Establishing the Independent Tunability of the Diffusive and Mechanical Properties of AB/ABA Block Copolymer Organogels

Physically cross-linked organogels are a unique class of polymeric materials, possessing many advantages over other widely studied polymer gels. Such advantages include facile reprocessiblity and the ability to endure repeated mechanical stress (fatigue). Further development of physically cross-linked organogels could lead to numerous applications including novel drug-delivery materials and musculoskeletal tissue replacements. It is reasonable to hypothesize that work conducted on physically cross-linked organogels can be applied to other materials with the resulting advances benefiting both the material science and polymer science communities. Organogels which use styrenic block copolymers represent a promising class of physically cross-linked organogels. The work conducted herein uses facile changes in the formulation of physically cross-linked styrenic AB/ABA block copolymer organogels to establish the independent tunability of their mechanical properties and facilitated diffusion of nanoscale probes. Such independent tunability is made possible by altering the ratio of triblock to diblock copolymer while maintaining a constant overall polymer composition. When changing the ratio of triblock to diblock copolymer, diffusion (which is dependent on overall obstructive mass) remains largely unchanged, while the mechanical properties of the gel change due to changes in the connectivity of the gel’s nanostructure. Small angle x-ray scattering (SAXS) shows that the only aspect of the gel’s nanostructure that is changing is the connectivity, and it is the change in connectivity at constant total polymer content which allows for the independent tunability to be achieved.