Supramolecular Architecture - American Chemical Society

Chapter 16

Intercalation and Polymerization of Aniline in Layered Protonic Conductors Deborah J. Jones, Raja El Mejjad, and Jacques Rozière

Downloaded by COLUMBIA UNIV on August 6, 2012 | http://pubs.acs.org Publication Date: July 14, 1992 | doi: 10.1021/bk-1992-0499.ch016

Laboratoire des Agrégats Moléculaires et Matériaux Inorganiques, URA Centre National de la Recherche Scientifique 79, Université Montpellier II, 34095 Montpellier Cedex 5, France

Aniline has been intercalated into the acidic host matrices of HFe(SO ) .4H O, and of α-Zr(HPO ) .H O and γ-Zr(HPO ) .2H O, and their partially copper exchanged phases. The nature of the guest species: neutral, protonated or polymerised, depends on the inorganic template. Polymerised aniline has been identified in both α and γ modifications of zirconium copper hydrogen phosphates. 4

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Amongst the strategies used for the optimisation of physicochemical properties of materials, one approach is the molecular level modification of the constitutive chemical units. A pathway to attaining this objective is through the intercalation by ion exchange, or by the insertion of new ionic or molecular species into open host structures having either a pronounced two-dimensionality, as i n clays, certain mineral classes or their synthetic analogues, or a three-dimensional framework structure, as in zeolites. The use of inorganic lamellar solids i n electron transfer reactions between intercalated species and the layers has recently been demonstrated (1-11), and the elaboration of occluded low dimen sional conductors has been realised (12-15). It may be desirable to associate two potential properties of the inorganic host namely, electron transfer and proton transfer characteristics. This may be achie ved by following the intercalation of the organic monomer into a Bronsted acid matrix by an oxidation step, or by the use of an acidic electron-active host matrix. This paper reports studies of the intercalation of aniline i n various layered proton conducting host matrices: ferric hydrogen sulphate, OTeCSO^^FÔ and two crystalline modifications of zirconium hydrogen phosphate o c - Z r ( H P O ^ . H p and y - Z r ( H P 0 ) . 2 H 0 , as well as i n the copper ion-exchanged derivatives of the zirconium phosphates. The first of these, and the zirconium-copper phosphates, combine the availability of transferable protons and potential electron accepting metallic sites, whilst the zirconium hydrogen phosphates only provide an acidic host framework for aniline molecules. 4

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0097-6156/92/0499-0220$06.00/0 © 1992 American Chemical Society

In Supramolecular Architecture; Bein, T.; ACS Symposium Series; American Chemical Society: Washington, DC, 1992.

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The proton conduction properties of layered matrices HM(III)(S0 ) .nH 0, M=Fe, In and n = 1 and 4, have previously been reported (16), and the redox transfer characteristics of the ferric tetrahydrate member have been demonstrated. Facile insertion of monovalent or divalent ions occurs, with retention of the layered structure, and reduction of Fe(III) centres (17). The negatively charged layers of H F e i S O ^ ^ F ^ O contain octahedral Fe(III), the coordination sphere of which is formed by 4 oxygen atoms from sulphate groups and two from water molecules (18) (Figure 1). 4

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The interlayer zone is occupied solely by diaquahydrogen ions H 0 , which are responsible for the proton transfer properties, and which are characterised by their hydrogen bond length of 2.44 À. The basal spacing is 9.2 Â. The zirconium hydrogen phosphates have interlayer distances of 7.6 Â (α-form) and 12.2 Â (γ-form). The structure of the former is made of sheets containing octahedral zir Figure 1. Structural arrangement of conium atoms with H P 0 groups H F e ( S 0 ) . 4 H 0 (filled circles, Fe; lying alternately above and below hatched circles, H Ô ; grey circles, O). the plane (19). N o proton transfer to Only the oxygen atoms of interlayer interlayer water molecules occurs H 0 ions are represented (18). (20). The structure of γ - Ζ Κ Η Ρ Ο ^ ^ Ι - ^ Ο is undetermined as yet, but partial resolu tion of the titanium analogue by Rietveld profile refinement of a powdered sample (21) agreed with previous conclusions from P M A S nmr (22), in the existence of two chemically distinct types of phosphate groups, leading to a formulation y-Ti(H FO )(PO ).2YLp. +


