The use of variable-temp. Fourier-transform IR measurements and rheooptical Fourier-transform IR studies at elevated temp. (380-500 K) was reported for polyester polyurethanes (I) [27083-55-2] prepd. from diphenylmethane 4,4'-diisocyanate and hydroxy-terminated adipic acid-butanediol-ethylene glycol copolymer (mol. wt. 2000). DSC diagrams of the I between 380 and 500 K were given. The results were discussed with ref. to phase sepn. and segmental orientation of I during uniaxial elongation and were interpreted in terms of the temp. dependence of H bonding and structural organization of hard segments.