Mechanical Behavior of Nanocluster-Based Nanocomposites Made Using Two-Photon Lithography

Mechanical metamaterials with nanoscale features exhibit exceptional properties, including high specific strength, modulus, energy absorption, and recoverability. The ability to fabricate these metamaterials out of complex nanocomposites could further boost their mechanical properties. Recently, two-photon lithography (TPL) has been used to fabricate architected microlattices out of high-performance polymer nanocomposites that contain metallic nanoclusters. However, the mechanism that leads to unique mechanical properties of the nanocomposites, such as high strain hardening, remains unclear. Here, TPL is used to fabricate nanocluster-based polymer nanocomposite micropillars and investigate how nanocluster content and chemical bonding with the polymer matrix impact their mechanical properties. The nanocomposites are tested in compression at strain rates of 10^-3 to 10² s^-1, and after heat treatment up to 550 °C. Findings show that nanoclusters establish hydrogen bonds and exhibit strong interfacial bonding with the polymer, restricting polymer chain movement and significantly enhancing mechanical strength compared to unfilled polymers.