Perovskite-structured compounds containing organic cations and inorganic anions have gained prominence as materials for next-generation electronic and energy devices. Hybrid materials possessing ferro- and piezoelectric properties are in recent focus for mechanical energy harvesting (nanogenerator) applications. Here, we report the ferroelectric behavior of A₂BX₄-type halogenocuprate materials supported by heteroleptic phosphonium cations. These lead-free discrete Cu(II) halides [Ph₃MeP]₂[CuCl₄] (1) and [Ph₃MeP]₂[CuBr₄] (2) exhibit a remnant polarization (P_r) of 17.16 and 26.02 μC cm^–2, respectively, at room temperature. Furthermore, flexible polymer films were prepared with various weight percentage (wt %) compositions of 1 in thermoplastic polyurethane (TPU) and studied for mechanical energy harvesting applications. A highest peak-to-peak voltage output of 25 V and power density of 14.1 μW cm^–2 were obtained for the optimal 15 wt % 1-TPU composite film. The obtained output voltages were utilized for charging a 100 μF electrolytic capacitor that reaches its maximum charging point within 30 s with sizable stored energies and accumulated charges.

Thermoplastic polyimides (TPIs) are promising lightweight materials for replacing metal components in aerospace, rocketry, and automotive industries. Key TPI attributes include low density, thermal stability, mechanical strength, inherent flame retardancy, and intrinsic fluorescence under UV light. The application of advanced manufacturing techniques, especially 3D printing, could significantly broaden the use of TPIs; however, challenges in melt-processing this class of polymer represent a barrier. This study explored the processability, 3D-printing and hence mechanical, and fluorescence properties of TPI coupons, demonstrating their suitability for advanced 3D-printing applications. Moreover, the study successfully 3D-printed a functional impeller for an overhead stirrer, effectively replacing its metallic counterpart. Defects were shown to be readily detectable under UV light. A thorough analysis of TPI processing examining its rheological, morphological, and thermal properties is presented. Extruded TPI filaments were 3D-printed into test coupons with different infill geometries to examine the effect of tool path on mechanical performance. The fluorescence properties of the 3D-printed TPI coupons were evaluated to highlight their potential to produce intricately shaped thermally stable, fluorescence-based sensors.

Ionic cocrystals with hydrogen bonding can form exciting materials with enhanced optical and electronic properties. We present a highly moisture-stable ammonium salt cocrystal [CH₃C₆H₄CH(CH₃)NH₂][CH₃C₆H₄CH(CH₃)NH₃][PF₆] ((p-TEA)(p-TEAH)·PF₆) crystallizing in the polar monoclinic C2 space group. The asymmetry in (p-TEA)(p-TEAH)·PF₆ was induced by its chiral substituents, while the polar order and structural stability were achieved by using the octahedral PF₆^- anion and the consequent formation of salt cocrystal. The ferroelectric properties of (p-TEA)(p-TEAH)·PF₆ were confirmed through P-E loop measurements. Piezoresponse force microscopy (PFM) enabled the visualization of its domain structure with characteristic "butterfly" and hysteresis loops associated with ferro- and piezoelectric properties. Notably, (p-TEA)(p-TEAH)·PF₆ exhibits a large electrostrictive coefficient (Q₃₃) value of 2.02 m⁴ C^-2, higher than those found for ceramic-based materials and comparable to that of polyvinylidene difluoride. Furthermore, the composite films of (p-TEA)(p-TEAH)·PF₆ with polycaprolactone (PCL) polymer and its gyroid-shaped 3D-printed composite scaled-up device, 3DP-Gy, were prepared and evaluated for piezoelectric energy-harvesting functionality. A high output voltage of 22.8 V and a power density of 118.5 μW cm^-3 have been recorded for the 3DP-Gy device. Remarkably, no loss in voltage outputs was observed for the (p-TEA)(p-TEAH)·PF₆ devices even after exposure to 99% relative humidity, showcasing their utility under extremely humid conditions.

Understanding how molecular weight distribution (MWD) influences the mechanical and fracture behaviour of additively manufactured PA12 is essential for establishing reliable process–structure–property relationships. An approach to minimize anisotropy has been to specifically target the feedstock materials with the goal of enhancing interlayer adhesion. In this study, polyamide 12 (PA12) grades of MWD were investigated to determine the effect of MWD on the interlayer bond formation and anisotropy of the printed samples. Three different grades of PA12 were printed into tensile coupons and double cantilever beam (DCB) specimens and the mechanical properties were assessed to study interlayer bond strength using standard fracture toughness technique. A significant improvement in mechanical properties and fracture toughness were observed with higher print temperatures attributed to strong interlayer adhesion owing to longer interlayer bonding times (verified through the Lumped Capacity model and thermocouple data). Fracture toughness assessment also demonstrated that amongst samples printed at the same temperature, PA12 with a lower average MWD provided the highest fracture toughness (G _1C ) values, attributed to the faster diffusion of short polymer chains across the interlayer interface. Tailoring the MWD of feedstock polymers utilized in 3D printing as a strategy to optimize performance and lower anisotropy was demonstrated to be a feasible pathway. These findings were utilized by developing a PA12 blend of broad MWD which provided the highest overall mechanical properties and G _1c , demonstrating the usefulness of incorporating a high proportion of fast diffusing short polymer chains in the development of polymeric feedstock materials. Additionally, for large scale 3D printing applications, where maintaining high chamber temperatures is impractical, these results suggest that optimizing MWD can be an alternative strategy to improve interlayer adhesion and mechanical properties without relying solely on elevated print temperatures.