AFM Observation of the Movements of Single Linear Chains in a Precursor Film of a Spreading Polymer Blend Melt

We have successfully visualized the movements of single chains in a precursor film of a spreading polymer melt on a substrate at the molecular level by atomic force microscopy (AFM). A polymer melt spreading on a substrate forms a precursor film with a thickness comparable to a monolayer at the flow front. Previously, Sheiko and coworkers successfully observed the movements of polymer brush molecules in the precursor film of a spreading melt (Phys. Rev. Lett. 2004, 93, 206103), however, those of conventional linear polymers have not yet been observed due to the limited resolution of the present AFM instruments. We observed a mixture of a poly(methyl methacrylate) (PMMA) oligomer with a small amount of a high-molecular-weight isotactic (it) PMMA polymer, and successfully observed the movements of the it-PMMA polymer chains flowing in the precursor film of the spreading melt at the molecular level. The movements of the individual PMMA chains will be discussed in detail.