Polyelectrolyte-stabilized polymer nanotubes with high rigidity are electro-optically characterized in the dilute and semidilute regimes. Nanotube alignment with the electric field and subsequent orientation relaxation in the absence of electric field are confirmed by optical microscopy, and a simple UV−vis electro-optical setup is used to detect the transient light transmittance. The effects of ionic strength, pulse duration, electric field strength, and particle concentration on particle alignment and orientation relaxation dynamics were systematically varied. The charge-dependent field-induced interfacial polarization, particularly the double layer polarization, plays a predominant role in the thin-walled nanotube alignment, which diminishes with increasing salt screening, approaching predictions for uncharged dielectric tubes. The experimentally obtained rotary diffusivity from nanotube orientation relaxation dynamics agrees with theoretical predictions, with negligible ionic strength effects, indicating the absence of salt-induced aggregation events. When the scaled particle concentration ϕ/ϕ* increases from 0.06 to 15, the alignment is slowed by crowding, whereas the measured collective rotary diffusion coefficient increases due to the gradient of orientation probability.

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Titanium-copper (Ti–Cu) coatings have attracted extensive attention in the surface modification of industrial and biomedical materials due to their excellent physical and chemical properties and biocompatibility. Here, Ti–Cu coatings are fabricated using a combination of high-power pulsed magnetron sputtering (HPPMS; also known as high power impulse magnetron sputtering (HiPIMS)) and DC magnetron sputtering followed by vacuum annealing at varied temperatures (300, 400, and 500 °C). X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) data showed that Ti, Cu, and CuTi3 are mainly formed in the coatings before annealing, while Ti3O, Cu2O, and CuTi3 are the main compounds present in the annealed coatings. The cross-sectional TEM micrographs and corresponding EDS results provided evidence that Ti is mainly present on the surface and interfaces of the silicon substrate and the Ti–Cu coatings annealed at 500 °C, while the bulk of the coatings is enriched with Cu. The resistivity of the coatings decreased with increasing the annealing temperature from 300 to 500 °C. Based on self-corrosion current density data, the Ti–Cu coating annealed at 300 °C showed similar corrosion performance compared to the as-deposited Ti–Cu coating, while the corrosion rate increased for the Ti–Cu coatings annealed at 400 and 500 °C. Stable release of copper ions in PBS (cumulative released concentration of 0.8–1.0 μM) for up to 30 days was achieved for all the annealed coatings. Altogether, the results demonstrate that vacuum annealing is a simple and viable approach to tune the Cu diffusion and microstructure of the Ti–Cu coatings, thereby modulating their electrical resistivity, corrosion performance, and Cu ion release behavior.

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