Anna University, Madras - 600 025, India Received 23 September 1997; accepted 15 January 1998
Abstract Copolymers of 3-methoxy-4-methacryloyloxybenzal phenylimine and methyl methacrylate were synthesized with dierent feed ratios in ethyl methyl ketone solution at 708 218C using benzoyl peroxide as initiator. The copolymers were characterized by IR and 1 H-NMR spectroscopic techniques. Copolymer compositions were determined by 1 HNMR analysis. The monomer reactivity ratios were determined by the application of conventional linearization methods such as Fineman±Ross and Kelen±TuÈdoÈs. Gel permeation chromatography was used for determining the molecular weights (Mn and Mw) and the polydispersity index. Thermogravimetric analysis of the polymers were performed in air. The intrinsic viscosities of polymers were also discussed. # 1999 Elsevier Science Ltd. All rights reserved.
1. Introduction Schi base containing polymers are found to have wide applications. Copolymers of Schi base containing monomer [N-( p-methacryloyloxy benzylidine-paminobiphenyl] and methacrylate are known to exhibit liquid crystalline properties [1]. Schi base polymers of azomethines-ester are used as ®bre [2±4]. Polymers of schi base having ethyl vanillin are used as perfumes [5, 6]. Schi base containing polymers are used as bio catalyst carriers [7], in communications technologies [8] and also used to prepare high quality dyes [9, 10]. Polymers based on Schi bases are used for the preparation of transition metal complexes [11± 13]. The estimation of copolymer composition and determination of reactivity ratios is signi®cant for tailormaking copolymers. In the past few decades, 1 H-NMR spectroscopic analysis has been established as a powerful tool for the estimation of copolymer composition [14]. The present article discusses the copolymerization behavior of Schi base containing
* Corresponding author.
monomer 3-methoxy-4-methacryloyloxybenzal phenylimine (MMBPI) and methyl methacrylate (MMA) in solution, characterization of the copolymers and determination of monomer reactivity ratios.
2. Experimental procedures Methyl methacrylate (MMA) was freed from inhibitor by washing with 5% aqueous sodium hydroxide solution followed by distilled water and dried over anhydrous sodium sulphate and distilled under reduced pressure. Benzoyl peroxide (BPO) was recrystallized from a chloroform±methanol (1:1) mixture. The solvents were puri®ed by distillation. 2.1. Synthesis of 3-methoxy-4-methacryloyloxybenzal phenylimine [MMBPI] Methacryloyl chloride was prepared by reacting methacrylic acid with benzoyl chloride [15]. 3Methoxy-4-hydroxybenzal phenylimine (MHBPI) was synthesized by re¯uxing vanillin (0.11 mol) with aniline (0.11 mol) in methanol solution. The MMBPI was synthesized by reacting MHBPI (0.11 mol) with methacry-
0014-3057/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S 0 0 1 4 - 3 0 5 7 ( 9 8 ) 0 0 0 9 1 - 3
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loyl chloride (0.11 mol) at 0 to 58C in the presence of triethylamine (0.11 mol) in ethyl methyl ketone solution. The quaternary ammonium salt was ®ltered o and the ®ltrate evaporated, the remaining fraction was 3-methoxy-4-methacryloyloxybenzal phenylimine. The formation of the monomer was con®rmed by IR and 1 H-NMR techniques. IR (cmÿ1): 3080 and 3050 (aliphatic and aromatic unsaturated .C±H stretching respectively), 2970 and 2870 (symmetric and asymmetric C±H stretching due to CH3 groups), 2800 (C±H stretching due to -CH.N), 1690 (ester carbonyl stretching), 1630 (C.N stretching), 1620 (aliphatic C.C stretching), 1550 and 1500 (aromatic C.C stretching), 1190 and 1050 (C±O stretching) 900, 700 (out of plane bending vibrations of C±H groups of benzene ring). 1 H-NMR (ppm): 8.07±7.61 (6H) and 7.46±7.23 (2H) (Aromatic protons), 6.61 (1H) (-CH.N), 6.21±6.05 (2H) (CH2.), 3.71 (3H) (O±CH3), 1.73 (3H) (CH3). 2.2. Copolymerization Copolymerization were carried out in ethyl methyl ketone (EMK) solution at 708C using BPO as initiator. Predetermined quantities of MMBPI, MMA and EMK were mixed in a reaction tube and purged with N2 for 30 min. After the sealed tubes had been kept at the required temperature, the contents were poured into a large excess of methanol. The polymers were puri®ed by repeated precipitation by methanol from solution in dimethyl formamide (DMF) and ®nally dried under vacuum. 2.3. Measurements Infrared spectra were recorded with a Hitachi 270-50 I.R. spectrophotometer on solid samples as KBr pellets. 1 H-NMR spectra were obtained with a JEOL JNX-100FT NMR Spectrometer in CDCl3 solution using TMS as the internal reference. Molecular weights (Mn and Mw) of the polymers were determined by gel
permeation chromatography (Waters 501) equipped with a RI detector and calibrated with polystyrene standards. THF was the eluent. Thermogravimetric analysis was performed with a Metler 3000 thermal analyzer at a heating rate of 158/min in air.
