Effect of the bulkiness of the end functional amide groups on the optical, gelation, and morphological properties of oligo(p-phenylenevinylene) π-gelators

Article abstract of DOI:10.1002/asia.201402235

Herein, we describe the role of end functional groups in the self-assembly of amide-functionalized oligo(p-phenylenevinylene) (OPV) gelators with different end-groups. The interplay between hydrogen-bonding and π-stacking interactions was controlled by the bulkiness of the end functional groups, thereby resulting in aggregates of different types, which led to the gelation of a wide range of solvents. The variable-temperature UV/Vis absorption and fluorescence spectroscopic features of gelators with small end-groups revealed the formation of 1D H-type aggregates in CHCl₃. However, under fast cooling in toluene, 1D H-type aggregates were formed, whereas slow cooling resulted in 2D H-type aggregates. OPV amide with bulky dendritic end-group formed hydrogen-bonded random aggregates in toluene and a morphology transition from vesicles into fibrous aggregates was observed in THF. Interestingly, the presence of bulky end-group enhanced fluorescence in the xerogel state and aggregation in polar solvents. The difference between the aggregation properties of OPV amides with small and bulky end-groups allowed the preparation of self-assembled structures with distinct morphological and optical features. Buying in bulk: OPV amides with small end-groups self-assemble into 2D/1D aggregates in toluene and 1D aggregates in CHCl₃. Bulky end-groups impede fluorescence quenching in the self-assembled state by blocking π-stacking and facilitate morphological transition in THF.