Aggregates molecular ordering

Tarek et al. [388] studied a system with some similarities to the work of Bocker et al. described earlier—a monolayer of n-tetradecyltrimethylammonium bromide. They also used explicit representations of the water molecules in a slab orientation, with the mono-layer on either side, in a molecular dynamics simulation. Their goal was to model more disordered, liquid states, so they chose two larger molecular areas, 0.45 and 0.67 nm molecule Density profiles normal to the interface were calculated and compared to neutron reflectivity data, with good agreement reported. The hydrocarbon chains were seen as highly disordered, and the diffusion was seen at both areas, with a factor of about 2.5 increase from the smaller molecular area to the larger area. They report no evidence of a tendency for the chains to aggregate into ordered islands, so perhaps this work can be seen as a realistic computer simulation depiction of a monolayer in an LE state. 

A series of aggregation structures of bilayer forming azobenzene amphiphiles, CnAzoCmN+Br, both in single crystals and cast films was determined by the X-ray diffraction method and uv-visible absorption spectroscopy. From the relationship between chemical structures and their two-dimensional supramolecular structure, factors determining the molecular orientation in bilayer structure were discussed. Some unique properties based on two-dimensional molecular ordering were also discussed. 

Let us begin with the question as to whether chemical process(es) exist which can bring about a spontaneous formation of order and molecular complexity. One answer that immediately comes to mind is self-assembly (polymerization may be the second answer). Many amphophilic molecules, which also include relatively simple molecules such as long-chain carboxylic acids and alkyl phosphates, have the capability to aggregate into ordered structures. 

Advincula RC, Fells E, Park M K. 2001. Molecularly ordered low molecular weight azobenzene dyes and polycation alternate multilayer films aggregation, layer order, and photoalignment. Chem Mater 13(9) 2870 2878. 

The conformation of macromolecules in solution can also be influenced by the molecular order of the solvent itself Benzene, for example, exists as money-roll-type aggregates, whereas CCI4 exhibits no order. An ordered solvent can induce the macromolecular chain to adopt a certain series of conformational diads, at least over short chain segments. 

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