In order to investigate the explicit effects of molecular structures with sterically perpendicular configuration on the general properties of fluorene-based polymers for electroluminescent applications

we designed and synthesized three topology-varied linear copolymers

CSSFX

USSFX and DSSFX.The photophysical properties of the copolymers

thermal stability

energy levels and light-emitting properties of annealed thin solid film under different environments were further illustrated step by step.These copolymer materials show relatively high glass transition temperature and thermal decomposition temperature.The introduction of spiro-fluorene-9

9'-xanthene can lower the highest occupied molecular orbital energy level of polymer DSSFX to -3.01 eV and highest occupied molecular orbital of polymer USSFX to -5.93 eV

both of which were slightly changed from those of polymer CSSFX

and the obtained polymer USSFX are expected to show improved hole injection properties.Especially

the thin solid film of polymer USSFX remains to be stable blue light emissive after being annealed at high temperatures in air for long time

and we have established an effective method to improve the spectral stabilites of polyfluorene-based blue light-emitting materials by introducing spiro-fluorene-9

9'-xanthene into their main chains.