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Synthesis and properties of novel copolymers of poly(ether ketone diphenyl ketone ether ketone ketone) and poly(ether amide ether amide ether ketone ketone).

INTRODUCTION

Poly(aryl ether ketone)s (PAEKs) are a class of high-performance engineering thermoplastics known for their excellent combination of chemical, physical and mechanical properties [1-3]. This class of advanced materials is currently receiving much attention for potential applications in aerospace, automobile, electronics, and other high technology fields [4-8]. There are two general synthetic pathways to preparing PAEKs [9, 10], The first approach is a synthesis involving nucleophilic aromatic substitution, in which a diaryl ether linkage is obtained [11-15]. The second one is a synthesis involving Friedel-Crafts electrophilic substitution, in which a diaryl ketone linkage is formed [16-21], Normally, the preparation involving nucleophilic aromatic substitution is conducted at 300[degrees]C and even higher temperatures. While each method has its own merits and drawbacks, the electrophilic route has usually been used to prepare various kinds of PAEKs because the polymerization reaction conditions are mild and the monomers, which are used in the electrophilic approach, have been more selective, cheaper, and readily available. The main drawbacks of poly(aryl ether ketone)s are high cost, high processing temperatures, and relatively low glass transition temperatures. It is desirable to utilize PAEK materials with higher glass transition temperatures in advanced composite applications.

Modification of PAEK properties is desired for many applications and has received considerable attention. On the other hand, the synthesis and investigation of novel poly(aryl ether ketone)s would be very useful for a more rigorous structure-property correlation of this very interesting class of polymers. One effective method of varying PAEK properties involves the incorporation of a variety of groups in the main chains. Among these, stiff and bulky groups such as diphenyl or naphthalene are of high interest because it offers good advantages concerning the stability and thermal resistance of the resulting PAEKs [22-26]. Introduction of pendant groups on to the poly(aryl ether ketone) main chain is another structural change [27-30]. Considering the fact that poly (aryl ether ketone)s (e.g. PEEK or PEK) suffer from poor creep behavior above their relatively low glass transitions, the synthesis of semicrystalline poly(aryl ether ketone)s with increased [T.sub.g] is of considerable interest. In recent years, some papers were published concerning the copolymerization of PEEK in order to improve its glass transition temperature ([T.sub.g]), and processability at high temperatures, and to obtain low-cost materials [31-33], But, the improvement of [T.sub.g] is not so marked for those reported PEEK copolymers. Shibata et al. reported the synthesis of the block copolymers of the poly(ether ether ketone) (PEEK) and the poly(aryl ether sulfone) containing biphenylene moiety (PEBS) [34]. Although the degree of crystallinity of the PEEK/ PEBS block copolymers decreased with the increase in PEBS content, the glass transition temperature ([T.sub.g]) rose greatly, and superior heat resistance and good mechanical properties at high temperatures were obtained.

It is well known that lowering the [T.sub.m] could improve the melt processabilities of the polymers, while raising the [T.sub.g] is advantageous for their in-service mechanical and thermal properties. To expand the application of PAEKs, their melt processabilities and thermal properties need to be improved by reducing the melting temperature and enhancing the glass transition temperature. To obtain semicrystalline poly(aryl ether ketone)s with high [T.sub.g]S and moderate [T.sub.m]s is our goal since they would have good melt processabilities, excellent thermal and mechanical properties, and solvent-resistance characteristics. Poly(aryl ether ketone)s containing both diphenyl moiety and amide linkages in the main chains are expected to combine high [T.sub.g] values and the other attractive features of aromatic polyamides with the excellent chemical, solvent, and stress-crack resistance of the poly(aryl ether ketone)s. In this paper, we synthesized two new monomers, 4,4'-bis(4-phenoxybenzoyl)diphenyl (BPOBDP) and N,N'-bis(4phenoxybenzoyl)--4,4'-diaminodiphenyl ether (BPBDAE), via simple synthetic procedures from readily available materials. Novel copolymers of poly(ether ketone diphenyl ketone ether ketone ketone) (PEKDKEKK) and polyfether amide ether amide ether ketone ketone) (PEAEAEKK) were synthesized by electrophilic Friedel-Crafts solution copolycondensation of isophthaloyl chloride (IPC) with a mixture of BPOBDP and BPBDAE, over a wide range of BPOBDP/BPBDAE molar ratios, in the presence of anhydrous A1[Cl.sub.3] and N-methylpyrrolidone (NMP) in 1,2-dichloroethane (DCE).

