wherein R1 is an alkylene group containing from 1 to about 25 carbon atoms; R2 and R3 are independently selected from the group consisting of at least one of hydrogen, alkyl containing from 1 to about 5 carbon atoms, aryl containing from about 6 to about 36 carbon atoms, and a poly(alkylene amino) group; and R4, R5, and R6 are independently selected from an alkyl group containing from 1 to about 6