Chain-Length Induced Structural Polymorphism for two-dimension self-assembly

Abstract

Structural polymorphism obtained through the 2D self-assembly which was made use of the chain-ength induced, has has aroused wide concern. On the one hand, owing to its significance meaning in crystal engineering, on the other hand, it has a broad application prospect in nano science and technolog.The assembly of symmetric 2, 7-bis (n-alkoxy) -9-fluorenone(F-OCn) with varying lengths of peripheral alkyl chains dissolved in homologous acids was investigated. The size and shape of molecules and the structure and position of substituents were critical factors that regulate the equilibrium of the interaction and formation of self-assembled patterns. Useing altered the symmetry and chain-length of the molecular structure, the self-assembly morphology and cellular properties can be predicted. The self-assembled strcture displayed the assembly of F-OCn (11-14). “S” shaped and alternating phases are the thermodynamic stable states. The competition between van der Waals forces from the interdigital alkyl chains and van der Waals forces between molecule-substrate takes effect. The vdW forces between the molecule-substrate was predominant when n varies from 15 to 18. The observation of the chain-length effects and odd-even effects showed that: F-OCeven developed from a loose-and close-packed patterns to a dislocated zigzag patterns.Self-assembled morphology of F-OCodd evolved from a well-distributed trimer monolayer to the dislocated zigzag pattern.These researches offers insight into the structural diversity by regulating the alkyl side chain-length and odd-even effects on two-dimension self-assembly and the construct a new molecular materials.