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

Abstract

AbstractThe 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 (λm) 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 λm 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 λm to 30 mol% decreases the degree of microphase separation to 0.16, resulting in an increase in tensile strength to 78 MPa.