Molecular dynamics simulation study of thermomechanical properties and hydrogen bonding structures of two‐component polyurethanes

Abstract

AbstractWe investigated the thermomechanical properties and hydrogen bonding (HB) structures of two‐component hexamethylenediisocyanate (HDI)‐poly(tetramethylene oxide) (PTMO) and 4,4′‐methylenediphenyldiisocyanate (MDI)‐PTMO polyurethanes with atomistic molecular dynamics simulations. We used different temperature‐scanning and sampling protocols to estimate the glass transition temperature (Tg) of these two polyurethanes. Our simulation results consistently predicted higher Tg values for MDI‐PTMO than those for HDI‐PTMO, in qualitative agreement with the same trend observed in experiments. We also studied two different types of HB interactions in these polyurethanes. At ambient temperature, more HB contacts between amide‐hydrogens and carbonyl‐oxygens of the carbamate groups along with longer lifetimes were noted in HDI‐PTMO than in MDI‐PTMO, while the latter revealed more HB contacts between amide‐hydrogens and ether‐oxygens of PTMO. MDI‐PTMO, encompassing more rigid chain structures, displayed higher stress values in stress–strain profiles from high strain‐rate tensile deformations at ambient temperature than HDI‐PTMO, which is consistent with a higher Tg value of MDI‐PTMO.