Synthesis and characterization of novel polyimides derived from2,6-bis[4-(3,4-dicarboxyphenoxy)benzoyl]pyridine dianhydride
危险的森林and aromatic diamines
Xiaolong Wang,Yan-Feng Li*,Tao Ma,Shujiang Zhang,Chenliang Gong
State Key Laboratory of Applied Organic Chemistry,College of Chemistry and Chemical Engineering,Institute of Biochemical Engineering and Environmental
Technology,Lanzhou University,Lanzhou730000,People’s Republic of China
Received2December2005;received in revid form26March2006;accepted29March2006
Abstract
A novel pyridine-containing aromatic dianhydride monomer,2,6-bis[4-(3,4-dicarboxyphenoxy)benzoyl]pyridine dianhydride,was synthesized from the nitro displacement of4-nitrophthalonitrile by the phenoxide ion of2,6-bis(4-hydroxybenzoyl)pyridine,followed by acidic hydrolysis of the intermediate tetranitrile and cyclodehydration of the resulting tetraacid.A ries of new
polyimides holding pyridine moieties in main chain were prepared from the resulting dianhydride monomer with various aromatic diamines via a conventional two-stage ing-opening polycondensation forming the poly(amic acid)s and further thermal or chemical imidization forming polyimides.The inherent viscosities of the resulting polyimides were in the range of0.51–0.68dL/g,and most of them were soluble in aprotic amide solvents and cresols,such as N,N-dimethylacetamide,N-methyl-2-pyrrolidone,and m-cresol,etc.Meanwhile,some strong andflexible polyimidefilms were obtained,which have good thermal stability with the glass transition temperatures of221–2788C,the temperature at5%weight loss of512–5408C,and the residue at 8008C of60.4–65.3%in nitrogen,as well as have outstanding mechanical properties with the tensile strengths of72.8–104.4MPa and elongations at breakage of9.1–11.7%.The polyimides also were found to posss low dielectric constants.
q2006Elvier Ltd.All rights rerved.
Keywords:Dianhydride monomer;Polyimides;Pyridine moieties
1.Introduction
Polyimides(PIs),as aromatic polymers,have exhibited a ries of outstanding llen
t thermostability, mechanical and electrical properties,as well as ability of solvent-resistance,so that they are being widely employed in the aerospace,microelectronics,optoelectronics,composites and so on[1,2].Becau many of them are insoluble and infusible,however,their applications in somefields were limited.It is well known that the poor properties of PIs have a clo connection with its chemical composition and chain structure,in other words,the chemical composition and chain structure of PIs will be a head ingredient leading them to infusible within processing temperature and insoluble in organic solvents.Thus,incorporating new functionalities to make polyimides more tractable without decreasing their many desirable properties has become one important target of polyimides chemistry[3,4].So far,many efforts on chemical modifications of polyimides structure have been done,such as introduction offlexible linkages in the polymer backbone,or incorporation of bulky side groups,which result in good solubility and processibility of the polyimides[5–10].
Considering heteroaromatic rings introduced into the main chain of a synthetic polymer could provide certain properties presumed upon them,pyridine ring with heteroaromatic structure has been applied to design and synthesis of some monomers,as well as preparation of advanced polymers becau its excellent stability resulting from corresponding molecular symmetry and aromaticity[11,12].In fact,tho pyridine-containing polymers also posss excellent thermal stability,
chemical stability,and retention of mechanical property at elevated temperature,as well as good solubility in organic solvents[13–15].Conquently,the studies utilizing monomers containing pyridine nucleus structures to synthesize novel heteroaromatic polymers have been focud widely [15–20].It was found that the incorporation of pyridine ring
to
Polymer47(2006)3774–3783
/locate/polymer
0032-3861/$-e front matter q2006Elvier Ltd.All rights rerved.
doi:10.1016/j.polymer.2006.03.101
*Corresponding author.
欧阳修的代表作
E-mail address:liyf@(Y.-F.Li).
the polyimide backbone should be contributed to increa its solubility while maintaining its excellent thermal properties [21].Comparing with pyridine-containing diamine monomers [20,21],unfortunately,pyridine-containing dianhydride mono-mers,which are need for synthesis polyimides containing pyridine moieties were reported very few so far,which should be due to purification hardness of pyridine-containing tetraacid intermediates.The investigation to overcome the above hardness and synthesize pyridine-containing dianhydride monomers,however,will be very interesting.
