Directed orientation of oligo(phenylene ethynylene)s using ureas or urethanes in rod-coil copolymers
in: Macromolecular Chemistry and Physics (2017)
Interchromophoric interactions between oligo(phenylene ethynylene)s incorporated in copolymers in solution as well as in solid state were investigated using UV/Vis and IR spectroscopy. One promising strategy to enable strong inter−chromophoric interactions was the introduction of hydrogen−bonding moieties. Together with the tendency of the chromophores to self-assemble via π−π−stacking a dense packing of the chromophores within a polymer film can be achieved. In order to demonstrate this strategy, oligo(phenylene ethynylene)s were used as monomers for copolymers using the highly efficient blocked isocyanate route and polymer films were prepared by spin coating technique. The copolymers were prepared by an in situ deprotection of a pyrazol protected bis−isocyanate functionalized rigid chromophore followed by subsequent polyaddition using a bis−amine or bis−alcohol linker unit. The specific introduction of urea as well as urethane moieties enhances coplanarization of the chromophores in the polymer films into well−organized structures, which can be characterized based on their specific optical properties.