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Relationship of structure to properties of surfactants. 15 Isomeric sulfated polyoxyethylenated Guerbet alcohols

1990; Wiley; Volume: 67; Issue: 4 Linguagem: Inglês

10.1007/bf02540642

1558-9331

Dennis S. Murphy, Zhen Huo Zhu, X. Y. Yuan, Milton J. Rosen,

Photochemistry and Electron Transfer Studies

Abstract The properties at 25°C in aqueous 0.1M NaCl at the aqueous solution/air, aqueous solution/hexadecane, and aqueous solution/hydrophobic solid interfaces of two isomeric Guerbet alcohol‐derived surfactants C 8 H 17 CH(C 6 H 13 )CH 2 (OC 2 H 4 ) 5 SO 4 Na, one in which the octyl and hexyl groups are both linear (L isomer), the other in which they are both highly branched (B isomer), have been investigated and compared in some cases with commercial sodium linear dodecylbenzene‐sulfonate (LAS). The cmc value increases, the pC 20 value decreases, and the ΔG o ad value becomes less negative in the order: L isomer—B isomer—LAS. The minimum area/molecule at the aqueous solution/air interface increases in the order: LAS≪L isomer<B isomer. The L isomer is slightly more hydrophobic than the B isomer, and both are considerably more surface‐active than LAS. The greater steric inhibition to micellization in the B isomer results in the lowest minimum surface tension. Both isomers have similar minimum interfacial tension values against hexadecane. Unusually small minimum area/molecule values for the two isomers at the aqueous solution/hydrophobic solid interface may indicate multilayer adsorption there. Both isomers are more efficient at reducing the contact angle than LAS. Mixtures of the B isomer with the corresponding unsulfated Guerbet alcohol show only weak interaction between the two. No synergism in surface (or interfacial) tension reduction efficiency or micelle formation exists at either the aqueous solution/air or aqueous solution interface but the mixture does show synergism in surface (or interfacial) tension reduction effectiveness, yielding a surface tension value of 28.2 dynes/cm, and an interfacial tension value of 0.1 dyne/cm against hexadecane. Draves wetting times increase in the order: B isomer<LAS<L isomer, and Ross‐Miles initial foam heights decrease in the order B isomer ≈LAS>L isomer.