Mechanical Behavior of Hybrid Thin Films Fabricated by Sequential Infiltration Synthesis in Water-Rich Environment.

Sequential infiltration synthesis (SIS) is an emerging technique for fabricating hybrid organic-inorganic materials with nanoscale precision and controlled properties. Central to SIS implementation in applications such as membranes, sensors, and functional coatings is the mechanical properties of hybrid materials in water-rich environments. This work studies the nanocomposite morphology and its effect on the mechanical behavior of SIS-based hybrid thin films of AlO x -PMMA under aqueous environments. Water-supported tensile measurements reveal an unfamiliar behavior dependent on the AlO x content, where the modulus decreases after a single SIS cycle and increases with additional cycles. In contrast, the yield stress constantly decreases as the AlO x content increases. A comparison between water uptake measurements indicates that AlO x induces water uptake from the aqueous environment, implying a "nanoeffect" stemming from AlO x -water interactions. We discuss the two mechanisms that govern the modulus of the hybrid films: softening due to increased water absorption and stiffening as the AlO x volume fraction increases. The decrease in the yield stress with SIS cycles is associated with the limited mobility and extensibility of polymer chains caused by the growth of AlO x clusters. Our study highlights the significance of developing hybrid materials to withstand aqueous or humid conditions which are crucial to their performance and durability.