Here we present the kinetics on the polymerization of poly(9,9-dioctylfluorene) using the Grignard metathesis method (GRIM). By adjusting the reaction conditions, we observed a chain-growth mechanism evidenced by the relatively high molecular weight polymer produced early in the reaction. Well-defined fluorene polymers with average molecular weights of about 10 kDa and with PDI values <1.2 have been produced. We have also found that under certain conditions end-capping of the polymer chain can be obtained. Using these conditions, we have also been able to synthesize two new block copolymers, poly(9,9-dioctyltluorene)-b-poly(3-hexylthiophene) (PF8-b-P3HT) and poly(9,9-dioctylfluorene)-b-poly(1,4-dioctyloxyphenylene) (PF8-b-PPP), that have been produced through chain extension by monomer addition.