Magnetic Field Alignment of Rod-Coil Block Copolymers and Identification of Liquid Crystalline Orientation

Conjugated rod-coil block copolymers are potentially useful for a number of optoelectronics applications, but properties rely strongly on the orientation of both the conjugated rods and of the nanodomains. Here, a magnetic field was used to control the self-assembly of a model conjugated rod-coil block copolymer (poly(alkoxyphenylenevinylene-b-isoprene) such that the rods align with the field direction. After alignment, the samples were re-annealed below the microphase order-disorder transition temperature to allow equilibration of the rod orientation within the lamellar nanodomains. Small angle and wide angle X-ray scattering simultaneously determine the rod tilt relative to the lamellar normal. Rods were found to be parallel to the lamellar normal for coil fractions of 42-85 percent at all temperatures below the microphase order-disorder transition temperature. The orientation of the rod blocks in rod-coil block copolymers impacts carrier transport and optical properties in organic electronic devices, making the control of rod orientation necessary for device optimization.