Chain folding of semi-crystalline polymers occurs as a consequence of the counteraction between the thermodynamic equilibrium and the kinetics barrier to chain extension. Undeniably, for years, it is the most controversial subject in the study of polymer crystallization because of lacking direct experimental evidence to reveal the interfacial structures and conformation of the polymer crystals. The original evidence came solely from the interpretation of the electron microscopic observations and electron diffractions of solution-grown single crystals of polyethylenes and these data unfortunately did not reveal the details of the molecular structures in the interfaces which were obtained by deductive reasoning from the properties, such as density and crystallinity measurements. Understan...[ Read more ]

Chain folding of semi-crystalline polymers occurs as a consequence of the counteraction between the thermodynamic equilibrium and the kinetics barrier to chain extension. Undeniably, for years, it is the most controversial subject in the study of polymer crystallization because of lacking direct experimental evidence to reveal the interfacial structures and conformation of the polymer crystals. The original evidence came solely from the interpretation of the electron microscopic observations and electron diffractions of solution-grown single crystals of polyethylenes and these data unfortunately did not reveal the details of the molecular structures in the interfaces which were obtained by deductive reasoning from the properties, such as density and crystallinity measurements. Understanding the interfacial conformation is important because this interface dictates the fold surface free energy of the formation of a nucleus and the lamellar thickness of the polymer crystals. We proposed a study using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and a statistical tool, principal component analysis (PCA), with the aim to establish a relationship between the crystalline morphology and the ion intensity analyses as a direct probe of the polymer chain arrangements at the fold surfaces. The new findings of the controllable behaviors of the surface conformations present new opportunities of using the ordering and folding of the chain molecules to tune the surface chemical properties of the organic thin films and ultra-thin films.