Synthesis and surface measurements of surfactants derived from dehydroabietic acid

• Dehydroabietates with poly(ethylene oxide) chains of average m=12, 17 and 45 units (DeHab(E)m) have been synthesized and some of their surfactant properties have been characterized. The results have been compared with common linear chain CnEm surfactants. The adsorption to the liquid-vapor interface was measured and the adsorbed amount and critical micelle concentrations, cmc, determined. The dehydroabietic acid as hydrophobe was found to result in the same cmc as a linear dodecyl chain. The DeHAb(E)45 was found to be insoluble above 400 mg/l, but the surface tension at lower concentrations were similar to those of the C11-13E38-40 surfactants, which exhibit cmcs in aqueous media. The reason for the insolubility of DeHab(E)45 is proposed to be the large size and rigid structure of the hydrophobe, which imposes a large micelle size. The curvature of such a micelle is too low for efficient packing of the large headgroup, so micelle formation becomes unfavorable. The foaming behavior of the DeHAb(E)12 and DeHab(E)17 surfactants was about the same as for common linear CnEm surfactants i.e. the foamability as well as the foam stability increased with ethylene oxide chain length. The cloud point was depressed by increased salt concentration and increased with the number of ethylene oxide units in the head-group. The cloud point was significantly lower than for the corresponding surfactant with a dodecyl chain with similar EO-chain length. The suggested reason for this is explained by the fact that the micelles of DeHab(E)m are larger, due to the large and more rigid dehydroabietic hydrophobe. The attractive forces between the micelles are larger for DeHab(E)m than for the linear CnEm surfactants. The more concentrated surfactant phase of DeHab(E)m leads to clouding phenomenon at lower temperatures than for CnEm. The wetting results, obtained by measuring the contact angle at similar surface tensions, indicate that surfactants of the DeHab(E)m type are more efficient wetting agents than both disaccharide sugar surfactants and CnEm type surfactants.

Nyckelord

Dehydroabietic acid

surfactants

PEG

sugar

foaming

wetting

surface tension

cmc

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)