EXPERIMENTAL

Materials

All reagents and solvents were of analytical grade and were used without further purification unless stated otherwise. Isophthaloyl chloride (IPC, Shuanglin Chemical Co., Nanchang, China) was purified by distillation under vacuum prior to use. 1,2-Dichloroethane (DCE, Shanghai Chemical Reagent), N-methylpyrrolidone (NMP, Shanghai Chemical Reagent), N,N-dimethylacetamide (DMAc, Shanghai Chemical Reagent), diphenyl ether (DPE, Shanghai Chemical Reagent), and N,N-dimethylformamide (DMF, Shanghai Chemical Reagent) were purified by distillation and dried by 0.4 nm molecular sieve. Aluminum chloride (Shanghai Chemical Reagent) was sublimed prior to use. 4,4'-Diaminodiphenyl ether (Shanghai Chemical Reagent), p-phenoxybenzoic acid (Shanghai Chemical Reagent) and 4,4'-diphenyldicarboxylic acid (Shanghai Chemical Reagent) were used as received.

Synthesis of 4,4'-Bis(4-phenoxybenzoyl)diphenyl (BPOBDP)

To a 250 mL, round-bottomed flask were added 4,4'diphenyldicarboxylic acid (4.84 g, 20 mmol), SO[Cl.sub.2] (50 mL), and DMF (1 mL). The mixture was stirred at reflux temperature for 4 h. After removal of SO[Cl.sub.2] under reduced pressure, the residue was dissolved in DCE (80 mL) under nitrogen, then A1[Cl.sub.3] (6.68 g, 50 mmol) and DPE (13.6 g, 80 mmol) were added at 0[degrees]C with stirring, the molar ratio of DPE to 4,4'-diphenyldicarboxylic acid dichloride was 4. The reaction mixture was stirred at 0[degrees]C for 4 h and at room temperature for 2 h, quenched with methanol (50 mL) at 0[degrees]C and the precipitate was crushed, washed with methanol and allowed to dry in air. The crude product was recrystallized from DMF and dried under vacuum at 100[degrees]C to afford 9.39 g of white crystals. Yield: 86%, m.p. 280-281[degrees]C, FT-IR (KBr): 3065, 1644, 1605, 1591, 1492, 1266, 853, 755 [cm.sup.-1]; [sup.1]H-NMR (CD[Cl.sub.3]): [delta] = 7.94 (d, 7 = 8.4 Hz, 4H), 7.92 (d, J = 7.6 Hz, 4H), 7.86 (d, 7=8.4 Hz, 4H), 7.47 (t, 7=8.0 Hz, 4H), 7.29 (t, 7 = 7.4 Hz, 2H), 7.17 (d, J = 7.6 Hz, 4H), 7.13 (d, J = 8.8 Hz, 4H); [sup.13]C-NMR (CD[Cl.sub.3]/C[F.sub.3]C[O.sub.2]H): [delta] = 201.12, 163.99, 154.53, 144.95, 136.17, 133.81, 131.27, 130.08, 129.86, 127.44, 125.33, 120.52, 116.95; MS (EI, 70 eV): m/z (%) = 546 ([M.sup.+], 33), 197 (100). Elemental analysis: calculated for [C.sub.38][H.sub.26][O.sub.4]; C, 83.50; H, 4.79; Found: C, 83.23; H, 4.61.

Synthesis of N,N'-Bis(4-phenoxyhenzoyl)--4,4'-diaminodiphenyl ether (BPBDAE)

