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Structural properties of polyaniline protonated with camphorsulfonic acid
SyntheticMetals 101(1999) 715-716
Structural properties of polyaniline protonated with camphorsulfonic acid* E.Bai&a” and W.Luinyb aDepartment of Materials Science & Ceramics, AGH, al.Mickiewicza bFacttlty of Physics & Nuclear Techniques, AGH, al.Mckiewicza
30, 30-059 Cracow, Poland 30, 30-059 Cracow, Poland -
Abstract Polyanilineprotonatedwith camphorsulfonic acid (PANIICSA) exhibitsvery interestingprocessingand electricaltransport properties.A seriesof morethan30 samples preparedin variousconditionswassubjectedto theX-ray diffraction measurements. The influenceof thesynthesisparametersonthestructureof the polymerwasinvestigated.Somecorrelationsbetweenthe sample preparationprocessand its structural propertieshave beenobtained.Besides,new conclusionsconcerningthe model of the crystalbnestructure of PANIiCSA have beenproposed. Keywor&: X-ray diffraction; Polyanihneand derivatives
1. Introduction Polyaniline (PANI) is currently the most attracrmg conducting polymer becauseof its good environmental stability [ 11,interestingelectricalandmechanical properties and potentialfor a variety of applications[2]. Cao et al. reportedthat PANI dopedwith camphorsulfonic acid(CSA) can be solublein commonorganicsolventssuchm-cresol [3]. Free standing films produced from this system (PANI/CSA inm-cresol)showhighconductivity(100+400 S/cm) and exhibit metallic-like transportproperties[4]. Furthermore,X-ray diffraction patternsof the filmscasted from m-cresolshow the presenceof the high degreeof crystahinity. It is very interestingto find the influenceof the synthesisparameterson the structure of PANIiCSA fiis for better knowledgeof their correlations.
a CuKo! radiation.The measurements were performedin typical Bragg geometry(8, 20) in the reflection mode.The f;. ‘r!t:t~c‘~r? i;q~t~er~:~ collectedfor t:.r: samplesin~:cstipared are dtfferent. Two typical dif‘fractogramsare presentedin Figure 1 (sampleNo 1, solid line, andsampleNo 2, dotted fine, weresynthesizedin the temperature-43’C and-lS°C, respectively).
100
f
-
;i:
2. Experimental 20PANI wassynthesizedaccordingto Beadleet al. [5] at different temperaturesdown to -43’C. in presenceof LiC1. Solutionscontaining 0,5% emeraldinebasein m-cresol protonatedwith CSA (with an acid/N molar ratio = 0,5) were preparedby magneticstirring for at leastthreeweeks at room temperature.Free standingthin f&ns (- 20 pm) were prepared from solutionby In-cresoievaporationat 50°Cfor three days. The X-ray diffraction experimentshavebeencarried out for thin films samples,on theSEIFERT diffractometerwith
*Thiswork wasfinancially supportedby KBN Grant No 3 T09B 049 14. The fruitful discussions with D.Djurado, Y.F.Nicolau andE.J.Samuelsen aregreatlyacknowledged.