In this work,a new kind of pyridine-containing aromatic dianhydride monomer,2,6-bis[4-(3,4-dicarboxyphenoxy)ben-zoyl]pyridine dianhydride,was synthesized successfully,mean-while,a ries of novel polyimides holding pyridine moieties in main chain were prepared from the resulting dianhydride monomer with various aromatic diamines via a conventional two-stage process undergoing ring-opening polycondensation to form the poly(amic acid)s and further thermal or chemical imidization to form polyimides.And the composition,structure and properties of the resulting pyridine-containing polyimides and dianhydride monomer are characterized by means of1H13C NMR,FT-IR(KBr plate),elemental analysis,DSC,TGA and Wide-angle X-ray diffraction(WXRD),as well as an Instron 1122testing instrument,Ubbelohde wiscosimeter and Agilent 4291B instrument.
2.Experimental
2.1.Materials
天地君亲师下一句2,6-Pyridinedicarboxyl chloride(TCI),4-nitrophthalonitrile (TCI)were ud as received.Phenyl ethyl ether(Chemspec Inc., Shanghai,China)was purified by distillation from calcium hydride and stored over anhydrous sodium sulfate.N-Methyl-2-pyrrolidone(NMP)and N,N-dimethylacetamide(DMAc)was distilled under reduced pressure over calcium hydride prior to u and stored over4A˚molecular siev
es.p-Phenylenediamine (PDA)and4,40-oxydianiline(ODA)were purified by vacuum sublimation prior to u.1,4-Bis(4-aminophenoxy)benzene (PAPB)and1,3-bis(4-aminophenoxy)benzene(MAPB)were recrystallized from ethanol.1,4-Bis(2-trifluoromethyl-4-amino-phenoxy)benzene(PFAPB)was prepared in our laboratory according to the method previously reported[22].
2.2.Monomer synthesis
2.2.1.2,6-Bis(4-hydroxybenzoyl)pyridine(BHBP)
24.5g(0.12mol)of2,6-pyridinedicarboxyl chloride was gradually added to a mixture of60mL of benzene,30.5g (0.25mol)of phenyl ethyl ether and64.0g(0.48mol)of anhydrous aluminum chloride at10–128C with continuous stirring.After addition,the mixture was slowly heated to408C and stirred for2h.Finally,the resulting reaction mixture was allowed to cool to room temperature and poured into500mL of a water solution of hydrochloric acid(5%)to precipitate out white solids.The solids was collected byfiltrating,and washed with hot methanol to give31.0g of white powder of compound 2,6-bis(4-hydroxybenzoyl)pyridine(BHBP).The yield is81%, and the melting point is2778C.
FT-IR(KBr):3352–3251(O–H stretching),1645(C a O stretching)and1326cm K1(C–N stretching).1H NMR (300MHz,DMSO-d6):d(ppm)10.50(s,2H,–OH),8.24(t, J Z8.4Hz,1H,H a),8.07(d,J Z7.4Hz,2H,H
b),7.92(d,J Z 8.6Hz,4H,H c), 6.84(d,J Z8.4Hz,4H,H d).13C NMR (300MHz,DMSO-d6):d(ppm)190.9(C5),162.4(C4),154.2 (C6),138.8(C8),133.3(C2),126.7(C1),125.8(C7),115.0(C3). Elem.Anal.Calcd for C19H13NO4(319.08):C71.47,H4.10,N 4.39.Found:C71.26,H4.20,N
4.32.
2.2.2.2,6-Bis[4-(3,4-dicyanophenoxy)benzoyl]pyridine (BCNP)
In a250mL round-bottomflask,16.0g(0.05mol)of BHBP and16.6g(0.12mol)of anhydrous potassium carbonate were suspended in a mixture of100mL of dry DMF and40mL of toluene.The mixture was then refluxed at1408C for4h using a Dean–Stark trap to facilitate dehydration.After most toluene was distilled,17.3g(0.1mol)of4-nitrophthalonitrile was added to the mixture when it was cooled to608C.The mixture was then allowed to warm to908C and stirred for5h.After the resulting reaction mixture cooling to room temperature,it was poured into600mL of ice/water to give white precipitates. Filtrating and washing with water,the crude product was recrystallized twice from acetonitrile to afford16.6g of white crystals2,6-bis[4-(3,4-dicyanophenoxy)benzoyl]pyridine (BCNP).The yield is58%,
while the melting point is1968C.
