Mechanisms of polyaniline film formation via solution casting: Intra-chain contraction versus inter-chain association

Dynamics of Excitons in Conjugated Molecules and Organic Semiconductor Systems

“…The reason for the blue shift of the exciton energy can be attributed to the reduced exciton delocalization due to torsional conformational disorder of the molecule. A similar phenomenon was found in PANI chains, which demonstrated a blue shift of the CT exciton energy, which was explained by specific compact-coil chain conformations. , Specifically, two different mechanisms of formation of PANI films have been shown . The first one is observed in relatively thick films due to entanglement of different polymer chains with plenty of entrapped solvent molecules when the film is formed, which results in relatively loose film morphology with fractal dimensionality of 1.68 and blue color of the film (Figure ), where the CT exciton behavior is the same as in free polymer chains dissolved in the solution.…”

“…282,283 Specifically, two different mechanisms of formation of PANI films have been shown. 284 The first one is observed in relatively thick films due to entanglement of different polymer chains with plenty of entrapped solvent molecules when the film is formed, which results in relatively loose film morphology with fractal dimensionality of 1.68 and blue color of the film (Figure 36), where the CT exciton behavior is the same as in free polymer chains dissolved in the solution. The second mechanism is normally observed for thin films cast from solutions of low concentration and is due to a prevailing tendency toward intramolecular compact-coil conformation, which results in formation of films of the grained morphology with fractal dimensionality of 1.56 and violet color, where the CT exciton can be blue-shifted from 638 nm (observed in thick films and solutions) to as far as 553 nm.…”

Engineering crystalline quasi-two-dimensional polyaniline thin film with enhanced electrical and chemiresistive sensing performances

“…Vigorous effort has been devoted to fabricating PANI thin films, including (i) top-down solution processing of PANI chains via spin coating 20 , drop casting 21 , and Langmuir-Blodgett technology 22 , and (ii) bottom-up synthesis from monomers via self-assembled monolayer (SAM) templating 23 , chemical vapor deposition 24,25 , and air (or liquid)-liquid interfacial method 26,27 . However, these strategies only produced inhomogeneous and amorphous (i.e., randomly compact-coil conformation) PANI films or partially crystalline nanofiber-, rod- and sphere-shaped PANIs 21,22,26 , due to the poor processability of PANIs and complex intermolecular interactions of aniline/oligomers 28 . Therefore, the conductivity of resultant PANI thin films (using HCl as dopant) is typically below 1 S cm −1 21–23,26 .…”

“…However, these strategies only produced inhomogeneous and amorphous (i.e., randomly compact-coil conformation) PANI films or partially crystalline nanofiber-, rod- and sphere-shaped PANIs 21,22,26 , due to the poor processability of PANIs and complex intermolecular interactions of aniline/oligomers 28 . Therefore, the conductivity of resultant PANI thin films (using HCl as dopant) is typically below 1 S cm −1 21–23,26 . Moreover, molecular-level structure of the reported PANI films has not yet been resolved.…”

Synthesis and Conductivity Studies of Poly(Methyl Methacrylate) (PMMA) by Co-Polymerization and Blending with Polyaniline (PANi)

“…A similar approach was done by Dimitriev et al (2015), but this study focused on different concentrations of PANi and determined the effects on the morphology, electronic absorption spectrum, and the ability for acid doping. Moreover, this approach was used to confirm the nature of a cast film that depends critically on the relative rate of solvent evaporation with respect to the changes in the rate and subsequently the molecular interaction that occurred [55].…”