Materials Science and Engineering B xxx (2009) xxx–xxx
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Materials Science and Engineering B
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ovel poly (arylene-ether-ether-ketone)s containing preformed imide unitnd pendant long chain alkyl group
aheboob M. Sayyed, Noormahmad N. Maldar ∗
epartment of Chemistry, Solapur University, Pune-Solapur High Way, Kegaon, Solapur 413 255, Maharashtra, India
r t i c l e i n f o
rticle history:eceived 19 August 2009eceived in revised form 1 November 2009ccepted 6 November 2009
eywords:romatic poly (ether-ether-ketone)s
mide PEEK
a b s t r a c t
The studies were carried out to get preformed imide unit containing PEEKs and Co-PEEKs with pendantlong chain alkyl group. Thus two new bisphenols; N,N′-bis (4-hydroxy 2-pentadecyl phenyl) pyromel-litimide (HPI) (I) and N,N′-bis (4-hydroxy 2-pentadecyl phenyl 3,3′,4,4′-benzophenone tetracarboxylicimide (HBI) (II) containing imide unit, pendant C-15 alkyl substituents were synthesized, characterizedby spectral data and polycondensed with 4,4′-difluorobenzophenone (DFB) to yield several PEEK andCo-PEEKs. The polymers were characterized by FTIR, inherent viscosity, solubility, and XRD. The poly-mers were obtained in good yields and had inherent viscosities up to 0.65 dL/g in NMP. Polymerization
of mixture of two bisphenols; [(I) and BPA]; and [(II) and BPA] in various mol%, with DFB gave numberof the copolymers viz. Co-PEEK-BPAPI and Co-PEEK-BPABI. Many of the Co-PEEKs had good solubility inpolar solvents. The solubility of PEEK containing bulky pendant alkyl substituents did not much improveprobably due to simultaneous presence of rigid imide structures. XRD analysis indicated that PEEK andCo-PEEKs were partially crystalline or amorphous depending on the nature and % content of imide-bisphenol. These new PEEK materials can be used as high performance films, coatings, gas separation
and
mide) membranes, in aerospace
. Introduction
Aromatic poly (ether-ether-ketone), PEEK is an important classf industrial plastic materials developed in the 1980s which haveeen widely used in the various fields due to their advanced prop-rties [1,2]. They have favorable combination of physical, chemicalnd mechanical properties. The PEEK first marketed by ICI is aemicrystalline polymer and it has a melting temperature (Tm)f 345 ◦C. However these polymers are generally intractable andack the properties essential for successful fabrication into usefulorms because of their high melting and their limited solubility inrganic solvents. The present study is part of our research on syn-hesizing modified high performance aromatic polymers via thencorporation of bulky pendant groups; to improve processabilityf polymers without impairment of the other properties any greatxtent [3].
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Introduction of flexible groups in main or side chain might ben effective way to increase the processability of polymers [4–8].ntroduction of rigid heterocyclic imide moiety into the polymerackbones is an effective way to increase the thermal stability of
polymers [9–13]. In order to combine these two fundamental con-cepts, it was thought to incorporate both pendant long chain alkylgroup and heterocyclic imide ring into high performance polymer.Therefore investigations were performed by introducing linear longalkyl flexible-C15 group to impart processability to high perfor-mance PEEK polymer and heterocyclic imide moiety to increasethermal stability.
PEEKs are obtained from bisphenols and hence, we thoughtto prepare new aromatic imide-bisphenols. Thus, the presentstudy describes the synthesis of two new aromatic bisphe-nols; N,N′-bis (4-hydroxy 2-pentadecyl phenyl) pyromellitimide(HPI) (I) and N,N′-bis (4-hydroxy 2-pentadecyl phenyl 3,3′,4,4′-benzophenone tetracarboxylic imide (HBI) (II). Further synthesisof series of PEEK and Co-PEEKs polymers from bisphenol-A; 4,4′-difluorobenzophenone (DFB) and novel imide-bisphenols, HPI (I);HBI (II) has been performed.
