Magnetismo a temperatura ambiente em polímeros derivados de politiofeno sintetizados eletroquimicamente.
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Data
2003-10-08Autor
Forner, Alessandra Alves Correa
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In this thesis two polymers obtained from alkyl derivatives of
thiophene, poly(3-methylthiophene) and poly(3-hexylthiophene) were studied.
The effects of preparation variables on their electrochemical properties using the
factorial design were analyzed. The preparation variables investigated were the
supporting electrolyte and the synthesis applied potential. Then, a factorial
design 22 was performed for each polymer and was made too a third factorial
design 22, comparing the monomer and the potential. All the electrochemical
analyses were made to understand the polymer behavior as a first step for the
magnetic study. The magnetic properties of poly(3-methylthiophene) were
analyzed and the weak ferromagnetic phase was observed in their pressed pellets
as the polymer was partially doped with ClO4
- anions. This magnetic behavior
was observed in full range from 1.8 K to 300 K with measurements performed
using a SQUID magnetometer. The magnetization depends on the pressure used
to prepare the pellets and the water content of the solvent used for the synthesis.
The intrinsic character of this behavior was shown from atomic absorption
analysis that discarded contamination. It was observed that the polymer shows
different magnetic phases: diamagnetic, paramagnetic, ferromagnetic,
antiferromagnetic and metamagnetic.