Publicación:
Dielectric and Molecular Dynamics Study of the Secondary Relaxations of Poly(styrene-co-methylmethacrylate) Copolymers: Influence of the Molecular Architecture

Fecha
2011-11-07
Editor/a
Director/a
Tutor/a
Coordinador/a
Prologuista
Revisor/a
Ilustrador/a
Derechos de acceso
info:eu-repo/semantics/openAccess
Título de la revista
ISSN de la revista
Título del volumen
Editor
EDP Sciences ; Springer Verlag (Germany) ; Società Italiana di Fisica
Proyectos de investigación
Unidades organizativas
Número de la revista
Resumen
The effect of the structure of copolymers (random, alternate or diblock) on their dynamics has been studied by dielectric spectroscopy. Six copolymers of styrene and methyl methacrylate (three diblocks, one alternate and two random) have been studied. The results show that the sub-Tg transitions of the diblock samples can be described by one asymmetric Havriliak-Negami (HN) function, while two are necessary for the rest of the copolymers (β and γ relaxations). The characteristic times of the sub-Tg relaxations show an Arrhenius temperature dependence and there is a strong coupling of the α and β relaxations at high temperatures. The deconvolution of the merging relaxations has been made in the framework of the Williams Ansatz set out in terms of Havriliak-Negami distributions. The γ relaxation may be assigned to the rotation of the methyl methacrylate group in a styrene-rich environment. The Molecular Dynamics simulations of a poly(methyl methacrylate) homopolymer and of the alternate copolymer are in qualitative agreement with the experimental results, although they predict smaller values for the activation energy of the sub-Tg relaxations.
Descripción
Categorías UNESCO
Palabras clave
Citación
Centro
Facultad de Ciencias
Departamento
Ciencias y Técnicas Fisicoquímicas
Grupo de investigación
Grupo de innovación
Programa de doctorado
Cátedra