Subi Jacob, George; Dr. Ajayaghosh, A(Regional Research Laboratory (CSIR), October , 2004)
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Abstract:
The main objective of the
present study is to have a detailed investigation on the gelation properties,
morphology and optical properties of small π-conjugated oligomers. For this purpose
we have chosen oligo(p-phenylenevinylene)s (OPVs), a class of molecules which
have received considerable attention due to their unique optical and electronic
properties. Though a large number of reports are available in the literature on the self-assembly properties of tailor made OPVs, none of them pertain to the design of
nanostructures based on organogels. In view of this, we aimed at the creation of
functional chromophoric assemblies of π-conjugated OPVs through the formation of
organogels, with the objective of crafting nanoscopic assemblies of different size and
shape thereby modulating their optical and electronic properties.In order to fulfill the above objectives, the design and synthesis of a variety of
OPVs with appropriate structural variations were planned. The design principle
involves the derivatization of OPVs with weak H-bonding hydroxymethyl end groups
and with long aliphatic hydrocarbon side chains. The noncovalent interactions in these
molecules were expected to lead the formation of supramolecular assembly and gels in
hydrocarbon solvents. In such an event, detailed study of gelation and extensive
analysis of the morphology of the gel structures were planned using advanced
microscopic techniques. Since OPVs are strongly fluorescent molecules, gelation is
expected to perturb the optical properties. Therefore, detailed study on the gelation
induced optical properties as a way to probe the nature and stability of the selfassembly
was planned. Apart from this, the potential use of the modulation of the
optical properties for the purpose of light harvesting was aimed. The approach to this
problem was to entrap an appropriate energy trap to the OPV gel matrix which may
lead to the efficient energy transfer from the OPV gel based donor to the entrapped
acceptor. The final question that we wanted to address in this investigation was the
creation of helical nanostructures through proper modification of the OPV backbone
With chiral handles.The present thesis is a detailed and systematic approach to the
realization of the above objectives which are presented in different chapters of the
thesis.