3. Results and discussion The copolymerization of MMBPI with MMA in EMK solution was studied in a wide composition interval with mole fractions of MMBPI ranging from 0.10 to 0.90 in the feed. The reaction time was selected to give conversions less than 10 wt% in order to satisfy the dierential copolymerization equation. The data of compositions of feeds and copolymers are presented in Table 1. The copolymers were soluble in chloroform, acetone, dimethyl formamide, dimethylsulfoxide and tetrahydrofuran but insoluble in nonpolar solvents (benzene and toluene and xylene) and hydroxy-groups containing solvents (methanol and ethanol). The IR spectra of the copolymers (Fig. 1) apparently show more prominent absorptions of MMBPI units since the absorption due to MMA overlap those of MMBPI. Peaks at 1450 cmÿ1, 1500 cmÿ1 and % $ 1590 cmÿ1 were attributed to aromatic $C.C% stretching. The vibrations due to the C±H stretching of the methyl groups were shown at 2960 cmÿ1 and 2850 cmÿ1. The ether link due to OMe group and C±O link in the ester of MMBPI units and C±O link in the ester of MMA units showed signals at 1110 cmÿ1, 1200 cmÿ1 and 1260 cmÿ1 respectively. The out-ofplane C±H bending vibrations of benzene ring were observed at 800 cmÿ1 and 750 cmÿ1. the C.N stretching due to imine group showed signal at 1640 cmÿ1. The absorption at 2800 cmÿ1 was due to the C±H stretching of the group -CH.N. The esters carbonyl stretching frequencies of MMBPI unit and MMA unit were shown at 1760 cmÿ1 and 1740 cmÿ1 respectively.
Table 1 Composition data of the free radical copolymerization of MMBPI (1) with MMA (2) in EMK solution at 708C Sample No. 1 2 3 4 5 6 7
Feed M1 0.10 0.20 0.35 0.50 0.65 0.80 0.90
Conversion % 8.54 7.88 8.85 8.12 9.45 8.33 9.25
C 0.4000 0.7097 1.0804 1.4167 1.7377 2.0755 2.3600
Copolymer m1 0.1500 0.2661 0.4052 0.5313 0.6516 0.7783 0.8850
M1 and m1 are the mole fractions of MMBPI and MMA in the feed and in the copolymer, respectively. C is the ratio of the integrated intensities of aromatic protons to that of methoxy protons in the 1 H-NMR spectrum of the copolymer.
R. Balaji, S. Nanjundan / European Polymer Journal 35 (1999) 1133±1138
1135
Fig. 3. Chemical structure of poly(MMBPI-co-MMA).
Fig. 1. I.R. Spectra of (a) MMBPI, (b) Poly(MMBPI), (c) Poly(MMBPI-co-MMA) [0.50:0.50].
