The physical processes leading to solvent swelling induced glassy- to beta-phase transition in poly(9,9-dioctylfluorene) thin films are investigated in real time by photoluminescence and confocal spectroscopy. We show that the vapor solvent swelling induced beta-phase formation takes place in much shorter times (few minutes) than the one usually employed in literature (several hours). Moreover, we show that the swelling is faster if the solvent mainly interacts with the PF8 aromatic rings (toluene) than with the octyl chains (isooctane). On the contrary, no swelling is caused by nonsolvents such as n-butylic alcohol. Finally, we demonstrate that the beta-phase formation is due to athermal (simultaneous) nucleation followed by diffusion controlled one dimensional crystallization.
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