Synthesis of Poly(Ether Ether Ketone) with High Content of Sodium Sulfonate Groups and Its Membrane Characteristics

ELSEVIER Polymer 40 (1999)795-799

Polymer Communication Synthesis of poly(ether ether ketone) with high content of sodium sulfonate groups and its membrane characteristics

Feng Wang*, Jianke Li, Tianlu Chen, Jiping Xu

Changchun Institute of Applied Chemistry, Changchun 130022, People’s Republic ofChina Received 16 December 1998; revised 12 March 1998; accepted 24 March 1998

Abstract

Poly(ether ether ketone) with high content of sodium sulfonate groups prepared directly from 5,5’-carbonylbis(2-fluorobenzene sulfonate), 4,4’-difluorobenzophenone and phenolphthalein via aromatic nucleophilic substitution reaction. The polymer showed excellent thermal stability, high permeability of water vapour, high permselectivity of water vapour over nitrogen, and high permselectivity of anions. 0 1998 Elsevier Science Ltd. All rights reserved.

Keywords: Poly(ether ether ketone); Sodium sulfonate; Permselectivity

1. Introduction In this communication, we describe the synthesis of poly (ether ether ketone) bearing 1.2 sodium sulfonate groups per Among the attractive properties of the engineering repeat unit. This is the first time that a poly(ether ether thermoplastic poly(ether ether ketone)s, good solvent resis- ketone) with degree of sulfonation above 1.0 was synthe- tance, high thermo-oxdative stability and good mechanical sized. The permeation behaviour of water vapour and nitro- properties are significant [l]. In the last decade, consider- gen through the membranes was studied, and the ion able effort was made to modify their chemical nature while permselectivity was determined as well. maintaining their excellent physical properties to find membrane applications in electrodialysis and gas dehumi- dification. It has been proven that sulfonation is an effective 2. Experimental method to increase both the permeation rate of water vapour and the separation factor of water vapour over gases [2]. In a 100 ml three-necked round bottom flask, fitted with a A number of groups have reported the sulfonation of Dean-Stark trap with reflux condenser, a nitrogen inlet, and a poly(ether ether ketone)s, using different sulfonating agents, thermometer, 2.530 g (6 mmol) of 5,5’-carbonylbis(2-fluoro- such as concentrated sulfuric acid [3], chlorosulfonic acid benzene sulfonate), 0.873 g (4 mmol) of 4,4’-difluorobenzo- [4], pure or complexed sulfur trioxide [4-61, and methane phenone, 3.183 g (10 mmol) of phenolphthalein and 1.520 g sulfuric acid/concentrated sulfuric acid [7]. Poly(ether ether potassium carbonate were dissolved in a mixture of dimethyl ketone)s can be sulfonated with a sulfonation degree of 1.0 sulfoxide (16 ml) and toluene (8 ml). The entire operation per repeat unit [8,9]. However, a greater degree of sulfona- was conducted under a constant stream of nitrogen. The mix- tion is difficult to achieve due to the insolubility and side ture was refluxed for 3 h. After the water was essentially reactions such as interpolymer crosslinking and degrada- removed from the reaction mixture by azeotropic distillation, tion. In a p?evious work, we reported the synthesis of sulfo- the temperature was raised to 175°C to distill out the toluene and nated poly(ether ether ketone) with a sulfonation degree of kept at this temperature for 6 h. Then the reaction mixture was 1.0 per repeat unit, using sodium 2,5_dihydroxybenzene poured into 500 ml acetone to precipitate the polymer. sulfonate as one of the monomers for polycondensation [lo]. Another monomer, sodium 5,5’-carbonylbis(2-fluorobenzene sulfonate) [ll], might be employed to prepare 3. Results and discussion poly(ether ether ketone) with a high degree of sulfonation. As shown in Scheme 1, polymer I (P-I) was synthesized * Corresponding author. by the aromatic nucleophilic substitution reaction of

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66L-56L (6661) OP ~~~‘+‘d/T la 8UvM 2 96L 797

I I I I I 1 1600 1400 1200 1000 600 600 Uavenunbers

Fig. 1. Ix. spectra of P-I (a) and PEK-C (b). between 250-420°C is only lo%, which corresponds to the K315-N-03(Rikaseiki, Japan) manometric permeation loss of 1.2 sulfonic acid groups per repeat unit. The second apparatus and the permeability of water vapour was thermal degradation above 450°C is attributed to the poly- measured by the cup method [14]. As shown in Fig. 3, mer degradation. both P-I and P-II exhibit high water vapour permeation, The permeability of nitrogen was measured on a model 3.33 X 104. 3.11 X lo4 barrer at 30°C respectively. The