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Experimental Preparation of host structures HFe(S0 ) .4H20 was synthesised as described previously (16), and α and γ zirconium hydrogen phosphates were prepared according to published methods (23,24). Copper exchange on these latter matri ces has been fully reported (25,26). For oc-ZriHPO^.I-Ô, a 60% copper loading was used, which corresponds to a biphasic system (25). 70% copper loadings were used for the γ modification. Despite partial exchange, y-ZrCu ^ (P0 ) .4 H 0 is monophasic, having an interlayer distance of 12.4 Â. The retention of a certain degree of acidity in both cases was intentional for the subsequent intercalation reaction. Reaction w i t h aniline H F e i S O p ^ P ^ O was placed in contact with solutions of aniline i n acetone with molar ratios HFe(S0 ) .4H 0 : aniline of 1:4, and reacted 4

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either at room temperature or under reflux. The progress of the reaction was monitored by powder X-ray diffraction (XRD, Philips instrument, C u Κ α radia tion). In the case of zirconium hydrogen phosphates and their copper derivati ves, intercalation reactions were performed either by contacting the solids with the pure liquid or with aniline diluted i n acetone, and the progress of the insertion reactions were followed as a function of the reaction temperature and time using X R D . A l l reactions were performed in an air atmosphere. The suspensions were then filtered and the solids washed with acetone until excess amine was removed. The products were air dried and stored. Elemental and thermogravimetric analyses were performed on the resulting materials for the determination of compound stoechiometry, aniline and water content. Spectroscopic investigation Diffuse reflectance spectra of powdered samples in the region 200 - 2000 n m (50,000 - 5000 cnr ) were recorded on a Cary instrument model 2300. Infrared spectra were recorded at room temperature as K B r discs using a Bomem FTIR D A 8 spectrometer between 4000 and 400 cnr . Incoherent inelastic neutron scattering (INS) spectra were recorded on powdered samples at the spallation neutron source ISIS (U.K.) on the T F X A spectrometer. 1

1

Results and Discussion Intercalation i n H F e ( S 0 ) . 4 H 0 , a - Z r ( H P 0 ) . H 0 and y - Z r ( H P 0 ) . 2 H 0 The intercalation of aniline in acetone solution into ferric hydrogen sulphate occurs readily at room temperature. The appearance of new X-ray diffraction lines indicates the progressive formation of a new phase of interlayer spacing 14.7 Â (phase I), with total consumption of the host matrix after 48h reaction time for a host : guest mole ratio of 1/4 (Figure 2 a, b). This is accompanied by partial amorphisation indicative of a rearrangement of the macrostructure. Reflux conditions, or the use of higher host : aniline ratios, leads to the appearance of X-ray diffractions lines characteristic of anilinium sulphate, resulting from progressive hydrolysis of the phase I intercalate. If the reaction is continued even further, a second phase is observed,which has a basal spacing of 13.7 Â (phase II) (Figure 2 c). The X-ray diffractograms of the intercalates indicate that a laminar structure is retained in both cases. The increase i n basal spacings amounts to 5.5 and 4.5 Â respectively, suggesting that the orientation of intercalated aniline molecules in the interlayer space is such that the C axis is almost perpendicular to the inorganic layers. The chemical compositions of the two aniline intercalates are different. Phase I contains the same Fe : S 0 stoechiometry as the starting host compound (1:2), which encloses ca. 2 moles of aniline per mole of iron. O n the other hand, phase Π contains Fe : S 0 : C ^ N F ^ in the ratio 1 : 1 : 1 . When heated in air from room temperature, the phase I intercalate eliminates a small and variable amount of water up to 90°C, without any appreciable change in the i n terlayer distance, indicating that the amines form organic pillars, and that any water is either superficial, or occupies interpillar sites. 4

