Two different polymeric materials were evaluated to determine their respective fatigue endurance behavior. both materials were tested separately in laboratory air and in flowing water. (water was selected as a suitable liquid test environment since neither polymer was adversely affected by its presence.) polymer a showed similar s-n plots in the two environments whereas polymer b revealed remarkably different results. speculate as to which environment was associated with the superior fatigue response in polymer b and characterize the structure and mechanical response of polymers a and b