Peaks at 3050 cmÿ1 was due to aromatic unsaturated .C±H stretching. 1 H-NMR spectrum (Fig. 2) of poly (MMBPI-coMMA) shows absorptions between 7.50±7.30 ppm (2H) and 8.12±7.62 ppm (6H) corresponding to aromatic protons of MMBPI. Signals at 3.73 ppm and 3.60 ppm were due to the methoxy protons attached to benzene ring of MMBPI and that of MMA unit respectively. The methine proton due to the -CH.N shows signal at 6.63 ppm. The methyl group attached to the unsaturated carbon gives signal at 1.26 ppm (3H). Peaks at 2.06 ppm was due to methylene proton of the copolymer.
sponding 1 H-NMR spectra. The assignment of the resonance peaks in the 1 H-NMR spectrum allow for the accurate evaluation of the content of each kind of monomeric unit incorporated into the copolymer chains. Thus, the mole fraction of MMBPI in the copolymer chains was calculated from the integrated intensities of aromatic protons of MMBPI and methoxy protons of MMBPI and MMA units. The following expression applies to copolymers. Let m1 be the mole fraction of MMBPI and (1 ÿ m1) that of MMA. There are 8 aromatic protons in MMBPI and 3 methoxy protons in MMBPI and another 3 methoxy protons in MMA. Therefore Intensities of aromatic protons IAr Intensities of methoxy protons IOMe 8m1 3m1 3 1 ÿ m1
C
1
which on simpli®cation gives, m1
3C 8
2
3.1. Copolymer compositions Since the chemical structure of copolymers may be represented as in Fig. 3, the average compositions of copolymer samples were determined from the corre-
Fig. 2. 1 H-NMR spectrum of poly(MMBPI-co-MMA).
Fig. 4. Composition diagram of MMBPI±MMA copolymer system.
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Fig. 5. Fineman±Ross plot for the MMBPI±MMA copolymer system.
Fig. 6. Kelen±TuÈdoÈs plot for the MMBPI±MMA copolymer system.
Table 2 Copolymerization parameters for the free radical copolymerization of MMBPI with MMA Methods Fineman±Ross Kelen±TuÈdoÈs Average
r1 0.80 0.82 0.81
r2
r1r2
0.60 0.58 0.59
1/r1
0.48 0.48 0.48
1/r2
1.25 1.22 1.24
1.67 1.72 1.70
r1 and r2 are the reactivity ratios for MMBPI and MMA, respectively.
Table 3 Molecular weight data for the copolymers of MMBPI with MMA and intrinsic viscosity data for polymers Molecular weights Polymers Poly(MMBPI) 1 2 3 4 5 6 7 Poly(MMA)
M1 1.00 0.90 0.80 0.65 0.50 0.35 0.20 0.10 0.00
Mw10ÿ4
Mn10ÿ4
Mw/Mn
2.96 2.83 2.68 2.72 2.49 ÿ 2.51 ÿ 2.43
1.53 1.47 1.42 1.43 1.32 ÿ 1.34 ÿ 1.32
1.94 1.93 1.89 1.90 1.89 ÿ 1.87 ÿ 1.84
M1 is the mole fraction of MMBPI in the feed.
Intrinsic viscosity [Z] (dl/g) 0.37 0.35 0.32 0.33 0.30 0.29 0.31 0.25 ÿ
R. Balaji, S. Nanjundan / European Polymer Journal 35 (1999) 1133±1138
N1
1137
1 ÿ r2 0:667 2 ÿ r1 ÿ r2
3
when the mole fraction of the monomer MMBPI in the feed is 0.667, the copolymer formed will have the same composition as that of the feed. When the mole fraction of the feed is less than 0.667 with respect to MMBPI, the copolymer is relatively richer in this monomer unit than the feed. When the mole fraction of the monomer MMBPI in the feed is above 0.667, the copolymer is relatively richer in MMA unit than in the feed. 3.3. Molecular weights
Fig. 7. TGA curves of (a) poly(MMA) (b) poly(MMBPI-coMMA) [0.50/0.50] (c) poly(MMBPI).
From Eq. (2), the mole fractions of MMBPI in copolymers were determined by measuring the intensities of aromatic proton signals and methoxy proton signals. Table 1 gives the values of C and the corresponding mole fractions of MMBPI in the copolymers. The plot of mole fraction of MMBPI (m1) in feed vs that in the copolymer (m1) (Fig. 4) indicates that the distribution of monomeric units is statistical with an azeotropic composition when the mole fraction of MMBPI in the feed is 0.667.