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The number and positions of the maxima i n the electronic spectra are characteristic of Fe(III) i n phase I (1680,830 and 340 nm) and of Fe(II) i n phase II (1450, 1020 nm), and indicate that the iron atoms occupy octahedral sites i n both phases. Similar conclusions may be drawn from the Môssbauer spectra, which show an evolution from resonance from Fe(III) ions (phase I) to a single final Fe(II) site i n phase II.

(a)

—— ι I ι ι I -— ι— (- ι h1--—— IΛ— t 1—ι

The intercalation of aniline into the solid acid matrices of α and γ zirconium hydrogen phosphates occurs at room temperature to give, i n the case of aΖ Κ Η Ρ Ο ^ , Η ^ Ο , a new product of inter layer distance 18.4 Â, of which brief mention has been made previously (27), after 7 days contact with the pure liquid. Reducing the reaction time, or the use of dilute aniline solutions leads to an intermediate compound of basal spacing 13.7 Â. Elemental and thermal analyses of the intercalate of 18.4 Â interlayer separation are compatible w i t h its formulation as Z r ( H P O ) . 2 C H N H . 0 . 4 H O , and the aniline molecules probably form a bilayer i n the interlaminar zone, anchoring through N - H — Ο hydrogen bonding to the mineral layers, while the packing of organic rings is stabilised through V a n der Waals inter actions. 4

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223


5

2

λ

(b)

(c)

^ ., j^.,

AvAÂ^L^,..

2 S 8 11 14 17 20 Figure 2. Reaction of aniline with H F e t S O ^ ^ R p : X-ray diffractograms recorded after reaction times of : (a) time = 0, HFe(S0 ) AHp (b) 24h, 25°C: host + phase I intercalate (c) 8 daysreflux: basal spacing 13.7 Â (phase Π)

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Reaction of aniline with y - Z r ( H P 0 ) . 2 H 0 leads to intercalates of composition Z r ( H P O ) . C H N H . 0 . 7 H O however, variation of the experimental condition* gives rise to two different X R D patterns, giving interlayer distances of 17.05 À (using pure aniline), and 18.15 Â (dilute acetone solutions) probably corresponding to two different phases. The average increase i n gallery height, 5.4 Â, is exactly half that observed for a-Zr(HPO ) .H 0 (18.4 - 7.6 = 10.8 Â) and geometrical considerations are thus i n agreement with the insertion of only one mole of aniline per mole of zirconium ions in y - Z r ( H P 0 ) . 2 H 0 . A n inter-digitating 4

