A Transparent, High Refractive, Shape-Memory, Healable, and Recyclable Phenolic Polyurethane Thermoset: Unexpected Roles of Bromine Substituents and Tertiary Amine Catalysts

The applications of polyurethane (PU) thermosets are limited by the lack of plasticity after curing due to permanent crosslinks. Besides, the low refractive index is insufficient for optical devices. Here, a transparent, high refractive, recyclable, and healable PU thermoset is developed based on dynamic bromined phenyl-carbamate bonds (BPCB). It exhibits tensile strength of approximate to 52 MPa, good shape-memory ability, and can be reprocessed or healed nearly completely at 110 degrees C in 30 min. Tertiary amine catalysts and bromine substituents jointly play unexpected roles to promote the forward and reverse reactions significantly, leading to high bond-exchange efficiency of BPCB. Furthermore, the introducing of BPCB can endow the material with higher refractive index (n(D) = 1.5850) simultaneously. In summary, this material is of potential as dynamic PU thermoset in various fields, especially in advanced optical devices.