Highly Anisotropic Rigidity of ``Ribbon-like'' Polymers: I. Chain Conformation in Dilute Solutions
Highly Anisotropic Rigidity of ``Ribbon-like'' Polymers: I. Chain Conformation in Dilute Solutions
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“带状”聚合物的高度各向异性刚性：I.稀溶液中的链构象
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发表时间：
1996
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影响因子：
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通讯作者：
A. Khokhlov
中科院分区：
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作者：
I. Nyrkova;I. Nyrkova;A. Semenov;J. Joanny;A. Khokhlov
我们讨论了具有高度各向异性刚性的聚合物的溶液性质，这些聚合物在平面（主要柔性平面）内相当自由地弯曲，并且在垂直于该平面的方向上极其刚性。这些聚合物的例子是最近合成的梯形聚合物或由肽棒状片段聚集形成的活性聚合物。这些聚合物具有比它们的面内余辉长度l高得多的面外余辉长度l2。在本系列的第一篇文章中，我们主要研究了单链在溶液中（极低浓度）的构象。具有高度各向异性刚性的孤立链的构象基本上取决于无量纲参数Ω= l2 d2 l-3，其中d是链直径。对于小的Ω，（l2 <$l），链表现为具有各向同性刚度的标准半柔性链。当$\Omega，（\Omega \gtrsim 1）$较大时，链在长度尺度小于l时呈一维棒状构象，在中间尺度（对应于轮廓长度L，使得$l\lesssim L \lesssim l_2$）时呈各向异性盘状构象，在较大长度尺度时呈三维溶胀卷曲构象.在$\Omega，l^2/d^2\lesssim \Omega\lesssim 1$的中间范围内，预期有相同的三个区域，但排除的体积相互作用在盘状区域中不起任何作用。在本文的最后，我们定性地讨论了可能的液晶相（与近晶或近晶对称），可以出现在这些解决方案中，在较高的浓度。
We discuss the solution properties of polymers with a highly anisotropic rigidity which bend rather freely in a plane (the plane of main flexibility) and are extremely rigid in the direction perpendicular to this plane. Examples of these polymers are the ladder polymers recently synthesized or living polymers formed by the aggregation of peptide rodlike fragments. These polymers have a much higher out of plane persistence length l2 than their in-plane persistence length l. In the first paper of this series, we mostly inverstigate the conformation of single chains in solution (at extremely low concentrations). The conformation of an isolated chain with a highly anisotropic rigidity essentially depends on the dimensionless parameter Ω= l2d2l-3 where d is the chain diameter. For small values of Ω, (l2∼l), the chain behaves as a standard semiflexible chain with isotropic rigidity. For large values of $\Omega, (\Omega \gtrsim 1)$, the chain adopts a one-dimensional rodlike conformation at length scales smaller than l, an anisotropic disc-like conformation at intermediate scales (corresponding to a contour length L such that $l\lesssim L \lesssim l_2$) and a three-dimensional swollen coil conformation at larger length scale. In the intermediate range of $\Omega, l^2/d^2\lesssim \Omega\lesssim 1$, the same three regimes are expected but the excluded volume interactions do not play any role in the disc-like regime. At the end of the paper we discuss qualitatively the possible liquid crystalline phases (with nematic or smectic symmetry) which can emerge in these solutions at higher concentration.