2. Experimental
2.1. Materials
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The commercial cashew nut shell liquid was distilled underreduced pressure to get cardanol. DMSO was dried over molec-ular sieves and distilled under reduced pressure. DMF was driedby azeotropic distillation with toluene and then distilled under
1132 (imide III) and 715 cm−1 (imide IV). The absence of bands at1670–1650 (amide I) and 1530–1520 cm−1 (amide II), 1410, 1312and 885 cm−1 in the spectra indicated the complete imidizationof intermediate (amic acid). The bands at the 1662, 1616, 1582
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educed pressure. Toluene was dried over metallic sodium. DFBSpectrochem) was used as received. Potassium carbonate wasried at 180 ◦C for 10 h. Pyromellitic dianhydride (PMDA) and,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA); pur-hased from Aldrich Chemical Company, USA, were recrystallizedrom acetic anhydride.
.2. Measurements
All melting points were determined on a Mel-Temp meltingoint apparatus and are uncorrected. The transmission IR spec-ra of polymers were recorded as a KBr pellet on a PerkinElmer83 IR spectrophotometer. 1H NMR spectra and 13C NMR spectraere recorded on a Bruker NMR spectrophotometer (200 MHz) inMSO-d6. Elemental analysis was performed with a PerkinElmerodel 2400 C, H, N, S, Cl, and analyzer. Inherent viscosity mea-
urements were made at polymer concentration of 0.5 g/dL in NMPt 30 ± 0.1 ◦C using suspended level Ubbelohde viscometer. Theolubility of polymers was determined at 3 wt% concentration inarious solvents at room temperature or on warming if needed.-ray diffraction patterns of polymers were obtained on a Rigakumax 2500 X-ray diffractometer at a tilting rate of 2◦/min. Driedolymer powder was used for X-ray measurements.
.3. Synthesis of monomers
.3.1. Synthesis of imide-bisphenol monomersSynthesis of 4-amino-3-pentadecyl phenol (4ATHA) was per-
ormed [14,15] from 3-pentadecyl phenol which was obtained fromardanol (distilled Cashew Nut Shell Liquid – CNSL) as reported bys earlier. CNSL is a byproduct obtained while roasting cashew nutsnd it is a mixture of naturally occurring substituted phenols. Car-anol is phenolic compounds with long chain substitution –C15H27t the meta position obtained by vacuum distillation of CNSL whichas purchased from M/s. Mercury Resins and Polymers Pvt. Ltd.,yderabad.
.3.2. Synthesis of N,N′-bis (4-hydroxy 2-pentadecyl phenyl)yromellitimide (HPI), (I)
PMDA 0.218 g (l mmol), 4ATHA 0.638 g (2 mmol) and DMF5 mL were added to a dry three necked 100 mL round bot-om flask equipped with a magnetic stirrer, an oil bath, a refluxondenser, a nitrogen gas inlet and a thermowell. The reactionixture was stirred at room temperature for 30 min. 25 mL dry
oluene was added and then heated to reflux under the nitro-en gas flow at 120 ◦C for 5 h. Toluene was used to removeater produced in polycondensation. After removing the calcu-
ated amount of water produced, toluene was distilled out; theeaction temperature was raised to 140 ◦C and kept for 6 h. Thenhe reaction mixture was cooled to room temperature, pouredn water. The solid produced was filtered, thoroughly washed
ith hot water and then with hexane. The product was dried at0 ◦C for 10 h under vacuum. Purification of HPI was performedy mixing with hot absolute ethanol (3 mL × 40 mL) and recrys-allization of the residue from a mixture of THF and methanol50:50).
Yield: 0.765 g (93%), m.p.: 193–194 ◦C.The elemental analysis calculated for C52H72N2O6: C – 76.09; H
08.78; N – 03.41%.Found: C – 76.64; H – 09.09; N – 03.04%Similarly N,N′-bis (4-hydroxy 2-pentadecyl phenyl 3,3′,4,4′-
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enzophenone tetracarboxylic imide HBI (II) was prepared byeacting two moles of 4ATHA in DMF with BTDA.
