Transition Kinetics of Self-Assembled Supramolecular Dodecagonal Quasicrystal and Frank-Kasper σ Phases in AB n Dendron-Like Giant Molecules.

A series of noncrystalline AB n dendron-like giant molecules DPOSS-MPOSS n ( n = 2-6, DPOSS: hydrophilic polyhedral oligomeric silsesquioxane (POSS) cage; MPOSS: hydrophobic POSS cage) were synthesized. These samples present a thermodynamically stable phase formation sequence from the hexagonal cylinder phase (plane group of P 6 mm ), to the Frank-Kasper (F-K) A15 phase (space group of Pm 3̅ n ), and further to the F-K σ phase (space group of P 4 2 / mnm ), with increasing the number of MPOSS in a single molecule ( n , from 2 to 6). Moreover, for DPOSS-MPOSS 5 and DPOSS-MPOSS 6 , an intriguing dodecagonal quasicrystal (DQC) structure has been identified and revealed as a kinetic favorable metastable phase at lower temperatures, while the thermodynamically stable phase is the σ phase. The detailed investigation of the transition kinetics between the DQC and σ phase in these samples makes it possible to identify how the self-assembly directs the phase transition in terms of molecular and supramolecular aspects.