In amorphous polymers that are capable of hydrogen bonding, adsorption of water molecules acts as a plasticizer to lower the glass transition temperature (Tg). When stored below Tg, the movement of the individual polymer chains is suppressed, which results in metastable to stable structures. However, when the Tg of hydrated nylon-6 is lower than the environmental temperature, increased molecular mobility results in an decrease in the amorphous structure and a concomitant increase in the -crystalline structure. Thus, it is of critical importance that the role of water on the structure and dynamics of amorphous polymers be uncovered in order to more effectively use such materials in advanced applications.