Correlation Between Molecular Conformation, Packing, and Dynamics in Oligofluorenes: A Theoretical/Experimental Study

Author(s)

Bernardinelli, Oigres Daniel ^[1] ; Faria, Gregorio Couto ^[1] ; de Oliveira Nunes, Luiz Antonio ^[1] ; Faria, Roberto Mendonca ^[1] ; deAzevedo, Eduardo Ribeiro ^[1] ; Siqueira Pinto, Melissa Fabiola ^[2]

Affiliation

^[1] Univ Sao Paulo, Inst Fis Sao Carlos, BR-13660970 Sao Carlos, SP - Brazil

^[2] Univ Fed Ouro Preto, Dept Fis, BR-3540000 Ouro Preto, MG - Brazil

• Document type: Journal article
• Source: Journal of Physical Chemistry A; v. 116, n. 17, p. 4285-4295, MAY 3 2012.
• Web of Science Citations: 13

Abstract

Fluorene-based systems have shown great potential as components in organic electronics and optoelectronics (organic photovoltaics, OPVs, organic light emitting diodes, OLEDs, and organic transistors, OTFTs). These systems have drawn attention primarily because they exhibit strong blue emission associated with relatively good thermal stability. It is well-known that the electronic properties of polymers are directly related to the molecular conformations and chain packing of polymers. Here, we used three oligofluorenes (trimer, pentamer, and heptamer) as model systems to theoretically investigate the conformational properties of fluorene molecules, starting with the identification of preferred conformations. The hybrid exchange correlation functional, OPBE, and ZINDO/S-CI showed that each oligomer exhibits a tendency to adopt a specific chain arrangement, which could be distinguished by comparing their UV/vis electronic absorption and C-13 NMR spectra. This feature was used to identify the preferred conformation of the oligomer chains in chloroform-cast films by comparing experimental and theoretical UV/vis and C-13 NMR spectra. Moreover, the oligomer chain packing and dynamics in the films were studied by DSC and several solid state NMR techniques, which indicated that the phase behavior of the films may be influenced by the tendency that each oligomeric chain has to adopt a given conformation. (AU)

• FAPESP's process: 07/08688-0 - Electronic and optoelectronic polymer devices
• Grantee: Roberto Mendonça Faria
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 09/18354-8 - Dynamics and structure of polymer systems as studied by nuclear magnetic resonance
• Grantee: Eduardo Ribeiro de Azevedo
• Support Opportunities: Regular Research Grants