Chapter-4CHARACTERIZATION OF POLYANILINE COMPOSITES4.1 Introduction It is said that a typical phenylene based polymer having a chemically flexible – NH – group in a polymer chain flanked either side by a phynelene ring is called PANI. Due to the presence of the -NH- group the protonation and deprotonation, and various other physico-chemical properties of PANI and its composites with V2O5, ZrO2 and PbS can be said to be there. Under acidic condition polyaniline and its composites with V2O5, ZrO2 and PbS are the oxidative polymeric products of aniline. Samples of PANI salt and its composites are characterized by Infrared and UV-visible spectroscopy, and by X-ray powder diffraction methods.
All types of electromagnetic radiations travel with the same speed, the velocity of light, but they differ in wavelength or frequency from each other. The increasing order of energies of the electromagnetic radiation is: Radiowaves < Microwaves < Infrared < Visible < Ultraviolet < X-rays < ?- rays n – ?* > ? – ?* > n- ?*, shown in figure 4.20.218-220 ENERGY ?* Anti-bonding ?* Anti-bonding n Lone-pair, Non-bonding ? Bonding ? BondingFig. 4.20 ? – ?* is a transition of a electron from a bonding sigma orbital to the higher energy antibonding sigma orbital. This type of transitions not belongs to UV-visible spectra, as it requires high energy in the range of far uv (190-100 nm). n – ?* transition involves the transition of unshared pair electrons to the higher energy antibonding sigma orbital.
These transitions require comparatively less energy than ? – ?* transitions. These are sensitive to hydrogen bonding, and occur due to the presence of non-bonding electrons on the hetero atoms and thus require greater energy. ? – ?* (K-band) transition is available in compounds with saturated centres, e.g.
, simple alkenes, aromatics, carbonyl compounds, etc. It requires lesser energy than n – ?* transition. In , ? – ?* transition, ? – bonding electron transfer to anti-bonding ?* orbital. In, n- ?* transition (R-band), an electron of unshared electron pair on a hetero atom is excited to anti-bonding ?* orbital. It requires least amount of energy than all other transitions and therefore, this transition gives rise to an absorption band at longer wavelengths.
This transition is forbidden by symmetry consideration, thus the intensity of the band due to this transition is low, although the wavelength is long. The band due to ? – ?* transition in a compound with conjugated ? system is usually intense and is frequently referred to as the K-band (German, Konjugierte) 347. The n- ?* transition is referred as R-band (German, Radikal). In conjugated system the energy separation between the ground and excited states is reduced and the system then absorbs radiation of longer wavelengths and with a increased intensity (i.e.
K-band is intense and at longer wavelength). Moreover, due to lessening of the energy gap, the n- ?* transition due to presence of the hetero atom, the R-band also undergoes a red shift with little change in intensity. The B-bands i.e.
, benzonoid bands are characteristics of aromatic and heteroaromatic compoundsd. In benzene the B-band is at 256 nm which displays a fine structure with multiple peaks. Significantly the K-band (at 184 nm and 203.5 nm) and B-band (256 nm) of benzenes have low intensities.
The UV-visible spectrum of a compound is a plot of absorbance of the compound as a function of wavelength of radiation. All molecules in general and organic molecules in particular can absorb radiation in the UV-visible region because they contain electrons, which can be excited to higher energy levels. These electrons in molecules can be classified as sigma (?), pi (?), and nonbonding (n) electrons. The ? electrons are those, which are associated with single covalent bonds. Since they are tightly bound, radiation of high energy is required for their excitation.
The electrons associated with multiple bonds are known as ? electrons. The ? electrons are rather easily excited to higher level. It is well known that the absorption of electromagnetic radiation in the U-V-region of the spectrum provides important information about the energy bands assigning the electronic transitions. Optical absorption in conducting polymer and its composites, which are mostly amorphous or polycrystalline, may be due to the transition of charge carriers through a forbidden energy band, called optical band gap.
On doping, it introduces additional energy band on the forbidden region, but it does not interfere with the principal energy band of the original polymer 4.3.2 Experimental Technique A variety of instruments are available commercially for absorbance measurements in the UV- visible region, the photo calorimeter and the spectrophotometer meter.
