Regulating Hard Segment Aggregation in Polyurethane Elastomers via Multiple Hydrogen Bonding Motifs for Enhanced Mechanical Properties

Abstract Controlling aggregation of soft and hard segments is a prevalent strategy to improve the mechanical performance of polyurethane elastomers, yet the regulatory actions of hydrogen bonding motifs governing the size and spatial distribution of hard and soft segments remain insufficiently understood. Here, polyurethane elastomers containing carbamate, urea, and acylsemicarbazide hydrogen bonding motifs were designed to establish the relationship among molecular interactions, hard segment aggregation behavior, and mechanical properties. Density functional theory (DFT) and molecular dynamics (MD) simulations were employed to verify the specificity of different hydrogen bonding motifs, while small angle X-ray scattering (SAXS) and atomic force microscopy (AFM) were utilized to investigate the regulatory effect of these motifs on the dimensional size and distribution of hard segments. Differential scanning calorimetry (DSC) demonstrated the modulatory effect of hard segments on soft segments, and dissipative particle dynamics simulations elucidated the regulatory mechanism of hydrogen bonding motifs on the interfacial compatibility between hard and soft phases. Multiple hydrogen bonding motifs promote the formation of small, uniformly distributed hard segment domains in polyurethane elastomers, thereby preserving molecular chain mobility while enabling efficient energy dissipation and ultimately enhancing the mechanical properties. The resulting polyurethane elastomer exhibits a tensile strength of 51.7 MPa, toughness of 271.7 MJ·m−3, and fracture energy of 181.2 kJ·m−2. This work should clarify the actions of hydrogen bonding motifs in regulating hard segment aggregation, providing a reliable molecular design strategy for the fabrication of high-performance and mechanically tunable polyurethane elastomers.