Novel Applications of the QCM Technique in Biomaterials Science
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1060-LL03-06
Novel Applications of the QCM Technique in Biomaterials Science Candida C Silva, David C Lin, Iren Horkayne-Szakaly, Peter J Basser, and Ferenc Horkay National Institutes of Health, Bethesda, MD, 20892 ABSTRACT A quartz crystal microbalance (QCM) has been used to investigate polymer samples. The vapor sorption of three different polymer samples (poly(vinyl acetate), polybutadiene and polydimethylsiloxane) was studied. The change in resonance frequency of the quartz sensor uniformly coated with polymer films was measured as a function of the film thickness and water absorption at different temperatures. The range of linear frequency vs. mass response was determined in the absence of absorbed water. The glass transition temperature of thin poly(vinyl acetate) films (10 nm 1 microgram) samples. In the present work we report experimental results obtained by this QCM technique for the hydration of polymer films. EXPERIMENT Sample Preparation Gold electrode quartz crystals were used in all QCM measurements. They were cleaned under UV light for 10 minutes, then rinsed first in a 2% SDS solution for 30 minutes and then in distilled water for 10 minutes before drying in a N2 flow. Finally, the crystals were exposed to UV light for 10 more minutes before being used.
The polymer samples: poly(vinyl acetate) (PVAc), polybutadiene (PBu) and polydimethylsiloxane (PDMS) were purchased from Sigma-Aldrich. The molecular weights of the polymers were: 113,000 (PVAc), 60,900 (PBu), and 95,000 (PDMS). PVAc and the PDMS were dissolved in toluene and PBu in cyclohexane. The polymers were uniformly deposited on the surface of the quartz crystal and air dried before being placed in the measurement chamber. QCM Experiment A QCM with dissipation monitoring capability [14] was used. The range of linear behavior of the QCM was determined using different concentrations of poly(vinyl acetate) solutions in toluene (from 0.02% to 2% (w/w)). They were uniformly deposited on quartz crystals (at 27°) and ∆F was measured until all the solvent was evaporated. Experiments were performed to determine the sensitivity of the instrument to temperature by first monitoring the response of bare quartz crystals and then of quartz crystals coated with the three different polymers studied here. These temperature dependence experiments were done with no water vapor flow, in the range of 27°C to 40°C, at different heating/cooling rates. Finally, the swelling/deswelling experiments on the polymers were done at fixed temperature (27°C). The swelling was induced by constant flow of water vapor in the sample chamber. RESULTS AND DISCUSSION Determination of the range of linearity Figure 1 shows the dependence of ∆F as a function of the mass of the polymer film deposited on the surface of the crystal. The data clearly indicate that ∆F decreases linearly with increasing mass over the range 0 < mass < 0.15 mg cm-2. Above m = 0.15 mg cm-2 the deviation from the linear response becomes pronounced. In this paper we report data measured in the linear range, in w
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