Photo calorimeter, however can be used to study the absorption of visible light only while spectrophotometers can be generally used, for studying both the UV and visible regions. The UV-visible spectra of the homopolymer, three inorganic additives (V2O5, ZrO2, and PbS) and their 14 composites with PANI under investigation were recorded in the dimethyl formamide (DMF) solvent at room temperature by using SL.171 Elico mini spectrophotometer, at department of pharmacy, R. T. M. Nagpur University, Nagpur. 4.
3.3 Result and Discussion U-V visible spectroscopy is a powerful tool for the study of protonation effect (and hence the formation of different oxidation states of the polymer) as well as for the elucidation of the interaction between the solvent, the dopant and the polymer chains. Figures 4.21 – 4.38 shows UV-Visible spectra for pure PANI and its composites. Each of spectra reveals the presence of two absorption bands, one in the visible region & the other in the UV region. The band in the UV region corresponds to the ?-?* transition and the band in the visible region corresponding to the inter ring charge transfer associated with excitation from benzonoid to quinoid moieties223,224. The ?max , their absorbance and band energies in UV-visible spectra for PANI, inorganic species V2O5, ZrO2, and PbS and their composites are shown in table 4.
5. For pure PANI salt (converted in to base in DMF84), the phenyl capped octa aniline shows two considerable absorption peaks in DMF179 viz., at 324 nm and 613 nm assigning the ? – ?* transition band (interband transition, transition in the benzenoid rings) and n- ?* exciton band (exciton transition from HOMO of benzenoid to LUMO of quinoid ring, or exciton absorption in quinoid rings)140,187,225 with absorbance 0.1464 and 0.0956 respectively, with their respective band gaps 3.826 and 2.
022 eV, shows good agreement for conjugated polymer chain in PANI synthesized in aqueous medium. This investigated data is well agreed with the literature reported data. The excitation (n- ?*) leads to formation of molecular exciton, i.e.
, positive charge on the benzenoid units and negative charge centred on quinoid unit138. This interchain charge transfer may lead to the formation of positive and negative polarons. Both ? – ?* transition band and n – ?* exciton band are abundant in UV-visible spectra of most of the composites. Table 4.5 Samples ?max (nm) Absorbance Band energy (eV) ? – ?*TransitionBand n- ?*ExcitonBand ? – ?*TransitionBand n- ?*ExcitonBand ? – ?*TransitionBand n- ?*ExcitonBandPANI 324 613 0.1464 0.0956 3.826 2.
0226V2O5 331 760 0.0336 0.0482 3.745 1.631ZrO2 265 —– 0.
2203 —– 4.678 —–PbS 333.5 > 800 0.0822 0.13 3.717 > 1.549Composites a 316 590 0.0996 0.
0457 3.923 2.101b 367 567 0.
3201 0.1201 3.378 2.186c 372 558 0.
2336 0.08 3.333 2.222d 379 543 0.
219 0.1133 3.271 2.283e 381.5 —– 0.6267 —– 3.25 —–f 327 615 0.
045 0.035 3.791 2.016g 355.5 —– 0.0115 —– 3.487 —–h —– —– —– —– —– —–i 326 621 0.
035 0.019 3.803 1.
996j 350.5 628 0.0084 0.009 3.537 1.974k 327 607 0.
3152 0.185 3.791 2.042l 320 605 0.2154 0.096 3.
874 2.049m 322 595 0.210 0.075 3.850 2.083n 315.5 604 0.
0831 0.055 3.929 2.
052 In case of samples a – e of PANI/V2O5 (organic-inorganic) composites, bathochromic shift or red shift (band energy decreases) of ? – ?* band and hypsochromic shift or blue shift (band energy increases) of n – ?* band is observed with increment in weight percent of V2O5 xerogel in composites. Also the absorbance at both bands increases (hyperchromic shift), become considerably high for up to 16% weight of V2O5, indicates the increased charge transfer from benzenoid to quinoid moieties, and decreases (hypochromic shift) for further increment in weight % of V2O5 in PANI/V2O5 organo-inorganic hybrids. High electrical conductivity of this composite has found for 16% weight of V2O5. For the higher weight % (40%) of V2O5 in sample, the peak at n – ?* obscured, corresponds to lowest electrical conductivity, it may because of over oxidation of PANI.
