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Synthesis and Surface Activities of Betaine Amphoteric Surfactant Having Ether Bond

Four novel amphateric surfactants of N-alkoxyethylcarboxybetaine series were synthesized via Schotten-Baumman reaction between four alkyl chlorides contaning 10, 12, 14 and 16 carbon atoms in their N-alkyl group and dimethylaminoethanol to give the intermediate products, alkoxyethyldimethylamine. Quaternization of these intermediates was permitted to form 2-(alkoxyethyldirnethylammonio) acetates, whose structures were identified by elemental analysis, IR spectrophotometry and ¹Hnmr spectrometry. The yield of the final products was shown in the range of 74~77% based on the yield of the intermediate products. Surface tension of the aqueous solution of the final products was measured, and the critical micelle concentrations(cmc) were shown in the range of 2.82×10⁻³~2.67×10⁻⁶mol/l, and the surface thension at cmc was 35~43dyne/cm. Cmc was lowered gradually by the increase of carbon numbers in N-alkyl ether containing group. The isoelectric point was shown in the range of 4.08~6.03. It showed a tendency to lean toward the acidic site and its range was broadened as increase of the hydrophobic group length. A linear relationship between log cmc and the number of carbon atoms(N) in the hydrophobic alkyl chain was shown in the relative equation of log cmc=2.49-0.50N.