Effect of polyoxybutylene chain length on the surface activity of butylene oxide-ethylene oxide block copolymers

Block copolymer surfactants (RBE) obtained by the addition of ethylene oxide to n-butyl, n-hexyl, n-octyl, and n-decyl ethers of mono- to tetrabutylene glycol are described. The surface activity of these nonionic surfactants has been determined, i.e., critical micelle concentration (CMC), surface excess concentration, Gamma, surface area demand per molecule, A, surface tension at CMC, gamma(CMC), and Delta G(ads)degrees. A linear decrease of log CMC vs number of oxybutylene units in a copolymer molecule is observed. The change in the work of cohesion per oxybutylene group when passing from a molecular into a micellar state, calculated from the Shinoda equation, is 0.99-0.92 kT for the studied compounds. The equivalent of CH2 in the aliphatic alcohol group is 1.06-1.15 oxybutylene units. Surface properties of these surfactants, i.e., cloud point, wetting ability, contact angle, and foam height, have also been determined. (C) 1998 Academic Press.