The monomer 9-[(tert-butyldimethylsilyl)oxy][2.2]paracyclophan- 1-ene (1) is polymerized by Mo(NAr)(CHCMe(2)Ph)(OCMe(CF3)(2))(2) (Ar = 2,6-diisopropylphenyl) in a living manner. Block copolymers containing poly(1) and polynorbornene (poly(NBE)) can be prepared and have narrow polydispersities. Treatment of poly(1) with NBu(4)F produces poly(9-hydroxy[2.2]paracyclophan-1-ene) which dehydrates to poly(p-phenylenevinylene) (PPV) under mild conditions. Block copolymers containing segments of size-specific and defect-free PPV with poly(NBE) of various dimensions can be prepared readily and are soluble in a variety of common organic solvents. These polymers serve as excellent candidates to measure the effect of chain length and frequency of interchain contacts on PPV’s fluorescence quantum yield (Phi(f)). Solution and solid-state quantum yield determinations, coupled to fluorescence lifetime measurements, reveal an acute drop in Phi(f) as the degree of polymerization of the emissive species increases and as the average distance between PPV chains decreases. PPVx-block-poly(NBE)(y) prepared in solution consistently shows larger Phi(f) than material prepared by solid-state dehydration. The poly(NBE) companion block also serves to protect PPV from atmospheric degradation.