Free volume distribution at polymer-solid interfaces

• Applicant: Professor Dr. Klaus Rätzke
• Subject Area: Polymer Materials
• Term: from 2008 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 67970895

Polymer-solid interfaces play a crucial role in many applications ranging from joining technology and organic electronics to nanocomposites. However, the present understanding of the structure, formation, and properties of the interfacial region (interphase), which can extend up to several μm into the bulk, is limited. The project aims at providing new insight into the structure and extension of polymer solid interfaces via investigation of the free volume distribution by means of depth resolved positron annihilation lifetime spectroscopy. Having demonstrated the great potential of the PALS technique in conjunction with a slow positron beam for selected model systems we now plan to extend the measurements to substrates with metallic and van der Waals interaction and to other polymers including polybutadiene which will allow direct comparison with computer simulations and other experimental techniques. The measurements will also be extended to crosslinked polymers prepared by UV crosslinking to avoid hardener effects. Methodologically, in addition to advanced profile simulations, we plan to measure depth profiles of the glass transition temperature Tg across the interface. Measurements at constant implantation energy as function of temperature will not only yield Tg as function of the distance from the substrate, but also provide profiles of the coefficients of thermal expansion below and above Tg and hence reveal important information on the polymer dynamics as function of depth.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1369: Polymer Solid Contacts: Interfaces and Interphases
• Participating Person: Professor Dr. Franz Faupel