Irreversible synthesis of an ultrastrong two-dimensional polymeric material

Polymers that extend covalently in two dimensions have attracted recent attention 1 , 2 as a means of combining the mechanical strength and in-plane energy conduction of conventional two-dimensional (2D) materials 3 , 4 with the low densities, synthetic processability and organic composition of their one-dimensional counterparts. Efforts so far have proven successful in forms that do not allow full realization of these properties, such as polymerization at flat interfaces 5 , 6 or fixation of monomers in immobilized lattices 7 – 9 . Another frequently employed synthetic approach is to introduce microscopic reversibility, at the cost of bond stability, to achieve 2D crystals after extensive error correction 10 , 11 . Here we demonstrate a homogenous 2D irreversible polycondensation that results in a covalently bonded 2D polymeric material that is chemically stable and highly processable. Further processing yields highly oriented, free-standing films that have a 2D elastic modulus and yield strength of 12.7 ± 3.8 gigapascals and 488 ± 57 megapascals, respectively. This synthetic route provides opportunities for 2D materials in applications ranging from composite structures to barrier coating materials.