Dynamic mechanical analysis (DMA) was used to explore the thermomechanical properties of dried polyelectrolytes and polyelectrolyte complexes (PECs) with different thermal and humidity histories. Although differences in the amount of water remaining in polyelectrolytes and PECs were small for ambient versus dessicator storage, the properties of polyelectrolyte-based materials were drastically different for different humidity histories. Glass transition temperatures (T(g)s) of poly(diallyldimethylammonium chloride) (PDADMAC) were shown to vary by 100 degrees C, depending on humidity and thermal histories. These parameters also change glassy storage modulus values by 100%. Furthermore, we observe that dried PDADMAC is highly lossy. DMA of dried poly(styrene sulfonate) (PSS) was more complex and did not exhibit a glass transition in the tested range. DMA of a PEC of PDADMAC and PSS revealed a humidity history-dependent water melt in the first heating cycle, as well as storage modulus values of dried and annealed PECs that only varied by 17-26% over a 275 degrees C temperature range. Based on these results, we report for the first time humidity history as controlling structure and properties of polyelectrolyte-based materials. (C) 2017 Wiley Periodicals, Inc.