These spectral changes indicate the coordination of V2O5 with nitrogen atoms226, and the blue shift of the band in visible region indicates the formation of composites between PANI and V2O5. Not very regular shifts are observed in samples f – j of PANI/ ZrO2 (organic-inorganic), but with much weak absorbance, for all. Bathocromic shift with increasing weight % of ZrO2 at ? – ?* band is observed for samples f to g, and for i to j (8% to 16%, 32% to 40% wt % of ZrO2). For the samples g and h peaks at n – ?* band obscured, and both peaks at ? – ?* and n – ?* are absent for the sample h. This may because of vanished bonds associates ? – ?* and n – ?* bands in PANI by some undesired structural changes involved by interaction or coupling of ZrO2 with PANI structure. As compared to pure PANI salt, its composites with ZrO2 show strong hypochromic shift from PANI to composites. All the samples from k to n of PANI/PbS composites shows very regular but slight hypsochromic shift (blue shift) and much large hypochromic shift at about both, transition and exciton bands, with increasing weight % PbS in composites. It indicates the formation of composites between PANI and PbS.
But from PANI to PANI/8%PbS show very strong absorbance, more than double, for both bands, indicates the high charge transfer within benzene rings and from benzenoid to quinoid rings and it may desire to think about high conductivity for 8% weight of PbS in composites. Most of the composites of PANI with inorganic additives, in their UV-visible spectra shows bathochromic (for a to e) shift, hypsochromic shift (k to n), hypochromic shift (for all, except a to b, and d to e), and hyperchromic shift (for a to b, and for d to e), with increasing weight % of inorganic species in composite samples. It quite sufficient to conclude that, the additives chemically interact/coupled with structure of PAN salt. Spectra of PANI/PbS series show hypsochromic shift in both bands, indicates an increase in band gap brought about through an increase in the torsion angle between the C-N-C plane and the plane of benzene ring thus decreasing the conjugation. Inversely, spectra of a – e series of PANI/V2O5 and f to j series of PANI/ ZrO2 shows bathochromic shift for ? – ?*, indicates the decrease in band gap brought about through decrease in the torsion angle between the C-N-C plane and the plane of benzene ring, thus increasing the conjugation with increasing wt % of V2O5 in samples37,193,227.
For all composites, their intrachain absorption lies in the range of band energy 3.929 – 3.25 eV, and interchain absorption in the range 2.283 to 1.
974 ev 47. When UV-Visible spectra of composites compared with the spectra of PANI, the introduction of the impurities in the aromatic ring of aniline produces a blue shift and also red shift for some samples. Ginder227 reported through the theoretical consideration that an increase in the dihedral angle or the ring torsion angle between adjacent aromatic ring of the polymer cause a blue shift. A twist in the torsion angle is expected to increase the average band gap in the ensemble of the polymer composites. Thus the result indicates that a polaron band is created in the band gap of polyaniline oxidation, and increase in the torsion angle (the angle by which the ring is twisted out of the plane of C-N band) will affect the bandwidth as well as average band energies37.In general the UV- Visible spectra of the synthesized polymer (PANI), its composites with V2O5, ZrO2, and PbS are similar in nature and there is shift in ?max values for most of composite samples due to their structural changes arises by added impurities. Fig.
4.21 UV-VISIBLE SPECTRA OF PANI Fig. 4.22 UV-VISIBLE SPECTRA OF V2O5 Fig. 4.23 UV-VISIBLE SPECTRA OF PANI + 8% V2O5 (a) Fig. 4.
24 UV-VISIBLE SPECTRA OF PANI + 16% V2O5 (b)4.4 X-Ray Diffraction 4.4.1 IntroductionCrystals are built up of small units having the same interfacial angles as the crystal. The distances between the atoms in crystals have been found to be roughly equal to 10-8 cm. So optical and electron microscopes can not be used in this field. X-rays diffracts by means of crystals, because the crystals acts as a three dimensional natural grating for X-rays, and X-rays acts as part of the em radiation with very small wavelength of the order of 10-8 cm. The X-ray diffraction (XRD) pattern depends upon the internal structure of crystal; hence this method is very useful for the structural study of the crystals.
The application of XRD method to chemical analysis is primarily in the identification of compounds present from their diffraction pattern, and determination of relative concentrations by the intensities of pattern lines. This method provides information about the dimensions of unit cell of the crystal lattice and the atomic arrangement within the cell. XRD provides qualitative identification of crystalline compounds. This application based on the fact that the XRD pattern is unique for each crystalline substance and so chemical identity can be assumed, if an exact match can be found between the pattern of an unknown and an authentic sample. Qualitative identification of structures can be made by comparison of the interplaner spacing values of the specimen pattern with an index of standard pattern. Diffraction data are also employed for the quantitative measurement of a crystalline compound in a mixture.
