Synthesis and Postmodification of High-Molecular-Weight Polythioether with Excellent Intrinsic UV-Shielding Performance

As a main chain sulfur-rich polymer, polythioether can be applied as an optical material, but its current synthesis methods have drawbacks such as harsh conditions and low molecular weight, which have a negative impact on the synthesis and properties of polymers. Constructing a facile approach for synthesizing polythioether with a high molecular weight is highly desirable. Herein, thiocyanate was found to have the ability to initiate anionic ring-opening polymerization of episulfide in an open-vessel, and high-molecular-weight (M_n > 140 kDa) polythioether with phenylacetonitrile pendants was produced. Knoevenagel reaction between the reactive methylene group and benzaldehyde bearing an electron-donating or -withdrawing group was used to introduce the conjugated side groups. The polythioether film exhibited a good tensile strength of 4.1 MPa and excellent intrinsic anti-UV performance with a superior UPF of 330.9. This work provided an effective approach for preparing functional polythioether and improving its UV-resistant properties by postmodification.