The Characterization of Polymer Interfaces

Abstract

Characterizing the manner in which polymer molecules behave at free surfaces, at interfaces between immiscible polymers, and at interfaces with solid substances is critical for understanding and improving the per­ formance of polymers in numerous applications. For example, the adhesion of two polymers strongly depends upon the extent to which polymer segments can mix and entangle across an interface. Com­ patibilization or the stabilization of phase separation to the tens of nano­ meter size scale depends upon the manner in which polymers behave at interfaces. These are just two of the many examples that have focused the attention of the polymer community on the characterization of polymer at interfaces. Polymer molecules are typically several tens of nanometers in size. Consequently, studying the surface and interfacial characteristics of poly­ mers requires the use of techniques with spatial resolutions on the same order of magnitude or less than chain dimensions. Several techniques have emerged as standard tools for studying polymer interfaces. A compilation of these different techniques is given in Table 1. X-ray photoelectron spectroscopy (XPS) provides information on the composition profile in a specimen at the air/polymer interface with an exceptionally high spatial resolution of 0.1 nm. However, the penetration depth is limited to the first 7.5 om of the specimen. Forward recoil spectrometry (FRES) has a much