Experimental FTIR and simulation studies on H-bonds of model polyurethane in solutions. I: In dimethylformamide (DMF).

Polyurethane (PU) hard segment is one of the key factors determining the final PU properties whereas dimethylformamide (DMF), with the simplest tertiary amide, is one of the good solvents for PU. In the present paper, both FTIR and molecular simulation (QM/B3LYP) were used to study the hydrogen bonds (H-bonds) of PU model hard segment (PUMHS) in DMF. The FTIR characteristics and the H-bonding interaction between DMF and PUMHS, as well as in DMF and PUMHS themselves have been investigated. The results showed that the H-bonds not only exist in DMF and in PUMHS themselves, but also exist between PUMHS and DMF. Among them, seven H-bonding complexes between DMF and PUMHS were found based on different conformations. The H-bonding properties and the forming probabilities have been obtained and compared. The evolution of H-bonds of PUMHS in DMF with different concentration was qualitatively analyzed.