Bond-Reversibility Effects on Self-Crowding of Unimacromolecular Nano-Objects

The scaling behavior of linear chains with reversible bonds and, in particular, its dependence on the concentration are fundamental problems of polymer physics that are not fully understood. By means of small-angle neutron scattering we investigate the conformations of reversibly bonding polymers from high dilution (where they form unimacromolecular nano-objects, usually known as single-chain nanoparticles) to crowded solutions and bulk state far above the overlap concentration (where they are expected to form a dynamic polymer network). Unlike the cases of simple linear chains with no bonds and of chains with strictly intramolecular irreversible bonds, no shrinkage is found, and the size and scaling exponent of the reversibly bonding polymers are essentially unperturbed by crowding. This is a relevant result that confirms the negligibility of many-body effects beyond the overlap concentration in crowded systems of reversibly bonding polymers and the validity of ultrasoft effective interactions for predicting their structural and phase behavior.