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We report frequency changes in AT‐cut quartz crystals for glassy polymers subsequent to temperature and carbon dioxide pressure changes. Anomalous frequency shifts are observed for the crystal subsequent to such changes. Since, the Sauerbrey equation has been applied routinely for mass uptake measurements in glassy polymers, using the quartz crystal microbalance fitted with AT‐cut quartz crystals, it is important that nongravimetric effects that impact the frequency change be well understood. In the present work, we provide a quantitative analysis of the breakdown of the Sauerbrey equation for viscoelastic materials by using the Johannsmann (Macromol Chem Phys 1999, 200, 501) treatment of the response of AT‐cut crystals. Clearly, there exist significant errors in mass uptake measurements for materials deposited on AT‐cut quartz crystals when precautions pertaining to film thickness and viscoelastic compliance are ignored. We show that while the early caution of EerNisse on stress effects in AT‐cut quartz crystals can be important in mass uptake measurements, for polymers, the major source of error arises from viscoelastic effects in the coating. We conclude that mass uptake measurements for films of compliant materials and polymers above their glass transition cannot be performed with accuracy, using AT‐cut quartz crystals if the results are not corrected for frequency shifts due to viscoelastic effects of the overlayer unless the films are extremely thin, that is, less than 100 nm. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 801–814, 2006

Novel volume measurements on an epoxy resin subjected to carbon dioxide pressure jumps (PCO2) are used to investigate the structural recovery of glassy polymers after plasticizer jumps. Previously, we had investigated an epoxy resin after plasticizer concentration jumps using relative humidity (RH) and CO2 and evidenced structural recovery and physical aging responses. − In that work, two things were demonstrated: (a) qualitatively, the physical aging (after CO2 and RH jumps) and structural recovery (after RH jumps) responses are similar to those observed after temperature jumps, and (b) quantitatively, the responses are not the same and, moreover, they exhibit anomalous behaviors. The purpose of the present work is to further investigate the nature of the anomalous behaviors by investigating the structural recovery response of the same epoxy when subjected to PCO2-jump conditions. We provide new data using CO2-jumps and show intrinsic isopiestics, asymmetry of approach, and memory effect and then compare these with similar data for temperature-jump histories. We show that the extended Kovacs−Aklonis−Hutchinson−Ramos does not adequately describe the structural recovery of the epoxy resin after PCO2-jumps. This is consistent with what was previously observed in our laboratory on modeling the structural recovery data of the epoxy resin subsequent to relative humidity changes. Finally, we show a further anomaly in that the volume in CO2-jump experiments seems to evolve toward a different final state than it does in temperature-jump experiments, suggestive of a metastable glassy state that differs from that of the temperature-jump created glass.

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