Elastic Modulus of Amorphous Polymer Thin Films: Relationship to the Glass Transition Temperature
Jessica M. Torres, Christopher Stafford, Bryan D. Vogt
Understanding the mechanical properties of polymers at the nanoscale is critical in numerous emerging applications. While it has been widely shown that the Tg in thin polymer films decreases due to confinement effects, there is little known about the modulus of sub-100 nm polymer films and features. Thus, one might use this depressed Tg as a surrogate to estimate how the modulus of nanoconfined polymeric materials deviates from the bulk, based on constructs such as Williams-Landel-Ferry (WLF) time-temperature superposition principles. However, such relationships have not been thoroughly examined at the nanoscale where surface and interface effects can dramatically impact the physical properties. Here, we measure the elastic modulus of a series of poly(methacrylate) films with widely varying bulk Tg as a function of thickness at ambient temperature exploiting the wrinkling instability of polymer thin film on an elastic thick substrate. A decrease in the modulus is found for all polymers in ultrathin (< 30 nm) films with the onset of confinement effects shifting to larger film thicknesses as the quench depth (Tg, bulk-T) decreases. We show that the decrease in Tg of ultrathin films is not correlated with the decrease in modulus of films of the same thickness.
, Stafford, C.
and Vogt, B.
Elastic Modulus of Amorphous Polymer Thin Films: Relationship to the Glass Transition Temperature, ACS Nano, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=902430
(Accessed December 2, 2023)