The number- and weight-average molecular weights of poly(MMBPI), poly(MMA) and ®ve samples of copolymers, determined by gel permeation chromatography, are presented in Table 3. The polydispersity index of poly(MMBPI), ®ve copolymers and poly(MMA) are very close to 2.0. The theoretical value of Mw/Mn for polymers produced via radical combination and disproportionation are 1.5 and 2.0, respectively [18]. In the homopolymerization of MMA the radical undergo termination mainly by disproportionation [19]. The values of Mw/Mn of these polymers suggest a strong tendency for chain termination by disproportionation when the mole fractions of MMBPI is higher than that of MMA in the feed. 3.4. Viscosity measurements
3.2. Reactivity ratios From the monomer feed ratios and the copolymer compositions, the reactivity ratios of MMBPI and MMA were determined by the application of methods due to Fineman±Ross (F±R) [16] and Kelen±TuÈdoÈs (K±T) [17]. The values from the F±R plot (Fig. 5) and K±T plot (Fig. 6) are presented in Table 2. Since the r1 and r2 values are less than 1, this system gives rise to azeotropic polymerization at a particular composition of the monomers which is calculated using the equation
The intrinsic viscosities [Z] were obtained by extrapolating Zsp/C to zero concentration. The data in Table 3 clearly indicates that the value of [Z] is aected by the composition of the copolymer and the change is not uniform. 3.5. Thermogravimetric analysis TGA curves for poly (MMBPI), poly (MMA) and sample of poly (MMBPI-co-MMA) are shown in Fig. 7. The results of the dierential thermogravimetric
Table 4 TGA data for MMBPI±MMA copolymer(s) and homopolymers Temperature (8C) at dierent weight loss (%) Polymers
IDT (8C)
10%
30%
50%
70%
90%
Poly(MMBPI) Copolymer 1a Poly(MMA)
276 263 244
306 288 275
375 344 319
469 413 350
556 475 381
631 575 413
IDT Ð initial decomposition temperature. Copolymer composition (mole fraction); (1) MMBPI/MMA: 0.50/0.50.
a
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analysis are presented in Table 4. Fig. 7 clearly indicates that poly (MMA) undergoes decomposition in a single stage whereas poly (MMBPI) and poly (MMBPI-co-MMA) undergo decomposition in three dierent stages. The initial decomposition temperature of poly (MMBPI) and poly (MMA) are 2768C and 2448C respectively; those of the copolymers are intermediate. TGA results indicates that the thermal stability of the copolymers increases with the increase of MMBPI content in the copolymer.
References [1] Zou Y, Lin G, Yao Q, Dai L, Pan R. Gaofeuzi Xuebao (China) 1996;1:116. [2] Kolot VN, Chernyk TE, Shugaeva TV, Batik'yan BA, Shchetinin AM, Kudryartsev GI. Khim Volokna (USSR) 1986;4:30. [3] Banerjee S, Saxena C. J Polym Sci A Polym Chem 1996;34:3565. [4] Biswas A, Gardner KH, Wojtkowski P. ACS Symp Ser 1990;435. [5] Mookherjee DB, Trenkle WR, Calderone N, Fenn SR. U.S. US 1989;4:853, 369; Chem Abstr, 1989;111:219137u.
