Quantitative Examination of Semicrystalline Polymers Via Atomic-Force Microscopy, Transmission Electron Microscopy, and Small-Angle X-Ray Scattering

The Atomic Force Microscope (AFM) has been used to reliably measure lamellar thickness in semi-crystalline polymers, and to distinguish phases within blends of these polymers. Traditionally, lamellar thicknesses of semi-crystalline polymers have been determined by (1) measuring structures directly from TEM micrographs or (2) using small angle X-ray scattering (SAXS) spectra. In the first case, the sample must either be etched and replicated, or stained with heavy metals or chlorosulfonic acid to reveal the lamellar structures. Good SAXS measurements require access to a synchrotron, or rotating anode diffractometer. In contrast, the AFM has been used to relaibly measure the lamellar structures in polymer specimens which have undergone minimal sample preparation. The tapping mode of operation of a Digital Nanoprobe AFM has been used on the free surfaces of polyethylene oxide (PEO) specimens to determine lamellar thicknesses that are in excellent agreement with measurements obtained from both TEM and SAXS. Examples of such comparisons in the existing literature are few.