Yield: 0.795 g (94%), m.p.: 199–202 ◦C.The elemental analysis calculated for C59H76N2O7: C – 76.62; H
08.22; N – 03.03%, found: C – 76.50; H – 08.44; N – 03.18%
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2.4. Synthesis of the polymer: (BPAPI-2)
A 100 mL three necked round bottom flask equipped with amagnetic stirrer, an oil bath, a reflux condenser, a nitrogen gasinlet and a thermowell; bisphenol-A 0.216 g (0.75 mmol), (I) 0.205 g(0.25 mmol) 4,4′-difluorobenzophenone 0.275 g (1 mmol), K2CO30.276 g (2 mmol), dry DMSO 5 mL, and dry toluene 15 mL werecharged and stirred at 140 ◦C for 4 h. Then toluene was distilledout, the reaction mixture was heated at 160 ◦C for 6 h, cooled toroom temperature and then poured into distilled water. Precipi-tated polymer BPAPI-2 was filtered, washed with hot water anddried under vacuum at 80 ◦C for 6 h. Yield – 0.550 g (96%).
By using similar procedure BPAPI-1 and BPAPI-3 to 5 were syn-thesized.
Similar procedure was used for preparation of BPABI-1 to 5 using[(II) and BPA] in various mol%, with DFB.
3. Results and discussion
3.1. Monomer synthesis and characterization
Two new imide heterocyclic ring and pendant alkyl groupcontaining bisphenol monomers (I) and (II), were obtainedin good yields and they were characterized by IR, NMR(1H and 13C) and elemental analysis. The novel N,N′-bis (4-hydroxy 2-pentadecyl phenyl) pyromellitimide (I) and N,N′-bis(4-hydroxy 2-pentadecylphenyl) 3,3′,4,4′-benzophenone tetracar-boxylic imide (II) were synthesized by nucleophilic condensationof PMDA/BTDA and 4ATHA in the DMF/toluene solvent system(Scheme 1).
Elemental analysis of (I) and (II) for C, H, and N was in goodagreement with theoretical values.
The FTIR spectra of (I) and (II) (Fig. 1 and Fig. 2) showed charac-teristic absorption bands at 1770, 1720 (imide-I), 1384 (imide-II),
M.M. Sayyed, N.N. Maldar / Materials Science and Engineering B xxx (2009) xxx–xxx 3
agap
ppTogtt4
n1a1bc
Fig. 3. 1H NMR spectrum of HPI (I).
Fig. 1. IR spectrum (KBr) of HPI (I).
nd 1500 cm−1 are for aromatic moiety; whereas phenolic hydroxyroup appeared as broad absorption at 3560–3222 cm−1. There wasbsorption band at 1622 cm−1 in the FTIR spectrum of (II) indicatingresence of ketone (CO) group.
The 1H NMR spectrum of (I) (Fig. 3) supported the structure pro-osed. Aromatic protons appeared in the range of 6.7–8.2, where inroton of PMDA moiety at appeared at 8.95 ppm as a singlet (2H).he signals at 6.57–7.42 ppm were assignable to aromatic protonsf phenolic ring. Signals at 0.8–1.53 ppm were due to aliphatic alkylroup (–C15 H31); of which the signal (triplet) at 0.85 ppm was dueo terminal –CH3 and signal at 1.51 ppm was due to benzylic pro-ons. Other (–CH2–)13 protons appeared at 1.2 ppm. The signal at.95 ppm was assigned to hydroxyl protons.
The 13C NMR spectrum of (I) (Fig. 4) indicated nine sig-als for imide carbonyl and aromatic carbons in the range13.3–167.1 ppm, aliphatic carbon due to pentadecyl substituents
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ppeared in range 14–33 ppm. Only one signal for imide CO at67.1 ppm indicated that all carbonyls were equivalent and car-onyl due to –CONH and –COOH groups were absent suggestingomplete imidization of intermediate (amic acid).
4 M.M. Sayyed, N.N. Maldar / Materials Science and Engineering B xxx (2009) xxx–xxx
spect
fawsb2
lasat
Fig. 6. 1H NMR
DEPT spectrum of (I) (Fig. 5) also confirmed the structure. Onlyour methine carbons (–CH–), (125.3, 122.70, 114 and 113.30 ppm)ppeared as downside signals; where as the five quaternary carbonsere absent. Among the carbon signals due to aliphatic pentadecyl
ubstituents; –CH3 was distinct downside at 14.13 ppm, where asenzylic –CH2 and (–CH2–)13 appeared at 31.84, 31.34, 30.16, 29.60,9.28 and 22.59 ppm.
