Síntese e caracterização físico-química e eletroquímica de materiais poliméricos derivados do tiofeno ß-substituído para aplicação em dispositivos optoeletrônicos

Abstract

This paper presents the study of polymeric materials with promising properties for application in organic electronics. Poly(3-methoxythiophene) (PMOT) and copolymers with 3-thiophenemethanol, 3-tiofenoetanol acid and 3-thiophenecarboxylic were obtained by electropolymerization and their spectroelectrochemical properties were studied (response time, opticalcontrast, and electrochromic efficiency). All polymers showed color reversible change between blue (oxidized state) and orange (reduced state). 3-methoxythiophene electropolymerization and electrochemical study of poly(3-methoxythiophene), by cyclic voltammetry using different electrolytes, were realized. Simultaneous measurements of the mirage effect and the quartz microbalance were alsoperformed. This study evaluated the influence of cations on the electrochemical monomer and polymer properties and allowed us to observe an anomalous synthesized polymer behavior in the presence of potassium ions (K+) when compared with other cations. The electrochemical reversibility of the polymers was also evaluated withrespect to the various electrolytes and the influence of the polymer film thickness, (deposited mass) on its electrochemical properties, was observed. Nanocomposites based on poly(3-hexylthiophene) (P3HT) and multi-walled carbon nanotubes (MWCNT) were prepared in situ through oxidative polymerization with 8% and 16% (w/w) MWCNT. The nanocomposites were highly soluble in common organic solvents and formed a dark orange solution as well as sustainable films (thickness > 1 m). The ATR-FTIR and 1H NMR analyses showed that the samples had head-to-tail (HT) regio-regularity and indicated a - and CH2- interaction between the polymer chain and the nanotubes. The samples absorbed in the violet region, and the emission (photoluminescence, PL) was visible to the naked eye in the orange region. The morphology and thermal behavior was evaluated. The SEM images showed nanotube adhesion to the polymer. The electrochemical profile was determined atdifferent scan rates. Spectroelectrochemical studies showed a significant reduction in oxidation response time (t) with nanotubes in the polymeric matrix; pure P3HT had a t of 6.2 s; while the 16% MWCNT nanocomposites had a t of 1.2 s. Poly(3-dodecylthiophene) composites and graphene nanosheets (GNS) were also produced. Physicochemical, electrochemical and optical characterizations were performed (ATR-FTIR, 1H NMR, TGA, CV, UV-vis, PL). Measures of cyclic voltammetry show a slight increase of redox process reversibility, identified by decreasing the difference between the oxidation and reduction potentials. Furthermore, the photoluminescence was performed to assess the possibility of graphene nanoplatelets act as electron trap, where it was possible to observe quenching of the excited state of the polymer (via PL) and indications of interactions of the type - between the polymeric matrix and the GNS