FT-IR(KBr):2231(C b N stretching),1248cm K1(C–O–C stretching).1H NMR(300MHz,DMSO-d6):d(ppm)8.32(t, J Z10.5Hz,1H,H a),8.17(d,J Z10.5Hz,2H,H b),7.89(d,J Z 12.9Hz,4H,H c),7.36(d,J Z9.3Hz,2H,H f),7.30(d,J Z 9.3Hz,2H,H e),7.26(s,2H,H g),7.10(d,J Z13.2Hz,4H,H d). 13C NMR(300MHz,DMSO-d
6
):d(ppm)195.0(C13),163.6 (C9),162.3(C7),157.0(C14),143.2(C16),140.2(C5),137.5 (C11),136.2(C12),130.9(C15),127.7(C6),127.2(C8),123.1 (C10),121.8(C1),120.7(C2),119.5(C3),113.1(C4).Elem. Anal.Calcd for C35H17N5O4(571.54)C73.55%,H3.00%,N 12.25%.Found C73.32%,H2.83%,N
12.21%.
2.2.
3.2,6-Bis[4-(3,4-dicarboxylphenoxy)benzoyl]pyridine (BACP)
11.4g(0.02mol)of BCNP and130mL of85%phosphoric acid were put into a250mLflask and refluxed for2.5h.After cooling to room temperature,the mixture was poured into
X.Wang et al./Polymer47(2006)3774–37833775
1200mL of cold,dilute aqueous potassium hydroxide (10%).The mixture was stirred at room temperature for 6h after modulating the pH value to 11,and then it was neutralized with 6M hydrochloric acid to pH 3–4,followed by stirring for 6h.The product was collected by filtration and dried in a vacuum at room temperature.After recrystallization from aqueous acetic acid (30%)using activated charcoal,10.9g of light yellow solid was obtained.The yield is 84%,and the melting point is 2268C.
FT-IR (KBr):2500–3500(C(O)O–H stretching),1709(C a O stretching),1267cm K 1(C–O–C stretching).1H NMR (300MHz,DMSO-d 6):d (ppm)8.34(t,J Z 5.7Hz,1H,H a ),8.25(d,J Z 5.7Hz,2H,H b ),8.12(d,J Z 6.3Hz,4H,H c ),7.91(d,J Z 6.0Hz,2H,H f ),7.39(s,2H,H g ),7.25(d,J Z 6.3Hz,2H,H e ),7.19(d,J Z 6.6Hz,4H,H d ).13C NMR (300MHz,DMSO-d 6):d (ppm)191.34(C 13),167.86(C 1),167.41(C 2),159.85(C 7),157.33(C 9),153.45(C 14),139.28(C 16),136.69(C 3),133.41(C 5),132.25
(C 11),131.31(C 12),128.14(C 15),126.73(C 4),120.52(C 6),119.12(C 10),118.24(C 8).Elem.Anal.Calcd for C 35H 21NO 12(647.54)C 64.92%,H 3.27%,N 2.16%.Found C 64.84%,H 3.20%,N
2.13%.
2.2.4.2,6-Bis[4-(3,4-dicarboxyphenoxy)benzoyl]pyridine dia-nhydride (BPDA)
6.5g (0.01mol)of the tetraacid precursor 2,6-bis[4-(3,4-dicarboxylphenoxy)benzoyl]pyridine (BACP)was refluxed in the mixture 100mL of acetic anhydride and 200mL of acetic acid for 12h in a 500mL round-bottom flask.After cooling to room temperature,the white solid was removed by filtration and dried overnight at 1508C under reduced pressure,which was then purified by recrystallization from acetic anhydride to yield 5.1g of white crystals.The yield is 83%,and the melting point is 2298C.
