Large scale synthesis of an amorphous polyester elastomer with tunable mechanoluminescence and preliminary application in optical strain sensing
In this work, a transparent thermoplastic elastomer, showing blue emission upon UV light excitation, has been synthesized via the block copolymerization of an amorphous polyester oligomer and flexible polyethylene glycol (PEG) on an industrial scale. Specifically, an alicyclic glycol named 1,4-cyclohexanedimethanol (CHDM) was introduced into the esterification of purified terephthalic acid (PTA) and ethylene glycol (EG) to synthesize the oligomer of glycol-modified polyethylene terephthalate (PETG), which was subsequently copolymerized with PEG to finally obtain the transparent thermoplastic elastomer. It should be noted that CHDM is found to break macromolecular regularity, which leads to the amorphous nature of the obtained copolyester. The flexible PEG not only contributes to the elasticity of the copolyester, but also in situ decomposes it into fluorescent carbon nanodots during polymerization, which finally endows the obtained elastomer with fluorescence that can be modulated by different mechanical stress (i.e. stretching and relaxing). Therefore, we have fabricated a prototype of a reusable strain sensor using the developed elastomer owing to its reversible mechanoluminescence.