Environment dependence of single polymer chain stretching and application to molecular spring

单链聚合物链拉伸的环境依赖性及其在分子弹簧中的应用

基本信息

批准号：
12650886
负责人：
KIKUCHI Hirotsugu
金额：
$ 2.56万
依托单位：
Kyushu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12650886/
关键词：
single chain entropic elasticity Langevan function freely-jointed chain

项目摘要

It is well known that a restoring force by entropic elasticity is acted on the ends of a polymer chain upon stretching a flexible poly* chain in a random coil state. The atomic force microscope (AFM) has enabled direct stretching measurement for single polymer chains * which both the ends of a polymer chain could be adsorbed at an AFM probe tip and substrate surfaces. In this study, an entro* elasticity of a stretched single polystyrene chain was directly measured with AFM in a dilute solution of mono-disperse polystyrene(* and the relationship between applied force and end-to-end distance of PS chain with different molecular weights was investigated.Each end of mono-disperse PS was modified with a carboxyl group which can form a linkage to an amino group on the surfaces * probe tip and a substrate. The shape of the force-distance curve could be explained by the model of freely jointed segments which * elastically deformable during stretching. The magnitude of the maximum stretching fo … More rce ranged 200-500 pN, which could correspo* to the breaking force of hydrogen bonding formed between a PS chain end and the probe tip or the substrate surface. The maxim* extension was found to be longer with increasing molecular weight. The average of the experimental maximum extensions was ab* 60〜70 % as long as of the molecular contour length. From analogy of simulations with the freely jointed chain model, the observ* curves could result from entropic elasticity of an elongated random coil. The extension of a PS chain in a methanol solution * smaller than that in a toluene one, though the Mn of a PS chain in each solution was same. Generally, the dimension of a random * of a polymer chain in a poor solvent is smaller than that in a good solvent. Since methanol is much poorer solvent to PS compared * toluene, a radius of gyration of a PS chain in a methanol solution should be much smaller than that in a toluene solution. Therefore* larger force was required to stretch a PS chain in a methanol solution in comparison with that in a toluene solution. Less

众所周知，熵弹性的恢复力在聚合物链的末端作用于在随机线圈状态下伸展柔性poly*链时。原子力显微镜（AFM）已实现了单个聚合物链 *的直接拉伸测量，这两种聚合物链的末端都可以在AFM探针尖端和底物表面上吸附。在这项研究中，直接用AFM在单分散聚苯乙烯的稀释溶液中直接测量了拉伸的单聚苯乙烯链的弹性（*以及PS链的施加力与不同分子量的端到端距离之间的关系。研究了单个示例的尖端和Amboxyl off of Amboxyl of amboxyl of Ambose and Ambino compe and Ambino组的端子的末端。力距离曲线的形状可以通过自由的接头段模型来解释，这些模型在拉伸期间可弹性变形。实验性最大延伸时间为AB* 60-70％，与分子轮廓长度相比，与自由接头链模型的模拟相比，观察曲线可能是由于伸长的随机线圈的熵弹性而产生的。甲基抗溶液中PS链的延伸 *比甲苯链小，尽管每种溶液中的PS链的Mn均相同。通常，较差的求解器中聚合物链的随机 *的尺寸小于良好溶液中的尺寸。由于甲基抗酚对PS的溶液比较 *甲苯的溶液差得多，因此在甲基抗溶液中PS链的旋转半径应比甲苯溶液中的甲苯链的半径小得多。因此，与甲苯溶液中相比，需要较大的力才能在甲基抗溶液中拉伸PS链。较少的