Molecular parameters for the prediction of polyurethane structures

Recent efforts to determine the structures of poly(MDI/diol) hard segments in polyurethane elastomers have relied on the structures determined by single-crystal x-ray methods for diphenylmethane urethane model compounds. We have surveyed the structure of six model compounds, and have derived average values for the bond lengths, bond angles, and bond torsion angles for use in future analyses. The applicability of these averages to polymer structures is discussed, and the data are used to derive models for the poly(MDI-butanediol) chain which are found to be consistent with the fiber repeat determine by x-ray methods.