The method may provide data that are difficult to obtain by other means. Quantitative analysis is carried out any comparing the intensity of a chosen diffraction line in a compound to the intensity of the same line in a standard mixture. Using this method, the unit cell parameters can be measured with high accuracy. Thus constitution of compounds in which there has been partial isomorphous replacement of one or more atoms in the unit cell can be accurately determined. Basic Physical Properties of the polymers are governed by supra molecular structure. X-ray have become an important tools for the study of physical properties the matter in the solid state. They are also used to reveal the other characteristics such as crystal size, orientation and strain. Since the polymers cannot be completely crystalline, they do not have perfect crystal Lattice.
According to original micellar37 theory of polymer crystallization, the polymeric material consists of numerous small crystallites, which are randomly distributed and linked by the intervening amorphous regions. X-ray diffraction methods generally used for investigation of the internal structures, these are Laue photographic method, Bragg’s X-ray spectrometer method, rotating crystal method, and Powder crystal method. In the powder method, the crystal sample need not be taken in large quantity but ~ 1 mg of the material is sufficient for the study. This method was devised by Debye and Scherrer (Germany) 219.
The structure of polycrystalline material is investigated by means of the powder photograph method. In this method a beam of monochromatic X-radiations is incident on a polycrystalline sample in powder form. There will always be proportion of small crystal in the sample that is under the condition for which the Bragg’s formula is satisfied; since there may be tiny crystals (crystallites) are oriented randomly in the sample. Upon reflections from each set of parallel planes inside such crystallites for which 2dh,kl sin ? = n? is satisfied. The dependence of intensity of diffracted X-rays on the angle ? can also be obtained from X-ray diffraction pattern from the Debye-Scherrer photograph; and the d value can be calculated from Bragg’s formula 2d sin ? = n ? – – – – – -1,Where, d is inter planer spacing, n is the order of reflection, ? is the wavelength of monochromatic X-rays, n is the order of reflection and ? is the glancing angle. The identification of a structure from its powder diffraction pattern is based upon the position of lines (? or 2?) and their relative intensities. The diffraction angle, 2? is determined by the spacing between a particular set of planes. This distance d is readily calculated by making use of Bragg’s equation, provided wavelength of the source and measured angle are known.
Line intensities depend upon the number and the kind of atomic reflection centres that exists in each set of planes. In general all polymers can be divided into two groups. The criteria for this classification are furnished by X-ray diffraction. (a) Crystalline polymer: The type of polymer gives sharply defined set of reflections on X-ray photograph or maxima on diffraction pattern.(b) Amorphous polymer: This type of polymer gives haloes instead of distinct reflections.The powder method can be used to determine the degree of crystallinity of the polymer. The non crystalline portion simply scatters the X-ray beam to give a continuous background, while the crystalline portion causes diffraction lines that are not continuous.
The amorphous material in the polymer will scatter at all wavelengths and give a scattered pattern; however, the crystalline material will include crystal structures and will produce definite diffraction lines. The ratio of the diffraction peaks to scattered radiation is proportional to the crystalline to noncrystalline material in the polymer. The ultimate quantitative analysis must be confirmed by using standard polymers with known crystallinities and basing the calculation on the known ratio of crystalline diffraction to amorphous scattering. In orthorhombic case228, starting with a list of sin 2? values in ascending order, the first three reflections are assigned indices 100, 010, 001 respectively. These three values yield calculated values of lattice constant.
These lattice constants are used to calculate the indices for further reflections. The chosen indices for those, whose calculated sin 2? values differ from the observed sin 2? values, less than the chosen error. The accepted set of indices gives the best sin 2? agreement. By interaction of this process, all reflections are indexed. For determination of lattice parameters following relations for orthorhombic case is used. Sin2 ? h,k,l = ?2 h2 + ?2 k2 + ?2 l2 4a2 4b2 4c2 – – – — 2 and Dhkl = 1 h2 + k2 + l2 a2 b2 c2 – – – — – 3 Many polymers show polycrystalline behavior, i.e.
