Hybrid Polymer Blends Covalent And Supramolecular Components

By combining monomers that form a covalently linked polymer with a monomer that assembles noncovalently into a supramolecular polymer, researchers have created a novel soft material that’s distinct from the forms these monomers take on their own. The new hybrid structure, created by Samuel I. Stupp and colleagues at Northwestern University, can be partially disassembled and reassembled on demand, creating a material that could have applications in drug delivery and self-healing materials (Science 2016, DOI: 10.1126/science.aad4091). The covalent portion of the material is based on an aromatic dialdehyde and an aromatic diamine. The aromatic groups of both monomers are attached to a hydrocarbon chain followed by several amino acids. When combined, these two monomers form an asterisk-like structure that has side chains protruding from a core made from a helical polymer with a rigid aromatic imine backbone. The noncovalent portion of the hybrid material is made up of the same hydrocarbon and amino acid chain as in the covalent monomers. These noncovalent monomers combine with the dialdehyde and diamine monomers to form a rodlike structure, supramolecularly filling in the spaces between the side chains of the asterisk. This supramolecular portion of the polymer can be removed via dialysis and added back to deliver drugs or repair larger structures.