FT-IR (KBr):1845and 1782(C a O stretching),1282cm K 1(C–O–C stretching).1H NMR (300MHz,DM
SO-d 6):d (ppm)8.38(t,J Z 9.3Hz,1H,H a ),8.34(d,J Z 9.3Hz,2H,H b ),8.19(d,J Z 9.3Hz,4H,H c ),8.07(d,J Z 8.7Hz,2H,H f ),7.62(s,2H,H g ),7.28(d,J Z 8.7Hz,2H,H e ),7.20(d,J Z 9.0Hz,4H,H d ).13C NMR (300MHz,DMSO-d 6):d (ppm)191.30(C 13),168.05(C 1),167.45(C 2),162.44(C 7),159.72(C 9),158.47(C 14),139.40(C 16),136.33(C 3),134.01(C 5),132.41(C 11),131.32(C 12),127.83(C 15),125.64(C 4),120.43(C 6),119.18(C 10),118.41(C 8).Elem.Anal.Calcd for C 35H 17NO 10(611.51)C 68.74%,H 2.80%,N 2.29%.Found C 68.71%,H 2.73%,N
2.26%.
夏天开花的树2.3.Polyimide synthesis
A typical polymerization is as follows: 2.4460g (4.0mmol)of dianhydride monomer,2,6-bis[4-(3,4-dicar-boxyphenoxy)benzoyl]pyridine dianhydride (BPDA),was gradually added to a stirred solution of 0.8009g (4.0mmol)of 4,40-oxydianiline (ODA)in 18.5mL of NMP in a 50mL three-necked flask equipped with a nitrogen inlet at 0–58C.The mixture was stirred for 24h at room temperature under n
itrogen atmosphere to form a viscous solution of poly(amic acid)(PAA)precursor solution in NMP.The PAA was converted into polyimide by either thermal or chemical imidization method.For the thermal imidization method,the PAA solution was cast on a clean glass plate,followed by thermal curing with a programmed procedure (808C/2h,1208C/1h,1508C/1h,1808C/1h,2508C/1h,2808C/2h)to produce a fully imidized polyimide film.The chemical imidization was carried out by adding 5mL of a mixture of an acetic anhydride/pyridine (6/4v/v)to the above-mentioned PAA solution with stirring at room temperature for 1h,then the mixture was heated to 1008C and stirred for 4h.After cooling,the homogeneous polyimide solution was sub-quently poured into 300mL of ethanol to produce a solid polymer precipitate,which was removed by filtration,washed thoroughly with hot ethanol,and finally dried in a vacuum oven at 1008C overnight.2.4.Measurements
1
结膜炎H and 13C NMR spectra were measured on a JEOL EX-300spectrometer using tetramethylsilane as the internal reference.Fourier transform infrared (FT-IR)spectra of intermediates,monomer and polyimides were obtained on a Micolet NEXUS 670spectrometer (KBr disks).Elemental analysis was determined on a Perkin–Elmer model 2400CHN analyzer.Differential scanning calorimetry (DSC)analys were performed on a Perkin–Elmer differential scanning calorimeter DSC 7at a heati
ng rate of 208C/min under flowing nitrogen.Glass transition temperature (T g )was taken as the midpoint of the inflection obrved on the curve of heat capacity versus temperature.Melting points were measured by DSC.Thermo-gravimetric analysis (TGA)was conducted with a TA Instruments TGA 2050,and experiments were carried out on approximately 10mg of samples under controlled flux of nitrogen at 208C/min.Wide-angle X-ray diffraction measure-ments were performed at room temperature on a Siemens Kristalloflex D5000X-ray diffractometer,using nickel-filtered
Cu K,radiation (l Z 1.5418A
˚,operating at 40kV and 30mA).The mechanical properties were measured on an Instron 1122testing instrument with 100!5mm 2specimens in accordance with GB 1040–79at a drawing rate of 50mm/min.Inherent viscosities were determined at 308C with an Ubbelohde wiscosimeter with DMAc as a solvent on polymer solutions with a concentration of 0.5g/dL.Qualitative solubility was determined with 10mg of polymer in 1mL of solvent at room temperature after 24h or heating until dissolution for samples
X.Wang et al./Polymer 47(2006)3774–3783
3776
soluble on heating.The dielectric constants were determined on an Agilent4291B instrument with25m m thickness specimens at frequencies of1and10MHz at room temperature.
