Correlation between chain packing and photoluminescence for PPV/PPE in macroscopically oriented state: Side chain effects

Self-organization features of poly(p-phenylene-vinylene)/poly(p-phenylene-ethynylene)s(PPV/PPE)s polymers of constitutional structure (-Ph-C C-Ph-C equivalent to C-Ph-CH equivalent to CH-Ph-CH=CH-)(n) and bearing two alkoxy side chains on either every one (1) or every second (2) phenylene moieties are presented. Formation of self-assembled structures on various size scales has been examined using a combination of experimental methods. Initial investigations performed for macroscopically isotropic samples by means of DSC, POM, and 2D SALS have revealed a strong dependence of the thermal behavior and related morphologies on the side chain densities. The existence of organizational features in macroscopically oriented bulk samples (extruded filaments) was also demonstrated using 2D WAXS. Self-organization of (PPV/PPE)s into biphasic structures made of spatially segregated main chain layers with the side chains filling the space between layers was postulated. The local arrangement of the macromolecular subunits was strongly dependent on the macromolecular architecture and temperature. Two types of organization of the polymer chains assuming translationally correlated (2) and uncorrelated (1) positions could be distinguished. Fluorescence investigations using a frontal geometry setup were performed on the extruded filaments. Side-chain-dependent correlation between the structure and the photophysical behavior of PPV/PPE could be established for the uniaxial orientation showing the bathochromic shift of the emission peak with the decrease of the interchain distances within layers.