Browsing by Author "Encinar, Mario"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Dielectric and dynamic-mechanical study of the mobility of poly(t-butylacrylate) chains in diblock copolymers: Polystyrene-b-poly(t-butylacrylate)
    (ELSEVIER SCI LTD, 2008) Encinar, Mario; Guzman, Eduardo; Prolongo, Margarita G.; Rubio, Ramon G.; Sandoval, Claudia; Gonzalez Nilo, Fernando; Gargallo, Ligia; Radic, Deodato
    A calorimetric, dielectric and dynamic-mechanical study of the dynamics of the poly(t-butyl acrylate) (PtBa) chains has been carried out in a PtBa homopolymer and two polystyrene (PS)-b-PtBa block copolymers with different PtBa chain lengths. The DSC results show that the size of the cooperative rearranging regions is similar in the homopolymers and the copolymers, both for the PtBa rich- and the PS-rich regions. Therefore, no significant contributions are found arising from composition fluctuations in the copolymers. The relaxation map obtained from dielectric relaxation indicates that there are no differences in the temperature dependence of the a-relaxation of the PtBa block in the three samples studied. However, there are larger differences for the values obtained from DMTA experiments. Contrary to the alpha-relaxation, the relaxation map for the beta-transition shows that the characteristic times for the PtBa blocks are smaller in the homopolymer than in the copolymers. In principle, these are unexpected results because the beta-relaxations have a more local character than the alpha-ones. The width of the alpha-relaxation increases with T for all the samples, and it is slightly larger for the copolymers.