part of material forms an ordered crystallite by folding of the molecule. One and the same molecule may well be folded into two different crystallites and thus form a tie between the two. The tie part is prevented from crystallizing. The result is that the crystallinity will never reach 100%. Powder XRD can be used to determine the crystallinity by comparing the integrated intensity of the background pattern to that of the sharp peaks. If the crystallites of the powder are very small the peaks of the pattern will broaden. From broadening it is possible to determine an average crystallite size, in Å, by Debye-Scherrer formula:Dhkl = K ? ? cos ? = 0.9 ? ? cos ? – – – – – – – – – – – 4Where, ? is wavelength of X-rays, ? is Bragg’s angle i.
e. position of the maximum diffraction, K is a constant generally taken as unity e.g. 0.9 (k = 0.8 – 1.39), and ? is full width at half maximum of the peak (FWHM) i.
e. ? (in radian unit) = half-width (degree) x ? / 180. 4.4.2 Experimental Technique Now a days, commercial X-ray diffractometer use powder photograph technique for x-ray diffraction studies.
Crystal structure, unit cell dimension and crystalline nature of the polymers can be studied by x-ray technique. Powder diffraction is mainly used for identification of compounds by their diffraction patterns. A diffractometer utilized a monochromatic beam of radiation to yield information about d-spacing and impurities from crystalline powder. The structures of homopolymer and composites, and qualitative and quantitative phases are determined by the collected data from the XRD patterns of PANI and its composites.
XRD patterns of PANI, and all its composites (Fig. 4.39 to 4.56) taken on X-ray diffractometrer PW 1710 Philips, Holland using radiation of wavelength (Cu- K?) 1.54056 and 1.54439 Å. 4.4.
3 Observations and Calculations The XRD crystallographic data (observed and calculated) of PANI, inorganic additives (V2O5, ZrO2, and PbS) and their composites is displayed on tables from 4.6 to 4.18 including calculated d-spacing and (h k l), and their calculated interchain lateral distances a, b, and c, cross section area for two chain i.e. A = a x b, and crystallite sizes Dhkl is given in table 4.19.
Table 4.6: XRD data of PANI2? dobs dcal h k l I/I019.23325.
30644.66672.622 4.46513.51942.02881.3008 4.46513.
51922.02851.3008 2 0 50 0 71 1 142 2 17 42.23100.
0040.1825.02 Table 4.8: XRD data of ZrO2a= 5.1477, b= 5.2030, c= 5.3156 Å2? dobs I/I024.18628.
97Table 4.9: XRD data of PbSa= 5. 9362 Å2? dobs I/I025.99930.11143.
523.811.52Table 4.7: XRD data of V2O5a= 11.51, b= 3.
559, c=4.371Å2? dobs I/I015.39620.29521.71226.
3912.978.39 Table 4.10: Crystallographic data of PANI + 16% V2O5 (b)2? dobs dcal h k l I/I019.
71001.61821.49541.36761.3265 8 8 35 17 5 0 0 7 17 4 0 0 11 12 42 0 0 7 6 0 29 0 11 16 12 14 43 9 0 22 9 0 29 10 0 21 0 23 14 9 0 35 17 13 0 20 0 17 0 28 16 0 26 17 16 16 0 20 16 0 0 21 26 13 34 0 0 22 31 0 32 28 22 0 35 9.
07 78.95 56.97 33.02 77.01100.00 91.29 86.68 81.
28 29.93 36.85 7.
25 13.29 11.91 22.17 30.08 74.
02 68.84 13.17 33.60 10.
63 7.56 9.63 7.23 10.91Table 4.11: Crystallographic data of PANI + 24% V2O5 (c)2? dobs dcal h k l I/I012.11420.