1H NMR spectrum of (II) (Fig. 6), aromatic protons of pheno-ic ring appear between 6.7 and 7.2, and protons of BTDA moiety
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ppeared at 8.13–8.57 ppm. Aliphatic protons of –C15H31 sub-tituents showed peaks at 0.8–1.53 ppm of which the signal (triplet)t 0.88 was due to terminal –CH3 and signal at 1.53 ppm was dueo benzylic protons. Other (–CH2–)13 protons appeared as broad
Fig. 7. 13C NMR spec
rum of HBI (II).
signal at 1.20 ppm. The signal at 3.9 ppm was assigned to hydroxylprotons.
The 13C NMR spectrum of (II) (Fig. 7), showed fourteen signalsfor aromatic and carbonyl carbons in the range 113.3–196, whereas aliphatic carbons due to pentadecyl substituents appeared inthe range 14–33 ppm. Only one signal for imide CO at 167.7 ppmindicated that all imide carbonyls were equivalent and carbonyldue to –CONH and –COOH groups were absent suggesting completeimidization of intermediate (amic acid). Ketone carbonyl due to
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BTDA moiety appeared at 196 ppm.In the DEPT spectrum of (II) (Fig. 8), only six methine car-
bons (–CH) signals were downside (133.1, 128.0, 127.3, 122.8,114.0 and 113.3 ppm) and remaining eight quaternary carbons
a Polymerization was carried out with 1 mmol each DBF and [BPA + (I)].
molecular weight polymers. The solubility of the polymers from(I) and (II) is represented in (Table 3) and (Table 4) respectively.It was expected heterocyclic that the polymers containing higher% of (I)/(II) would show good solubility in organic solvent dueto pendant alkyl groups. However PEEK containing pendant C-
Table 2Synthesis of PEEKa from [BPA + (II)]b and 4,4′-difluorobenzophenone (DFB).
ere absent. Among the pentadecyl substituents –CH3 was distinctownside at 14.13 ppm, where as benzylic –CH2 and –(CH2)13–ppeared at 31.84, 31.34, 30.16, 29.60, 29.28, 22.59 ppm as distinctpside.
.2. Polymer synthesis and characterization
Novel PEEK polymers were obtained when stoichiometricmounts of (I) and (II) were condensed with DFB by nucleophiliceaction in dry DMSO solvent. K2CO3 was used as the salifyingeagent means it help in the formation of phenoxide salts whichncreases reaction rate and toluene was used to azeotropicallyemove the water produced during the reaction. Similarly, othero-PEEK were obtained through polymerization of [(I) and BPA];nd [(II) and BPA] in various mol%, with DFB (Scheme 2). Polymer-zation reactions proceeded in a homogenous solution and there
as no precipitation of polymers as reaction was carried out up toh.
PEEK and Co-PEEK polymers were characterized by FTIR, inher-nt viscosity, solubility and XRD.
FTIR of BPAPI-3 and BPAPI-5 showed characteristic bands at780, 1720 (imide-I), 1370 (imide-II), 1120 (imide III) and 720 cm−1
imide IV) indicating incorporation of the structural imide moi-ty from (I). Polymers showed the absorption bands at 1716,235 cm−1 corresponding to ketone (–CO–) and ether (–C–O–C–)ibration respectively. Absorption bands at 2970 and 2830 cm−1
ere assigned to –CH2–/–CH3, vibration of aliphatic CH stretching,f –C15H31 pendant group.
FTIR spectrum of control PEEK-BPAPI-1 derived from only BPA,howed absorption bands at 2968, 1716 and 1235 cm−1 which cor-esponded to vibrations of aliphatic CH of –CH3 group, ketonend ether linkages respectively. Absorption peaks at 1780, 1370,120 and 720 cm−1 were absent as BPAPI did not involve imide-isphenol (I).
FTIR spectra of polymers from (II); BPABI-2 to 5 showed charac-
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eristic bands at 1716, 1235 indicating ketone and ether functionalroups and at 1780 and 1720 (imide-I), 1370 (imide II), 1120 (imideII), and 720 cm−1 (imide IV) corresponding to imide heterocycle inolymer chain. Absorption peas at 2968, 1363 cm−1 correspondedo vibration CH from pendant –C15H31 alkyl group in BPABI-2 to
c Measured at concentration of 0.5 g/dL in NMP at 30 ± 0.1 ◦C.
5; where as for BPABI-1 these absorption bands were due to –CH3group.
