Efficient room-temperature synthesis of crosslinked polyhydroxyurethanes from 5-membered cyclic carbonates without solvent or catalyst We report the first solvent- and catalyst-free synthesis of crosslinked polyhydroxyurethanes (PHUs) at room temperature from five-membered cyclic carbonates (5CC). A trifunctional carbonate (tri-5CC) combined with tetraethyleneglycol diamine (tDA) formed homogeneous, gelled networks within 24 h (carbonate conversion = 90%, gel time = 6 h).