PPV dimer based copolymers were synthesized to investigate their applicability to the microcavity device. The blue emitting copolymers consist of strictly alternating conjugated PPV dimer unit and non-conjugated alkyl group. Two microcavity devices based on distributed Bragg reflector (DBR) and the spin-coated copolymer thin film show promising lasing characteristics. The gain narrowed blue emissions at 374.5 and 428.5 nm with 3.0-4.2 nm linewidth were obtained and those are the lowest wavelength among the devices based on PPV derivatives. N-2 laser (337 nm) was used as a pulsed pump source and their lasing thresholds were around 0.3-1 microjoules. The lasing characteristics strongly depended on the microcavity structure and the copolymer film processing. Q factor of each devices were calculated to be 120 and 102, respectively. The stability of the copolymer under UV excitation was excellent that the devices have the operational lifetime of over 3 x 10(5) pulses at 10 mu J.