Uniaxial Strain in Molecular Nanowires: A Case Study of β-phase Polyfluorenes

Abstract

The response of flexible organic semiconducting fluorene nanowires to structural manipulation and adsorption-induced uniaxial strain is investigated using first-principles methods. In agreement with experiments, the calculated shifts in transition energies of strained planar fluorenes do not lead to a molecular phase change but are modified according to whether deformations promote or suppress conjugation along the backbone. We identify two energetically identical modes for compressing the molecule, which cause shifts in opposite directions, depending on the impact of the deformation on the strength of conjugation. We also consider surface adsorption as a practical means for inducing strain. Although the polymer can be linearly extended through mismatch with the surface lattice, properties are likely to be dominated by local compressed regions. SECTION Nanoparticles and Nanostructures

Role of Planar Conformations in Aggregation Induced Spectral Shifts of Supermolecular Oligofluorenols in Solutions and Films: A Combined Experimental and MD/TD-DFT Study

“…56,74 The GEBF has been demonstrated to be a powerful tool in treating long oligomers of ionically functionalized polyacetylenes. 75 Similar to what was reported for the polyacetylenes 75 and other PF oligomers, 76 R-PFOHn and PFOHn (n = 4 and 8) also show an arched structure.…”

“…Here, we adopt the generalized energy-based fragmentation (GEBF) approach, − in which, the ground-state energy of a large system can be directly estimated from the assembly of energies of several small electrostatically embedded subsystems. , The GEBF has been demonstrated to be a powerful tool in treating long oligomers of ionically functionalized polyacetylenes . Similar to what was reported for the polyacetylenes and other PF oligomers, R-PFOH n and PFOH n ( n = 4 and 8) also show an arched structure.…”

Correlating elastic properties and molecular organization of an ionic organic nanostructure

“…[3][4][5] For high performance practical applications of organic semiconducting nanostructures (light-emitting diodes, 6 eld-effect transistors, 7 photoswitches, 1 sensors, 8,9 solar cells, 10,11 and memory devices 12 ) fast and efficient carrier mobility needs to be coupled with low internal stress and superior tensile characteristics. 13 For example, both increased elastic modulus and conductivity were observed for polypyrrole nanotubes with improved longitudinal alignment of the polymer chains via p-p interactions. 5 Metal-like stiffness and transparent optical properties were reported for nanospheres formed from aromatic dipeptides.…”