Helical Self-Assemblies Of Segmented Poly(Phenylenevinylene)S And Their Hierarchical Donor-Acceptor Complexes

We report aromatic pi-stack-driven helical self-assemblies of segmented poly(phenylenevinylene)s and their hierarchical helical donor-acceptor assemblies with electron deficient molecules by a solvent-induced self-organization process. New segmented PPVs were designed and synthesized having tricyclodecane-substituted oligophenylenevinylene (OPV) pi-core with flexible methylene chains of variable carbon atoms 4, 8, and 12. The polymers were obtained in high molecular weights with very good solubility in common organic solvents. The polymers were found to be amorphous, and their glass transition temperature varied from 100 to 170 degrees C with respect to the increase in the rigidity of the polymer backbone. The flexible segmented polymer underwent aromatic it-stack interaction to produce pi-conjugated polymer aggregates in methanol and tetrahydrofuran (THF) solvent combinations. Electron microscopic studies confirmed that these it-aggregates appeared as bundles of helical assemblies. An electron deficient perylenebisimide derivative was complexed with segmented polymers to produce stable and helical donor-acceptor hierarchical assemblies. The formation of D-A assemblies was confirmed by detail photophysical studies such as absorbance, emission, time-resolved fluorescence decay, and FRET mechanism. A controlled experiment with structurally identical rigid polymer revealed that appropriate polymer design in the segmented skeleton is essential for making stable helical D-A assemblies. Thus, the present study provides insight into the formation of stable helical donor-acceptor assemblies in pi-conjugated polymers that are useful for application in optoelectronics.