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

Abstract

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 polymers fabricated by LS showed better results, suggesting that the organization provided by the Langmuir-Blodgett (LB) technique was not enough to overcome the insulating characteristic of the SA molecules in this specific configuration.

Ligand influence in electrocatalytic properties of Cu(ii) triazole complexes for hydrogen peroxide detection in aqueous media

“…With the information given by the electrochemical waves a reported method was used to estimate the energy of HOMO and LUMO orbitals, taking the onset value of the first oxidation peak to estimate the energy HOMO, equivalent to the ionization potential. 40,43 The cyclic voltammograms depicted in Fig. 3 just already corrected with the E 1/2 (Fc/Fc + ).…”

Molecular Organization of Functionalized Carbon Nanotube at the Water-Air Interface and in Solid Thin Film

“…These transitions are followed by a reorganization of the mixture, where the peaks represent the maximum compressibility of that phase. We can notice that the pure CNTs did not have a peak higher than 125 mN m -1 , in the case of the mixed CNTs (Figure 4b) it reached a maximum above 250 mN m -1 , corresponding to the liquid-condensed phase 22,24,29 .…”

“…Which has as variables: A12 is the average molecular area in the two-component film, X1 and X2 are the two-component molar fractions, and A1 and A2 are the molecular areas of two unique components at the same chosen surface pressure [22][23][24] .…”

“…As already calculated, the value of 0.295nm 2 is not null, meaning that the two materials aren't a perfect mixture 25,26 . The fact that the value is positive indicates a thermodynamically unstable process, that is, the binding energy between the components of the mixture does not present considerable binding forces between them, this compared to a pure solution 22,27,28 .…”

Regioregularity and deposition effect on the physical/chemical properties of polythiophene derivatives films

“…Morphology is another feature that can tune the electrical behavior of polymeric materials [14,15], and the deposition technique applied to fabricate thin films constitute a practical way of tuning the electrical response of a based-film device [16,17]. The P3ATs can be transferred onto a solid substrate making use of many techniques [18,19], among the options, Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) allow molecular assemblies of the materials [20], which can lead to the alignment of the film in a proper manner, thus enabling the construction of a customized device [21].…”