A molecular view on a polyaniline–TiO2 nanostructured thin film: Effect of temperature and pressure on the thermal, mechanical, and dynamical properties

• Polyaniline (PANI) and TiO2 thin films were prepared using the sol–gel dip-coating method.
• The dynamical and mechanical properties of the PANI nanostructured film were investigated.
• AFM-based nano-indentation tests were used to determine Young's modulus values.
• The physical properties of the PANI and PANI–TiO2 interface were studied computationally.
• Molecular dynamics simulation results were in good agreement with the experimental data.

The present work adopts experimental studies and molecular dynamics (MD) simulations to investigate the thermal, mechanical, and dynamical properties of polyaniline (PANI) coated on a TiO2 nanostructured film. At first, a series of the PANI and TiO2 nanostructured thin films were prepared using the sol–gel dip-coating method. The dynamic mechanical thermal analysis (DMTA) was used to measure glass transition temperature, Tg. AFM-based nano-indentation tests were used to determine the values of hardness, Young's modulus and Poisson's ratio of the prepared thin films. Second, MD simulations were performed using COMPASS force field associated with energy minimization approach. The density and free energy profiles were calculated to determine the molecular structure and thermodynamic equilibrium state of the simulated PANI structures with different monomer chains at various temperatures. The value of Tg of the PANI film under different pressures was also determined from the simulation. The mechanical properties of PANI film and the PANI–TiO2 interface such as the normal stresses, tangential stresses, surface tension, bulk and shear modulus and Poisson's ratio were determined computationally. The dynamic properties of simulated films were studied by the terms of torsion time autocorrelation function. In all cases, MD simulation results were in good to excellent agreement with the experimental data.