Increased Toughness and Excellent Electronic Properties in Regioregular Random Copolymers of 3‐Alkylthiophenes and Thiophene

Lightweight, flexible, low-cost, and disposable electronics have transformed modern life and promise to continue to drive a diversity of applications from defense to medicine. For flexible and stretchable devices, the mechanical demands are actually quite great, requiring a material to maintain its ability to undergo elastic deformation, in both tension and compression, through many cycles of deformation. Traditional electronics are fabricated using organic semiconductors, which offer excellent electronic performance, but are often stiff and brittle. Conductive polymers offer potential for electronic materials with high toughness and an ability to deform elastically, making inexpensive, flexible electronics possible in a way no other material can. This paper reports the bulk thermal, electronic, and mechanical properties of a series of conductive polymers based on regioregular poly(3-alkylthiophenes) (P3ATs) with randomly incorporated polythiophene (PT) in 3:1 (P3AT3-ran-PT1) and 1:1 (P3AT1-ran-PT1) ratios. These random copolymers are synthesized with no added synthetic complexity with respect to the homopolymer, and reproducibly give polymers with dramatically different mechanical and electronic properties. It is shown that random incorporation of the unsubstituted thiophene results in conductive polymers with excellent electronic properties (conductivities up to 500 S/cm, mobilities up to 0.11 cm2 V−1 s−1) and enhanced toughness (up to 760% improvement).