100

._%l g 6C)-

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0 200 400 Temp. (C)

Fig. 2. T.g.a. curves of P-I and P-II. 798 F. Wang etal./Polymer40(1999) 795-799

2oooo I---____ 3.05 3.10 3.15 3.20 3.25 3.30 3.35

l/T X 1000(1/K)

Fig. 3. The relationship between P, and l/T for P-I and P-II. water vapour permeation (P,) shows an approximate presented in Fig. 4. It is obvious that a linear relationship Arrhenius-type temperature dependence with E, = exists between lgPN and l/T in each case. The apparent 18.6 kJ mol-’ for P-I and E, = 16.5 k.I mol-’ for P-II. activation energies of nitrogen for P-I and P-II are Arrhenius plots of the permeability of nitrogen (PN) are 16.7 and 16.8 k.I mol-’ respectively. P-I exhibits a high

0.05

I I I I I 3.10 3.15 3.20 3.25 3.30

1/T X 1000(1/K)

Fig. 4. The relationship between PN and l/T for P-I and P-II. F. Wang etal./Polymer40(1999)795-799 799

l.O- . . m

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Fig. 5. Cation transport numbers across P-I membrane. selectivity of 1.89 X IO6 of water vapour over nitrogen at References 30°C. In order to characterize the pennselectivity of P-I [I] Moulinie P, Paroli RM, Wang ZY. J Polym Sci, Polym Chem Ed membrane to ions, the concentration membrane potentials 1995;33:2741. [2] Fu H, Jia L, Xu J. J Appl Polym Sci 1996;60:123 1. in KC1 solutions of different concentration (N 1and N2) were [3] Jin X, Bishop MT, Ellis TS, Karasz FE. Br Polym J 1985;17:4. measured, using the conventional method as described else- [4] Litter MI, Marvel CS. J Polym Sci, Polym Chem Ed 1985;23:1231. where [ 15,161. In Fig. 5, the cation transport numbers [5] Noshy A, Robeson LM. J Appl Polym Sci 1976;20:1885. calculated from membrane potentials by the Nemst [6] Ogawa T, Marvel CS. J Polym Sci, Polym Chem Ed 1985;23:1231. Equation are plotted versus the geometric mean (NJ of NL [7] Bailly C, Williams D, Karasz FE, MacKnight WJ. Polymer 1987;28:1009. and Nz, where N, was kept at a constant concentration (with [8] Bishop MT, Karasz FE, Russo PS, Langley KH. Macromolecules N, = 0.01 N) and N2 varied but was always maintained at a 1985;18:86. higher concentration than N1 (with N2 = 0.05-2.0 N). As [9] Shibuya N, Porter RS. Macromolecules 1992;25:6495. shown in Fig. 5, P-I membrane had a strong screening effect [lo] Wang F, Chen T, Xu J. Macromol Rapid Commun, 1998 in press, for chloride ions. However, the efficiency of electrolyte [ 111 Wang F, Chen T, Xu J. Macromol Chem Phys, 1998 in press, [12] Sivanshinsky N, Tanny GB. J Appl Polym Sci 1983;28:3235. exclusion decreased slightly with increasing KC1 concen- [13] Chen T, Yuan Y, Xu J. Chinese Patent no. 1038098, 1988. tration, showing the lower transport selectivity for [14] Fu H, Jia L, Xu J. J Appl Polym Sci 1994;51:1405. potassium ions. This can be explained by the Donnan [ 151 Yamaguchi A, Okazaki Y, Kurosaki R, Hirata Y, Kimizuka H. J Memb equilibrium, i.e. the decreasing efficiency of electrolyte Sci 1987;32:28 1. exclusion with increasing solution concentration is due to 1161 Hirata Y, Yamamoto Y, Date M, Yamaguchi A, Kimizuka H. J Memb Sci 1989;41:177. the increasing tendency of the electrolyte permeating by 1171 Juda W, Rosenberg NW, Marinsky JA, Kasper AA. J Am Chem Sot diffusion as a result of the Donnan equilibrium [17]. 1952:74:3736.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (NNSFC).