In one preferred embodiment, the segmented copolymers are the block copolymers of ethylene oxide and propylene oxide having the formulas: in which x, y, z, i and j have values from about 2 to about 800, preferably from about 5 to about 200, more preferably from about 5 to about 80, and wherein for each R1, R2 pair, one is hydrogen and the other is a methyl group.