The composition and data on inherent viscosities of PEEK andCo-PEEK from (I) and (II) are presented in (Table 1) and (Table 2)respectively. The inherent viscosity of polymers ranged from 0.34to 0.65 dL/g. This indicated the formation of moderate to high
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BPABI-5 00 100 96.25 0.34
a Polymerization was carried out with each 1 mmol of DBF and [BPA + (II)].b BPA = bisphenol-A and (II) = N,N′-bis (4-hydroxy 3-pentadecyl phenyl) 3,3′ ,4,4′-
benzophenone tetracarboxylic imide.c Measured at concentration of 0.5 g/dL in NMP at 30 ± 0.1 ◦C.
6 M.M. Sayyed, N.N. Maldar / Materials Science and Engineering B xxx (2009) xxx–xxx
(I)] an
1ppeptB
TS
S
Scheme 2. Synthesis of PEEK-BPAPI from [BPA +
5 alkyl and imide heterocyclic groups showed limited solubilityrobably due to presence of rigid imide moieties in main chainolymer and contribution of imide structures over weighed the
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ffect of pendant alkyl groups. BPAPI-2 to 4 were soluble in aolar aprotic solvent (NMP), CHCl3, THF and hot m-cresol andhis is partly due to copolymerization effect and presence ofPA moiety. The BPAPI-5 derived from (I) was soluble in NMP;
able 3olubility of PEEK from [BPA + (I)] and 4,4′-difluorobenzophenone (DFB).
oluble at R.T.: ++; soluble on heating: +; partly soluble: +−; insoluble: −.
d DBF and PEEK-BPABI from [BPA + (II)] and DFB.
whereas polymer BPAPI-1 showed good solubility in NMP, DMAC,DMSO and in common organic solvent like THF, pyridine and conc.H2SO4.
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All PEEK and Co-PEEK based on (II), BPABI-2 to 5 was insolublein most of the solvents; except BPABI-2 which dissolved in NMPand m-cresol. Thus BTDA derived rigid imide heterocyclic units inthe polymer chain contributed to insolubility of polymers.
Table 4Solubility of PEEK from [BPA + (II)] and 4,4′-difluorobenzophenone (DFB).
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Fig. 9. XRD curves of PEEK-BPAPI-1 to PEEK-BPAPI-5.
Fig. 10. XRD curves of PEEK-BPABI-2 to PEEK-BPABI-5.
Fig. 11. DSC curves of PEEK-BPABI.
(
(
[[[[
[
[
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The XRD pattern of the PEEK and Co-PEEK polymers from (I) and(II) are presented in (Fig. 9) and (Fig. 10), respectively. All the poly-mers exhibited partially crystalline nature; however none of thesepolymers showed a melting point in DSC curves of the polymers.The insertion of rigid heterocyclic imide rings into the repeatingunits of polymer resulted in a slight increase in the crystallinenature of the polymers as the presence of pendant long alkyl group–C15H31, imparted the flexibility. The glass transition temperaturesof BPABI-3 to BPABI-5 were in range 268–288 ◦C; whereas Tg forBPABI-1 was 144 ◦C indicating that incorporation of rigid imidelinkage increased the glass temperature (Fig. 11).
4. Conclusions
Based on results presented, following conclusions have beendrawn.
(a) Syntheses of new imide-bisphenols, N,N′-bis (4-hydroxy2-pentadecyl phenyl) pyromellitimide (HPI), (I) and N,N′-bis (4-hydroxy 2-pentadecyl phenyl 3,3′,4,4′-benzophenonetetracarboxylic imide (HBI), (II) was successfully accomplishedand they were characterized by elemental analysis, and spectraltechniques.
b) Series of PEEK and Co-PEEK polymers was synthesized from(I)/(II), bisphenol-A and 4,4′-difluorobenzophenone.
(c) Viscosity values of these polymers were in the range0.34–0.65 dL/g, indicating built up of a moderate to high molec-ular weight; as inherent viscosity about 0.4 and above areconsidered to have high molecular weights and these polymersare film forming.
d) Many of the copolymers were soluble in polar aprotic solventsand in some organic solvents; due to randomness imparted bycopolymerization.
(e) The polymers exhibited partially crystalline nature.
Acknowledgement
Authors are thankful to University Grants Commission, New-Delhi for the financial support [UGC F.12-67/2003 (SR)].
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