New spiro-functionalized polyfluorenes: synthesis and properties.

The synthesis of several new spirocycloalkane functionalized polyfluorenes is described. Poly[2,7-(9,9-dioetylfluorene)-alt-2',7'-spiro(cyclohexane-1,9'-fluorene)] (PH), poly[2,7-(9,9-dioctylfluorene)-co-2,7'-spiro(cyclohexane-1,9'-fluorene)] (PF2), poly (2',7'-bis[(9,9-dioctylfluoren-2-yl)]-spiro(cyclohexane-1,9'-fluorene)-7,7-diyl] (PF3), poly[2,7-(9,9-dioctylfluorene)-alt-2',7'-spiro(cyclopropane-1,9'-fluorene)] (PF4) and poly [2,7- (9,9-dioctylfluorene)-co-2',7'-spiro(cyclopropane-1,9'-fluorene)] (PF5) were synthesized by Pd(O) and Ni(O) mediated coupling reactions. All polymers were characterized by NMR, UV-vis, DSC-TGA and PL. Efficient prevention of interchain interactions by the spirocyclohexane moieties guarantees pure blue emission from pristine PF1-3 as revealed by solid state PL spectra. On the other hand, solid state PL spectra of PF4 and PF5 are characterized by an additional emission band in the green region. Thermal annealing on PF1-3 at 150degreesC under nitrogen atmosphere does not cause any substantial changes in their solid state PL spectra, whereas after carrying out the same treatment for 20 h at 110 degreesC under air the polymers show a low-energy emissionbandin the green region which is presumably brought about by chemical modifications.