EFFECTIVE CHAIN LENGTH OF POLYOXYPROPYLATED IONIC AND NONIONIC SURFACTANTS.

The effect of polyoxypropylene chain length in ionic surfactants and block copolymers on the c. m. c. and HLB was considered, using the concepts of effective chain length (n(eff)) and hydrophobic index (HI). As the propylene oxide chain lengthens, the HI increases and the c. m. c. decreases, depending on the hydrophilic group (ionic or nonionic) present. This effect was compared with that of lengthening of the aliphatic chain. The equivalence of the oxypropylene unit and the minus CH//2-group in the aliphatic chain was attributed to coiling of the surfactant molecule in water, with the attendant effective decrease in chain length. Theoretical HLB values calculated according to Davies' and Lin's formulae were examined for the surfactants under study.