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Novel zwitterionic organofunctional siloxane aqueous surfactants, composed of a short siloxane chain hydrophobic portion and an organobetaine hydrophilic portion, are prepared by the quaternization of precursor tertiary amine functional siloxanes with iodoalkylcarboxylate salts. These surfactants are of the general formula (Me3SiO)(SiMe20)0(SiMeRO)SiMe3 (R = (CH2)3+NMe2(CH2)6COO"; a = 0,1; b = 1, 2). Purified samples reduce the surface tension of water to a minimum of 21 mN/m. The surface areas of coverage of the a = 0 species ( = 1,70 A2; b = 2,85 Á2) are similar to the related sulfobetaine functional species. The surface area of coverage of the a = 1 species is unexpectedly small, although a similar result was noted for the analogous sulfobetaine species. Both molecular size and surfactant concentration directly correlate with the dynamic surface tensions of dilute aqueous solutions of these surfactants. These surfactants rapidly decompose in both acidic and basic aqueous solutions, due to the hydrolysis of siloxane bonds. The aqueous solution mixtures of (Me3SiO)2Si(Me)-(CH2)3+NMe2CH2COO" and ZnC^f orm addition compounds, possibly due to the complexation of the Zn(II) metal ion through the carboxylate groups of the surfactant.

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