Pathway-dependent properties of a multi-stimuli sensitive biosynthetic hybrid network

We study the self-assembly of an asymmetric triblock copolymer consisting of an elastin-like and a silk-like block bridged by a hydrophilic spacer. The elastin-like block aggregates at high temperature, leading to thermo-reversible micellization. The silk-like block self-assembles at low pH, and forms long fibrils, which dissociate again at high pH. The self-assembly of both blocks is strongly enhanced by increasing the salt concentration. When two blocks are sequentially triggered to self-assemble, the reversibility is lost; the final morphology and mechanical properties depend on the pathway that is chosen. A micellar solution formed at high temperature transforms into a gel network of sticky fibrils when the pH is lowered. Heating a solution of fibrils, formed at low pH, leads to the irreversible formation of bundles and large aggregates.