O-
0
/y
y?&j&
.,.~; ‘;i
,;; ,y” 7’: “.:‘, ‘.._ _, ,.‘. ._.. 10
20
I 30
2.rheto Figure1. Thediffractograms obtainedfor twoselected samples of PANUCSAsystem. The first conclusionfrom this diagramis that there is a significantdifferencebetweenaLIthe diffraction patterns obtainedin this work and thosepublishedearlier for the PANIiCSA samples: the diffraction maximumat 20 = 9.4’ doesnot occur for any of our patterns. This effect is relatedto the orientationalphenomena andit wassubjected to further careful analysis.It was proved so far, that the
0379-6779/99/$ - seefrontmatter0 1999ElsevierScience S.A. All rightsreserved. PII: SO379-6779(98)0 1 15 l-5
716
E. Baiika,
W. Lutny
I Synthetic
films subjected to the diffraction measurements were completely m-plane isotropic. However, the results presented recently in the literature [6,7 suggest, that the missing reflection related to the repetition distance close to 9 A may have quite different orientation than the other ones. We have proved this point by diffraction experiment done in the transmission mode. Indeed, the diffraction patterns obtained in this way show only one dominating reflection for 20 =: 9.6’. Such remarkable anisotropy of diffractograms obtained in transmission and in reflection is a really striking property of the samples investigated and it will be subjected to further, careful analysis. All recorded diffraction patterns are typical of semicrystalline polymers with the degree of crystallinity between 10 and 35 %. The crystalline component of diffractograms (recorded in reflection) consists of four more or less intensive reflections related to the following interplanar distances: -18,6.1,4.3and3.5A.Thefourt.h maximum shows large relative intensity and it is visible for all samples investigated - even for those with the lowest crystallinity. The parameter which describes the diffraction patterns quite well, is the ratio of intensities of the first peakto the fourth one: it is close to 1 for themostordered samples,and closeto 0 for the leastorderedones. ASimpliesfrom themodelsof tbc P.*fi!T’CS.4c~.??lli?~ :mxkm [S;, die ori;i;; 2: t!:, LSL diLr;~c,:onisa,..,tiu, (for d = 18A) is closely reiatedto the orderingof dopant molecuiesin ‘tunnels’ betweenpolymerchains.Contrary, the fourth reflection originatesfrom therepetitiondistance betweentwo adjacentspecies:a macromoleculeand a dopant. Therefore it is reasonableto conclude,that the samples with we11definedfirst diffraction peakshowhighly orderedarrangement of CSAmolecules alongPAN1chains,
i 20
1
Metals
101 (1999)
715-716
It is well confiied by the electrical conductivity measurements:these samplesshow remarkably higher conductivity than the other ones, for which the relative intensity of the fist reflectionis closeto zero. 3. The effect chloroform
emeraldine
base
estraction
with
SomePANI/CSA sampleswere cast using emeraldme baseextracted with chloroform. This extraction induced remarkableimprovementof physical properties of the polymersample.It may bedemonstrated by comparisonof two diffraction patterns(seeFigure2), obtainedbeforeand after extraction respectively, as well as by comparisonof the electrical conductivity. This
parameteris equal -70 S/cm for the first caseand -270 S/cm for the secondone.Without any doubt onecanstate, that this effect is related to better ordering of CSA moleculesinducedby extraction. 4. Discussion and conclusions Zci Lffrccrion palternsarc different in:6 ~L-c: .z.~i;~t with respectto thosereportedbyD.Djurado el al (seethese Proceedings) recordedin transmission usingsomecommon samples.The differencescomeprobablyfrom the different experimentalset-up. The basic correlations between the structure and electrical conductivity may be well studied for the PANIKSA system. Presentedresults have thrown new light into the problem of its crystalline structure: the questionof the origin andanisotropyof the experimental diffraction maxima, especiallythe peak for d = 9A is subjectedto ihe further, carefulexperimentalandcomputer modellingstudies.
i 03
References
20
30
Z&theta
Figure 2. Thediffractograms obtained for thePANI/CSA sampie before (solid line) and after chloroform, respectively.
(dotted
line) extraction
in
[l] Y.Yue, A.J.Epstein, Z.Zong and P.K.GalIager, Synth.Met. 41-43(1991)765. [2] W.R.Salaneck,D.T.Clark andE.J.Samuelsen,Science andApplicationsol ConductingPolymers, Hilger, Bristol, 1991. [3] Y.Cao, PSmith andA.J.Heeger,Synth.Met. 48 (1992) 91. [4] M.Reghu, Y.Cao, D.Moses and A.J.Heeger, Phys.Rev.B 47 (1993) 1758. [5] P.M.Beadle, Y.F.Nicolau, E.Bar?ka,P.Ran.nouand D.Djurado, Synth.Met. 95 (1998) 29. [6] LAbeII, P.N.AdamsandA.P.Monkman, Polymer 37 (1996) 5927. [q C.D.G.Minto andA.S.Vaughan, Polymer 38 (1997) 2683. [8] WLuiny, E..J.Samuelsen, D.DjuradoandY.F.Nicolau, Synth.Met. 90 (1997)19.
