Bottlebrushes and Combs With Bimodal Distribution of the Side Chains: Scattering Function

We use a combination of the Random Phase Approximation (RPA) calculations and coarse-grained molecular dynamics (CGMD) simulations to study scattering from melts of graft polymers with bimodal distribution of the side chains. The chemical structure of this type of graft polymers is described by grafting density of side chains 1/n_g, fraction of short side chains f, and degree of polymerization (DP) of the short (n_sc,1) and long (n_sc,2) side chains into combs and bottlebrushes. The evolution of the peak position in the static structure factor S(q) obtained in these simulations is analyzed by using the expression for S(q) derived in the framework of RPA. In the bottlebrush regime, the peak position in the scattering function is shown to scale as q^*∝〈n_sc〉^{−0.39±0.03} with the number average DP of the side chains〈n_sc〉, which is in good agreement with the result of the RPA calculations, q^*∝〈n_sc〉^−3/8. However, this is a weaker dependence than one expected for q^* to be associated with the inter-backbone distance, q^*∝〈n_sc〉^−0.5. The results of the CGMD simulations and RPA calculations for the peak position scaling with the DP of the side chains are in a very good agreement with scattering data from melts of bottlebrushes with acrylate and norbornene backbones.