β-phase formation in a crosslinkable poly(9,9-dihexylfluorene)

The synthesis of a crosslinkable poly(9,9-dihexylfluorene) derivative is reported. Vinyl ether moieties allow for photolithographic patterning, resulting in an immiscible polyfluorene network, which enables subsequent wet thin-film processing. The metastable β-phase morphology, inherent to most polyfluorene homopolymers, can be induced in this crosslinkable polymer. This is verified by optical spectroscopy, X-ray diffraction and by thermal analysis. The β-phase in polyfluorenes is of interest due to its superior optical and electrical characteristics compared to the amorphous phase. Here, amplified stimulated emission is studied. Surprisingly, the β-phase polymer exhibits higher emission thresholds than the amorphous analogue.