title: Effect of the bulkiness of the end functional amide groups on the optical, gelation, and morphological properties of oligo(p-phenylenevinylene) π-gelators.
abstract: 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 CHCl(3). 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.
authors.affiliation: Photosciences and Photonics Group, Chemical Sciences and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Trivandrum-695 019, Kerala (India), Fax: (+91) 471-249-1712.
authors.forename: Sukumaran Santhosh
authors.initials: SS
authors.lastname: Babu
authors.forename: Vakayil K
authors.initials: VK
authors.lastname: Praveen
authors.forename: Kalathil K
authors.initials: KK
authors.lastname: Kartha
authors.forename: Sankarapillai
authors.initials: S
authors.lastname: Mahesh
authors.forename: Ayyappanpillai
authors.initials: A
authors.lastname: Ajayaghosh
keywords: gels; hydrogen bonds; phenylenevinylenes; pi interactions; self-assembly