Thermal Cycling Reprograms Solution Aggregation and Strain‐Tolerant Charge Transport in Polymer Blends for Stretchable Electronic Films

ABSTRACT Blending conjugated polymers with thermoplastic elastomers (TPEs) is a key strategy for creating stretchable electronics such as solar cells/photodetectors and transistors, yet how realistic thermal cycling reshapes solution‐state aggregation and propagates into film stretchability remain poorly defined. Here, we introduce variable‐temperature solution X‐ray scattering and complementary methods to quantify solution‐to‐solid structural inheritance in three stress‐dissipative polymer blends (SY‐PPV, IDTBT, and PM6 with TPE). By using a multiscale characterization workflow combining X‐ray scattering, microscopy and tensile testing, this study reveals that thermal cycling reprograms the ink nanostructure by relaxing conjugated‐polymer aggregates (decreased Kuhn length) and redistributing the elastomer, producing improved mechanical performance at moderate cycling. After five cycles, films exhibit up to 43% increase in fracture strain relative to uncycled controls, together with reduced modulus and enhanced toughness. Moreover, charge transport becomes more strain‐tolerant, evidenced by improved strain‐stable mobility during stretching. Beyond this window, continued cycling drives domain coarsening and suppresses mechanical and electrical gains. Notably, the PM6/TPE blend exhibits the highest cycling tolerance, correlating with its stronger miscibility. A miscibility‐guided map rationalizes distinct cycling responses and optimal processing window is predicted. These results delineate competing structural evolution pathways and provide transferable guidelines for designing robust stretchable electronics.