Organic vapour permeation in amorphous and semi-crystalline rubbery membranes: Experimental data versus prediction by solubility parameters

Bidirectional Bending Soft Actuator with Multistimuli Responsiveness for Environmental Pollutant Monitoring

Soft actuators have emerged as promising tools for environmental monitoring; however, most existing actuators suffer from multistimuli cross-sensitivity and limited adaptability across various environments. Herein, we propose a bilayer soft actuator composed of a graphene-doped polydimethylsiloxane (G@PDMS) layer and a poly(vinylidene fluoride) (PVDF) layer, capable of effective deformation in both air and aqueous environments while exhibiting selective responsiveness. The actuator demonstrates multistimuli responsiveness to organic solvents/vapors, thermal radiation, and infrared (IR) radiation in air, achieving bidirectional deformation under organic stimuli with a remarkable bending angle of 630° and a load capacity of 180 times its self-weight. In aqueous environments, the actuator exhibits minimal response to thermal and IR light stimuli but shows high selectivity and rapid response to specific organic pollutants, with a response time of just 1.77 s to dichloromethane. Leveraging these properties, we developed a series of functional actuators─including Miura origami, airfoil, and artificial muscle configurations─demonstrating their capability to replicate complex movements. Moreover, a water lily-inspired multienvironmental actuator was designed to effectively shield against underwater temperature fluctuations, IR light, and nontarget organic solvent interference, showing its cross-insensitivity and potential for real-time environmental monitoring applications.

Optical Response of PDMS Surface Diffraction Gratings under Exposure to Volatile Organic Compounds

Monitoring volatile organic compounds (VOCs) in indoor air is significantly gaining importance due to their adverse effects on human health. Among the diverse detection methods is optical sensing, which employs materials sensitive to the presence of gases in the environment. In this work, we investigate polydimethylsiloxane (PDMS), one of the materials utilized for gas sensing, in a novel transducer: a surface relief diffraction grating. Upon adsorption of the volatile analyte, the PDMS grating swells, and its refractive index changes; both effects lead to increased diffraction efficiency in the first diffraction order. Hence, the possibility of VOC detection emerges from the measurement of the optical power transmitted or diffracted by the grating. Here, we investigated responses of PDMS gratings with varying surface profile properties upon exposure to VOCs with different polarities, i.e., ethanol, n-butanol, toluene, chloroform, and m-xylene, and compared their response in the context of the Hansen theory of solubility. We also studied the response of the grating with a 530 nm deep surface profile to different concentrations of m-xylene, showing a sensitivity and limit of detection of 0.017 μW/ppm and 186 ppm, respectively. Structures in the PDMS were obtained as copies of sinusoidal surface gratings fabricated holographically in acrylamide photopolymer and revealed good sensing repeatability, reversibility, and a fast response time. The proposed sensing technique can be directly adopted as a simple method for VOC detection or can be further improved by implementing a functional coating to significantly enhance the sensitivity and selectivity of the device.

Chromatographic Method for Evaluation of Polymeric GC Stationary Phases Ageing Using the Novel Non-Cross-Linked Poly(3-(Tributoxysilyl)Tricyclononene-7) as the Model Stationary Phase

The chromatographic properties and thermal stability are investigated for the polymeric stationary phase based on the norbornene polymer. It was shown that without additional cross-linking, poly(3-(tributoxysilyl)tricyclononene-7) demonstrates properties similar to liquid chromatographic stationary phases. It was also found to be more thermally stable than previously studied trimethylsilyl- and trimethoxysilyl- derivatives. The long-term heating at 170 °C resulted in an increase of mass transfer rate between stationary and mobile phases which could be observed as a decrease of parameter C of Van Deemter equation. This effect is rather unusual, as the polymeric stationary phases tend in decrease of the layer volume and porosity while ageing. Additionally, the values of thermodynamic parameters of sorption are calculated for the polymeric stationary phase: enthalpy of sorption varied −28 to −37 kJ/mol, entropy change was −41 to −51 J/mol K. The compensation curves were plotted for the alkanes, arenes, and alcohols, and the parameters of compensation plot were calculated, demonstrating the different sorption mechanisms both for hydrocarbons and oxygen-containing compounds, and different classes of organic compounds.