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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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2楼2011-04-19 17:17:53
zhuangyujiayou
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3楼2011-04-19 17:19:34
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4楼2011-04-19 17:19:45
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5楼2011-04-19 17:20:52
slz146
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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
slz146
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7楼2011-04-21 13:05:33
slz146
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8楼2011-04-21 19:52:35
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9楼2011-04-21 22:22:39
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LZ,下面的材料是我逐字逐句翻译出来的。请检验之。 1. 相互作用 分子自组装中最常见的非共价键相互作用包括库伦力、亲水作用、疏水作用、范德华力、π-π堆积和氢键。相对较弱的共价键也是一种分子自组装相互作用。当分子组成元件之间吸引和排斥作用达到相互平衡时,就会产生分子自组装分子组成元件具有形状上的互补特点对于发生分子自主装是至关重要的(尤其对于识别)。分子组成元件之间的相互作用必须是可逆的、或者形成分子集团时能够调整相对位置,这样才能形成有序结构。分子组成元件之间的作用力必须与破坏分子结构的作用力相当。对于分子而言,热运动很容易产生这种作用力。分子经过1反应、碰撞不可逆接触产生玻璃而不能形成有序材料。利用非共价作用产生的一些纳米结构,尤其是有机材料的纳米结构在下文1.6.2部分进行了讨论。 2 环境 特殊环境对于分子相互作用最大化从而产生最稳定、最有序的结构是最基本的要求。通常情况是,分子自组装过程是在液体环境中进行,比如溶液。溶液作为组装环境对于分子组成元件之间非共价作用发生是有利的。两种或多种溶液的界面处也可实现分子自组装。这是因为局部环境的改变常常有利于形成更稳定的状态。最近,从技术角度讲,巧妙利用界面组装分子(通过溶剂蒸发)使其形成目标性状非常有用、也非常重要。在(特定)环境中分子组成元件的相互作用显著的影响分子自组装。在溶液里,热运动是分子发生接触的主要作用力。 在界面上,溶剂极性(溶剂/组分的可溶性)的剧烈变化使得相互作用达到最大化。在不同界面,根据分子和底物的亲水性和疏水性,由于分子自主装分子元件和底物的相互作用能够形成有趣的形态状态。上述所有情况下,分子必须能够运动才能找到最优位置从而通过非共价作用实现分子自主装。设计分子自主装系统最关键的挑战是确保分子组成元件的运动性。当发生自主装时,负责溶液中分子运动的布朗运动成了外部运动,因为分子自组装形成了比分子元件更大的分子。在界面上,热运动和溶剂退火法的高效利用确保了分子的运动性。 因此,自组装系统内选择恰当的相互作用实现平衡对于分子自组装是必须的。有两种分子自组装系统:静态系统和动态系统。大多数复杂的生物学分子自组装是基于动态自组装、能量耗散的。形成分子晶体时,需要消耗能量的蛋白折叠是静态分子自组装控制的。超分子化学里面研究的大多数自组装结构都属于静态分子自组装,需要以扰动的方式提供能量。这也形成了研究分子自组装机理的高潮。虽然各种多样的分子元件能够形成分子自组装,但是分子自组装的机理和理论问题还没有弄清楚。目前的理论研究试图整合实验结果和分子元件的结构性质,从而建立起经验上的联系。理论模型,比如“主要角色”“军士-士兵”模型的提出解释了手性单体和非手性单体是怎样形成手性组装和螺旋超分子组装的。鉴于大多数分子自组装的本质,最近分子自组装的机理研究集中于理解平衡过程。一些理论研究根据平衡过程提出“自解离”模型。 |

10楼2011-04-22 11:35:47













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