Assessing Wear Characteristics of Sprayable, Diacetylene-Containing Sensor Formulations

This work extends recent developments in diacetylene-based, sprayable sensors by identification and assessment of formulations which facilitate their use for wearable sensing. Diacetylene-based spray-on sensors have the potential to be a widely deployed sensing technology, as they require no power and can be applied as thin coatings onto surfaces to provide a colorimetric response to target exposure. In responding to radiation, liquid-phase targets, or gas-phase targets specifically determined by the formulation of the sprayable sensor used, this technology is amenable to wearable sensors for measuring exposure to different environmental risks. Here, we provide the means to improve wear resistance, reduce false-positive signals due to wetting, and enhance color fastness for coatings of sprayable, diacetylene-based sensor formulations on cotton fabric. These sensor formulations possess polymethyl methacrylate (PMMA), which enhances the coating stability to only 8% color loss due to wear compared to 18-25% without PMMA, while maintaining the inherent ability of diacetylene-component formulations to detect radiation as well as gas or liquid phase analytes. This represents a significant step toward the use of diacetylene-based sensing formulations for wearable sensing. In the future, the form of spray-on sensor materials demonstrated here may find use in wearable sensing applications for detection of cumulative exposure to UV radiation, hydrogen peroxide vapors, or solvent exposure. We expect trends toward applications toward other wearable sensors for environmental monitoring given the well-known customizability in target response of diacetylene-containing monomers by modifying their headgroup chemistry.

Fabrication of High-Performance Colorimetric Membrane by Incorporation of Polydiacetylene into Polyarylene Ether Nitriles Electrospinning Nanofibrous Membranes

Polyarylene ether nitrile (PEN) is a novel high-performance engineering plastic with various applications, particularly in thermoresistance-required fields. In this study, a well-known stimuli-response polydiacetylene monomer, 10, 12-pentacosadiynoic acid (PCDA), was encapsulated within electrospun PEN nanofibers to fabricate a colorimetric membrane with satisfactory thermal and corrosion resistance. To optimize the compatibility with PCDA, two PENswith distinct molecular chains were utilized: PEN−PPL and PEN−BPA. The chemical structure and elemental mapping analysis revealed that the PCDA component was successfully incorporated into the PEN fibrous. The PCDA bound significantly better to the PEN−PPL than to the PEN−BPA; due to the carboxyl groups present on the side chains of PEN−PPL, the surface was smooth and the color changed uniformly as the temperature rose. However, owing to its poor compatibility with PEN−BPA, the PCDA formed agglomerations on the fibers. The thermal analysis demonstrated that the membranes obtained after PCDA compounding maintained their excellent heat resistance. The 5% weight loss temperatures of composite nanofibrous membranes manufactured by PEN−PPL and PEN−BPA were 402 °C and 506 °C, respectively, and their glass transition temperatures were 219 °C and 169 °C, respectively, indicating that the blended membranes can withstand high temperatures. The evaluation of application performance revealed that the composite membranes exhibited good dimensional stability upon high thermal and corrosive situations. Specifically, the PEN−P−PCDA did not shrink at 170 °C. Both composite membranes were dimensionally stable when exposed to the alkali aqueous solution. However, PEN−P−PCDA is more sensitive to OH−, exhibiting color transition at pH > 8, whereas PEN−B−PCDA exhibited color transition at high OH− concentrations (pH ≥ 13), with enhanced alkali resistance stability owing to its nanofibrous architecture. This exploratory study reveals the feasibility of PEN nanofibers functionalized using PCDA as a desirable stimulus-response sensor even in high-temperature and corrosive harsh environments.