To a 250 mL, round-bottomed flask were added 4phenoxybenzoic acid (15.0 g, 70 mmol), SO[Cl.sub.2] (50 mL), and DMF (1 mL). The mixture was stirred at reflux temperature for 4 h. After removal of SO[Cl.sub.2] under reduced pressure, the residue was dissolved in DMAc (180 mL) under nitrogen, then 4,4'-diaminodiphenyl ether (6.0 g, 30 mmol) was added at 0[degrees]C with stirring. The reaction mixture was stirred at 0[degrees]C for 1 h and at room temperature for 4 h, poured into water (100 mL). The solid product was filtered and washed with water and ethanol, respectively. The crude product was recrystallized from DMF and dried under vacuum at 100[degrees]C to afford 14.39 g of white crystals. Yield: 81%, m.p. 299-300[degrees]C, FT-IR (KBr): 3302, 3042, 1648, 1591, 1501, 1405, 1253, 846 [cm.sup.-1]; [sup.1]H-NMR (DMSO-[d.sub.6]): [delta] = 10.16 (s, 2H), 7.95 (d, J = 8.8 Hz, 4H), 7.71 (d, J = 9.2 Hz, 4H), 7.41 (t, J = 8.0 Hz, 4H), 7.18 (t, J = 7.4 Hz, 2H), 7.07 (d, J = 8.8 Hz, 4H), 7.05 (d, 7=8.8 Hz, 4H), 6.96 (d, 7 = 8.8 Hz, 4H); [sup.13]C-NMR (DMSO-[d.sub.6]): (5=165.02, 160.18, 156.05, 153.27, 135.19, 130.75, 130.37, 129.96, 124.83, 122.51, 119.99, 119.06, 117.91; MS (El, 70 eV): mlz (%) = 592 ([M.sup.+], 3.8), 141 (13), 197 (100); Elemental analysis: calculated for [C.sub.38][H.sub.28][N.sub.2][O.sub.5]; C, 77.01; H, 4.76; N, 4.72; Found: C, 76.75; H, 4.54; N, 4.61.

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Synthesis of Polymers

The general procedure for the synthesis of PEKDKEKK/PEAEAEKK copolymers can be illustrated by the preparation of the polymer VI.

To a 100 mL, three-necked, round-bottomed flask equipped with a mechanical stirrer, a thermometer, nitrogen inlet and outlet tubes, was added anhydrous AI[Cl.sub.3] (6.54 g, 49 mmol) and DCE (20 mL). The flask was cooled to 0[degrees]C using an ice-water bath, then a solution of NMP (2 mL, 21 mmol) in DCE (10 mL) was added dropwise with stirring over a period of 10 min and the mixture was stirred for 30 min and then cooled to -15[degrees]C. Into the resulting suspension were added BPBDAE (1.480 g, 2.5 mmol), BPOBDP (1.365 g, 2.5 mmol) and IPC (1.015 g, 5 mmol) with stirring and the reaction mixture was warmed to 20[degrees]C over 2 h and the reaction was continued at this temperature for 18 h. The reaction mixture was treated with 0.5 mL of diphenyl ether (DPE) as the end-capper for 1 h, quenched with methanol (50 mL) at 0[degrees]C and the precipitate was crushed, washed with methanol and extracted with boiling methanol for 24 h and allowed to dry in air. The air-dried product was heated at 100[degrees]C overnight under vacuum to give the polymer VI. Other polymers were also obtained by varying the molar ratio of BPOBDP to BPBDAE in a similar manner.

Instrumental Techniques

Elemental analysis was performed with Perkin-Elmer Model 2400 CHN analyzer. The FTIR spectra of the monomers and polymers in KBr pellets (2%) were recorded using a Nicolet FTIR (51 OP) spectrophotometer. [sup.1]H-NMR (400 MHz) and [suyp.13]C-NMR (100 MHz) spectra were obtained with a Bruker Avance 400 MHz spectrometer at an operating temperature of 25[degrees]C using CD[Cl.sub.3] or DMSO-[d.sub.6] as a solvent. Inherent viscosities were obtained with a concentration of 0.2 g/dL in 95% [H.sub.2]S[O.sub.4] at 25[degrees]C using an Ubbelhode suspended level viscometer. Differential scanning calorimetry (DSC) measurements were performed on a Mettler Toledo DSC 821e instrument at a heating rate of 10[degrees]C/min under nitrogen. The glass-transition temperature ([T.sub.g]) was taken in DSC curve as the center of the step transition in the second heating run. Thermogravimetric analysis (TGA) was performed on a Netzch Sta 449c thermal analyzer system at a heating rate of 10[degrees]C/min in nitrogen. The mechanical properties were measured at 25[degrees]C using a Shimadzu AG-2000A tester at a crosshead speed of 5 mm/min. The samples are dog bone shape and have dimensions of 4.0 X 6.0 X 55 [mm.sup.3]. The temperatures for the polymers to process are 30[degrees]C higher than the [T.sub.m]s. At least five samples for each polymer were tested, and the average value was reported. Wide angle X-ray diffraction (WAXD) was measured with a Rigaku D/MAX-IIA X-ray diffractometer, using CuKa radiation, at 30 KV and 20 mA. The diffractograms of powdered samples were recorded at room temperature over the range of 10-40[degrees].

