Dynamic-mechanical and dielectric relaxations of SBS block copolymer: polyaniline blends prepared by mechanical mixing

Blends of SBS with polyaniline doped with dodecylbenzenesulfonic acid (Pani(.)DBSA) or its deprotonated form (emeraldine base) were obtained by mechanical mixing and characterized by dynamical-mechanical and dielectric thermal analysis techniques. The dynamic-mechanical characterization revealed that both Pani.DBSA and its non-conducting, deprotonated form exhibits different degrees of interaction with the two phases of the SBS block copolymer. The tan delta peak position on temperature scale corresponding to the T-g of the PB block did not change with the addition of the conducting polymer, but there is progressive drop of peak height with the increase in Pani(.)DBSA concentration, probably because of the rigidity of this component. The activation energies E-a for glass-rubber transition process for both the phases of SBS were calculated using Arrhenius equation from DMTA results. From dielectric studies, it was possible to detect conductivity relaxations, at temperatures above the glass transition of the PS phase. Concerning the blend with 15 wt% of Pani(.)DBSA, the relaxations attributed to both Pani.DBSA blend component and PS phase of the SBS copolymer can be observed only when the measurement are performed at frequencies lower than 10(3) Hz. (C) 2002 Elsevier Science Ltd. All rights reserved.