Catalyst-Free Construction of Versatile and Functional CS2-Based Polythioureas: Characteristics from Self-Healing to Heavy Metal Absorption

As typical of sulfur-containing polymers, polythiourea is a promising polymeric material because of its outstanding properties such as self-healing, high refractive index, high dielectric constant, and good coordinating ability to heavy metal ions. However, examples of versatile polythioureas are relatively scarce as a result of the limited methods for their synthesis. Herein, we report a mild and easily accessible strategy for the preparation of polythioureas by a catalyst-free copolymerization of CS2 and diamines in the absence of an inert/anhydrous atmosphere. The copolymerization of 1,8-diamino-3,6-dioxaoctane (DA1) and carbon disulfide was selected as the model reaction for optimizing conditions for the polymerization process. DA1 and CS2 afforded well-defined polythiourea P1 with high molecular weight (25.5 kg/mol) in good yield (96%) at 45 °C, which was shown to be mechanically robust and readily self-healable. This method displayed a wide scope, providing 23 polythioureas with structural diversity and high molecular weights in excellent yields from CS2 and commercially available diamines. The aliphatic polythiourea P4 was examined for its ability as a heavy metal absorbent, effectively sequestering Hg2+ ions with greater than 99.9% efficiency. Hence, this study provides an easily accessible method for synthesizing various polythioureas with diverse structures and functionalities.