98653.58456.67962.09268.65670.929 7.30604.26923.81393.62813.42543.33603.22053.01062.97132.76712.70142.61952.40832.27912.16772.10222.06962.02961.97411.79111.71031.62401.49481.36701.3276 7.30604.26923.81393.62813.42543.33603.22043.01042.97132.76672.70162.61952.40832.27902.16772.10252.06972.02951.97411.79111.71031.62411.49471.36701.3276 9 3 0 0 4 0 0 14 9 4 0 024 10 21 0 0 7 0 12 13 9 0 21 7 19 0 8 0 37 0 9 29 8 0 2929 21 2230 0 1317 13 018 0 1828 11 011 24 018 0 28 0 22 2315 23 0 0 35 2023 0 27 0 29 3022 0 35 27.9698.1660.3739.2597.1791.0983.15100.0097.7940.3839.2214.8017.8018.7723.0056.9877.7950.2717.0139.7213.8814.7408.1406.9416.10Table 4.12: Crystallographic data of PANI + 32% V2O5 (d)2? dobs dcal h k l I/I010.18711.64713.59416.93421.53222.17125.19144.69372.680 8.68337.59806.51385.23574.12694.00943.53522.02761.2999 8.68337.59806.51335.23574.12694.00943.53522.02761.2998 0 2 00 0 35 19 83 0 024 5 05 20 024 9 2426 0 1626 25 0 10.4026.2310.3813.2712.7911.95100.0060.035.57Table 4.13: Crystallographic data of PANI + 16% ZrO2 (g)2? dobs dcal h k l I/I020.79925.39028.24931.42734.21840.74644.72150.14453.97155.47959.852 4.27083.50793.15912.84652.62042.21452.02641.81921.69891.65631.5453 4.27113.50793.15912.84602.62102.21452.02641.81931.69891.65581.5453 0 14 170 0 65 0 010 14 00 25 110 8 038 11 00 15 3314 31 017 0 2932 0 20 7.0134.91100.0064.7324.409.8814.7724.789.1111.786.81Table 4.14: Crystallographic data of PANI + 24% ZrO2 (h)2? dobs dcal h k l I/I024.22428.17631.50234.08340.70144.68850.21755.33859.92162.618 3.67413.16712.83992.63062.21682.02781.81671.66011.54371.4835 3.67413.16712.83812.63062.21682.02791.81681.66021.54391.4835 0 0 6 5 0 014 27 21 15 0 14 0 8 038 11 036 0 16 0 29 2127 0 2328 0 24 18.08100.0054.3921.7310.7615.8923.0112.1511.316.08Table 4.15: Crystallographic data of PANI + 8% PbS (k)2? dobs dcal h k l I/I020.81023.28524.54525.96526.68027.69029.69030.09032.33533.16537.30039.550 41.66043.71544.56045.94050.88053.84056.72562.05063.31064.65070.935 4.27563.82653.63283.43733.34623.22693.01402.97482.77322.70572.41472.28242.17152.07412.03671.97871.79761.70561.62551.49821.47141.44411.3308 4.27563.82893.63283.43733.34623.22693.01402.97482.77322.70572.41262.28292.17152.07402.03671.97871.79781.70561.62551.49801.47141.44411.3307 0 4 0 5 20 0 19 6 0 5 37 014 11 29 19 7 0 0 0 7 5 0 020 12 35 0 8 3712 0 1814 14 010 25 0 0 38 1310 0 3926 0 15 0 23 2025 0 1921 0 2320 0 2429 0 2217 30 023 25 0 74.343.828.254.575.565.1100.0040.331.235.211.011.417.159.739.414.422.010.112.49.188.8.131.52 Table 4.16: Crystallographic data of PANI + 16% PbS (m)2? dobs dcal h k l I/I0 7.72519.25520.80523.33024.60025.14025.59026.74527.69529.68532.30733.17534.24037.31039.54041.71543.77544.65545.97548.38550.89553.84556.71062.10064.65566.60568.59578.230 11.46334.61724.27663.81923.62483.54823.48683.33883.22643.01452.77112.70492.62322.41412.28292.16882.07142.03261.97731.88431.79711.70541.62591.49711.44401.40641.37041.2240 11.46334.61724.27663.81883.62483.54823.48643.33883.22643.01232.77132.70492.62262.41412.28292.16882.07142.03591.97611.88671.79711.70541.62591.49711.44351.40641.37041.2223 7 2 260 9 80 4 015 6 04 0 07 35 225 0 375 39 012 13 3114 0 117 0 310 9 2730 8 00 0 90 28 139 0 397 0 00 18 200 0 1117 0 210 29 1813 29 014 29 00 37 2127 0 2427 0 2517 0 420 14 0 19.311.179.954.429.115.851.3100.0078.695.839.844.410.212.614.721.367.744.416.38.512.6184.108.40.206.220.127.116.11Table 4.17: Crystallographic data of PANI + 24% PbS (m)2? dobs dcal h k l I/I020.82623.32924.58625.97226.42427.70829.67230.05332.36633.17334.29037.28139.54941.71443.04443.73444.61245.99950.94253.58056.84362.07266.59068.69970.910 4.26543.81303.62093.43073.33583.21953.01082.97352.76602.70062.61522.41192.27872.16522.10142.06982.03111.97301.79261.71041.61981.49531.40441.36631.3279 4.26543.81303.62093.43073.33583.21953.01082.97362.76642.70092.61522.41192.27872.16532.10142.06932.03111.97311.79261.71011.61971.49531.40441.36631.3279 