Infrared Spectra and Structure of Polyurethane Elastomers from Polytetrahydrofuran, Diphenylmethane-4, 4′-diisocyanate, and Ethylenediamine

Abstract

The infrared spectra (4000–650 cm⁻¹) of a series of polyurethane elastomers synthesized from polytetrahydrofuran, diphenylmethane-4,4′-diisocyanate, and ethylenediamine were examined. By comparing the spectra with those of the constituent polytetrahydrofuran and of the model compounds for the hard segments of the elastomers containing the urea, urethane, and diphenylmethane groups, most of the stronger bands could be assigned with reasonable assurance to the vibrations of each constituent part. The frequencies of the urea and the urethane characteristic bands correspond to complete association of the polar groups in the polymers. The spectral changes produced by uniaxially stretching polyurethane films can be interpreted as due to the induced crystallization of the polyether blocks in the elastomer, which remain amorphous in the undistorted state. Polarization measurements on stretched samples confirmed that the polyether chains are oriented parallel to the direction of the stretch.