Mapping In Situ the Internal Structure and Dynamics of Supramolecular Homopolymers and Copolymers

Supramolecular polymers are assemblies of monomers bonded non-covalently, thereby having potential to emulate the dynamic nature of biological ones such as those in the cytoskeleton, muscle, and extracellular matrices. Understanding the nature of dynamics in synthetic analogues of these assemblies is crucial to develop adaptive and functional biomaterials. Using three positively charged peptide amphiphiles, we introduce here a general base-titration methodology to systematically decrease electrostatic repulsion among monomers and probe in situ polymerization. In one-component systems, we demonstrate that weaker cohesive hydrogen bonding and stronger electrostatic repulsion enhance supramolecular dynamics and shift the assembly equilibrium from elongated polymers to spheroidal micelles. In binary systems, we find a tendency to form blocky copolymers but a reduced level of internal phase separation within the assembly is observed with less mismatch in peptide sequence. Well-mixed systems acquire different dynamics but interestingly mismatched ones retain their characteristic supramolecular motion as homopolymers. These findings provide strategies to tailor dynamics and internal structure in the assemblies of supramolecular materials, factors that can strongly impact on their useful functions.