AbstractWell‐defined poly(4,4′‐isopropylidenediphenyl carbonate)‐block‐polystyrene multiblock copolymers, PC‐b‐PS, were prepared by condensation of PC prepolymers having chloroformyl end‐groups with PS prepolymers having hydroxyl end‐groups. Both prepolymers had narrow molecular weight distribution (PC prepolymer:M̄w/M̄n≤ 1,31, PS prepolymer:M̄w/M̄n≤ 1,03). The course of the polycondensation reaction depends on the molecular weight of the prepolymers used as substrates. After fractionation, the obtained multiblock copolymers are homogeneous in chemical composition and have a narrow molecular weight distribution. The mechanical properties of the copolymers depend on the weight fraction of the PS blocks. All copolymers exhibit two glass transition temperatures, close to those o