SORPTION OF MONODISPERSE ALCOHOL ETHOXYLATES AND THEIR EFFECTS ON THEMOBILITY OF 2,4-D IN ISOLATED PLANT CUTICLES

The sorption of homologous monodisperse alcohol ethoxylates in cuticle s isolated from the leaves of bitter orange (Citrus aurantium L.) and thoroughly extracted with chloroform (yielding polymer matrix membrane s, MX) has been investigated. Sorption isotherms exhibited a linear ph ase at low aqueous concentrations of surfactant, while above the criti cal micelle concentrations (cmc) the concentration sorbed in the MX wa s independent of external concentration. MX/water partition coefficien ts (25-148 000, depending on the homologue), maximum concentrations in the MX (91-318 mmol/kg), and cmc were derived from the isotherms. Qua ntitative structure-property relationships were established for estima ting the MX/water partition coefficients, cmc, and maximum cuticular c oncentrations of alcohol ethoxylates from the number of carbon atoms a nd oxyethylene groups of their alcohol and poly(oxyethylene) moieties, respectively. These relationships were used for analyzing the effects of monodisperse alcohol ethoxylates and primary alcohols on the mobil ity of (2,4-dichlorophenoxy)acetic acid in isolated cuticular membrane s from bitter orange leaves.