Micro-thermomechanical properties of heterogeneous polymer films

We studied the surface distribution of the adhesive forces and elastic moduli for heterogeneous polymer films. Micromechanical properties of polysterene/polybutadyene (PS/PB) thin films were probed by scanning probe microscopy in a range of temperatures, from room temperature to above the glass transition of the PS matrix. We demonstrated that for heterogeneous composite films fabricated from polymer blends, the micromapping of surface properties can be obtained concurrently for glassy and rubber phases as well as across the interface with a lateral resolution better than 100 nm. Histograms of the surface distribution display two very distinctive maxima, which allows concurrent measurements of micromechanical properties of glassy and rubber phases. Depth profile measurements demonstrate the gradual increase of the rubber phase thickness with an increasing distance from the PS/PB interface. Glass transition temperature of the glassy matrix and the flow temperature of the rubber phase can be detected by this technique, and both temperatures are close to the known bulk values. (C) 2000 Elsevier Science Ltd. All rights reserved.