RESULTS AND DISCUSSION

The route to the synthesis of 4,4'-bis(4-phenoxybenzoyl)diphenyl (BPOBDP), was shown in Scheme 1. The precursor 4,4'-diphenyldicarboxylic acid dichloride was conveniently obtained by the acyl chloride reaction of thionyl chloride with 4,4'-diphenyldicarboxylic acid at 80[degrees]C. The acylation of DPE with 4,4'-diphenyldicarboxylic acid dichloride for the preparation of BPOBDP was carried out in DCE at 0-25[degrees]C using aluminum chloride as a catalyst. 4,4'-Bis(4-phenoxybenzoyl)diphenyl was obtained as a pure material after recrystallization from DMF. FTIR, NMR, MS spectroscopies, and elemental analysis were used to confirm the structure of BPOBDP. In the IR spectrum, the key structural features include the following absorptions: aromatic C--H, 3065 [cm.sup.-1], aromatic ketone C=O, 1644 [cm.sup.-1], and aromatic ether Ar--O--Ar, 1266 [cm.sup.-1]. Figure 1 shows the 'H-NMR and [sup.13]C-NMR spectra of BPOBDP, all the signals corresponding to the proposed structure can be clearly observed.

As shown in Scheme 2, N,N'-bis(4-phenoxybenzoyl)--4,4'-diaminodiphenyl ether (BPBDAE), was conveniently prepared by the condensation reaction of 4,4'-diaminodiphenyl ether with 4-phenoxybenzoyl chloride in DMAc at 0-25[degrees]C and could be obtained as a pure material after recrystallization from DMF. FTIR, NMR, MS spectroscopies, and elemental analysis were used to confirm the structure of BPBDAE. In the IR spectrum, the key structural features include the following absorptions: N--H stretch, 3302 [cm.sup.-1], amide C=O stretch, 1648 [cm.sup.-1], amide C--N stretch, 1405 [cm.sup.-1], and Ar-O-Ar stretch, 1253 [cm.sup.-1]. The [sup.1]H-NMR and [sup.13]C-NMR spectra of BPBDAE were in accordance with the proposed structure (Fig. 2).

A series of novel copolymers of the poly(ether ketone diphenyl ketone ether ketone ketone) (PEKDKEKK) and the polyfether amide ether amide ether ketone ketone) (PEAEAEKK) were synthesized by electrophilic Friedel-Crafts solution copolycondensation of isophthaloyl chloride (IPC) with a mixture of BPOBDP and BPBDAE, over a wide range of BPOBDP/BPBDAE molar ratios, as shown in Scheme 3. It is generally accepted that premature polymer precipitation from initially homogeneous solution in Friedel-Crafts acylation polycondensation synthesis prevents further macromolecular chain growth reactions and produces polymer of undesirably low molecular weight and of poor thermal stability. Furthermore, such precipitation Friedel-Crafts polymerization generally produces an intractable product difficult to remove from the reaction vessel and to purify. It is well-known that ortho substitution and alkylation of the polymer in electrophilic polymerizations are more likely to occur if the reaction is conducted at elevated temperatures for a relatively long time [35], Janson et al. have reported that the FriedelCrafts polymerization reaction can be controlled by the addition of a controlling agent to obtain the desired meltprocessable, high molecular weight, substantially linear poly(aryl ether ketone)s [36]. The controlling agent can efficiently suppress undesirable side reactions such as ortho substitution of activated aryloxy groups and alkylation of the polymer, which can lead to branching or cross-linking. Suppression of side reactions results in a thermally stable polymer that does not degrade or cross-link when subjected to elevated temperatures, e.g., temperatures above the melting point of the polymer for a period of time. Preferred controlling agents for the electrophilic polymerization reaction are organic Lewis bases such as DMF, DMAc, and NMP. The 1:1 complex of Lewis acid (Al[Cl.sub.3])/Lewis base appears to act as a solvent for the polymer/Lewis acid complex formed during the reaction, thereby maintaining the polymer in solution or in a reactive gel state. Furthermore, the reaction mixture is more tractable, making work up of the polymer easier and ensuring effective removal of catalyst residues during purification. The solublization property of the Lewis acid (Al[Cl.sub.3]/Lewis base complex is particularly significant in the preparation of para-linked poly(aryl ether ketone)s. The preparation of PAEKs by electrophilic Friedel-Crafts acylation polycondensation generally starts at low temperature. The initial low temperature is needed to maintain control over the reaction rate. A reaction temperature of about -15[degrees]C to --5[degrees]C has been found to be particularly effective. Thereafter, the reaction temperature is slowly increased and maintained at room temperature.