0 4 00 14 94 0 0 0 8 180 0 7 6 0 2913 9 017 0 11 0 10 2225 0 110 18 1413 0 1815 13 00 11 3818 0 187 0 014 16 018 0 2039 12 00 17 3324 0 2314 37 023 22 022 0 33 0 31 30 95.5244.3693.28100.0075.5895.8389.7835.5113.9918.7816.9821.2448.4868.8552.1519.5138.5511.699.4010.845.817.2413.73Table 4.18: Crystallographic data of PANI + 32% PbS (n)2? dobs dcal h k l I/I012.16518.68020.05520.79523.34524.53025.17525.57525.95526.71527.67029.65530.08031.98532.33033.17034.24537.31539.51540.73541.70543.05543.73044.63545.94050.96052.48553.81556.68062.04564.59565.22566.655 7.28764.75804.43484.27873.81683.63503.54333.48883.43863.34253.22923.01752.97582.80282.77362.70532.62282.41382.28432.21872.16932.10442.07342.03351.97871.79501.74641.70631.62671.49831.44521.43281.4055 7.28764.75824.43424.27873.81683.63503.54333.48883.43863.34253.22923.01752.97582.80292.77302.70532.62282.41382.28432.21892.16932.10442.07342.03351.97871.79501.74641.71631.62631.49831.44521.43281.4055 4 14 90 32 510 7 4210 4 07 33 185 26 014 20 1312 35 120 6 360 6 4319 7 00 0 75 0 019 13 3014 10 08 0 2521 16 2529 9 026 10 028 17 3120 12 025 0 1423 12 011 0 31 0 30 150 18 250 19 250 18 280 0 130 25 2617 30 024 0 260 23 32 22.06.332.796.053.037.519.645.447.2100.0075.898.667.811.628.242.617.214.520.27.424.022.784.351.020.221.46.713.515.613.07.86.09.4Table 4.19Samples d-spacingÅ CrystalliteSize Dhkl Å aÅ bÅ cÅ A = (a x b)x 10-16 cm2PANIabcdefghijklmn 3.51943.52283.33493.01043.53523.51453.16313.15913.16713.17033.17643.01403.33883.33583.3425 103.416127.192691.446835.095129.23684.8159227.532231.253260.072585.00511.814684.8031022.058829.71583.15 16.6347- – – – – -14.511214.512815.7071- – – – – — – – – -15.795515.8355- – – – — – – – -14.874014.499214.483614.8790 17.4213- – – – – -17.063617.076817.3666- – – – – — – – – -17.716017.7344- – – – – — – – – – -17.102417.106417.061617.1148 24.9716- – – – -23.344323.352022.7940- – – – – — – – – – -21.047422.0452- – – – — – – – -21.098021.731523.350621.1225 289.79- – – – – -247.61247.83272.77- – – – — – – – – -278.25280.83- – – – – — – – – – -254.38248.02247.11254.654.4.4 Results and discussion: The pure PANI exhibits its four characteristic peaks (may be assigned to the scattering from PANI chains at interplaner spacing154) at 2? angles around 19.2330, 25.3060, 44.660, and 72.62 0 (in table 4.6), out of which first two peaks are diffuse broad, which indicates that the PANI has crystallinity to a certain extent (polycrystalline). The significant crystallization of PANI by chemical oxidative route ensures the formation of PANI salt because it has amorphous nature in its base form229. The d-spacing is calculated from the 2? values which represents the characteristic distance between the ring planes of benzene ring in adjacent chains and it is also said to be the inter chain distance or the close contact distance between two adjacent chains84. XRD pattern of PANI under investigation well agree with reported data193,230. XRD patterns reveal that the structures of the polymers under study are polycrystalline because of some reflections and the diffused background. The crystal structures for PANI and composites are fond to be orthorhombic231. Hence it is considered that the unit cell dimensions a ? b ? c and ? ? ? ? ?. Maximum intensity peak due to reflection from PANI structure is at 2? = 25.3070 for d- value 3.5194 Å shifts to high d-value upto 8% of V2O5 in composite, and with further increment upto 24% weight of V2O5 it shifts to lower d-value. For the samples, from ‘c’ to ‘e’ (24% to 40% wt of V2O5) this peak assigning PANI in composite shifts towards higher value of d-spacing again. In pure V2O5 structure its maximum intensity peak at 2? = 20.2950 correspond to 4.3757 Å value of d-spacing. This peak is absent in composite having 8% wt of V2O5. Same peak arises for increased weight % of V2O5 in composite (sample ‘b’ and ‘c’) with shifting towards