Phenolphthalein (PP series) or 4-tritylaniline (TA series) was used for grafting onto polyurethane (PU), and the effects of two grafted groups on the soft segment glass transition, tensile strength, recovery to original shape, and flexibility at freezing temperature were investigated. The soft segment melting of PP series and TA series was not significantly affected with increases in phenolphthalein or tritylaniline content. The soft segment glass transition temperature (T g ) of PP series clearly increased as the PP content increased, whereas TA series exhibited a little increase in T g with increases of TA. Solution viscosity, degree of cross-linking, shape recovery at 10 °C, and tensile strength of PP series clearly increased with increases in PP because of cross-linking in the grafted phenolphthalein, whereas TA series did not demonstrate the same degree of enhancement with increases in TA. In contrast to plain PU and TA series, PP series displayed outstanding flexibility below 0 °C. Therefore, compared to plain PU, the grafting of phenolphthalein clearly enhanced the tensile strength, flexibility under freezing, and recovery to original shape of the polymer.