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In the synthesis of novel PEKDKEKK/PEAEAEKK copolymers, different molar ratios of BPOBDP to BPBDAE were taken to obtain the copolymers. But the sum of moles of BPOBDP and BPBDAE should be equal to that of isophthaloyl chloride (IPC), which would produce a high molecular weight according to the modified Carothers equation, i.e., [X.sub.n] = (1 + r)/(1 - r), where [X.sub.n] is the number-average degree of polymerization and r is the sum of the molar ratio of both BPOBDP and BPBDAE to IPC. The molar ratios and inherent viscosities of the polymers are given in Table 1. The inherent viscosity ([[eta].sub.inh]) values of the polymers are above 0.72 dL/g and increased with the increase in concentration of BPBDAE in polymer due to the increase in strength of hydrogen bonding in the polymers. The inherent viscosity ([[eta].sub.inh]) values reveal that high molecular weight polymers are obtained in DCE/NMP medium since the [[eta].sub.inh] values of the polymers are higher than the critical inherent value [[eta].sub.inh] = 0.60 dL/g) of polyfaryl ether ketone)s [36], Thus, the modified electrophilic Friedel-Crafts polycondensation route is appropriate.

The key structural features of the polymers obtained could be identified by FTIR spectroscopy. The FTIR spectra of all the polymers show no absorption at about 1740 [cm.sup.-1] indicating the absence of -COCI groups. All the spectra of the polymers except for the polymer I without BPBDAE show characteristic bands at 3419 [cm.sup.-1] due to N--H stretch, at 1656 [cm.sup.-1] due to aromatic ketone and amide C=0 stretch, at 1411 [cm.sup.-1] due to amide C--N stretch and at 1240 [cm.sup.-1] due to Ar--O--Ar stretch. The FTIR spectrum of the polymer VI is shown in Figure 3.

The crystallinities of the polymers were evaluated by WAXD. The WAXD patterns of the polymers I-VI are presented in Figure 4. It is well documented that poly(ether ketone ketone) with 100 mol% IPC (PEKwK) had three major diffraction peaks at 20 that are 18.7[degrees] (110), 23.3[degrees] (200), and 28.9[degrees] (211) [18], As shown in Figure 4, the WAXD patterns of the copolymers I-V with 60-100 mol% BPOBDP fundamentally bore the same number and site of diffraction peak of every crystal facecrystal plane in comparison with that of the PEKmK, which indicated that the polymers I-V had the chain similar to that of the PEK/mK to form the crystal that was included in the orthorhombic system

with the PEKmK. But the diffraction peaks decreased in intensity with the increase in BPBDAE content due to the incorporation of N,N'-dibenzoyl-4,4'-diaminodiphenyl ether moieties in the main chains, which disrupted the regularity of molecular chains and inhibited the close packing of the polymer chains. When the molar ratio of BPBDAE to BPOBDP was up to 50/50, the copolymer VI obtained was amorphous and no obvious diffraction peak was observed. The polymers VII-XI with 60-100 mol% BPBDAE was also amorphous and showed only one diffuse diffraction peak.

