Nanomechanical Thermal Analysis with Silicon Cantilevers of the Mechanical Properties of Poly(vinyl acetate) near the Glass Transition Temperature

Abstract

Poly(vinyl acetate) (PVAc) was coated onto one side of a silicon cantilever, and the variations with temperature in the deflection, resonance frequency, and Q factor of the PVAc-coated silicon cantilever were measured simultaneously. The changes in the resonance frequency and the inverse of the Q factor of the cantilever are related to the variations in the elastic modulus and the loss tangent of PVAc, respectively. The loss modulus of PVAc was calculated from the resonance frequency and Q factor and used to determine the glass transition temperature (T-g) of PVAc (66 degrees C), which was found to be higher than that obtained from the cantilever deflection (43 degrees C); this difference is attributed to the high resonance frequency of the cantilever (or the fast rate of the applied stress). A series of measurements at various frequencies were carried out to obtain the accurate T-g and apparent activation energy for the glass transition.