Two phosphonate-functionalized, side-chain modified copolymers were synthesized by utilizing either a Yamamoto or a Suzuki protocol, correspondingly. The copolymers' backbones were comprised of 2,7-dibromo-9,9-bis(6-bromohexyl)-9H-fluorene and 2,7-dibromo-9,9-dioctyl-9H- fluorene or 2,2′-(9,9-dioctyl-9H-fluorene-2,7-diyl)bis(1,3,2- dioxaborinane), respectively. These precursor polymers were subjected to a post-functionalization using triethyl phosphite and the resulting target copolymers were fully characterized. The optical classification parameters were determined in solutions and in films as well. The copolymers revealed blue light emission with wide optical bandgaps Egopt of 2.93 eV and quantum yields of 0.54 in chloroform solutions. After following a precipitation method, facilitated by means of an ultrasonic bath, stable dispersions of copolymer microparticles in water were achieved. These particles revealed bright and stable emission with colors ranging from blue to white, only depending on the catalysis method applied. Note the quantum yields beneficially increase up to 0.84 due to the particle formation. Additionally, the combination of the copolymers with semiconductor CdTe nanocrystals, applying again the ultrasonic bath-precipitation method, allowed the formation of copolymer-CdTe composites, furthermore usefully tuning their emission intensity and color differing from the original colors of the involved partners.