Synthesis and properties of molecularly uniform model compounds for the hard segments of 1,5‐naphthylene diisocyanate based polyurethane elastomers

Two homologous series of molecularly uniform oligourethanes based on 1,5-naphthylene diisocyanate (NDI) and 1,4-butanediol (BDO) were synthesized and used as model compounds for the investigation of the structure/properties relations regarding the hard segment domains of NDI-based polyurethane (PUR) elastomers. The NDI/BDO oligourethanes show extremely high crystalline melting points and unusually high heats of fusion. This is attributed to strong intermolecular interactions combined with the rigid structure of the naphthalene-butanediol units. Decomposition occurred before the melting was completed. Annealing led to an improved crystal structure and higher softening points as long as decomposition in the amorphous regions was prevented by the choice of sufficiently low annealing temperatures.