Thermomechanical Behavior and Local Dynamics of Dendronized Block Copolymers and Constituent Homopolymers

摘要

We employ Brillouin light scattering (BLS) and dielectic spectroscopy (DS) to study the phononic behavior, thermomechanical properties, and segmental dynamics of symmetric block copolymers (BCP) constructed from discrete wedge-type repeat units and the corresponding dendronized constituent homopolymers over a broad temperature range. In spite of the sufficiently large elastic contrast between the bulk homopolymers, for the BCPs an absence of a bandgap in the phonon dispersion relation along the periodicity direction implies different modified sound velocities in the photonic BCP lamellar films. The anticipated rich segmental dynamics reveal interfacial mixing as well as confinement effects of the two blocks. This class of amorphous dendronized homopolymers and BCPs reveal strong effects of the wedge-like side groups manifested in the vastly different glass transition temperatures (T_g), free-volume domination of the temperature dependence of the elastic modulus, and heterogeneous segmental dynamics represented by four relaxation processes.