%0 journal article
%@ 0743-7463
%A Knaapila, M., Evans, R.C., Gutacker, A., Haramus, V.M., Torkkeli, M., Adamczyk, S., Forster, M., Scherf, U., Burrows, H.D.

%D 2010
%J Langmuir
%N 7
%P 5056-5066 
%R doi:10.1021/la903520w
%T Solvent Dependent Assembly of a Polyfluorene−Polythiophene “Rod−Rod” Block Copolyelectrolyte: Influence on Photophysical Properties
%U https://doi.org/10.1021/la903520w
7 
%X We report the solvent-driven assembly of a polyelectrolytic polyfluorene−polythiophene diblock copolymer−poly[9,9-bis(2-ethylhexyl)fluorene]-b-poly[3-(6-trimethylammoniumhexyl)thiophene] (PF2/6-b-P3TMAHT)−in tetrahydrofuran (THF), water, their 1:1 mixture and in subsequently prepared thin films, as investigated using a combination of scattering, microscopic and photoluminescence techniques. In solution PF2/6-b-P3TMAHT forms large (>100 nm) aggregates which undergo a transition from objects with surface fractal interface (THF) to ones with a significant planar component due to the presence of the 2-dimensionally merged ribbon-like aggregates or fused walls of the observed vesicular aggregates [THF−water (1:1)]. In THF−water and water the blocks are loosely segregated into P3TMAHT and PF2/6 rich domains, with PF2/6 dominating the aggregate interior. Depending on solvent, the spun films contain either aggregates with a crystalline interior (THF) or large 200 nm−2 μm vesicular aggregates embedded in a featureless matrix (THF−water and water). Structural variations are concomitant with distinctive solvatochromic changes in the photophysical properties including a color change from deep red (THF) to pale orange (THF−water and water) in solution, a decrease in fluorescence quantum yield with increasing water content, and a shift from photoluminescence of individual PF2/6 blocks (THF) to efficient PF2/6 → P3TMAHT energy transfer (THF−water and water).