Polythioethers and methods for forming polythioethers are disclosed herein. The polythioethers are prepared from thiols and hexahydrotriazines. The thiols may be, for example, dithiols, trithiols, monothiols, or mixtures thereof. The polythioethers are prepared from an efficient and simple synthetic method, and the properties of the prepared polythioethers can be readily tuned. The prepared polythioethers may additionally have improved thermal properties, improved mechanical properties, and enhanced functionality.