The thermal properties of the polymers were evaluated by DSC and TGA and the results are given in Table 2. Samples were heated up to 400[degrees]C at the rate of 10[degrees]C/min in [N.sub.2], quenched to --50[degrees]C and rerun to obtain [T.sub.g]. The [T.sub.g]S of the polymers I-XI were 170-209[degrees]C, which exhibited much higher [T.sub.g]S than those of commercially available PEEK and PEKK, [T.sub.g]S of which were 143 and 156[degrees]C, respectively. This attributed to the presence of hydrogen bonding and diphenyl moieties in the polymers. The [T.sub.g] values of the polymers I-XI increased with the increase in concentration of BPBDAE in the polymer, the polymer XI with 100 mol% BPBDAE had the highest [T.sub.g] of 209[degrees]C, 39[degrees]C higher than that of the polymer I with 100 mol% BPOBDP, which indicated that the amide linkages due to the formation of hydrogen bonding are more effective than diphenyl moieties due to the rigidity for the improvement of [T.sub.g]. The increased [T.sub.g] values of the polymers II--XI can be explained by the fact that the intermolecular interaction force was enhanced and the segmental motion was hindered due to the presence of intermolecular hydrogen bonding of amide groups. The crystalline temperatures ([T.sub.c]s) of the polymers I-V were 225-286[degrees]C and also increased with the increase in concentration of BPBDAE in the polymer. The [T.sub.m]s of the polymers I-V with 60-100 mol% BPOBDP were 326-365[degrees]C and the polymer I with 100 mol% BPOBDP had the highest [T.sub.m] of 365[degrees]C due to the high regularity of molecular chains. The [T.sub.m] values of the polymers I-V decreased gradually with the increase in concentration of BPBDAE in the polymer due to the decrease in regularity of molecular chains with the introduction of N,N'-dibenzoyl-4,4'-diaminodiphenyl ether moieties in the main chains. When the molar ratio of BPBDAE to BPOBDP was up to 50/50, no melting endothermic peak was observed from DSC curve of the resulting polymer VI. The polymers VII-XI with 60-100 mol% BPBDAE also showed only a glass transition endothermic peak in their DSC curves. The above results agreed with the WAXD results. The polymer I had a higher [T.sub.g] of 170[degrees]C, but its high [T.sub.m] of 365[degrees]C made it unsuitable for the melt processing. However, the copolymers IV and V with 30-40 mol% BPBDAE had not only high [T.sub.g]S of 185-188[degrees]C, but also moderate [T.sub.m]s of 326-330[degrees]C, having good potential for the melt processing. DSC curves of the polymers I-XI are illustrated in Figure 5.

The novel PEKDKEKK/PEAEAEKK copolymers exhibited high thermal stability. As shown in Table 2, the temperatures at 5% weight loss ([T.sub.d]s) of all the polymers were above 478[degrees]C in [N.sub.2]. The [T.sub.d] values of the polymers decreased with the increase in BPBDAE content in polymer since poly(aryl ether ketonefs had higher [T.sub.d]s than aromatic polyamides. The polymer I without BPBDAE had the highest [T.sub.d] of 550[degrees]C, while the polymer XI with 100 mol% BPBDAE had the lowest [T.sub.d] of 478[degrees]C. The semicrystalline copolymers II-V had high [T.sub.d]s of 506537[degrees]C. The temperature difference between [T.sub.m] and [T.sub.d] of the copolymers IV and V was large, thus the melt processing can be easily accomplished. A typical TGA curve of copolymer IV is illustrated in Figure 6.

The solubility behavior of the polymers prepared in this study was examined for powdery samples at a concentration of 10 mg/mL in various solvents at room temperature for 24 h and the results are listed in Table 3. As shown in Table 3, the polymer I-V with 60-100 mol% BPOBDP had excellent resistance to organic solvents. The solubility of the polymers increased with the increase in BPBDAE content in polymer. The copolymers VI and VII were insoluble in highly polar solvents such as NMP, DMAc, DMSO, and DMF except for concentrated sulfuric acid, but they can be swelled in NMP. The polymers V1II-XI were soluble in NMP and can also be swelled in DMSO. However, the polymers I-XI were insoluble in common organic solvents such as THF, CH[Cl.sub.3], DCE, EtOH, acetone, toluene, and so on. Thus, from the results above, we conclude that semicrystalline copolymers II-V had excellent resistance to organic solvents.

The mechanical properties of the semicrystalline copolymers II-V were measured, and the results are summarized in Table 4. From these data, it can be seen that the copolymers II-V had tensile strengths of 101.7-104.3 MPa, Young's moduli of 2.19-2.42 GPa, and elongations at break of 13.2-16.6%, indicating that they are strong materials.

