Structural Analysis Of Bottlebrush Block Copolymer Micelles Using Small-Angle X-Ray Scattering

We present structural analysis of spherical diblock copolymer micelles where core blocks have bottlebrush architecture. The dependence of the core radius (R-core) and the corona thickness (L-corona) on the core block length (N-core) is investigated using small-angle X-ray scattering (SAXS) and discussed in terms of the stiffness of a core-forming polymer posed by its long fluoroalkyl side chains. The conformation of the core block is strongly stretched, and the measured exponents a and beta from power-law correlations, R-core similar to N-core(alpha) and L-corona similar to N-core(beta), respectively, are greater than those from any scaling predictions for block copolymer micelles with a flexible, linear core-block. Such deviations are attributed to the appreciable chain stiffness of the bottlebrush core block, and a simple model is suggested to understand how the core block stiffness influences both the dimensions of core and corona.