Gradient sequence copolymers, which exhibit a gradual change in comonomer composition along the polymer chain, are classically interesting materials with unique properties. This intriguing gradient sequence typically requires synthesis by controlled/�living� polymerization, which has been limited to electrically insulating polymers, because conjugated materials are traditionally made by uncontrolled step-growth processes. With the advent of controlled chain growth polymerization for conjugated polymers such as polythiophene, we have recently expanded the cannon of gradient sequence copolymers to include pi-conjugated examples for the first time. Sequence plays a subtle but crucial role in the thermal, optical and electronic properties of these new materials, as well modulating their thin film morphology. While alternating, random, and block copolymers have been examined previously as active components in bulk heterojunction solar cells, no examples of pi-conjugated gradient copolymers were available until recently. Our group has shown synthesis of gradient copolymers with different backbone and side chain functionalities. Ultimately, the goal of our program is to incorporate donor-acceptor gradient copolymers into the active layer of bulk heterojunction organic solar cells to demonstrate their impact on morphology and device performance.

Pi-conjugated gradient sequence copolymers

246th National Meeting (2013)

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