Synthesis and characterization of MDI‐butanediol urethane model compounds

Abstract

Abstract Hard‐segment model compounds containing one to five 4,4′‐methylene bis( p ‐phenylisocyanate) (MDI) units extended with 1,4‐butanediol (BD) were synthesized. The ends of the model compounds were reacted with ethanol. The melting point ( T m ) of the model compounds increased with the number of MDI units to an extrapolated value of 299°C for the homopolymer using Flory's equation accounting for chain end defects. The Δ H of fusion was 5.3 kcal/mol. Intrinsic viscosity measurements in DMA solutions revealed a Mark Houwink exponent of 1.43 suggesting that the hard‐segment model compounds are rodlike in solution. Wide‐angle X‐ray diffraction showed that the percentage of hard‐segment crystallinity decreased as the oligomer length increased. Infrared spectroscopy studies showed that the distribution of hydrogen bond distances between CO and NH groups became broader with increasing segment length.