Bottlebrush Polymers in the Melt and Polyelectrolytes in Solution Share Common Structural Features

Uncharged bottlebrush polymer melts and highly charged polyelectrolytes in solution exhibit correlation peaks in scattering measurements and simulations. Given the striking superficial similarities of these scattering features, there may be a deeper structural interrelationship in these chemically different classes of materials. Correspondingly, we constructed a library of isotopically labeled bottlebrush molecules and measured the bottlebrush correlation peak position q* = 2π /ξ by neutron scattering and simulations. We find that the correlation length scales with the backbone concentration, ξ ~ c_BB^−0.47, in striking accord with the scaling of ξ with polymer concentration c_p in semi-dilute polyelectrolyte solutions ( ξ ~ c_p^−1/2 ). The bottlebrush correlation peak broadens with decreasing grafting density, similar to increasing salt concentration in polyelectrolyte solutions. ξ also scales with sidechain length to a power in the range of 0.35 to 0.44, suggesting that the sidechains are relatively collapsed in comparison to the bristle-like configurations often imagined for bottlebrush polymers.