Unraveling thermo-oxidation degradation pathways of polymers by in-situ differentiating the alkyl-related reactive oxygen radicals

Alkoxy radicals (RO•) and peroxy radicals (ROO•) are generated during thermo-oxidation of polymers under oxygen environment, leading to RO•-dominated or ROO•-dominated reaction pathways with severely deteriorated polymer chains or terminated reaction. However, it has been a long-standing challenge to in-situ distinguish RO• and ROO• radicals due to their short-lived lifetime. In principle, chemiluminescence (CL) deserves to become an efficient strategy for in-situ monitoring for various radicals. However, it fails to differentiate RO• and ROO• radicals due to their fully overlapping emission wavelengths. In this contribution, we have proposed a CL dynamic fitting strategy to distinguish RO• and ROO• radicals of in-situ production during thermal oxidation under the different oxygen-containing environment. Based on two equations, $\ln I=\ln A·k_{\mathit{RO}}-\ln \left(1+Y·e^{-k_{\mathit{RO}}t}\right),and\ln I=\ln B-k_{\mathit{ROO}}t-2\ln \left(1+Y·e^{-k_{\mathit{ROO}}t}\right)$$\ln I=\ln A·k_{\mathit{RO}}-\ln \left(1+Y·e^{-k_{\mathit{RO}}t}\right),and\ln I=\ln B-k_{\mathit{ROO}}t-2\ln \left(1+Y·e^{-k_{\mathit{ROO}}t}\right)$, respectively, the CL dynamic fitting was implemented to identify RO• and ROO• generated during the oxidative reactions of polymers. It is anticipated that the proposed strategy could be further explored for the identification of other radicals during thermo-oxidation, providing possibilities for regulating oxidative reaction pathways of polymers.