Morphology and Deformation Mechanisms and Tensile Properties of Tetrafunctional Multigraft Copolymers

Authors

Yongxin Duan, Institute of Materials Science and Technology (IMT), Friedrich-Schiller-University Jena, Lobdergraben 32, D-07743 Jena, Germany
Mahendra Thunga, Institute of Materials Science and Technology (IMT), Friedrich-Schiller-University Jena, Lobdergraben 32, D-07743 Jena, Germany
Ralf Schlegel, Institute of Materials Science and Technology (IMT), Friedrich-Schiller-University Jena, Lobdergraben 32, D-07743 Jena, Germany
Konrad Schneider, Leibniz-Institute of Polymer Research Dresden, Hohe Strasse 6, D-01069 Dresden, Germany
Erik Rettler, Department of Physical Chemistry, University of Duisburg-Essen, Schutzenbahn 70,D45117 Essen, Germany
Roland Weidisch, Institute of Materials Science and Technology (IMT), Friedrich-Schiller-University Jena, Lobdergraben 32, D-07743 Jena, Germany
Heinz W. Siesler, Department of Physical Chemistry, University of Duisburg-Essen, Schutzenbahn 70,D45117 Essen, Germany
Manfred Stamm, Department of Physical Chemistry, University of Duisburg-Essen, Schutzenbahn 70,D45117 Essen, Germany
Jimmy W. Mays, Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, and Chemical Sciences Division and Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
Nikos Hadjichristidis, Department of Chemistry, University of Athens, Athens, Greece

Date of this Version

2009

Comments

Published in Macromolecules 2009, 42, 4155–4164.

Abstract

Morphology and deformation mechanisms and tensile properties of tetrafunctional multigraft (MG) polystrene-g-polyisoprene (PS-g-PI) copolymers were investigated dependent on PS volume fraction and number of branch points. The combination of various methods such as TEM, real time synchrotron SAXS, rheo-optical FTIR, and tensile tests provides comprehensive information at different dimension levels.TEMand SAXS studies revealed that the number of branch points has no obvious influence on the microphase-separated morphology of tetrafunction MG copolymers with 16 wt % PS. But for tetrafunctional MG copolymers with 25 wt % PS, the size and integrity of PS microdomains decrease with increasing number of branch point. The deformation mechanisms ofMGcopolymers are highly related to the morphology. Dependent on the microphase-separated morphology and integrity of the PS phase, the strain-induced orientation of the PS phase is at different size scales. Polarized FT-IR spectra analysis reveals that, for all investigated MG copolymers, the PI phase shows strain-induced orientation along SD at molecular scale. The proportion of the PI block effectively bridging PS domains controls the tensile properties of the MGcopolymers at high strain, while the stress-strain behavior in the low-mediate strain region is controlled by the continuity of PS microdomains. The special molecular architecture, which leads to the higher effective functionality of PS domains and the higher possibility for an individual PI backbone being tethered with a large number of PS domains, is proposed to be the origin of the superelasticity for MG copolymers.