Electrostatic Mediation in Synthesis of Single-Chain Nanoparticles in Concentrated Solutions

Rational design and large-scale synthesis of polymer single-chain nanoparticles (SCNPs) via intramolecular cross-linking of polymers in concentrated solutions is of great significance in polymer and nanomaterials science. It is urgently required to develop methods to suppress intermolecular cross-linking in highly concentrated polymer solutions. Yang et al. have recently proposed a novel effective method of electrostatics-mediated intramolecular cross-linking of polymer single-chains in concentrated solutions. Herein, we develop a scaling theory and perform large-scale dissipative particle dynamics simulation to elucidate the key role of electrostatic mediation in the intramolecular cross-linking. Specifically, the effectiveness of electrostatic repulsion, hence electrostatic mediation, is confirmed, which exhibits a nonmonotonic dependence on electrostatic strength. The effectiveness is enhanced to the maximum when the electrostatic strength is increased to the transition boundary between the weak and strong electrostatic coupling regimes. Such nonmonotonic behavior is attributed to the onset of counterion condensation to suppress the formation of SCNPs under strong electrostatic coupling conditions. The current finding helps to further understand the electrostatic mediation and guides the design and large-scale synthesis of SCNPs in concentrated solutions.