Synthesis and characterization of linear hybrid aliphatic/aromatic copolyurea via one-step feeding method

The combination of aromatic and aliphatic structures can endow polyurea with distinct performance advantages. A one-step feeding method is used to synthesize linear hybrid aliphatic/aromatic copolyureas by varying the ratio of m -phenylenediamine (MPD) and polyoxypropylenediamine (D2000) reacting with 4,4′-diphenylmethane diisocyanate (MDI). Real-time Fourier-transform infrared spectrometer monitoring reveals that D2000 exhibits higher reactivity than MPD. Consequently, in the MDI/MPD/D2000 system, D2000 initially reacts with MDI to form an isocyanate-terminated prepolymer, which subsequently reacts with MPD. Compared with the two-step feeding method, this approach successfully eliminates biuret formation and enhances tensile strength. Additionally, decreasing the molar ratio of D2000 to MPD ( λ m ) reduces the size and degree of microphase separation in the polyurea by increasing the ordered hydrogen bonding and benzene conjugation, leading to an increase in tensile strength. Specifically, as λ m decreases from 70 mol% to 30 mol%, the degree of microphase separation decreases from 0.47 to 0.2, causing the tensile strength to rise from 28 to 48 MPa. Further reducing λ m to 30 mol% decreases the degree of microphase separation to 0.16, resulting in an increase in tensile strength to 78 MPa.