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monolayer arrangement of the aniline molecules can be envisaged whereby hy drogen bonding alternately to the layer above and the layer below is favoured. Vibrational spectroscopy The question thus arises as to the nature of occluded aniline in the ferric hydrogen sulphate and zirconium hydrogen phosphate hosts: neutral, protonated, polymerised, or a mixture of these forms. This problem can be usefully addressed using vibrational spectrosopic me thods: infrared, Raman, and incoherent inelastic neutron scattering. The last is sensitive only to vibrational modes involving large amplitude displacement of hydrogen, and is essentially "transparent" to other vibrations of a molecule. The particular advantage i n the case of intercalation chemistry is the absence of any signal i n the INS spectrum resulting from an aprotic host lattice, which confers almost "guest-specific" characteristics to the method. Furthermore, any vibra tional regions masked in the infrared or Raman spectrum (strong S 0 and P 0 stretching modes around 1000 -1100 cnr in the present case) become accessible. The infrared spectra of H F e ( S 0 ) . 2 C H N H (phase I), aZriHPO^C^N^.OAHp and T - Z K H P O ^ . C . H g N H ^ . T H p indicate that proton transfer to intercalated aniline has occured. Characteristic absorption bands are observed in infrared i n the N - H stretching region: ~ 2930 cm" [v ,v (NH )] and a combination band at ~ 2650 c m , and i n the region of deformation vibrations: δ ^ Ν Ρ ^ ) at -1550 cnr and 5 (NH3 ) at -1500 c m . The C - N stretching vibration is observed at -1200 - 1220 cnr . The exact positions vary slightly according to the nature of the host matrix. Other vibrations of the phenyl group can be identified, and differ little from those of of neutral aniline, for example. Maxima in the INS spectra should arise from librational modes of the N H ^ group, in addition to phenyl ring vibrations. The torsion, τ ί Ν Η ^ ) , dominates the INS spectrum of a-Zr(HPO ) .2C H NH .0.4H O; it is observed at 506 c m , close to its position i n the spectra of y - Z r ( H P O ) . C H N H . 0 . 7 H O and H F e ( S 0 ) . 2 C H N H : 483 and 502 cnr respectively. The frequency range cha racteristic of the torsional mode is superimposed on those of certain ring vibrations, i n particular mode 16a at 405 cm' ,16b at 502 c m , 6a at 527 cnr (where the numbers are those of Wilson's notation (28) ), nevertheless τ ( Ν Η ) may be identified by its high intensity. The presence of neutral aniline is also detected to a variable extent i n the different phases. This is expected for H F e ( S 0 ) . 2 C H N H , in view of charge balancing considerations on the basis of elemental analyses, and indicates that proton transfer is incomplete in α and γ zirconium hydrogen phosphate interca lates. Usually intense bands due to the N H group are observed i n aZ K H P O p ^ C ^ N ^ . O ^ H p at 3299 and 3357 cnr ( v ( N H ) and v ( N H ) res pectively), and the scissoring vibration δ(ΝΗ ) is seen at 1610 c m . In all cases, the infrared spectra show two bands for the C - N stretching vibration at 1200 1220 and 1290 cnr , corresponding to protonated and "free"aniline respectively. The strong and sharp absorptions at 3329 and 3264 c m i n the infrared spectrum of F e S O ^ C ^ N F L , (phase Π) attest to the presence of neutral aniline only. However, these wavenumbers are lower than those in free aniline (vapour 4

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Intercalation and Polymerization of Aniline 1

Y

—^^^^

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or solution), where typical values are 3481 and 3360 cnr , which suggests the coordination of aniline to metal centres. The different infrared spectral charac teristics of aniline i n γ - Ζ Κ Η Ρ Ο ^ . ^ Η , , Ν ί ^ .0.7Hp and F e S O ^ C ^ N H ^ are shown i n Figure 3.

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Figure 3. Infrared spectrum of (a) anilinium ion in y-Zr(HPO ) .C H NFI .0.7H O and (b) coordinated aniline in F e i S O p . C . H ^ H , 4

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In none of the above intercalation compounds would it appear that electron transfer from the organic guest has occured. This is not unexpected for the zirconium hydrogen phosphates, although the possibility has been envisaged i n the case of the insertion of cobaltocene in o t - Z K H P O ^ . P ^ O (29). However, in the potentially electron-active matrix of ferric hydrogen sulphate, neither phase I nor phase II has a colouration suggesting that polymerisation of aniline mono mers has occured: phase I is brick red and phase II beige i n colour. Reduction to Fe(II) has nevertheless taken place in the latter phase.