Structural properties of polyaniline protonated with camphorsulfonic acid* E.Bai&a” and W.Luinyb aDepartment of Materials Science & Ceramics, AGH, al.Mickiewicza bFacttlty of Physics & Nuclear Techniques, AGH, al.Mckiewicza
30, 30-059 Cracow, Poland 30, 30-059 Cracow, Poland -
Abstract Polyanilineprotonatedwith camphorsulfonic acid (PANIICSA) exhibitsvery interestingprocessingand electricaltransport properties.A seriesof morethan30 samples preparedin variousconditionswassubjectedto theX-ray diffraction measurements. The influenceof thesynthesisparametersonthestructureof the polymerwasinvestigated.Somecorrelationsbetweenthe sample preparationprocessand its structural propertieshave beenobtained.Besides,new conclusionsconcerningthe model of the crystalbnestructure of PANIiCSA have beenproposed. Keywor&: X-ray diffraction; Polyanihneand derivatives
1. Introduction Polyaniline (PANI) is currently the most attracrmg conducting polymer becauseof its good environmental stability [ 11,interestingelectricalandmechanical properties and potentialfor a variety of applications[2]. Cao et al. reportedthat PANI dopedwith camphorsulfonic acid(CSA) can be solublein commonorganicsolventssuchm-cresol [3]. Free standing films produced from this system (PANI/CSA inm-cresol)showhighconductivity(100+400 S/cm) and exhibit metallic-like transportproperties[4]. Furthermore,X-ray diffraction patternsof the filmscasted from m-cresolshow the presenceof the high degreeof crystahinity. It is very interestingto find the influenceof the synthesisparameterson the structure of PANIiCSA fiis for better knowledgeof their correlations.
a CuKo! radiation.The measurements were performedin typical Bragg geometry(8, 20) in the reflection mode.The f;. ‘r!t:t~c‘~r? i;q~t~er~:~ collectedfor t:.r: samplesin~:cstipared are dtfferent. Two typical dif‘fractogramsare presentedin Figure 1 (sampleNo 1, solid line, andsampleNo 2, dotted fine, weresynthesizedin the temperature-43’C and-lS°C, respectively).
100
f
-
;i:
2. Experimental 20PANI wassynthesizedaccordingto Beadleet al. [5] at different temperaturesdown to -43’C. in presenceof LiC1. Solutionscontaining 0,5% emeraldinebasein m-cresol protonatedwith CSA (with an acid/N molar ratio = 0,5) were preparedby magneticstirring for at leastthreeweeks at room temperature.Free standingthin f&ns (- 20 pm) were prepared from solutionby In-cresoievaporationat 50°Cfor three days. The X-ray diffraction experimentshavebeencarried out for thin films samples,on theSEIFERT diffractometerwith
*Thiswork wasfinancially supportedby KBN Grant No 3 T09B 049 14. The fruitful discussions with D.Djurado, Y.F.Nicolau andE.J.Samuelsen aregreatlyacknowledged.
