Structure and dynamics of complex random heteropolymers

Random heteropolymers (RHPs) have been a theoretical model system to understand properties of proteins and other sequence-defined polymers. In real life, RHPs have been used to tailor the properties of plastics and solutions for different applications. Recently, however, a new class of complex synthetic RHPs has displayed protein-like properties, which in turn has reinvigorated our imagination of what is possible with RHPs. In this talk, we will present our work on the atomistic structure and dynamics of a class of complex random heteropolymers composed of 4 or more chemically distinct monomers. Our work shows that these polymers display protein-like properties in terms of having a heterogenous surface, frozen backbones, and complex unfolding behavior. These results are also dependent on the backbone chemistry and medium. In the melt state, RHPs display a subtle glass transition, which can be tuned by the composition as well as the chemistry of the counterions. Their adsorption propensity to interfaces is also of much interest. Here we find that their adsorption potential is strongly dependent on temperature due to energy barriers in the reorganization pathway, yet one can accelerate the process by orders of magnitude with minimal amounts of “molecular plasticizers” or by working at liquid-liquid interfaces. To end this talk we will discuss our findings in light of different important applications where such RHPs may be of use.