Conformation and aggregation of polyelectrolyte in poor solvents

Understanding the conformation of polyelectrolyte (PE) is not only a fundamental challenge in polymer science but also critical for understanding the folding and aggregation of proteins. Here, we develop a theory by systematically including the electrostatic interactions into the self-consistent field theory for polymers to study the single-chain conformation and multi-chain aggregation of PE in poor solvents. For the single-chain conformation, we find that a stable vesicle structure can exist at an intermediate salt concentration besides the traditional elongated pearl-necklace structure. The structure of the vesicle such as the volume of the interior hole and the thickness of the shell can be fine-tuned by controlling the external stimuli. For the multi-chain aggregation, we find a two-step nucleation to the bulk condensation transition. A metastable spherical cluster intermediate having some preferred size is formed through the first nucleation, but may elongate into rod-like cluster during the the second nucleation for releasing the electrostatic repulsion. This kinetic process may be a very general phenomenon which applies to aggregation of other charged systems such as protein or colloidal particle.