high value of d-spacing. For further increment in wt % of V2O5 in composites (samples’d’ and ‘e’) the peaks assigning V2O5 structure vanishes. Peaks assigning the identity of PANI and V2O5 shifts and shows variations in their intensity with increasing wt% of V2O5 in composites ensure the intercalation of PANI in V2O5 structure by two different phases123. High crystallinity is observed for these composites for 16 to 24 wt % of V2O5 in composites. Remaining PANI/ V2O5 composites shows very low crystallinity approaching towards amorphous nature. In XRD patterns of PANI/ZrO2 series from ‘f’ to ‘j’, the maximum intensity peak of PANI shifts towards shorter d-values with decrease in their intensity from pure PANI to composite which consist 8% wt of ZrO2. For further increment in wt% of ZrO2 in composites, from 8% to 32%, maximum intensity reflection from PANI slightly shifts to high d-values with large decrement in their intensity, and laps for composite having 40% weight of ZrO2. The maximum intensity peak, assigning ZrO2, slightly shifts to shorter d-value, from pure ZrO2 to 8% wt of ZrO2 in composite. For further increment in percent weight of ZrO2 this peak shows slight shifting towards high d-value. This shifting of high intensity peak indicates the interaction of ZrO2 with PANI structure in composites. These composites show high crystallinity for 16 to 24 wt %of ZrO2 in it. Remaining samples approaches to amorphous nature. When ZrO2 particles is incorporated into PANI, the broad diffraction peaks of the PANI become very weak, and the diffraction pattern of composite PANI/24% ZrO2 become like as that of ZrO2 diffraction pattern. Near about same situation is observed for PANI/ V2O5 and PANI/PbS composites. In case of PANI/PbS samples (‘k’ to ‘n’), the identity reflections of maximum intensity assigning PANI, shifts toward shorter d-value and that of PbS shifted towards longer d-values. Its crystallinity increases and become high for 24% wt of PbS in composite. For further increment of wt% of PbS, the crystallinity of composites decreases, approaching to amorphous nature. In case of all composites, the crystallite size increases with increase in weight % of additives up to 24%, and decreases for further increment of weight % of additives. There may be some error in calculated crystallite sizes as reported for Debye-Scherrer formula – – 4. Most of the composites show their polycrystalline nature except few of them which acquired very less crystallinity. Each series of composites shows composite of high crystallinity for net 16% to 24% weight of additives (V2O5, ZrO2, and PbS) in PANI. Observed varying crystallinity of samples with changing impurity percentage in composites suggests the considerable interfacial interactions of additives with PANI. It is more probable to change the interchain distance with addition of inorganic impurities in pure PANI structure and consequently the changed delocalization length. This is very crucial and favorable fact to obtain changed electrical conductivity of PANI composites with variation in added weight % of inorganic species like V2O5, ZrO2, and PbS. The d-spacing values and lattice parameters a, b, and c of composites are differ from those of PANI. Also these values of d-spacing and lattice parameters are varied with weight % of additives. The values of d-spacing of PANI and composites show that their local chain arrays are similar193. The inter-chain lateral distance, a and b gives the cross section area for two chains i. e. A = a x b. For all samples, large value of c confirms that the C-N-C angle is larger. This increase may be due to steric interaction between H and the substituted group of benzene ring37. Fig. 4.39- XRD spectra of PANI Fig. 4.40- XRD spectra of V2O5 Fig. 4.41- XRD spectra of PANI + 8%V2O5 (a) Fig. 4.42- XRD spectra of PANI + 16%V2O5 (b) Fig. 4.43- XRD spectra of PANI + 24%V2O5 (c)