Polythiophenes functionalized with polar groups at the end of side-chain have emerged as an alternative method to obtain good compatibility between this class of conjugated polymers and electron acceptor compounds. The aim is to prevent phase segregation and to improve the efficiency of the polythiophene technological devices. However, homopolymers synthesized from thiophene rings with high polar groups at the end of the side-chain, such as hydroxyl and carboxylic acid groups, are poorly soluble in common volatile organic solvents. We report on a systematic preparation of copolymers of 3-hexylthiophene (HT) and thiophene-3-acetic acid (TAA), using different feed ratios. The chemical structures of the copolymers were confirmed by FTIR and ¹H-NMR. The TAA content in these copolymers were 33, 38 and 54 mol %. HPSEC results did not show any remarkable correlation with TAA contents in the copolymers. In contrast, the thermal analyses showed a decrease in the thermal stability and an increase in rigidity of their backbones, for the copolymers with high amounts of TAA. The solubility and optical property of copolymers were also related to the TAA contents. Thus, the properties of these copolymers can be modulated by a simple control of feed ratio of TAA in the copolymerization.

Er-doped SnO2 thin films and xerogels are obtained by sol-gel technique. In order to understand the Er³+ rare-earth ion activity in SnO2 matrix, a characterization of Er incorporation is done through emission and excitation spectra of xerogels, besides thin film electrical characterization. Effects to grain dimensions are also analyzed based on X-ray diffraction data showing the particle growth with annealing temperature and inhibition of this growth by Er doping. Electrical characterization results suggest that Er³+ has an acceptor-like character in SnO2, and that codoping with Yb³+ allows an energy transfer process Yb³+ -> Er³+.

Transparent electrically conducting antimony-doped SnO2 thin films have been prepared by sol-gel dip-coating process from colloidal aqueous suspension. The effect of doping content on the structural, optical and electrical properties is analyzed. Results from infrared optical transmission and reflection have shown that the higher the Sb concentration the lower the transmission intensity and the higher the reflection signal. Absorption intensity increases as well. Results of X-ray reflectometry and electron microscopy have shown that the density of films fired at 400 °C after each dip is higher than that of multi-dipped films prepared with a single annealing. Both the electrical characteristics in the dark and the increase in conductivity as function of illumination through different filters, at 190 K, evidence that the transport properties of these films are dominated by the presence of defects, including the trapping at grain boundary due to excess of oxygen.

Híbridos siloxano-PMMA apresentando ligações covalentes entre as fases orgânica e inorgânica foram preparados a partir do processo sol-gel. O efeito da fração em massa de fase siloxano no mecanismo de secagem dos géis a 50ºC foi estudado através de medidas de perda de massa e retração linear. Pode-se distinguir os três períodos clássicos de secagem já observados em géis inorgânicos. A duração do primeiro período (estágio de velocidade constante) aumenta com o teor de polímero, o que pode ser explicado pelo menor tamanho dos poros presentes nos géis contendo concentrações elevadas de PMMA. Com o aumento da concentração da fase siloxano observou-se o aumento da perda de massa total e da retração linear final do material após o terceiro período de secagem. Este comportamento deve-se ao aumento do teor de água livre resultante da policondensação das espécies siliciosas nestes sistemas, o que leva a uma maior plasticidade do material. O volume poroso do material aumenta com o teor de fase siloxano, o que é consistente com a perda de massa observada durante a secagem.

Siloxane-PMMA (polymethylmethacrylate) hybrid materials presenting covalent bonds between the organic (polymer) and inorganic (siloxane) phases were prepared by the sol-gel process. The effect of siloxane content on the drying mechanism at 50ºC was investigated by in-situ weight loss and linear shrinkage measurements. The three classical regimes observed during drying of pure inorganic gels were observed. The duration of the first regime (constant rate period, CRP) increases by increasing the quantity of PMMA in the hyibrids, which was attributed to the low average pore diameter observed in these systems. The increase in siloxane content increases the weight loss and linear shrinkage at the end of the drying process due to the high quantity of solvent resulting from condensation reactions of silicon species. It leads to the diminution of the gel stiffness. The porosity of dried hyibrids increases with the siloxane content due to the high weight loss observed during drying.