Effect of conformational asymmetry on self-assembly of linear–brush block copolymers

Control over morphology and nanostructure size of linear–linear AB block copolymers is achieved by varying the Flory-Huggins interaction parameter, χ, overall degree of polymerization, N, and composition of the block copolymer, f. For nonlinear AB block copolymers, conformational asymmetry also comes into play as the relative sizes of monomers A and B may induce shifts in phase transitions and thermodynamically favor morphologies with curved interfaces at equal f values. We synthesized a series of linear–brush BCP and explored the effect of conformational asymmetry as function of side-chain length on their self-assembly in bulk. We built the corresponding phase diagrams by small-angle X-ray scattering experiments and found that a subtle variation in side-chain length from 5 to 9 units dramatically changes self-assembly behavior. Our findings were confirmed by coarse-grained simulations. By coupling experiments and simulations we will set out to better understand the molecular underpinnings controlling self-assembly in these systems, which will help to finely tune morphology and nanostructure size at mesoscale through molecular architecture design.