Chains are more flexible under tension.
Chains are more flexible under tension.
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DOI：
10.1021/ma101860t
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发表时间：
2010-11-09
期刊：
影响因子：
5.5
通讯作者：
Rubinstein M
中科院分区：
文献类型：
--
作者：
Dobrynin AV;Carrillo JM;Rubinstein M
网络、凝胶和刷状层的机械响应是单个大分子的弹性性质的表现。此外，大分子对外力的弹性响应是单分子力谱技术的基础。描述链弹性的两类主要模型包括蠕虫状链模型和自由连接链模型。这两类模型之间的选择是基于对链柔性的假设。在许多实验情况下的选择是不明确的，因此，这两个限制类之间的交叉描述模型的需求很高。我们提出了一个统一的链变形模型，该模型用链弯曲常数K和键长B来描述力-变形曲线。该模型表明，蠕虫状和自由连接的链模型对应于两个不同的制度的聚合物变形和这两个制度之间的交叉依赖于链的弯曲刚度和所施加的力的大小。弯曲常数K>1的高分子链在外力f ≤ KkBT/B范围内表现为受拉的蠕虫状链，当f ≥ KkBT/B时表现为自由连接链（kB为玻尔兹曼常数，T为绝对温度）。建议的交叉表达链变形的分子动力学模拟的结果和单分子变形实验的生物和合成的大分子链变形是非常一致的。
The mechanical response of networks, gels, and brush layers is a manifestation of the elastic properties of the individual macromolecules. Furthermore, the elastic response of macromolecules to an applied force is the foundation of the single-molecule force spectroscopy techniques. The two main classes of models describing chain elasticity include the worm-like and freely-jointed chain models. The selection between these two classes of models is based on the assumptions about chain flexibility. In many experimental situations the choice is not clear and a model describing the crossover between these two limiting classes is therefore in high demand. We are proposing a unified chain deformation model which describes the force-deformation curve in terms of the chain bending constant K and bond length b. This model demonstrates that the worm-like and freely-jointed chain models correspond to two different regimes of polymer deformation and the crossover between these two regimes depends on the chain bending rigidity and the magnitude of the applied force. Polymer chains with bending constant K>1 behave as a worm-like chain under tension in the interval of the applied forces f ≤ KkBT/b and as a freely-jointed chain for f ≥ KkBT/b (kB is the Boltzmann constant and T is the absolute temperature). The proposed crossover expression for chain deformation is in excellent agreement with the results of the molecular dynamics simulations of chain deformation and single-molecule deformation experiments of biological and synthetic macromolecules.
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