Peculiar 'reptational' movements of single synthetic polymer chains on substrate observed by AFM

Peculiar 'reptational' movements of isotactic PAAMA chains on mica are observed by in situ AFM. The polymer molecules comprise long flexible chains that exhibit reptative, or snakelike, motion on the substrate along the direction of the polymer chain. Intriguingly, some chains underwent forward then backward motion in which the head of the chain moved in a curvilinear manner along the previous contours of the polymer chain. No limitation in the direction of movement for the ends of the polymer chain was anticipated based on an assumed reptational mechanism. As a result, the chains recovered a conformation that had been adopted prior to the initial movement. Several factors that may affect the movement are discussed.