Abstract:We theoretically investigate the energetically favorable orientation of poly(3-hexylthiophene) (P3HT) on self-assembled monolayers (SAMs) using molecular dynamics simulations. The effects of different kinds of SAMs are studied by examining a CH3-terminated SAM with a hydrophobic surface and an NH2-terminated SAM with a hydrophilic surface. We also investigate dynamic behavior of the systems with limited numbers of P3HT molecules on the SAM surfaces. The important factors in controlling the molecular orientatio… Show more
“…In order to keep the computational workload affordable we restricted our analysis to the two extreme values of g, namely 01 (face-on) and 901 (edge-on). [80][81][82] The atomic partial charges of the polymer were calculated according to the standard AM1-BCC method. The vertical configuration is a special case in which the face-on and edge-on configurations are identical.…”
Semiconducting polymer/water interfaces are gaining increasing attention due to a variety of promising applications in the fields of biology and electrochemistry, such as electrochemically-gated transistors and photodetectors, which have been used for biosensing and neuroscience applications. However, a detailed characterization of the polymer surface in the presence of an aqueous environment is still lacking. In this work, we employed sum-frequency generation vibrational spectroscopy, a surface-specific technique compatible with electrochemical/biological conditions, to demonstrate that the surface of thin films of regio-regular poly-3-hexylthiophene (rr-P3HT) undergoes a molecular reorientation when exposed to aqueous electrolytes, with respect to their surface structure in air. Experimental results are corroborated by molecular dynamics simulations. Since surface molecular orientation is believed to play a fundamental role in electrochemical and environmental stability of conjugated polymers, the reported findings not only contribute to the fundamental understanding of conjugated polymer/water interfaces, but they may also have implications in the design of conjugated polymers for enhancing their performance in electrolytic environments. † Electronic supplementary information (ESI) available: Sum-frequency generation theory and P3HT molecular modelling; analysis of thick samples; surface energy calculation from molecular dynamics simulations; Fig. S1-S7. See Fig. 7 (top panels) Averaged formation energy for the P3HT surface in vacuo (left) and in water (right). (bottom panels) Atomistic configurations corresponding to the minimum energy. Journal of Materials Chemistry B Paper
“…In order to keep the computational workload affordable we restricted our analysis to the two extreme values of g, namely 01 (face-on) and 901 (edge-on). [80][81][82] The atomic partial charges of the polymer were calculated according to the standard AM1-BCC method. The vertical configuration is a special case in which the face-on and edge-on configurations are identical.…”
Semiconducting polymer/water interfaces are gaining increasing attention due to a variety of promising applications in the fields of biology and electrochemistry, such as electrochemically-gated transistors and photodetectors, which have been used for biosensing and neuroscience applications. However, a detailed characterization of the polymer surface in the presence of an aqueous environment is still lacking. In this work, we employed sum-frequency generation vibrational spectroscopy, a surface-specific technique compatible with electrochemical/biological conditions, to demonstrate that the surface of thin films of regio-regular poly-3-hexylthiophene (rr-P3HT) undergoes a molecular reorientation when exposed to aqueous electrolytes, with respect to their surface structure in air. Experimental results are corroborated by molecular dynamics simulations. Since surface molecular orientation is believed to play a fundamental role in electrochemical and environmental stability of conjugated polymers, the reported findings not only contribute to the fundamental understanding of conjugated polymer/water interfaces, but they may also have implications in the design of conjugated polymers for enhancing their performance in electrolytic environments. † Electronic supplementary information (ESI) available: Sum-frequency generation theory and P3HT molecular modelling; analysis of thick samples; surface energy calculation from molecular dynamics simulations; Fig. S1-S7. See Fig. 7 (top panels) Averaged formation energy for the P3HT surface in vacuo (left) and in water (right). (bottom panels) Atomistic configurations corresponding to the minimum energy. Journal of Materials Chemistry B Paper
“…4. To conduct further calculations with respect to the film structure, molecular dynamics (MD) simulations for many P3HT molecules would be useful because intermolecular π–π interaction is important to determine the microstructure in P3HT films 47 . However, there have been no reports on calculations of the molecular structures for the orientations of both small and polymer molecules on any brushed substrates, and there have been no reports on such calculations for rubbing studies yet.Figure 5SEM images of ( a ) brushed and ( b ) non-brushed substrates.…”
The realization of room-temperature processes is an important factor in the development of flexible electronic devices composed of organic materials. In addition, a simple and cost-effective process is essential to produce stable working devices and to enhance the performance of a smart material for flexible, wearable, or stretchable-skin devices. Here, we present a soft friction transfer method for producing aligned polymer films; a glass substrate was mechanically brushed with a velvet fabric and poly(3-hexylthiophene) (P3HT) solution was then spin-coated on the substrate. A P3HT film with a uniaxial orientation was obtained in air at room temperature. The orientation factor was 17 times higher than that of a film prepared using a conventional friction transfer technique at a high temperature of 120 °C. In addition, an oriented film with a thickness of 40 nm was easily picked up and transferred to another substrate. The mechanism for orientation of the film was investigated using six experimental methods and theoretical calculation, and was thereby attributed to a chemical process, i.e., cellulose molecules attach to the substrate and act as a template for molecular alignment.
“…To investigate the stability of a P3HT chain in helical conformation, atomistic molecular dynamics simulation is performed using the GROMACS software package, that is widely used for studying the structure and properties of polymers such as P3HT . The structural formula of P3HT repeat unit is shown in Figure .…”
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