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Photo-induced conductivity modulation of stimuli-responsive materials is of great importance from the viewpoint of fundamental research and technology. In this work, 5 new kinds of azobenzene-based photo-responsive ionic liquids were synthesized and characterized, and UV/vis light modulation of their conductivity was investigated in an aqueous solution. The factors affecting the conductivity modulation of the photo-responsive fluids, such as photo-isomerization efficiency, photo-regulation aggregation, concentration and chemical structure of the ionic liquids, were examined systematically. It was found that the conductivity of the ionic liquids in water exhibited a significant increase upon UV light irradiation and the ionic liquids with a shorter alkyl spacer in the cation showed a more remarkable photo-induced conductivity enhancement with a maximum increase of 150%. In addition, the solution conductivity was restored (or very close) to the initial value upon an alternative irradiation with visible light. Thus, the solution conductivity can be modulated using alternative irradiation with UV and visible light. Although the reversible photo-isomerization of the azobenzene group under UV/vis irradiation is the origin of the conductivity modulation, the photo-regulated aggregation of the ionic liquid in water is indispensable for the maximum degree of conductivity modulation because UV irradiation can weaken, even break the aggregated cis-isomers of the ionic liquids in an aqueous solution.

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Land application of animal manure introduces large quantities of ROX to the environment. ROX is highly water-soluble and easily adsorbs on iron hydro­(oxides). Photolysis of ROX in goethite (α-FeOOH) suspensions was investigated under simulated sunlight irradiation. The rate of ROX photodegradation in the presence of 2.2 mM α-FeOOH was four times faster than that in pure water. The initial rate equation for ROX photodegradation was determined to be r init = (2.3 ± 0.4) × 10–4[ROX]0.5[α-FeOOH]1.1[H+]0.1 (μM·h–1) at initial pH values of 2.5–7.0, ROX concentrations of 2.5–10.0 μM, and α-FeOOH dosages of 0.6–2.2 mM. Approximately 6.2% of ROX underwent direct photolysis ([ROX]0 = 5.0 μM, [α-FeOOH]0 = 2.2 mM), while the others were attributed to the indirect photolysis introduced by α-FeOOH. The second-order rate constants determined for the reactions between ROX and •OH and O2 •– were 3.07 ± 0.09 × 109 and 2.08 ± 0.03 × 104 M–1·s–1, respectively. Inorganic arsenics were the main arsenic-containing products, most of which were adsorbed on α-FeOOH. Photodegradation pathways of ROX were delineated based on the intermediates detected. The effects of water constituents on photodegradation were evaluated. Results obtained are helpful for better understanding the fate of ROX in aquatic environments.

Room temperature vulcanized (RTV) silicone rubber is extensively used in power system due to its hydrophobicity and hydrophobicity transfer ability. Temperature has been proven to markedly affect the performance of silicone rubbers. This research investigated the degradation of RTV silicone rubber under temperature cycling treatment. Hydrophobicity and its transfer ability, hardness, functional groups, microscopic appearance, and thermal stability were analyzed using the static contact angle method, a Shore A durometer, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetry (TG), respectively. Some significant conclusions were drawn. After the temperature was cycled between −25 • C and 70 • C, the hydrophobicity changed modestly, but its transfer ability changed remarkably, which may result from the competition between the formation of more channels for the transfer of low molecular weight (LMW) silicone fluid and the reduction of LMW silicone fluid in the bulk. A hardness analysis and FTIR analysis demonstrated that further cross-linking reactions occurred during the treatment. SEM images showed the changes in roughness of the RTV silicone rubber surfaces. TG analysis also demonstrated the degradation of RTV silicone rubber by presenting evidence that the content of organic materials decreased during the temperature cycling treatment.

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