Micro-thermomechanical properties of heterogeneous polymer films

We studied the surface distribution of the adhesive forces and elastic modu li for heterogeneous polymer films. Micromechanical properties of polystere ne/polybutadyene (PS/PB) thin films were probed by scanning probe microscop y in a range of temperatures, from room temperature to above the glass tran sition of the PS matrix. We demonstrated that for heterogeneous composite f ilms fabricated from polymer blends, the micromapping of surface properties can be obtained concurrently for glassy and rubber phases as well as acros s 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 interfac e. Glass transition temperature of the glassy matrix and the flow temperatu re of the rubber phase can be detected by this technique, and both temperat ures are close to the known bulk values. (C) 2000 Elsevier Science Ltd. All rights reserved.