Controlling polymer shape through the self-assembly of dendritic side-groups
Controlling polymer shape through the self-assembly of dendritic side-groups
复制标题
DOI：
10.1038/34384
复制
发表时间：
1998-01-08
期刊：
影响因子：
64.8
通讯作者：
Sheiko, SS
中科院分区：
文献类型：
--
作者：
Percec, V;Ahn, CH;Sheiko, SS
聚合物的链构象在控制其相行为和相关材料性质方面起着重要作用。在柔性聚合物的情况下，构象由聚合度（DP）控制，其中低DP聚合物具有延伸的聚合物链，而高DP聚合物在溶液和本体无定形状态（1）中采用无规卷曲构象，在结晶相中采用折叠构象（2）。遵循这一一般规则的是含有结构刚性结构单元的聚合物，或者在固化过程中经受定向剪切力的聚合物。例如，半柔性和刚性棒状聚合物的主链总是在液晶和结晶相中延伸（3-5），并且凝胶纺丝柔性聚合物形成延伸链晶体（2）。在这里，我们报告了一个一般的战略，合理控制聚合物的构象，通过自组装的准等效单枝晶在低DP下，圆锥形单树枝状单元组装以产生具有无规卷曲骨架构象的球形聚合物。在增加DP时，单树枝状单元的自组装模式改变以产生具有延伸骨架的圆柱形聚合物，聚合物构象和DP之间的这种相关性与大多数合成和天然大分子中所见的相反。我们预计，我们的策略将在诸如纳米技术、功能膜和纤维、分子器件和膜等领域为有组织的超分子材料的合理设计提供新的方法（6-9），扩展树枝状结构单元的合成和技术用途（7，10-15）。
The chain conformation of polymers plays an important role in controlling their phase behaviour and associated material properties, In the case of flexible polymers, conformation is controlled by the degree of polymerization (DP), with low-DP polymers having extended polymer chains and high-DP polymers adopting random-coil conformations in solution and the bulk amorphous state(1), and folded conformations in the crystalline phase(2). Exceptions to this general rule are polymers that contain structurally rigid building blocks, or that are subjected to directional shear forces during solidification, The backbones of semi-flexible and rigid rod-like polymers, for example, are always extended in liquid crystalline and crystalline phases(3-5), and gel-spun flexible polymers form extended-chain crystals(2). Here we report a general strategy for the rational control of polymer conformation through the self-assembly of quasi-equivalent monodendritic (branched) side-groups attached to flexible backbones, At low DPs, the conical monodendrons assemble to produce a spherical polymer with random-coil backbone conformation, On increasing the DP, the self-assembly pattern of the monodendritic units changes to give cylindrical polymers with extended backbones, This correlation between polymer conformation and DP is opposite to that seen in most synthetic and natural macromolecules, We anticipate that our strategy will provide new approaches for the rational design of organized supramolecular materials(6-9) in areas such as nanotechnology, functional films and fibres, molecular devices, and membranes, expanding the synthetic and technological uses of dendritic building blocks(7,10-15).