Dramatic effect of the slower component topology on the matrix dynamics in polymer mixtures

Abstract

Single-chain nano-particles (SCNPs) are polymeric soft nano-objects consisting of individual linear macromolecules collapsed to a certain degree by means of intramolecular cross-linking. These new nano-particles are attracting increasing interest due to their intriguing physical properties toghether with potential applications. In particular, they can be used as components of all-polymer nanocomposites, i.e., systems formed by a polymeric matrix and polymeric nanoparticles instead of hard inorganic nano-particles. Since SCNPs are soft particles, all-polymer nano-composites can be compared with conventional nanocomposites. Moreover, as any SCNP is made of only one macromolecule, the Polymer/SCNPs mixture should also be compared with traditional polymer blends. In this contribution, the dynamics of Polymer/SCNPs blends studied by means of dielectric relaxation methods is presented. Mixtures of poly(vinyl methyl ether) (PVME) and poly(styrene) (PS), either in linear chain form or as SCNP, with different relative concentrations have been investigated. These systems show a strong dynamic asymmetry due to the huge difference in the glass transition temperatures of the components. Moreover, the dielectric response of the PVME/PS mixtures is largely dominated by the fluctuation of the molecular dipole moment associated to PVME. Thus, using dielectric relaxation techniques the molecular mobility of the matrix has been characterized in detail highligting the dramatic effect of the SCNP topology on the segmental dynamics of the PVME matrix.