Scattering from Melts of Combs and Bottlebrushes: Molecular Dynamics Simulations, Theory and Experiments.

We combine coarse-grained molecular dynamics simulations, random phase approximation (RPA) theory, and scattering experiments to establish correlations between the peak position q* in structure factor S(q) and architecture of graft copolymers with miscible and immiscible backbones and side chains in melts and networks. For copolymers with side chain degree of polymerization n_sc grafted every n_g repeat units of the backbones, analysis of the scattering functions for systems with miscible backbones and side chains shows that q^* first increases as side chain grafting density decreases, then begins to decrease. This behavior agrees with scaling laws q^*∝n_sc^-3/8and q^*∝(n_gn_sc)^-1/4 derived in the framework of RPA theory for high and low side chain grafting densities, respectively.  For copolymers with immiscible backbones and side chains, the peak position moves monotonically towards smaller q values with decreasing the side chain grafting density reflecting growth of microphase separated domains. At high grafting densities, steric repulsion between side chains suppresses backbone aggregation, resulting in copolymer conformations like those in systems with miscible backbones and side chains.