CONCLUSIONS

Novel copolymers of the polyfether ketone diphenyl ketone ether ketone ketone) (PEKDKEKK) and the poly (ether amide ether amide ether ketone ketone) (PEAEAEKK) were synthesized by electrophilic Friedel-Crafts solution copolycondensation of isophthaloyl chloride (IPC) with a mixture of BPOBDP and BPBDAE, over a wide range of BPOBDP/BPBDAE molar ratios, under very mild conditions. The [T.sub.g]S of the semicrystalline copolymers II-V were 175-188[degrees]C, which exhibited much higher [T.sub.g]S than those of commercially available PEEK and PEKK, [T.sub.g]S of which were 143 and 156[degrees]C, respectively. The [T.sub.m] values of the polymers decreased and then disappeared with increasing BPBDAE content. The [T.sub.m] (365[degrees]C) of the polymer I can be reduced to 326[degrees]C when the molar ratio of BPBDAE to BPOBDP is 40/60, moreover the glass transition temperature of the resulting copolymer V can be up to 188[degrees]C, 18[degrees]C higher than that of polymer I. The copolymers IV and V with 30-40 mol% BPBDAE had not only high [T.sub.g]S of 185-188[degrees]C, but also moderate [T.sub.m]s of 326-330[degrees]C, having good potential for the melt processing. The copolymers IV and V had tensile strengths of 101.7-102.3 MPa, Young's moduli of 2.19-2.42 GPa, and elongations at break of 13.2-16.6% and exhibited high thermal stability and excellent resistance to organic solvents.

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Bin Huang, Jiangping Qian, Guixia Wang, Mingzhong Cai

Department of Chemistry, Jiangxi Normal University, Nanchang 330022, People's Republic of China

Correspondence to: Mingzhong Cai; e-mail: caimzhong@l63.com

Contract grant sponsor: National Natural Science Foundation of China; contract grant number: 21264010; contract grant sponsor: Science Foundation of Department of Education of Jiangxi.

DOI 10.1002/pen.23721

Published online in Wiley Online Library (wileyonlinelibrary.com).

TABLE 1. Polymerization results. (a)

           BPOBDP    BPBDAE                 [[eta].sub.inh] (b)
Polymer    (mol%)    (mol%)    Yield (%)          (dL/g)

I            100        0          93              0.72
II           90        10          93              0.75
III          80        20          94              0.83
IV           70        30          95              0.90
V            60        40          94              0.95
VI           50        50          95              1.02
VII          40        60          95              1.08
VIII         30        70          94              1.15
IX           20        80          95              1.19
X            10        90          96              1.22
XI            0        100         96              1.26

(a) Polymerized at 20[degrees]C with 5 mmol of IPC, 5 mmol of
(BPOBDP + BPBDAE), 21 mmol of NMP, and 49 mmol of AI[C1.sub.3]
in 30 mL of DCE for 20 h.

(b) Measured with a concentration of 0.2 g/dL in 95% sulfuric
acid at 25[degrees]C.

TABLE 2. Thermal properties of the polymers.

             [T.sub.g]       [T.sub.m]
Polymer    ([degrees]C)    ([degrees]C)

I               170             365
II              175             344
III             182             337
IV              185             330
V               188             326
VI              194
VII             200
VIII            204
IX              207
X               208
XI              209

             [T.sub.c]       [T.sub.d]
Polymer    ([degrees]C)    ([degrees]C)

I               225             550
II              247             537
III             265             522
IV              272             510
V               286             506
VI                              502
VII                             492
VIII                            487
IX                              481
X                               479
XI                              478

TABLE 3. Solubility of the polymers. (a)

            [H.sub.2]
Polymer    S[0.sub.4]    NMP    DMAc   DMSO   DMF

I               +         -      -      -      -
II              +         -      -      -      -
III             +         -      -      -      -
IV              +         -      -      -      -
V               +         -      -      -      -
VI              +         +      -      -      -
VII             +         +      -      -      -
VIII            +         +      -     + -     -
IX              +         +      -     + -     -
X               +         +      -     + -     -
XI              +         +     + -    + -     -

Polymer    THF    CH[Cl.sub.3]   DCE    EtOH

I           -          -          -       -
II          -          -          -       -
III         -          -          -       -
IV          -          -          -       -
V           -          -          -       -
VI          -          -          -       -
VII         -          -          -       -
VIII        -          -          -       -
IX          -          -          -       -
X           -          -          -       -
XI          -          -          -       -

(a) The solubility was tested at a concentration of
10 mg/mL in the solvent at room temperature for 24 h.

+ : soluble, +-: swollen, insoluble.

TABLE 4. Mechanical properties of the copolymers II-V.

              Tensile          Young's       Elongation
Polymer    strength (MPa)   modulus (GPa)   at break (%)

II             104.3            2.24            16.1
III            103.2            2.33            14.5
IV             102.3            2.42            13.2
V              101.7            2.19            16.6
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Date:Aug 1, 2014
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