AbstractThe polycondensation reaction between telechelic poly(dimethylsiloxanes) and α,ω‐difunctional polystyrenes (or substituted polystyrenes) in toluene solution is very fast, in spite of the heterogeneous nature of the reaction medium. In the first part of the article is reported a qualitative approach of the condensation reaction in relation to the microscopic structure of the reaction medium. The second part is devoted to an investigation of the mechanical and thermomechanical behaviour of the multiblock copolymers which results from intramolecular phase separat