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    Molecular organization relationship of low-bandgap polymers at the air water interface and in solid films

    Year: 2018

    Journal: J. Mol. Liq., Volume 268, OCT 15, page 114–121

    Authors: Rodrigues de Oliveira, Vinicius Jesse; da Silva, Edilene Assuncao; Braunger, Maria Luisa; Awada, Hussein; de Santana, Henrique; Hiorns, Roger C.; Lartigau-Dagron, Christine; Olivati, Clarissa de Almeida

    Organizations: CAPES; CAPES/COFECUB (NANOSOL) [Ch 748 26805WM]; FAPESP [2010/20094-1]; INEO/CNPq; LNNano (CNPEM-Brazil) [LMF 16557]

    Country: Aguas de Lindoia, BRAZIL

    Keywords: Low-bandgap polymers; Langmuir films; Solid thin films; Energy diagram; Photoconductivity effect

    Low-bandgap organic polymers, poly( (4,4 bis(2 ethylhexyl)cyclopenta [2,1 b:3,4 b']dithiophene) 2,6 diyl al (2,1,3 benzothiadiazole) 4,7 diyl(PCPDTBT), and poly [(4,4' dioctyldithieno[3,2 b:2',3'd] silol 2,6 diyl) alt (2,1,3 benzothiadiazole) 4,7 diyl)], (Si-PCPDTBT) were analyzed at the air-water interface forming a Langmuir monolayer. In order to form stable monolayers and to transfer to solid supports, amphiphilic molecules of stearic acid (SA) were mixed with them. For the pristine polymers, the floating monolayers were transferred onto solid substrates via the Langmuir-Schaefer (LS) technique. Surface pressure-area isotherms and compressibility modulus curves demonstrated that the SA incorporation to the polymers at the air-water interface modified the rheological properties of the Langmuir films, since the films became less compressible at higher pressures and there is clear conformational reorganization taking place at intermediary pressures. The UV-Vis absorption also depicted the changes on the overall film morphology by the shift on the maximum absorption bands, and along with cyclic voltammetry curves the absorption spectra made it possible to estimate the energy diagrams for the polymers. Photoconductivity effects were observed for all the sample, among which the pristine polymersfabricated by LS showed better results, suggesting that the organization provided by the Langmuir-Blodgett (LB) technique was not enough to overcome the insulating Lharacteristic-olthe-SA molecules in this specific configuration. (C) 2018 Elsevier B.V. All rights reserved.
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