骨刺消痛胶囊
3.Results and discussion
3.1.Synthesis of dianhydride monomer
To date,reports on the synthesis of pyridine-containing dianhydride monomers that can be ud to prepare polyimide have appeared very few in the literature.In the prent work,the new pyridine-containing dianhydride,2,6-bis[4-(3,4-dicar-boxy phenoxy)benzoyl]pyridine dianhydride(BPDA),was successfully synthesized through a four-step synthetic route starting from2,6-pyridinedicarbonyl chloride,as shown in Scheme1.First,diphenol2,6-bis(4-hydroxybenzoyl)pyridine (BHBP)was prepared by Friedel–Crafts acylation of phenyl ethyl ether with2,6-pyridinedicarbonyl chloride using anhy-drous aluminum chloride as a catalyst.Then the tetranitrile intermediate2,6-bis[4-(3,4-dicyanophenoxy)benzoyl]pyridine (BCNP)was readily synthesized from the nitro displacement of 4-nitrophthalonitrile by the phenoxide ion of BHBP in a good yield,according to the procedure of Takekoshi[23].After
that, Scheme1.Synthesis procedure of the dianhydride monomer
BPDA.
hydrolysis of the tetranitrile compound BCNP,which was carried out by the method of phosphoric acid[24],afforded the tetraacid compound2,6-bis[4-(3,4-dicarboxyl phenoxy)ben-zoyl]pyridine(BACP),which was further purified by recrys-tallization in30%of aqueous acetic acid using activated charcoal.Finally,the pyridine-containing pyridine diaanhy-dride,2,6-bis[4-(3,4-dicarboxyphenoxy)benzoyl]pyridine dia-nhydride(BPDA),was obtained by chemical cyclodehydration of tetraacid precursor BACP with acetic anhydride.The synthesis route was confirmed by the FT-IR spectrum of the dianhydride monomer BPDA,and the intermediate BCNP and BACP,as shown in Fig.1.The IR spectrum of intermediate tetranitrile BCNP is characterized by absorption at2231cm K1 becau of the cyano group.The most characteristic bands of tetraacid precursor BACP can be obrved near1709cm K1 (C a O stretching)and in the region of2500–3500cm K1(O–H stretching).The disappearance of the characteristic cyano stretching band on the IR spectrum revealed completion of hydrolysis.The IR spectrum of dianhydride BPDA shows two characteristic cyclic anhydride absorptions near1845and 1782cm K1,attributed to the asymmetrical and symmetrical stretching vibrations of C a O.The disappearance of the characteristic bands of tetraacid precursor BACP,as well as the appearance of two characteristic cyclic anhydride absorptions indicat
ed the conversion from tetraacid to dianhydride.According to the date from FT-IR,1H,and13C NMR spectroscopy prented in Section2.2,the dianhydride monomer BPDA,and the intermediates BHBP,BCNP and BACP hold the structure as uniform as that shown in Scheme1. All intermediate compounds and the dianhydride BPDA were also confirmed by elemental analysis,which were in good agreement with the calculated values.The results indicate that the design and synthesis of the novel pyridine-containing aromatic dianhydride monomer BPDA should be successful and feasible in this work.Furthermore,the yield of BHBP, BCNP,BACP and BPDA was81,58,84and83%, successively,and the white crystal pyridine-containing aromatic dianhydride in this work was stable in air at room temperature and pure enough to be employed for polyconden-sation with diamine.This is to say that the dianhydride monomer could satisfy the requirement of preparation of polyimides with high molecular
weight.
Scheme2.Synthesis of the polyimides.
Table1
Physical properties and elemental analysis of the polyimides
坚韧不拔的近义词Polyimide Yield(%)h inh a(dL/g)Composition of
repeating unit
Elemental analysis(%)
C H N BPDA–PDA97–C41H21N3O8Calcd72.03 3.10 6.15
Found71.86 3.17 5.98 BPDA–ODA980.68C47H25N3O9Calcd72.77 3.25 5.42
Found72.63 3.29 5.38 BPDA–PAPB980.54C53H29N3O10Calcd73.35 3.37 4.48
Found73.31 3.28 4.51 BPDA–MAPB960.51C53H29N3O10Calcd73.35 3.37 4.48
Found73.41 3.33 4.46 BPDA–PFAPB950.60C55H27F6N3O10Calcd65.81 2.71 4.19
Found65.77 2.73 4.22 a Measured on0.5%polymer solution in DMAc,at30.0G0.18C;–,not dissolved.
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