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Open Access Dissertation
Doctor of Philosophy (PhD)
Year Degree Awarded
Paul M. Lahti
Aggregation and folding events in conjugated polymers have a dramatic effect on the photophysics, and in turn, the efficiency of said species in organic electronic devices. The factors that lead to twisting, bending and folding in conjugated polymers have been studied in numerous polymeric materials, but due to the variability of these events, they remain poorly understood.
To probe the spectroscopic signatures of folding and to link them with conformational and morphological features formed by these species in the solid state, a series of alternating co-polymers were then synthesized, incorporating the 2- and 4-carbon tethers with oligo-phenylenevinylene derivatives. Static absorption, photoluminescence and TEM images of drop-cast films indicate that the length of the linker has a dramatic effect on the fluorescence and morphological behavior of segmented alternating copolymers. Given that the linker length also shows variations in resistance to thermal reorganization, incorporating flexible linkers into polymeric systems provides a method of tuning morphological features within polymeric thin films by changing the length of the flexible tether.
In a study to further test the folding capacity of aliphatic linkers, dyads of trimethoxystyrene-functionalized fluorenone linked by 2-, 4-, and 8-carbon flexible tethers were studied by static absorption spectroscopy and both static and time-resolved photoluminescence (TRPL) spectroscopy. The unique behavior of the 2-carbon tethered system is attributed to an ability to fold into a geometry that favors intramolecular excimer emission, while the other linkers possess too large a number of conformational degrees of freedom to favor folding events.
Lucas, Jeffrey M., "FLEXIBLE TETHERS IN MULTI-CHROMOPHORIC SYSTEMS: LINKING PHOTOPHYSICS WITH ASSEMBLY" (2014). Doctoral Dissertations. 264.