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zhuangyujiayou金虫 (小有名气)
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论文翻译---简单（超分子自组装）
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1.3.2 Interactions The most common non covalent interactions involved in self-assembly are the columbic interactions, hydrophobic interactions, hydrophilic interactions, van der Waals forces, π-π stacking and hydrogen bonds. The relatively weak covalent bonds (coordination bonds) can also be considered as appropriate interactions for selfassembly. Self-assembly occur when the components interact with one another through a balance of attractive and repulsive forces. The complementary nature in shapes among the self-assembling components is also considered to be crucial (particularly for recognition). For self-assembly to generate ordered structures, the association (between the components) must either be reversible or must allow the components to adjust their positions within an aggregate once it has formed. The strength of the bonds between the components, therefore, must be comparable to the forces that tend to disrupt them. For molecules, the forces can easily be generated by thermal motion. 17Processes in which collision between molecules leads to irreversible sticking generate glasses and not organized materials. Some of the nanostructures generated by utilizing the use of non covalent interactions particularly for oraganic materials are discussed below in section 1.6.2. 1.3.3 Environment The use of a particular environment is essential to maximize the interactions among the components in order to result in the most stable and organized structure. Most often, the self-assembling process is carried out in liquid environments such as solutions, which acts as the environment to enable the favorable non covalent interactions amongst the components to occur. Interface of two or more solutions are also used in this regard to achieve self assembly of components due the changes in the local environment of the components and often leads to a more ordered state. More recently, the elegant use of surface to organize the molecules (by using solvent vapors) into desired shape has also proven to be useful and is important from a technological stand point.26,27The interaction of the components with the environment affects the self assembling process significantly. In solution, thermal motion provides the major part of the motion required to bring the molecules into contact. At the interface, interactions between the components are maximized because of the drastic changes in the polarity (solubility of the solute/component) of the solvents. At surfaces, depending on the hydrophobic or hydrophilic nature of the molecule and substrate, the interactions between component and substrate can lead to interesting morphological conditions due to self-assembly (essentially the wetting and de wetting of the surface). In all of the above cases, the molecules need to be mobile in order to find the most optimized situation to self-assemble using the non covalent forces of interactions. The key challenge in designing systems for self assembly is to assure the mobility of the components. As the self assembly occurs the Brownian motion that is initially responsible for the mobility of the components in solution becomes extraneous as the self-assembled structure becomes larger than the component. At surfaces, the effective use of thermal and solvent based annealing methods ensures the mobility of the molecules for self assembly to occur. Thus, it is essential to also approach the self assembly with appropriate choice of interaction in the system to establish equilibrium. This leads to two types of self-assembled systems: static and dynamic self-assembly.15 Most of the complex biological self-assemblies are a result of dynamic self-assembly and in principle involves the dissipation of energy. 15While the formation of molecular crystal, folding of the proteins where the formation of the self-assembled structures requires energy are governed by static self-assembly.Most of the self-assembled structures studied under supramolecular chemistry also fall under the static self-assembly as the energy is supplied in the form of stirring in most of the cases. This has indeed leaded to an upsurge to understand the mechanism of self-assembly. Even though numerous examples of self-assembly from a variety of components exist, the mechanisms and the theoretical aspects of self-assembly remain elusive.28 Some of the theoretical efforts to this end have focused on integrating the experimental results with the structural properties of the components in order to establish empirical relationships. 29Theoretical treatments such as “majority rules”30,31 and “sergeant and soldier”32,33principles have emerged to explain the mechanism for chiral assemblies and the helical supramolecular assemblies resulting from both chiral and achiral monomers. The recent mechanistic efforts in self-assembly have focused on understanding the equilibrium processes because of the nature of the self assembly in most systems. Some of the theoretical efforts have thus lead to the emergence of a few “self-association” models depending on the equilibrium process along with the interactions involved. 2011年4月25日之前有效 |
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cam967
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2楼2011-04-19 17:17:53
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【答案】应助回帖
zhuangyujiayou(金币+10): 唉 一般般 2011-04-21 13:47:53
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1.3.2作用力 自组装所包括大多数的非共价作用力包括库伦作用、憎水作用、亲水作用、范德华力、π-π叠加和氢键作用。相对较弱的共价键作用力（络合键）也可看作对于自组装是合适的作用力。通过吸引力与排斥力的相互平衡组分之间相互作用导致自组装的发生，在发生自组装的组分中，较好的互补性质也是至关重要的（尤其对于识别）。自组装产生有序结构，组分之间的联系要么是可逆的，要么一旦自组装形成集合体，组分就能适应其在集合体的位置。因此，组分之间键的强度可以达到几乎能使他们断裂的力度。对于分子，这种作用力很容易由热运动产生。过程17所示，分子之间的碰撞导致不可逆吸附，过程17产生了玻璃状材料而不是具机体构造的物质。在以下1.6.2部分我们会了解到，尤其对于有机材料，一些利用非共价作用力而制备的纳米结构。 |
6楼2011-04-21 11:30:35