高分子研究中的一个知识问题——柔性链“从线团到小球”的构象变化

发布时间：2018-06-02 21:08

本文选题：柔性链 + 高分子溶液　；参考：《高分子学报》2017年09期

【摘要】：一条大分子链由许多小分子通过共价键连接而成.正是这一"连接"导致了大分子一些独特的物理性质及相关问题.本文希望阐明的就是这样一个小分子物理中没有的知识问题:小分子在溶剂中仅有溶或不溶2个状态;而自60年代起,理论学家们就预言一条柔性大分子链在溶解的状态下,其构象随着溶剂性质变差可以从无规线团蜷缩成一个单链小球.为了证明这一构象变化,实验学家们从70年代末起进行了大量的研究,直至90年代初期仍未观察到稳定的单链蜷缩小球.实验上这一长期悬而未解的问题困惑着众多研究者.甚至有理论学家在1993年报道,当今的样品制备和实验手段无法观察到一个热力学稳定的单链蜷缩小球.中国钱人元先生和一些其他研究者自80年代末期也开始关注与单链有关的问题.我们实验室从1993年开始另辟蹊径,通过制备和采用窄分布的热敏性水溶性高分子超长链,终于在1995年利用激光光散射首次观察到理论上预测的"线团到小球"的构象变化.随后,又揭示了变化过程中存在着一个全新的"融化球"构象以及在单链蜷缩小球中并无理论上预计的额外链互穿和打结.从得到的稳定单链蜷缩小球出发,我们又首次在实验上研究了"小球到线团"的过程,意外地观察到其在准理想状态附近滞后于"线团到小球"的构象变化,并证明该滞后可归于链蜷缩过程中形成的额外链内氢键.最后,借用红外纳秒脉冲激光加热的方法研究了"线团到小球"的蜷缩动力学,并发现其包含了在单个高分子链上"成核"和"粗化"先后2个过程.其中,"成核"过程与链长无关.经过近20年的努力,我们终于基本解决了这一近代高分子物理研究中与知识有关的重要问题,揭示了与其相关的一些大分子特有的物理性质.
[Abstract]:A chain of large molecules is made up of many small molecules connected by covalent bonds. It is this connection that leads to some unique physical properties of macromolecules and related problems. What this paper wants to clarify is a knowledge problem that is not found in the physics of small molecules: small molecules are only dissolved or insoluble in solvents, and since the 1960s, theorists have predicted that a flexible macromolecular chain is in a dissolved state. The conformation can be curled up from a random coil to a single chain ball with the change of solvent properties. In order to prove this conformational change, the experimenters have carried out a great deal of research since the late 1970s, and until the early 1990s, no stable single chain curled ball was observed. Experimentally, this long-hanging and unsolved problem puzzles many researchers. Even some theorists reported in 1993 that a thermodynamically stable single chain curled ball could not be observed by the present sample preparation and experimental methods. Mr. Qian Renyuan and other researchers in China have been concerned about single-stranded issues since the late 1980 s. Since 1993, our laboratory has been looking for a new way. By preparing and using narrow distribution of thermosensitive water-soluble polymer super-long chains, we finally observed the conformation change of "core-to-sphere" theoretically predicted for the first time in 1995 by using laser light scattering (LLS). Then, it is revealed that there is a new "melting ball" conformation in the process of change and that there is no theoretical expectation of extra chain interpenetrating and knots in the single chain curling ball. Starting from the stable single chain curled ball, we have studied the process of "small ball to wire ball" for the first time in experiments. We have accidentally observed the conformational change of the "ball to ball" which lags behind the "coiled ball" in the vicinity of the quasi-ideal state. It is also proved that the hysteresis can be attributed to the formation of extra intrachain hydrogen bonds in the process of chain curling. Finally, by using infrared nanosecond pulsed laser heating method, the curling kinetics of "coiled to small ball" is studied, and it is found that it includes two processes of "nucleation" and "coarsening" on a single polymer chain. The nucleation process has nothing to do with chain length. After nearly 20 years of hard work, we have basically solved this important problem related to knowledge in the study of modern polymer physics, and revealed some special physical properties of macromolecules related to it.
【作者单位】：中国科学技术大学化学物理系合肥微尺度物质科学国家实验室(筹);美国德州大学西南医学中心Simmons癌症研究中心;香港中文大学化学系;
【分类号】：O631.1

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