[6] Mcritchie AC, Green M. The P&G Company, USA, PCT Int Appl WO, 1996, 29 281; G B Appl 1995/5, 518, 48pp. (Eng). [7] Krylova V, Gibietis J. Latv Kim Z (Russ) 1996;1-2:143. [8] Nuyken O, Scherer C, Baindi A, Brenner AR, Dahn U, Gaertner R, Kaiser-Roehrich S, Kolle-Frath R, Matnsche P, Voit B. Prog Polym Sci (Eng) 1997;22:93. [9] Vashi HJ, Desai KR. Ind J Fibre Text Res 1996;21:225. [10] Shi D, Jia C, Peng S. Linchan Huaxue Yu Gongye (China), 1996;16:7; Chem Abstr, 1996;20167 h. [11] Garnovskii AD, Gerbelen NV, Kochin SG, Arion VB, Minkina LS, Indrichan KM, Vasol'chenko IS, Revenko MD, Konstantinovskii LE. Dokl Akad Nauk SSSR, (Russ), 1989;306:872; Chem Abstr, 1989;111:224066z. [12] Osaka Gas Co Ltd. Jpn Kokai Tokkyo Koho JP 01, 1989;118:515, US Appl 1987;665; Chem Abstr 1989;111:215126s. [13] Patel MN, Patel MM, Cassidy PE, Fitch WJ. Inorg Chim Acta 1986;118:33. [14] Narasimhaswamy T, Sumathi SC, Reddy BSR, Rajadurai S. J Polym Mater 1989;6:209. [15] Stampel GM, Cross RP, Maliella RP. J Am Chem Soc. 1950;72:2899. [16] Fineman M, Ross SD. J Polym Sci 1950;5:259. [17] Kelen T, TuÈdoÈs F. J Macromol Sci-Chem A 1975;9:1. [18] Teramachi S, Hasegara A, Akatsuka M, Yamashita A, Takemoto N. Macromolecules 1978;11:1206. [19] Bevington JC, Melville HW, Taylor RP. J Polym Sci Chem. Edn 1954;12:449.
European Polymer Journal 35 (1999) 1133±1138
Copolymerization of 3-methoxy-4-methacryloyloxybenzal phenylimine with methyl methacrylate R. Balaji, S. Nanjundan * Department of Chemistry, College of Engineering, Anna University, Madras - 600 025, India Received 23 September 1997; accepted 15 January 1998
Abstract Copolymers of 3-methoxy-4-methacryloyloxybenzal phenylimine and methyl methacrylate were synthesized with dierent feed ratios in ethyl methyl ketone solution at 708 218C using benzoyl peroxide as initiator. The copolymers were characterized by IR and 1 H-NMR spectroscopic techniques. Copolymer compositions were determined by 1 HNMR analysis. The monomer reactivity ratios were determined by the application of conventional linearization methods such as Fineman±Ross and Kelen±TuÈdoÈs. Gel permeation chromatography was used for determining the molecular weights (Mn and Mw) and the polydispersity index. Thermogravimetric analysis of the polymers were performed in air. The intrinsic viscosities of polymers were also discussed. # 1999 Elsevier Science Ltd. All rights reserved.
1. Introduction Schi base containing polymers are found to have wide applications. Copolymers of Schi base containing monomer [N-( p-methacryloyloxy benzylidine-paminobiphenyl] and methacrylate are known to exhibit liquid crystalline properties [1]. Schi base polymers of azomethines-ester are used as ®bre [2±4]. Polymers of schi base having ethyl vanillin are used as perfumes [5, 6]. Schi base containing polymers are used as bio catalyst carriers [7], in communications technologies [8] and also used to prepare high quality dyes [9, 10]. Polymers based on Schi bases are used for the preparation of transition metal complexes [11± 13]. The estimation of copolymer composition and determination of reactivity ratios is signi®cant for tailormaking copolymers. In the past few decades, 1 H-NMR spectroscopic analysis has been established as a powerful tool for the estimation of copolymer composition [14]. The present article discusses the copolymerization behavior of Schi base containing
* Corresponding author.
monomer 3-methoxy-4-methacryloyloxybenzal phenylimine (MMBPI) and methyl methacrylate (MMA) in solution, characterization of the copolymers and determination of monomer reactivity ratios.
