Kumaki Jiro, Hashimoto Takeji
Hashimoto Polymer Phasing Project, ERATO, Japan Science and Technology Corporation, Japan.
J Am Chem Soc. 2003 Apr 23;125(16):4907-17. doi: 10.1021/ja0290429.
The random coil conformation of an isolated conventional synthetic polymer chain was clearly imaged by atomic force microscopy (AFM). The sample used was a poly(styrene)-block-poly(methyl methacrylate) diblock copolymer. A very dilute solution of the copolymer with benzene was spread on a water surface. The structure thus formed on water was subsequently transferred and deposited onto mica at various surface pressures and observed under AFM. The AFM images obtained with films deposited at a low surface pressure (<0.1 mN/m) showed a single polystyrene (PS) block chain aggregated into a single PS particle with a single poly(methyl methacrylate) (PMMA) block chain emanating from the particle. Immediately after the deposition, the single PMMA block chain aggregated to form a condensed monolayer around the polystyrene particles. However, after exposing the deposited film to highly humid air for 1 day, the PMMA chains spread out so that the single PMMA block chain could be identified as a random coil on the substrate. The thin water layer formed on the mica substrate in humid air may enable the PMMA block chain to be mobilized on the substrate, leading to the conformational rearrangement from the condensed monolayer conformation to an expanded and elongated coil. The elongation of the PMMA chain was highly sensitive to the humidity; the maximum elongation was obtained at 79% relative humidity. The elongation was a slow process and took about 20 h.
通过原子力显微镜（AFM）清晰地成像了孤立的传统合成聚合物链的无规线团构象。所使用的样品是聚（苯乙烯）-嵌段-聚（甲基丙烯酸甲酯）二嵌段共聚物。将该共聚物与苯的极稀溶液铺展在水面上。随后将在水面上形成的结构在不同表面压力下转移并沉积到云母上，并在AFM下进行观察。在低表面压力（<0.1 mN/m）下沉积薄膜获得的AFM图像显示，单个聚苯乙烯（PS）嵌段链聚集成单个PS颗粒，有一条单个聚（甲基丙烯酸甲酯）（PMMA）嵌段链从该颗粒发出。沉积后立即，单个PMMA嵌段链聚集在聚苯乙烯颗粒周围形成凝聚单层。然而，将沉积的薄膜暴露在高湿度空气中1天后，PMMA链展开，使得单个PMMA嵌段链在基底上可被识别为无规线团。在潮湿空气中云母基底上形成的薄水层可能使PMMA嵌段链能够在基底上移动，导致构象从凝聚单层构象重排为伸展和拉长的线团。PMMA链的伸长对湿度高度敏感；在相对湿度79%时获得最大伸长。伸长是一个缓慢的过程，大约需要20小时。
