Role of polarity of surfactants on the morphology of electrochemically synthesized polyaniline nanostructures: Towards faster and efficient electrochromic response

Polyaniline nanowire arrays generated through oriented mesoporous silica films: effect of pore size and spectroelectrochemical response

“…Accordingly, one always obtained thin layer contributions in the 99–100% range for all PANI nanofilaments after silica template removal, confirming a real interest of such ultra-small nanostructures for ensuring fast electron transfer processes, contrary to bulkier PANI deposits (even nanostructured ones) for which diffusion-controlled processes have been most often reported (as a result of rather slow counter-ions diffusion through the polymeric material). 71,74–76 For PANI wires in the silica membrane ( i.e. , before etching), some contributions of diffusion-controlled reactions were evidenced (65%, 25%, 21% and 11%, respectively, for PANI deposits at 60 s, 100 s, 120 s and 160 s in CTAB-based films, and 11% for both PANI deposits at 60 s and 100 s in ODAB-based films (and less than 1% for those PANI deposits at 120 s and 140 s with ODAB films)), confirming the above qualitative observations.…”

“…, 0.12 s for coloration and 0.10 s for bleaching with PANI nanofilaments electropolymerized for 120 s using the CTAB-based template; and 0.11 s for coloration and 0.10 s for bleaching with PANI prepared for 100 s from the ODAB-based template) are among the best in comparison to other PANI nanostructures. 71,74–76 Note that lengthening the electropolymerization time for PANI growth ( i.e. , up to reaching PANI deposits not only in the nanochannels but also on top of the silica membrane) resulted in response times of the same order of magnitude as for a bulk PANI layer on bare ITO and larger variations of absorbance, but it was at the expense of some lack of long-term stability, especially after removal of the silica template (Table 1).…”

“…Accordingly, one always obtained thin layer contributions in the 99-100% range for all PANI nanolaments aer silica template removal, conrming a real interest of such ultra-small nanostructures for ensuring fast electron transfer processes, contrary to bulkier PANI deposits (even nanostructured ones) for which diffusion-controlled processes have been most oen reported (as a result of rather slow counter-ions diffusion through the polymeric material). 71,[74][75][76] For PANI wires in the silica membrane (i.e., before etching), some contributions of diffusioncontrolled reactions were evidenced (65%, 25%, 21% and 11%, respectively, for PANI deposits at 60 s, 100 s, 120 s and 160 s in CTAB-based lms, and 11% for both PANI deposits at 60 s and 100 s in ODAB-based lms (and less than 1% for those PANI deposits at 120 s and 140 s with ODAB lms)), conrming the above qualitative observations. Yet the contributions of thin layer behaviour remain in the majority (except for the very short PANI nanolaments prepared for 60 s in CTAB-based lms), suggesting that even in such conned environments the electron transfer processes were quite fast and not signicantly restricted by diffusion phenomena, consistent with the above estimation of PANI occupying roughly 1 2 to 1 3 of the mesopore section (thus keeping some space for easy mass transport of counter ions).…”

“…79,80 However, the rigidity of PANI chains and the lack of access to aniline units in bulk polymer can hinder the transport of counter ions during doping/dedoping processes, undermining the electrochromic response. Among the strategies developed to overcome such limitations, one can cite the nanostructure of PANI 71,[74][75][76] or the design of PANI-based hybrid nanocomposites. [81][82][83][84] We have thus evaluated the possible interest of the PANI nanolaments developed here as electrochromic materials.…”

“…The shortest response times obtained for the most efficient systems (i.e., 0.12 s for coloration and 0.10 s for bleaching with PANI nanolaments electropolymerized for 120 s using the CTAB-based template; and 0.11 s for coloration and 0.10 s for bleaching with PANI prepared for 100 s from the ODABbased template) are among the best in comparison to other PANI nanostructures. 71,[74][75][76] Note that lengthening the electropolymerization time for PANI growth (i.e., up to reaching PANI deposits not only in the nanochannels but also on top of the silica membrane) resulted in response times of the same order of magnitude as for a bulk PANI layer on bare ITO and larger variations of absorbance, but it was at the expense of some lack of long-term stability, especially aer removal of the silica template (Table 1). A compromise thus has to be found, ensuring an amount of PANI deposits large enough to get signicant coloration efficiency with fast response time aer template removal, but not too large to avoid problems related to possible degradation over prolonged use which could contribute to the lack of long-term stability.…”