2. Experimental procedures Methyl methacrylate (MMA) was freed from inhibitor by washing with 5% aqueous sodium hydroxide solution followed by distilled water and dried over anhydrous sodium sulphate and distilled under reduced pressure. Benzoyl peroxide (BPO) was recrystallized from a chloroform±methanol (1:1) mixture. The solvents were puri®ed by distillation. 2.1. Synthesis of 3-methoxy-4-methacryloyloxybenzal phenylimine [MMBPI] Methacryloyl chloride was prepared by reacting methacrylic acid with benzoyl chloride [15]. 3Methoxy-4-hydroxybenzal phenylimine (MHBPI) was synthesized by re¯uxing vanillin (0.11 mol) with aniline (0.11 mol) in methanol solution. The MMBPI was synthesized by reacting MHBPI (0.11 mol) with methacry-
0014-3057/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S 0 0 1 4 - 3 0 5 7 ( 9 8 ) 0 0 0 9 1 - 3
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loyl chloride (0.11 mol) at 0 to 58C in the presence of triethylamine (0.11 mol) in ethyl methyl ketone solution. The quaternary ammonium salt was ®ltered o and the ®ltrate evaporated, the remaining fraction was 3-methoxy-4-methacryloyloxybenzal phenylimine. The formation of the monomer was con®rmed by IR and 1 H-NMR techniques. IR (cmÿ1): 3080 and 3050 (aliphatic and aromatic unsaturated .C±H stretching respectively), 2970 and 2870 (symmetric and asymmetric C±H stretching due to CH3 groups), 2800 (C±H stretching due to -CH.N), 1690 (ester carbonyl stretching), 1630 (C.N stretching), 1620 (aliphatic C.C stretching), 1550 and 1500 (aromatic C.C stretching), 1190 and 1050 (C±O stretching) 900, 700 (out of plane bending vibrations of C±H groups of benzene ring). 1 H-NMR (ppm): 8.07±7.61 (6H) and 7.46±7.23 (2H) (Aromatic protons), 6.61 (1H) (-CH.N), 6.21±6.05 (2H) (CH2.), 3.71 (3H) (O±CH3), 1.73 (3H) (CH3). 2.2. Copolymerization Copolymerization were carried out in ethyl methyl ketone (EMK) solution at 708C using BPO as initiator. Predetermined quantities of MMBPI, MMA and EMK were mixed in a reaction tube and purged with N2 for 30 min. After the sealed tubes had been kept at the required temperature, the contents were poured into a large excess of methanol. The polymers were puri®ed by repeated precipitation by methanol from solution in dimethyl formamide (DMF) and ®nally dried under vacuum. 2.3. Measurements Infrared spectra were recorded with a Hitachi 270-50 I.R. spectrophotometer on solid samples as KBr pellets. 1 H-NMR spectra were obtained with a JEOL JNX-100FT NMR Spectrometer in CDCl3 solution using TMS as the internal reference. Molecular weights (Mn and Mw) of the polymers were determined by gel
permeation chromatography (Waters 501) equipped with a RI detector and calibrated with polystyrene standards. THF was the eluent. Thermogravimetric analysis was performed with a Metler 3000 thermal analyzer at a heating rate of 158/min in air.
3. Results and discussion The copolymerization of MMBPI with MMA in EMK solution was studied in a wide composition interval with mole fractions of MMBPI ranging from 0.10 to 0.90 in the feed. The reaction time was selected to give conversions less than 10 wt% in order to satisfy the dierential copolymerization equation. The data of compositions of feeds and copolymers are presented in Table 1. The copolymers were soluble in chloroform, acetone, dimethyl formamide, dimethylsulfoxide and tetrahydrofuran but insoluble in nonpolar solvents (benzene and toluene and xylene) and hydroxy-groups containing solvents (methanol and ethanol). The IR spectra of the copolymers (Fig. 1) apparently show more prominent absorptions of MMBPI units since the absorption due to MMA overlap those of MMBPI. Peaks at 1450 cmÿ1, 1500 cmÿ1 and % $ 1590 cmÿ1 were attributed to aromatic $C.C% stretching. The vibrations due to the C±H stretching of the methyl groups were shown at 2960 cmÿ1 and 2850 cmÿ1. The ether link due to OMe group and C±O link in the ester of MMBPI units and C±O link in the ester of MMA units showed signals at 1110 cmÿ1, 1200 cmÿ1 and 1260 cmÿ1 respectively. The out-ofplane C±H bending vibrations of benzene ring were observed at 800 cmÿ1 and 750 cmÿ1. the C.N stretching due to imine group showed signal at 1640 cmÿ1. The absorption at 2800 cmÿ1 was due to the C±H stretching of the group -CH.N. The esters carbonyl stretching frequencies of MMBPI unit and MMA unit were shown at 1760 cmÿ1 and 1740 cmÿ1 respectively.
