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Progress on the phase behavior of organic molecules at the solid/liquid interface
发布人:管理员LI  发布时间:2011-11-24   浏览次数:14

The self-assembly of nanometer-sized building blocks on surfaces and at  interfaces is a powerful way to fabricate complex molecular nanostructures  following the bottom-up principle. Surface-confined two-dimensional (2D)  molecular networks, especially those with void spaces, so-called “2D porous  networks”, attract a lot of interest. These 2D porous networks are used as hosts  to immobilize functional units as guest molecules in a repetitive and spatially  ordered arrangement, and also as platform for the construction of molecular  devices. The size and geometry of the pores, actually nanowells, in the networks  could be easily tailored by adjusting the size and symmetry of the building  blocks as well as the substrate. Among them the networks formed by alkoxylated  dehydrobenzo annulenes (DBAs) via alkyl chain interdigitation represent an  interesting case. The flexibility of the alkyl chains and the weak van der Waals  interactions between them make the supramolecular network quite flexible. These  networks were observed to change their structure not only in response to the  inclusion of ’static’ guest molecules, but also in response to the dynamics of  clusters of guest molecules captured in the nanowells. (CryEngComm, 2010, 12,  3369-3381, Chem. Commun., 2010, 46, 9125-9127).

Molecular recognition at interfaces involves many simultaneous interactions  based on molecular shape, size, functional groups, etc. When a binary mixture is  applied to a interface the recogonition between similar molecule determines the  phase behavior of the mixture. Collaborated with researchers from Katholieke  Universiteit Leuven, Osaka University and Maria-Curie Skłodowska  University professor Shengbin Lei’s group has systematically investigated the  mixing behavior of molecules (DBAs) with different alkyl substituents at the  solid-liquid interface to reveal the phase behavior of complex systems. Scanning  tunneling microscopy and Monte Carlo simulations demonstrate that the phase  behavior of binary mixtures of alkylated DBAs at the solid-liquid interface can  be predicted by the 2D isomorphism coefficient. In addition we also investigated  the influence of coadsorption of template molecules on the phase behavior of DBA  mixtures. Co-adsorption of these molecules significantly promotes mixing of  DBAs, possibly by affecting the recognition between alkyl chains. Monte Carlo  simulations proof that the 2D isomorphism coefficient can predict the phase  behavior at the interface. These results are helpful for the understanding of  phase behavior of complex assembling systems and also for the design of  programmable porous networks and hierarchical architectures at the solid-liquid  interface. (ACS nano, 2011, 5, 4145-4157).