Most preferably, R1 and R2 are independently methyl, and R3 is a linear or branched alkyl group having from about 8 to about 18 carbon atoms; or R1 and R2 are independently ???(R4O)xR5, R3 is a linear or branched alkyl group having from about 8 to about 18 carbon atoms, R4 in each of the x (R4O) groups is ethylene or propylene, R5 is hydrogen or an alkyl group having from about 8 to about 18 carbo