Table 1 Composition data of the free radical copolymerization of MMBPI (1) with MMA (2) in EMK solution at 708C Sample No. 1 2 3 4 5 6 7
Feed M1 0.10 0.20 0.35 0.50 0.65 0.80 0.90
Conversion % 8.54 7.88 8.85 8.12 9.45 8.33 9.25
C 0.4000 0.7097 1.0804 1.4167 1.7377 2.0755 2.3600
Copolymer m1 0.1500 0.2661 0.4052 0.5313 0.6516 0.7783 0.8850
M1 and m1 are the mole fractions of MMBPI and MMA in the feed and in the copolymer, respectively. C is the ratio of the integrated intensities of aromatic protons to that of methoxy protons in the 1 H-NMR spectrum of the copolymer.
R. Balaji, S. Nanjundan / European Polymer Journal 35 (1999) 1133±1138
1135
Fig. 3. Chemical structure of poly(MMBPI-co-MMA).
Fig. 1. I.R. Spectra of (a) MMBPI, (b) Poly(MMBPI), (c) Poly(MMBPI-co-MMA) [0.50:0.50].
Peaks at 3050 cmÿ1 was due to aromatic unsaturated .C±H stretching. 1 H-NMR spectrum (Fig. 2) of poly (MMBPI-coMMA) shows absorptions between 7.50±7.30 ppm (2H) and 8.12±7.62 ppm (6H) corresponding to aromatic protons of MMBPI. Signals at 3.73 ppm and 3.60 ppm were due to the methoxy protons attached to benzene ring of MMBPI and that of MMA unit respectively. The methine proton due to the -CH.N shows signal at 6.63 ppm. The methyl group attached to the unsaturated carbon gives signal at 1.26 ppm (3H). Peaks at 2.06 ppm was due to methylene proton of the copolymer.
sponding 1 H-NMR spectra. The assignment of the resonance peaks in the 1 H-NMR spectrum allow for the accurate evaluation of the content of each kind of monomeric unit incorporated into the copolymer chains. Thus, the mole fraction of MMBPI in the copolymer chains was calculated from the integrated intensities of aromatic protons of MMBPI and methoxy protons of MMBPI and MMA units. The following expression applies to copolymers. Let m1 be the mole fraction of MMBPI and (1 ÿ m1) that of MMA. There are 8 aromatic protons in MMBPI and 3 methoxy protons in MMBPI and another 3 methoxy protons in MMA. Therefore Intensities of aromatic protons IAr Intensities of methoxy protons IOMe 8m1 3m1 3 1 ÿ m1
C
1
which on simpli®cation gives, m1
3C 8
2
3.1. Copolymer compositions Since the chemical structure of copolymers may be represented as in Fig. 3, the average compositions of copolymer samples were determined from the corre-
Fig. 2. 1 H-NMR spectrum of poly(MMBPI-co-MMA).
Fig. 4. Composition diagram of MMBPI±MMA copolymer system.
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Fig. 5. Fineman±Ross plot for the MMBPI±MMA copolymer system.
Fig. 6. Kelen±TuÈdoÈs plot for the MMBPI±MMA copolymer system.
Table 2 Copolymerization parameters for the free radical copolymerization of MMBPI with MMA Methods Fineman±Ross Kelen±TuÈdoÈs Average
r1 0.80 0.82 0.81
r2
r1r2
0.60 0.58 0.59
1/r1
0.48 0.48 0.48
1/r2
1.25 1.22 1.24
1.67 1.72 1.70
r1 and r2 are the reactivity ratios for MMBPI and MMA, respectively.
Table 3 Molecular weight data for the copolymers of MMBPI with MMA and intrinsic viscosity data for polymers Molecular weights Polymers Poly(MMBPI) 1 2 3 4 5 6 7 Poly(MMA)
M1 1.00 0.90 0.80 0.65 0.50 0.35 0.20 0.10 0.00
Mw10ÿ4
Mn10ÿ4
Mw/Mn
2.96 2.83 2.68 2.72 2.49 ÿ 2.51 ÿ 2.43
1.53 1.47 1.42 1.43 1.32 ÿ 1.34 ÿ 1.32
1.94 1.93 1.89 1.90 1.89 ÿ 1.87 ÿ 1.84
M1 is the mole fraction of MMBPI in the feed.
