FTIR was used to investigate the effects of thermal annealing on the hydrogen-bonding properties of a poly(urethane urea) copolymer. The copolymer was based on ethylene oxide-capped poly(propylene oxide) diol, 4,4‘-diphenylmethane diisocyanate (MDI), and 3,5-diethyltoluenediamine (DETDA). The result showed that thermal annealing caused the rise of the number of free urethane groups and the ordering of urea groups. The ordered urea hydrogen bonds were not destroyed below the melting point of the DETDA−MDI hard domain.