Self-organization of comb-like macromolecules comprised of four-fold alkoxy substituted (PPV-PPE) rigid backbone repeat units: role of length variation of side chains attached on phenylene ring surrounded by vinylene moieties

Comb-like macromolecules 3-n consisting of poly(p-phenylene-vinylene)/poly(p-phenylene-ethynylene) polymer backbones bearing four flexible alkoxy substituents per constitutional unit are examined in their bulk states with respect to the length of the side chains attached on the phenylene ring located between the vinylene moities. Characterization of phase behaviour has been performed by means of polarized optical microscopy and differential scanning calorimetry. Structural ordering on the molecular size scale was deduced from a qualitative analysis of wide-angle X-ray scattering effects recorded for macroscopically oriented filaments using a two-dimensional detector. Macromonomer 1 was also considered. All experimental results pointed out a highly ordered self-organization of these materials with structure parameters depending on molecular details. For both macromonomer 1 and polymers 3-n, formation of supramolecular assemblies is detected as temperature dependent contributions of (1) spatial segregation between aromatic and aliphatic segments, (2) stacking properties of pi-conjugated fragments and (3) crystallization of the alkoxy side chains.