We report the highly controlled synthesis of conjugated random copolymers in a droplet-based microfluidic reactor. Using two optically distinct polymers, poly(3-hexylthiophene) (P3HT) and poly(3-hexylselenophene) (P3HS), a series of highly regioregular random copolymers is generated with physical properties intermediate to those of the parent homopolymers. Analysis by 1H nuclear magnetic resonance spectroscopy reveals the co-polymerisation process to follow ideal Bernoullian behavior.