The solid state structure of soluble conducting diblock copolymers of polyacetylene-polyisoprene (PA-PI), before and after I-2-doping, was investigated in this study using scanning electron microscope (SEM) and small angle X-ray scattering (SAXS). The SAXS study demonstrated that I-2-doping of the PA-PI diblock copolymer in the solid state resulted in the formation of a rod-like structure of polyacetylene chains, at the nanometre scale, caused by the strong self-association of the doped polyacetylene segments. On the other hand, the SEM micrographs revealed a doping-induced morphology transformation from a homogeneous state to a phase-separated fibrous network at the micrometre scale reflecting the formation of a pseudo interpenetrating polymer network (PIPN) due to the thermodynamic immiscibility between the I-2-doped polyacetylene ’rods’ and polyisoprene chains. These results indicate that multiphase materials with ordered structures ranging from the nanometre to micrometre scale can be obtained by I-2-doping of the PA-PI diblock copolymers in the solid state. The PIPN network thus formed plays an important role in regulating the electrical properties of the I-2-doped copolymer films.