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Understanding the retention of a layer structure for F e S O ^ F y S i F ^ is not straightforward, but a structural model can be proposed i n which sulphate groups and an aniline molecule participate i n the coordination sphere, analagous to that of divalent metals in monohydrated M(II) phosphonates (30). Intercalation i n copper-exchanged α and γ zirconium hydrogen phosphates Despite the biphasic nature of a - Z r C u H (PO ) A¥Lp, its reaction with aniline leads to a single phase product of slightly reduced crystallinity and dark green colour, having an interlayer distance of 18.5 Â. Similarly, the reaction of γZ r C u ^ ( Ρ 0 ) . 4 Η 2 θ with aniline leads to a colour change from white to dark blue, whereas intercalation into the fully protonated matrix gives a white product. The dark blue-black material shows some amorphous character, and has an interlayer distance of 19.1 Â, slightly variable with the duration of the reaction with aniline. Figure 4 compares the X-ray diffractograms of the intercalates obtained with and without prior exchange of copper into the y-Zr(HP0 ) .2 H 0 host matrix. Thermal and elemental analyses show that less aniline is inserted into pre-copper exchanged matrices than into their fully protonated analogues, and less copper is retained than i n the starting material, such that the product after intercalation into 7-ZrH C u ( P 0 ) 4 ¥ i p may be formulated as Zr(PO ) Cu ( C H N H ) This stoechiometry does not exclude the participation of an additional oxidant besides Cu(II) during the reaction, as reported for the FeOClpolyaniline system, where only ~ 25% of the electrons removed were transferred to Fe(III) (V. 06


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Spectroscopic analyses As described above, the nature of the guest can be readily identified from its infrared spectrum. Figure 5 shows the (c) infrared spectra of aniline intercalated γ-zircon i u m copper phosphate over the region 1200 1900 cm . In this spectrum, the absorption maxima at 1309,1496 and 1576 cnr are charac teristic of the emeraldine salt form of polyani line, (typical frequencies for bulk polyaniline 2 6 10 14 18 22 formed by oxidation using H / ( N H ) S O are Figure 4. X-ray diffractograms of 1302,1496, and 1578 cnr (1221,32)). In α-zirco (a^ZrH^CX/PO^Hp nium copper hydrogen phosphate intercalate, (b) Z r ( P O ) C u ( C H N H ) the band at 1309 cnr is weak, but more intense (c) Z K P O ^ H . q H ^ H j 0 . 7 Υ ψ -1

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absorption is observed at 1396 c m . According to vibrational studies on polyanilines and model oligomeric species, the wavenumber of this mode is sensitive to electron délocalisation around the C - N - C part. It is lower for a more delocalised structure, converging to a value of 1310 c m . For short oligomers, where electron deloWavenumber (cm 1 • . . 1 calisation is limited, characterisi2oo 1300 1400 1500 1600 1700 1800 1900 tic positions are 1401 -1383 (32). The observation of two bands with different relative intensities indi Figure 5. FTIR spectrum of cates the presence of various parts -Zr(PO ) Cu .(C H NH) of different electron delocalised structures. It may be concluded that polymerised aniline is formed in both host lattices, and that the nature of the polymer is different, particularly in respect of its length and the extent of oxidation. Similar conclusions may be drawn from the electronic spectra, reproduced in Figure 6. Diffuse reflectance measurements are similar to those on bulk polyaniline, with absorptions indicating the presence of phenyl groups (~ 300-320 nm), radical cations (~ 390 - 410 nm) and quinone diimine units (~ 610 nm) (33,34). The relative intensity of the maxima at400 and 600 - 650 nm, and the tail of absorption at lower energies are consistent with a higher degree of oxidation of polyaniline in the host derived from the γ-zirconium copper hydrogen phosphate than the ocanalogue, and less relative protonation i n the latter. Pretreatment conditions affect the extent of protonation of the hosts which may influence the extent of po lymerisation and oxidation. Pressed discs of both samples show no measurable conductivity, for reasons probably related to the inhibition of chain to chain charge transport, because of the short chain length, and the presence of an insulating inorganic matrix. 1


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Figure 6. Electronic absorption spectra of zirconium copper hydro gen phosphate/aniline samples (a) from α-modification (b) from γmodification

