Micromechanical Fast Quasi-Static Detection of α and β Relaxations with Nanograms of Polymer

Sanjukta Bose, Silvan Schmid, Tom Larsen, Stephan Sylvest Keller, Anja Boisen, Kristoffer Almdal

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Micromechanical string resonators are used as a highly sensitive tool for the detection of glass transition (Tg or α relaxation) and sub-Tg (β 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. α and β relaxations in the polymer affect the net static tensile stress of the microstring and result in measureable local frequency slope maxima. Tg of PS and PMMA is detected at 91 ±2°C and 114 ±2°C, respectively. The results match well with the glass transition values of 93.6°C and 114.5°C obtained from differential scanning calorimetry of PS and PMMA, respectively. The β relaxation temperatures are detected at 30 ± 2°C and 33 ± 2°C for PS and PMMA which is in accordance with values reported in literature.
Original languageEnglish
JournalJournal of Polymer Science. Part B, Polymer Physics
Issue number15
Pages (from-to)1035-1039
Publication statusPublished - 2015


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