| Popis: |
ELATIVELY FEW papers on the physico-chemical propert ies of nonionic detergents have appeared so fa r in the l i terature, in contrast to the numerous papers published on ionic detergents. This delay in exploring a field of growing industr ial importance must be a t t r ibuted to the fact that monodisperse materials are difficult to prepare. Their synthesis by the Will iamson method has been repor ted for a chain length of one to six ethylene oxide units only (9,34, 35,50). Nonionic detergents, whieh have been prepared by the condensation of ethylene oxide with aliphatie alcohols, earboxylic acids, amides, mercaptans and alkylphenol% yield products in which the chain length of the hydrophil ie port ion has a Poisson distr ibution (14,15,20). In order to cover a wide range of molecular structures, these ethylene oxide condensates have been used in the last decade to elucidate the physico-chemieal propert ies of nonionic detergents in aqueous solutions. In many instances, these samples were molecularly distilled in order to remove unreaeted components and reduce the width of molecular weight distribution. The inverse tempera ture solubility relation of nonionie detergents indicates that the overall solubility of these materials depends on the extent of hydrat ion of the hydrophilic port ion; the water molecules being affixed to the ether oxygens by hydrogen bonding. At least four to six ethylene oxide units per molecule are required, depending on the nature of the hydrophobie group, in order to produce a sur fac tan t with distinctly hydrophil ic characteristics. Let us first br ief ly review the methods of preparation of nonionic detergents and the ana ly t i ca l procedures for the determinat ion of the average ethylene oxide chain length. Homogeneous samples of u-alkyl polyoxyethylene monoethers have been prepared by means of the Williamson ether synthesis, wherein n-alkyl bromide was reacted with the monosodium salt of the appropr ia te homogeneous polyoxyethylene glycol (9,34,35,50), e.g'. |
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