Metastable Globules in Good Solvents: Topologically Stabilized State of Polymers

A novel state of polymers in solution is proposed. It is suggested that macromolecules which are initially collapsed in a poor solvent maintain a long-lived, partially collapsed conformation upon a fast temperature jump into the good-solvent regime. This metastable state is stabilized by topological constraints, i.e. tight intra-molecular knots. The number of tight knots and the tensile forces which generate them are related to experimentally observable quantities such as the radius of gyration and the relaxation time of the partially swollen globule. An experimental test of the theoretical prediction is proposed, including an analysis of the role of control parameters such as degree of polymerization, chain flexibility and the depth and kinetics of the temperature quenches.