Surface chain dependent arrangement and self-assembly of polyhedral oligomeric silsesquioxane for supramolecular gels

In this study, a series of amino acid grafted inorganic/organic hybrid POSS (Cn@POSS) were designed and synthesized. In order to investigate the surface chain dependent arrangement and self-assembly of POSS in supramolecular self-assembly, the molecular stacking, gelation abilities, thermal stability, morphology and mechanical properties of Cn@POSS gels were evaluated. From the obtained self-assembly mechanism of hybrid POSS, we discovered that the arrangement of hybrid POSS regularly stacking on a hexagonal columnar pathway and assembled into fibrous networks to form the gel in colloid self-assembly. The peripheral segments on the surface of hybrid POSS in a loosely extended state instead the collapse which provide a better position for the closely stacking and oriented aggregation of POSS. As the hierarchical assembled fibrous network, the length of surface chain (L-s) induced bending of assembled nano-fibers helps the efficient gelation by entanglement of surface chains, but weaken the self-recovery of gels. In contrast, in bulk self-assembly, the stacking of hybrid POSS were obviously affected and perturbed by the length of surface chain, with the shorter L-s the closer packing of POSS. This fundamental research helps the understanding of hierarchical self-assembly behaviours of nano-building block POSS in supramolecular gels and inspire the discovering on the applications of POSS based organic-inorganic hybrid molecules in functional soft materials.