In the study reported here, of the poly(ester urethane), Estane 5703, simultaneous dynamic mechanical analysis (DMA) and dynamic infrared linear dichroism (DIRLD) measurements have been carried out at continuously variable temperatures from -50 to +30 degrees C. Multivariate curve resolution-alternating least squares (MCR-ALS) analysis of the spectral data has been correlated with the thermo-mechanical properties. Spectral changes, analyzed as a function of temperature, are compared with the storage and loss moduli to provide insight into viscoelastic behavior at the molecular level. In addition, the data for pure Estane have been compared to those for plasticized Estane samples, which contain 10 and 30% plasticizer by weight. These comparisons show a strong and consistent correlation between the macroscopic rheological properties and the microscopic (molecular, inter-molecular, and sub-molecular) responses of this block co-polymer.