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A s described above, optical vibrational spectra undergo considerable modification i n the mid-frequency range on polymerisation of aniline. Between 740 -1600 cm' the modes most affected have been summarised as: 8a, 19b, 13,9a and 11, of Wilson's notation (35). However other, low frequency, vibrations are also modified when aniline is polymerised; these correspond to modes which are known to be affected by the nature of the substituent on the phenyl ring (36)and which are also modified, not unexpectedly, by oligomerisation. Some are skeletal vibrations modified by coupling with C - N modes: 16b, (out-of plane skeletal vibration), 1 and 6a (radial skeletal vibrations), i n addition to the C - N inplane (15) and out-of-plane (10b) deformations and C - N stretching mode (13) (36), which might be expected to show enhancement or reduction in intensity, or displacement. Spectral evolution of these modes can be detected using INS spectroscopy. The INS spectra of various forms of intercalated aniline within the various hosts described here are compared i n Figure 7.


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Figure 7. Incoherent inelastic neutron scattering spectra of (a) Fe(S0 ).C H NH (b) y-ZrH(PO ) .C H NH .0.7H O (c) Y-Zr(PO ) .Cu .(C H NH) containing coordinated, protonated, and polymerised aniline respectively. 4

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Modes 10b and 16b respectively, are observed to radically decrease i n intensity from maxima at 262 cnr and 485 cnr of medium intensity i n the INS spectrum of the aniline intercalate in y - Z r ( H P 0 ) . 2 H 0 , where anilinium ion is the sole organic species, to virtual absence i n that containing polyaniline. In contrast, mode 15 increases i n intensity, whereas the radial skeletal vibrations, expected to be coupled with the C - N stretch, undergo little modification. It is interesting to note that the same modes experience very similar intensity transformations by coordination of aniline to the metal centre, as i n FeS0 .1

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Conclusion The above results demonstrate the existence of three well-differentiated groups of intercalates. In the poorly oxidising α and γ zirconium hydrogen phosphates, intercalation of aniline readily proceeds with proton transfer from the host matrix. A s in zeolites Y and mordenite (13), pre-inserted Cu(II) ions i n the host structure act as oxidants in the reaction with organic monomers, such that a certain degree of charge transfer from aniline and polymerisation seem to have taken place, as evidenced by the spectroscopic results. Considerable modification of the X-ray diffractograms suggests polymer formation within the interlayer region. It is surprising that under conditions seemingly appropriate which are united i n the layered acidic redox ion exchanger H¥e(SO ) A¥Lf), intercalation with proton transfer is favoured relative to electron transfer, and even prolonged reflux leads instead to modification of the inorganic layers by a grafting reaction involving coordination of aniline. The question of the inac tivity of Fe(III) towards aniline in H F e i S O p ^ F ^ O , i n view of the reported polyaniline formation in FeOCl (1), needs to be further investigated. A 2

Acknowledgments We thank the Science and Engineering Research Council (U.K.) for access to the spallation neutron source, ISIS. This research is financially supported in France by the Centre National de la Recherche Scientifique.

Literature Cited 1. Kanatzidis, M. G.; Wu, C-G.; Marcy, H. O.; DeGroot, D. C.; Kannewurf, C. R.; Kostikas, Α.; Papaefthymion, V. Adv. Mater. 1990 2 364 2. Kanatzidis, M. G.; Wu, C-G. J. Am. Chem. Soc. 1989 111 4139 3. Kanatzidis, M. G.; Hubbard, M.; Tonge, L. M.; Marks, T. J.; Marcy, H. O.; Kannewurf, C. R. Synth. Metals 1989 28 C89 4. Kanatzidis, M. G.; Marcy, H. O.; McCarthy, W. J.; Kannewurf, C. R.; Marks, T. J. Solid State Ionics 1989 32/33 594 5. Bringley, J. F.; Averill, B. A. Chem.Mat.1990 2 180 6. Bringley, J. F.; Fabre, J. M.; Averill, B. A. Mol. Cryst, Liq. Cryst. 1988 170 215


230 7. 8. 9. 10. 11.


