Tailoring the physical properties of non-isocyanate polyurethanes by introducing secondary amino groups along their main chain

Abstract

A series of linear non-isocyanate polyhydroxyurethanes (NIPUs) were synthesized by aminolysis of a PPO bis-cyclic carbonate with two diamines, one of which (triethylenetetramine, TETA) contains non-reacting secondary amino groups. Thus, varying the composition of the diamine component modulates the density of proton donors. Fourier Transform Infrared Spectroscopy (FTIR) showed that with increasing TETA content in the amine components (20–100 wt%) carbonyl groups tend to form progressively more double hydrogen bonds (HBs). Interestingly, the system without this amine deviates from the trend. In the whole composition range, a higher amount of double HBs correlates monotonously with reduced molecular mobility as observed by differential scanning calorimetry (DSC), dielectric relaxation spectroscopy (DRS), and dynamic mechanical analysis (DMA). It also correlates with the mechanical properties of studied NIPUs which range at room temperature from a viscous liquid to a dimensionally stable, flexible, and durable elastomer, depending on the density of double hydrogen-bonded carbonyls. Hence, the herein proposed approach allows for tailoring thermomechanical properties of NIPUs by modulating density of double hydrogen-bonded carbonyls.