Ultratough Yet Dynamic Crystalline Poly(thiourethane) Network Directly from Low Viscosity Precursors

Thermosets based on direct curing of multifunctional monomers offer processing flexibility that thermoplastics cannot provide. However, this type of thermoset is typically amorphous since it is difficult to meet the stringent requirement of long-range molecular regularity for crystallization. However, we report here a crystallizable poly(thiourethane) thermoset synthesized directly from the curing of low-viscosity liquid precursors that does not employ any solvent. Its crystalline nature results in superior toughness, comparable to commercial high-density polyethylene, in sharp contrast to the brittleness of the typical, rigid, glassy thermoset materials. Beyond that, the network polymer exhibits shape-memory behavior in which the crystalline transition is utilized for temporary shape fixing/recovery whereas the dynamic thiourethane bonds can be activated for bond exchange as a mechanism for complex shape manipulation. Materials with these combined features represent attractive options for demanding engineering applications due to their high performance and multifunctinality.