Polyurethane (PU) with a diphenylamino side group is tested for low temperature flexibility at 30 degrees C and compared with a linear PU without the diphenylamino side group. The PU is composed of 4,4-methylenebis(phenylisocyanate) (MDI), poly(tetramethyleneglycol) (PTMG), 1,4-butanediol (BD), and the diphenylamino group that is grafted to PU chains by a second MDI. The mechanical and shape memory properties of these two types of PU, which differ in the PTMG and the diphenylamino group content, are compared. In the best case, a 306% increase in the maximum stress compared with the linear polymer is attained with a little decrease in the strain. Shape recovery at 45 degrees C increases to 94% and remains approximate to 90% after four cyclic tests. Low temperature flexibility can be improved by increasing the diphenylamino content. The PU with a diphenylamino side group demonstrates the low temperature flexibility at 30 degrees C, whereas the linear PU must be warmed to room temperature to attain the same degree of flexibility. The exceptional low temperature flexibility is analyzed and is discussed together with the experimental data. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013