Intrachain and interchain complexation of polyacrylic acids bottlebrush chains with Ca2+ in aqueous solutions

In this work, by combing static light scattering (SLS), dynamic light scattering (DLS) and atomic force microscopy (AFM), we have explored how the topological effect influences the intrachain and interchain complexation of polyelectrolytes and divalent ions. First, by a combination of atom transfer radical polymerization (ATRP) and click reaction, two polyacrylic acid (PAA) bottlebrush samples, i.e. PPA 1210 - g -PAA 20 and PPA 2570 - g -PAA 20 , with nearly identical graft density and PAA sidechain length but different backbone lengths, have been prepared. Second, for comparison, a linear sample l -PAA 7710 , with a similar chain size compared to PPA 1210 - g -PAA 20 , has been also prepared. Third, we have systematically investigated the intrachain and interchain complexation between NaPAA topological chains and divalent calcium ions . It is revealed that the intrachain interaction for linear l -PPA 7710 is much stronger than that for bottlebrush samples due to the flexibility feature, while the interchain interaction displays the opposite trend. It is also found that the addition of Ca 2+ results in the change of conformation from loose random coils to dense sphere for l -PAA 7710 , while the overall conformations of PPA 1210 - g -PAA 20 and PPA 2570 - g -PAA 20 almost remain unchange, which can be ascribed to the unique branched structure and enhanced structural rigidity .