ydrocarbon residue, each R5 is the same or different and is a substituted or unsubstituted divalent hydrocarbon residue, R6 is hydrogen, a substituted or unsubstituted monovalent hydrocarbon residue or an ionic substituent, a and b are the same or different and are a value of 0 or greater; provided at least two of R1, R2, R3, R4, R5 and R6 are a hydrocarbon residue having greater than 2 carbon ato