MRSEC Seminar

Confinement Effects on the Elastic Modulus of Polymer Thin Films

Bryan Vogt

Assistant Professor
Department of Chemical Engineering
Arizona State University

Tuesday, January 6, 2:00 pm
Cook Hall 2058

Understanding the mechanical properties of polymers at the nanoscale is critical in numerous emerging applications due to their prevalence as sacrificial templates.  Due to difficulties in measuring the modulus of sub-100 nm soft polymeric features, it has been suggested that the glass transition temperature (Tg) of thin films and nanostructures can be utilized as a surrogate to estimate how the modulus of nanoconfined polymeric materials deviates from the bulk based upon time-temperature superposition principles.  However, it is unclear that this macroscopic correlation applies to polymers at length scales comparable to the molecule.  The elastic moduli of thin films of polymers will be elucidated utilizing wrinkling instabilities of thin films supported on elastomeric sheets.  To test the impact of polymer chemistry on the elastic moduli of thin films, a homologous series of polymethacrylates is examined for films ranging from 5 nm to 200 nm at ambient temperature.  A decrease in the modulus in ultrathin (<30 nm) films was observed in all cases; however as the Tg of the bulk polymer decreases, deviations from the bulk-like modulus occur at progressively larger thickness.  These data will be discussed in terms of the changes in Tg of thin film and the simulations from de Pablo and coworkers.   

Host: Kenneth Shull, MSE