Fractal growth, growth kinetics, and electrical conductivity of aggregates obtained during electropolymerization in the systems (A) pyrrole-4-toluene sulfonic acid silver salt (4-TSS)-acetonitrile, (B) pyrrole-4-TSS-ZnSO(4)-acetonitrile, and (C) pyrrole-4-TSS-aniline-acetonitrile were investigated. In the case of system (A), effect of [4-TSS], [pyrrole], field intensity, and solvents H(2)O and CH(3)OH on morphology, fractal character, and growth kinetics was also studied. Fractal growth data were examined in detail. During studies on system (A), electric potential oscillations were observed and subjected to detailed study. The results indicate that fractal growth pattern and electric potential oscillations are inter-related. The mechanism of development of fractal growth, dendritic structure, and electric potential oscillations is discussed in terms of diffusion-limited aggregation and modified Diaz's mechanism, which explains the random movement of radical cations.

TABLE VI: Comparison of Core Representations0 P&D all electron4 H&W ECP, P&D basis set0 BE Zn(OH2)2+ 112.4 119.5 BE Zn(OH)+ 461 460 PA Zn(OH)+ 81.7 90.2 PA (OH)' 441 441.9 °A11 results in kilocalories per mole. 4 From ref 8. °ECP from H&W and valence basis set from ref 8.energy and proton affinities were reproduced (see Table VI). This eliminates the ECP's as the source of error.The results obtained for the large complexes (Table V) indicate that water and hydroxide ion bind to (NH3)3Zn2+ by 43 and 284 kcal/mol, respectively (see Table V, footnote a for the definition of binding energies). These results do not include electron correlation, but the results on the smaller complexes suggest that the increase in binding due to electron correlation is only 2-3%.Zero-point-energy corrections (ZPE) are also of the same magnitude but opposite direction. The proton affinity of the hydroxide complex is calculated to be 167 kcal/mol. Since the proton affinity is also equal to the difference in binding of hydroxide and water subtracted from the proton affinity of the hydroxide ion, the correlation correction in the latter will have an effect on the correlation correction of the proton affintity of the complexed hydroxide ion. Assuming a 2.5% increase in the binding energies due to the correlation correction and an 8 kcal/mol decrease in the hydroxide ion proton affinity, the net correlation correction for the proton affinity of the complexed hydroxide is a decrease of 14 kcal/mol. ZPE corrections would also decrease the proton affinity, but the correction would be less than the correction for the hydroxide proton affinity (8 kcal/mol) since the ZPE corrections for the binding of hydroxide and water are likely to be the same sign but subtracted from the hydroxide correction. We therefore believe that the estimates found in Table V of the binding energies of these large complexes are indeed good estimates for these properties and are not likely to need future modification. However, the proton affinity may be as much as [14][15][16][17][18][19][20][21][22] kcal/mol

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Fractal and dendrimer growth patterns of polypyrrole were obtained during electrochemical polymerization of pyrrole in systems (A) pyrrole-sodium dodecyl sulfate (NaDS)-water and (B) pyrrole-NaDS-cetyl trimethyl ammonium bromide (CTAB)-water. Different morphological transitions including compact → flower-like and fractal → dendrimer → fractal were observed depending on experimental conditions. Growth kinetics during electropolymerization of pyrrole was studied. Growth rate was found to be higher in system A than in B. Effect of [NaDS], [pyrrole], and field intensity on morphology and weight of polymer aggregates was also studied in both the systems. Different empirical equations were obeyed under different conditions. Electropolymerized aggregates were characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), electrical conductivity measurement, and reflectance spectroscopy. TEM studies revealed that the particle size decreased to ∼140-200 nm in the presence of CTAB. The decrease in particle size on addition of CTAB was also observed in XRD studies. Reflectance spectra of the polymer aggregates support the large π-conjugation in the dendrimer. During electropolymerization, oscillations in potential were monitored as a function of time. Results indicated that growth pattern and electric potential oscillations were interrelated. In the case of fractal growth, the amplitude of chaotic oscillation was higher than the amplitude of oscillation during the growth of dendrimer. Growth morphologies and electric potential oscillations have been explained on the basis of modified Diaz's mechanism.