12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36.


Kauzlarich, S. M.; Ellena, J.; Stupik, P. D.; Reiff, W. M.; Averill, B. A.J.Am. Chem. Soc. 1987 107 4561 Kauzlarich, S. M.; Stanton, J. L.; Faber Jr.; J., Averill, B. A.J.Am. Chem. Soc. 1986 108 7946 Kauzlarich,S. M.; Teo, Β. K.; Averill, B. A. Inorg. Chem. 1986 25 28 Averill, Β. Α.; Kauzlarich, S. M.; Teo, Β. K.; Faber Jr.,J.Mol. Cryst. Liq. Cryst. 1985 120 259 Averill, Β. Α.; Kauzlarich, S. M.; Antonio, M. R.J. Phys., (Paris) 1983 44 C3 1373 Enzel, P.; Bein, T.J.Phys. Chem. 1989 93 6270 Enzel, P.; Bein, T.J. Chem. Soc. Chem. Commun. 1989 1326 Brandt, P.; Fischer, R. D.; Sanchez-Martinez, E.; Diaz-Calleja, R. Angew. Chem. Int. Ed. Engl. 1989 28 1265 Wu, C.-G.; Marcy, H. O.; DeGroot, D.C.;Schindler, J. L.; Kannewurf, C. R.; Kanatzidis, M. G. Int. Conf. Synth. Metals, Tübingen 1990 Brach,I.;Jones, D. J.; Rozière, J. Solid State Ionics 1989 34 181 Jones, D. J.; Rozière, J. Solid State Ionics 1989 35 115 Mereiter, K. Tschermaks Min. Petr. Mitt. 197421216 Clearfield, Α.; Troup, J. M. Inorg. Chem. 1977 16 3311 Jones, D. J.; Rozière, J.; Penfold, J.; Tomkinson, J.J.Mol. Struct. 1989 297 113 Christensen, A. N.; Krogh Andersen, E.; Krogh Andersen, I. G.; Alberti, G.; Nielsen, M.; Lehmann, M. S. Acta Scandinavia 1990 44 Clayden, N. J.J.Chem. Soc. Dalton Trans. 1987 1877 Alberti, G.; Torraca, E.J.Inorg. Nucl. Chem. 1968 30 77 Clearfield, Α.; Blessing, R. H.; Stynes, J. A.J.Inorg. Nucl. Chem. 1968 30 2249 Clearfield, Α.; Kalnins, J. M.J.Inorg. Nucl. Chem. 1976 38 849 Clearfield, Α.; Kalnins, J. M.J.Inorg. Nucl. Chem. 1978 40 1933 Costantino, U. In Inorganic Ion Exchange Materials; Clearfield, Α., Ed.; CRC Press, Boca Raton, FA, 1982; pp 112-132 Wilson, Ε. B. Phys. Rev. 1934 45 706 Johnson, J. W.J.C. S. Chem. Comm. 1980 263 Cao. G.; Lee, H.; Lynch, V. M.; Mallouk, T. E. Inorg. Chem. 1988 27 2781 Furukawa, J.; Ueda, F.; Hyodo, Y.; Haroda,I.;Nakajima, T.; Kawagoe, T. Macromolecules 1988211297 Ueda, F.; Mukai, K.; Harada,I.;Nakajima, T.; Kawagoe, T. Macromolecules 1990 23 4925 Glarum, S. H.; MacDiarmid, A. G.J.Phys. Chem. 1988 92 4210 McManus, P. M.; Cushman, R. J.; Yang, S. C.J.Phys. Chem. 198791744 Raupach, M.; Janik, L. J.J.Colloid Interface Sci. 1988121449 Whiffen, D. H.J.Chem. Soc. 1956 1350

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