Crystallization of Isotactic Poly(methyl methacrylate) Monolayer Observed by High-Resolution Atomic Force Microscopy in Real Time

In the early 2000s, the crystallization behaviors of polymer films were successfully visualized by AFM in real time, and the growth of individual lamellae could be analyzed by AFM (Hobbs et al., Macromolecules, 34, 5508 (2001)). However, high-resolution (HR) imaging at the molecular level has not been attained, because relatively thick spin-cast films were used for the observations.
We showed that a HR images could be attained by AFM using Langmuir-Blodgett (LB) films, which are suitable for observation by scanning probe microscopy (Kumaki, Polym. J., 48, 3 (2016)), and observed folded-chain crystals of an isotactic poly(methyl methacrylate) (it-PMMA) at the molecular level (Kumaki et al. , JACS 127, 5788 (2005)). If we used the it-PMMA LB film, the crystallization behavior could be visualized at the molecular level. However, if we apply a temperature jump for crystallization from an amorphous state, an unavoidable large thermal drift prevents the HR imaging.
Recently, we found that an it-PMMA monolayer deposited in the amorphous state crystallized under humid air at room temperature, and the crystallization was successfully followed by AFM at the molecular level in real time. We will discuss the various crystallization behaviors observed by the HR AFM.