Micromechanical fast quasi-static detection of and relaxations with nanograms of polymer

Micromechanical string resonators are used as a highly sensitive tool for the detection of glass transition (T-g or relaxation) and sub-T-g ( relaxation) temperatures of polystyrene (PS) and poly (methyl methacrylate) (PMMA). The characterization technique allows for a fast detection of mechanical relaxations of polymers with only few nanograms of sample in a quasi-static condition. The polymers are spray coated on one side of silicon nitride (SiN) microstrings. These are pre-stressed suspended structures clamped on both ends to a silicon frame. The resonance frequency of the microstrings is then monitored as a function of increasing temperature. and relaxations in the polymer affect the net static tensile stress of the microstring and result in measureable local frequency slope maxima. T-g of PS and PMMA is detected at 91 +/- 2 degrees C and 114 +/- 2 degrees C, respectively. The results match well with the glass transition values of 93.6 degrees C and 114.5 degrees C obtained from differential scanning calorimetry of PS and PMMA, respectively. The relaxation temperatures are detected at 30 +/- 2 degrees C and 33 +/- 2 degrees C for PS and PMMA which is in accordance with values reported in literature. (c) 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1035-1039