From 09/29/2014 through 4/2/2013
1. “Self-assembly is a type of process in which a disordered system of pre-existing components forms an organized structure or pattern as a consequence of specific, local interactions among the components themselves, without external direction. When the constitutive components are molecules, the process is termed molecular self-assembly.
Self-assembly can be classified as either static or dynamic. In static self-assembly, the ordered state forms as a system approaches equilibrium, reducing its free energy. However in dynamic self-assembly, patterns of pre-existing components organized by specific local interactions are not commonly described as "self-assembled" by scientists in the associated disciplines. These structures are better described as "self-organized".
Self-assembly (SA) in the classic sense can be defined as the spontaneous and reversible organization of molecular units into ordered structures by non-covalent interactions. The first property of a self-assembled system that this definition suggests is the spontaneity of the self-assembly process: the interactions responsible for the formation of the self-assembled system act on a strictly local level—in other words, the nanostructure builds itself.
First, the self-assembled structure must have a higher order than the isolated components, be it a shape or a particular task that the self-assembled entity may perform. This is generally not true in chemical reactions, where an ordered state may proceed towards a disordered state depending on thermodynamic parameters.
The second important aspect of SA is the key role of slack interactions (e.g. Van der Waals, capillary, , hydrogen bonds) with respect to more "traditional" covalent, ionic, or metallic bonds. Although typically less energetic by a factor of 10, these weak interactions play an important role in materials synthesis. It can be instructive to note how slack interactions hold a prominent place in materials, but especially in biological systems, although they are often considered marginally with respect to "strong" (i.e. covalent, etc.) interactions. For instance, they determine the physical properties of liquids, the solubility of solids, and the organization of molecules in biological membranes.
The third distinctive feature of SA is that the building blocks are not only atoms and molecules, but span a wide range of nano- and mesoscopic structures, with different chemical compositions, shapes and functionalities. These nanoscale building blocks (NBBs) can in turn be synthesized through conventional chemical routes or by other SA strategies.”
(Self-Assembly, Wikipedia, 4/2/2013)
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Roger D. Corneliussen
Maro Polymer Links
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Copyright 2013 by Roger D. Corneliussen.
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* Date of latest addition; date of first entry is 4/2/2013.