Local Mechanical Properties of Polymer Interphase and Free Surface
The nanoconfinement effects in polymer thin film have been a major interest in past decades. It was observed by using various experimental methods, that the glass transition temperature (Tg) differs from the bulk material value at both polymer/substrate interfaces and free surfaces, which indicates the altered polymer molecular structure under confinements. To approach this topic from another angle, local mechanical properties of polymer thin films near substrate interfaces and free surfaces would be the interest of the field. In this work, an AFM nanomechanical testing based method was developed to study the change of elastic modulus and time dependent viscoelastic properties at both polymer/substrate interfaces and free surfaces. The new method is capable of providing the local mechanical properties mapping with nanometer resolution inside sub-micron spatial range. Therefore the full gradient of modulus change can be revealed for the first time with ultrahigh resolution on both sides of the film, which facilitates the further understanding of polymer confinement effects. The material system studied in this work included rubber matrix nanocomposites, as well as PMMA and PS thin films on silicon substrates.
Active Researchers on this project:
Xu Cheng, Karl Putz, Charles D. Wood, L. Catherine Brinson, Characterization of Local Elastic Modulus in Confined Polymer Films via AFM Indentation, Macromolecular Rapid Communications, 36 (2015)