Display of hidden properties of flexible aerogel based on bacterial cellulose/polyaniline nanocomposites with helping of multiscale modeling

Tuning the synthesis conditions of polyaniline (PANI) such as aniline monomer's protonation states and adding surfactants into polymerization mixture or even the existence of bacterial cellulose (BC) had a substantial influence on the final properties. To explore the relationship between components presented in the polymerization mixture, simulation tools (molecular dynamics (MD)/Monte Carlo (MC)/Density functional theory (DFT)) can be used. Herein, nanocomposite aerogels of BC/PANI were fabricated in the presence of anionic surfactants; sodium dodecyl benzene sulfonate (SDBS) or sodium dodecyl sulfonate (SDS) at two different concentrations (0.05 M and 1 M) of HCl solution. Two types of aniline monomers were considered in the polymerization mixture based on HCl solution's concentrations including neutral and protonated aniline in 0.05 and 1 M, respectively. Various morphologies from nanobelts (with a width of 100-500 nm) and polyhedrons (with a thickness of 100-700 nm) in 0.05 M of acid solution in the presence of SDBS or SDS, respectively, were detected. Based on DFT computations it was found that electrostatic interactions and the formation of hydrogen bonds play a vital role in the interfacial interaction mechanism between both surfactants (SDBS and SDS) and different protonation forms of aniline monomers. Nevertheless, in the case of SDBS and aniline monomers (in both 0.05 and 1 M of HCl solutions), an excess interaction mechanism, namely pi-pi stacking, was observed, which enhanced the interaction between them and confirmed by experimental results. Therefore, the highest conductivity of 0.8 S/cm was obtained for the BC/PANI prepared with SDBS in 1 M of HCl solution. Besides, the smallest energy gap of 2.74 eV was predicted from DFT calculations for this sample that further confirmed its high electrical properties and smaller band gap at 3 nm, which was also confirmed by MD and MC.