Stretchable semiconductors are vital for the development of emerging electronic biointerfaces. The physical blending of polymer semiconductors into elastomers presents a promising and straightforward method for creating stretchable films with high charge carrier mobilities. However, the understanding of the interplay between film morphology and the associated mechanical and electronic characteristics in blends is still limited. Especially, investigations into the blending behavior of more complex conjugated polymers, such as block copolymers, are lacking. In this study, we investigate the blending behavior of two semiconducting and stretchable triblock copolymers (TBCs). These copolymers comprise a middle block of poly(diketopyrrolopyrrole-co-thienothiophene) (PDPP-TT) and two outer blocks of poly(dimethylsiloxane) (PDMS) with different block-size ratios (85:15 and 40:60). The TBCs are blended into a crosslinked PDMS matrix. The resulting blends exhibit superior stretchability compared to the PDPP-TT homopolymer and retain their electric properties down to 40% PDPP-TT content in the blend. Increasing the PDMS block size inhibits macrophase separation and results in drastic decrease in charge carrier mobility, suggesting the necessity for macrophase separation within TBC/elastomer blends to maintain superior electric properties.