Efficient Degradation of Cis-Polyisoprene by GQDs/g-C3N4 Nanoparticles Under UV Light Irradiation

Rubber material with high elasticity and viscoelasticity has become the most widely used universal material, and the study of the aging failure mechanism of rubber has been meaningful research in the polymer materials field. Cis-polyisoprene was employed to analyze the mechanism of oxidative degradation under artificial UV irradiation, and the GQDs/g-C3N4 photocatalysis with a 2D layered structure prepared by the method of microwave-assisted polymerization enabled to accelerate the degradation procedure. The results showed that the oxidation of cis-polyisoprene occurred during the irradiation for 3 days and the structure of cis-polyisoprene changed. The α-H of the double bond was attacked by oxygen to form hydroperoxide. Then, aldehydes and ketones generated as the addition reaction of double bonds occurred. The content of the hydrogen of C=C reduced, and the oxidative degradation was dominant at the initial aging stage. The crosslinking reaction was dominant at the final aging stage and the average molecular weight decreased from 15.49 × 104 to 8.78 × 104. The GQDs could promote the charge transfer and the photodegradation efficiency and inhibit the electron–hole recombination. The light capture ability of GQDs was improved after compositing with g-C3N4. The free radicals ·O22− generated after adding GQDs/g-C3N4 nanoparticles, and the molecular weight of cis-polyisoprene decreased to 5.79 × 104, with the photocatalytic efficiency increasing by 20%. This work provided academic bases and reference values for the application of photocatalysts in the field of natural rubber degradation and rubber wastewater treatment.