The effect of water uptake on the mechanical behavior of hybrid thin films fabricated by sequential infiltration synthesis (SIS)

Hybrid organic-inorganic materials are an exciting subclass of composites due to their unique structures and properties. Control over their mechanical properties is central to their implementation in various advanced applications. In recent years, sequential infiltration synthesis (SIS) has emerged as a promising new technique for fabricating hybrid materials with nanoscale precision. In SIS, inorganic materials are grown within polymers from vapor phase precursors using atomic layer deposition (ALD) chemistry. Several studies have demonstrated the potential of SIS to tune the mechanical properties of polymers. However, a full understanding of the nanostructure mechanical behavior is still an ongoing effort.

This research studies the mechanical response of SIS-based hybrid thin films and probes the effect of water uptake on their behavior. Hybrid thin films were fabricated by growing AlO_x within PMMA films via SIS process, using trimethylaluminum and H₂O as precursors. Tensile measurements of the thin films (~50 nm, supported by water surface) reveal counter-intuitive behavior with a softening effect despite the growth of AlO_x clusters. Water uptake measurements carried out via in-situ microgravimetric measurements indicate that aluminum-oxide induces water uptake from the aqueous environment, implying a possible interaction between AlO­_x and water.