Intrinsic viscosity [Z] (dl/g) 0.37 0.35 0.32 0.33 0.30 0.29 0.31 0.25 ÿ
R. Balaji, S. Nanjundan / European Polymer Journal 35 (1999) 1133±1138
N1
1137
1 ÿ r2 0:667 2 ÿ r1 ÿ r2
3
when the mole fraction of the monomer MMBPI in the feed is 0.667, the copolymer formed will have the same composition as that of the feed. When the mole fraction of the feed is less than 0.667 with respect to MMBPI, the copolymer is relatively richer in this monomer unit than the feed. When the mole fraction of the monomer MMBPI in the feed is above 0.667, the copolymer is relatively richer in MMA unit than in the feed. 3.3. Molecular weights
Fig. 7. TGA curves of (a) poly(MMA) (b) poly(MMBPI-coMMA) [0.50/0.50] (c) poly(MMBPI).
From Eq. (2), the mole fractions of MMBPI in copolymers were determined by measuring the intensities of aromatic proton signals and methoxy proton signals. Table 1 gives the values of C and the corresponding mole fractions of MMBPI in the copolymers. The plot of mole fraction of MMBPI (m1) in feed vs that in the copolymer (m1) (Fig. 4) indicates that the distribution of monomeric units is statistical with an azeotropic composition when the mole fraction of MMBPI in the feed is 0.667.
The number- and weight-average molecular weights of poly(MMBPI), poly(MMA) and ®ve samples of copolymers, determined by gel permeation chromatography, are presented in Table 3. The polydispersity index of poly(MMBPI), ®ve copolymers and poly(MMA) are very close to 2.0. The theoretical value of Mw/Mn for polymers produced via radical combination and disproportionation are 1.5 and 2.0, respectively [18]. In the homopolymerization of MMA the radical undergo termination mainly by disproportionation [19]. The values of Mw/Mn of these polymers suggest a strong tendency for chain termination by disproportionation when the mole fractions of MMBPI is higher than that of MMA in the feed. 3.4. Viscosity measurements
3.2. Reactivity ratios From the monomer feed ratios and the copolymer compositions, the reactivity ratios of MMBPI and MMA were determined by the application of methods due to Fineman±Ross (F±R) [16] and Kelen±TuÈdoÈs (K±T) [17]. The values from the F±R plot (Fig. 5) and K±T plot (Fig. 6) are presented in Table 2. Since the r1 and r2 values are less than 1, this system gives rise to azeotropic polymerization at a particular composition of the monomers which is calculated using the equation
The intrinsic viscosities [Z] were obtained by extrapolating Zsp/C to zero concentration. The data in Table 3 clearly indicates that the value of [Z] is aected by the composition of the copolymer and the change is not uniform. 3.5. Thermogravimetric analysis TGA curves for poly (MMBPI), poly (MMA) and sample of poly (MMBPI-co-MMA) are shown in Fig. 7. The results of the dierential thermogravimetric
Table 4 TGA data for MMBPI±MMA copolymer(s) and homopolymers Temperature (8C) at dierent weight loss (%) Polymers
IDT (8C)
10%
30%
50%
70%
90%
Poly(MMBPI) Copolymer 1a Poly(MMA)
276 263 244
306 288 275
375 344 319
469 413 350
556 475 381
631 575 413
IDT Ð initial decomposition temperature. Copolymer composition (mole fraction); (1) MMBPI/MMA: 0.50/0.50.
a
1138
R. Balaji, S. Nanjundan / European Polymer Journal 35 (1999) 1133±1138
analysis are presented in Table 4. Fig. 7 clearly indicates that poly (MMA) undergoes decomposition in a single stage whereas poly (MMBPI) and poly (MMBPI-co-MMA) undergo decomposition in three dierent stages. The initial decomposition temperature of poly (MMBPI) and poly (MMA) are 2768C and 2448C respectively; those of the copolymers are intermediate. TGA results indicates that the thermal stability of the copolymers increases with the increase of MMBPI content in the copolymer.
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