O-
0
/y
y?&j&
.,.~; ‘;i
,;; ,y” 7’: “.:‘, ‘.._ _, ,.‘. ._.. 10
20
I 30
2.rheto Figure1. Thediffractograms obtainedfor twoselected samples of PANUCSAsystem. The first conclusionfrom this diagramis that there is a significantdifferencebetweenaLIthe diffraction patterns obtainedin this work and thosepublishedearlier for the PANIiCSA samples: the diffraction maximumat 20 = 9.4’ doesnot occur for any of our patterns. This effect is relatedto the orientationalphenomena andit wassubjected to further careful analysis.It was proved so far, that the
0379-6779/99/$ - seefrontmatter0 1999ElsevierScience S.A. All rightsreserved. PII: SO379-6779(98)0 1 15 l-5
716
E. Baiika,
W. Lutny
I Synthetic
films subjected to the diffraction measurements were completely m-plane isotropic. However, the results presented recently in the literature [6,7 suggest, that the missing reflection related to the repetition distance close to 9 A may have quite different orientation than the other ones. We have proved this point by diffraction experiment done in the transmission mode. Indeed, the diffraction patterns obtained in this way show only one dominating reflection for 20 =: 9.6’. Such remarkable anisotropy of diffractograms obtained in transmission and in reflection is a really striking property of the samples investigated and it will be subjected to further, careful analysis. All recorded diffraction patterns are typical of semicrystalline polymers with the degree of crystallinity between 10 and 35 %. The crystalline component of diffractograms (recorded in reflection) consists of four more or less intensive reflections related to the following interplanar distances: -18,6.1,4.3and3.5A.Thefourt.h maximum shows large relative intensity and it is visible for all samples investigated - even for those with the lowest crystallinity. The parameter which describes the diffraction patterns quite well, is the ratio of intensities of the first peakto the fourth one: it is close to 1 for themostordered samples,and closeto 0 for the leastorderedones. ASimpliesfrom themodelsof tbc P.*fi!T’CS.4c~.??lli?~ :mxkm [S;, die ori;i;; 2: t!:, LSL diLr;~c,:onisa,..,tiu, (for d = 18A) is closely reiatedto the orderingof dopant molecuiesin ‘tunnels’ betweenpolymerchains.Contrary, the fourth reflection originatesfrom therepetitiondistance betweentwo adjacentspecies:a macromoleculeand a dopant. Therefore it is reasonableto conclude,that the samples with we11definedfirst diffraction peakshowhighly orderedarrangement of CSAmolecules alongPAN1chains,
i 20
1
Metals
101 (1999)
715-716
It is well confiied by the electrical conductivity measurements:these samplesshow remarkably higher conductivity than the other ones, for which the relative intensity of the fist reflectionis closeto zero. 3. The effect chloroform
emeraldine
base
estraction
with
SomePANI/CSA sampleswere cast using emeraldme baseextracted with chloroform. This extraction induced remarkableimprovementof physical properties of the polymersample.It may bedemonstrated by comparisonof two diffraction patterns(seeFigure2), obtainedbeforeand after extraction respectively, as well as by comparisonof the electrical conductivity. This
parameteris equal -70 S/cm for the first caseand -270 S/cm for the secondone.Without any doubt onecanstate, that this effect is related to better ordering of CSA moleculesinducedby extraction. 4. Discussion and conclusions Zci Lffrccrion palternsarc different in:6 ~L-c: .z.~i;~t with respectto thosereportedbyD.Djurado el al (seethese Proceedings) recordedin transmission usingsomecommon samples.The differencescomeprobablyfrom the different experimentalset-up. The basic correlations between the structure and electrical conductivity may be well studied for the PANIKSA system. Presentedresults have thrown new light into the problem of its crystalline structure: the questionof the origin andanisotropyof the experimental diffraction maxima, especiallythe peak for d = 9A is subjectedto ihe further, carefulexperimentalandcomputer modellingstudies.
i 03
References
20
30
Z&theta
Figure 2. Thediffractograms obtained for thePANI/CSA sampie before (solid line) and after chloroform, respectively.
(dotted
line) extraction
in
[l] Y.Yue, A.J.Epstein, Z.Zong and P.K.GalIager, Synth.Met. 41-43(1991)765. [2] W.R.Salaneck,D.T.Clark andE.J.Samuelsen,Science andApplicationsol ConductingPolymers, Hilger, Bristol, 1991. [3] Y.Cao, PSmith andA.J.Heeger,Synth.Met. 48 (1992) 91. [4] M.Reghu, Y.Cao, D.Moses and A.J.Heeger, Phys.Rev.B 47 (1993) 1758. [5] P.M.Beadle, Y.F.Nicolau, E.Bar?ka,P.Ran.nouand D.Djurado, Synth.Met. 95 (1998) 29. [6] LAbeII, P.N.AdamsandA.P.Monkman, Polymer 37 (1996) 5927. [q C.D.G.Minto andA.S.Vaughan, Polymer 38 (1997) 2683. [8] WLuiny, E..J.Samuelsen, D.DjuradoandY.F.Nicolau, Synth.Met. 90 (1997)19.