Design of Thermochromic Polydiacetylene-Based Dielectric for Soft Stretchable Sensors

Polydiacetylene (PDA) is a conjugated polymer with alternating ene-yne moieties, known for its distinct and rich optical properties. Synthesized through the topochemical photopolymerization of 1,3-butadiyne-containing precursors, polymer can be formed <i>via</i> a 1,4-addition reaction when exposed to UV light. The synthesis process is simple and regioselective, resulting in high-purity PDA products without the need for catalysts or chemical initiators. Notably, PDAs can undergo a blue to red phase transition in response to various external stimuli, such as pH, temperature, chemical exposure, molecular bonding, or mechanical stress. This thermochromism is directly attributed to a a change in backbone conformation, going from planar (blue phase) to nonplanar (red phase). This unique thermochromism made PDAs particularly promising for chemo- and biosensing applications. Despite these features, the rigid backbone of PDAs can limit solubility and processibility, posing challenges for their application in organic electronics.<br/>To address these limitations, our group developed novel soluble and processable PDA materials by synthesizing 1,3-butadiyne-containing oligosiloxane precursors. The resulting materials, after photocrosslinking to form PDA, were found to be soluble in common organic solvents and easily processable into thin films. Additionally, these crosslinked siloxane-PDA materials exhibited good optoelectronic properties and interesting thermochromism. Upon synthesis and optical characterization, we used these new crosslinked materials as a dielectric in a capacitive temperature sensor, thus enabling the detection of temperature through another mechanism (optical and electronic sensing). This dual-sensing mechanism from the same materials is particularly interesting for smart packaging and wearable sensing, where multiple readout can be used simultaneously to monitor small temperature changes. In this presentation, we will discuss the design and synthesis of the new materials and their application in dual-mode temperature sensing. Various properties of the PDA polymer characterized using techniques such as Raman spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and UV-vis Spectroscopy will also be discussed.<br/><br/><br/><br/><br/><b>References:</b><br/>Hussain, Shazidul, et al. "Polydiacetylene a unique material to design biosensors." <i>Materials Today: Proceedings</i> (2022).<br/>Wen, Jessica T., Jenna M. Roper, and Hideaki Tsutsui. "Polydiacetylene supramolecules: synthesis, characterization, and emerging applications." <i>Industrial & Engineering Chemistry Research</i> 57.28 (2018): 9037-9053.<br/>Filhol, Jean-Sébastien, et al. "Polymorphs and colors of polydiacetylenes: a first principles study." Journal of the American Chemical Society 131.20 (2009): 6976-6988.<br/>Hu, Keda, et al. "Solution processable polydiacetylenes (PDAs) through acyclic enediyne metathesis polymerization." Chemical Science 4.9 (2013): 3649-3653.