Insoluble monolayers of a preformed polymer containing carboxylic acid hydrophilic groups - cadmium ion binding to monolayers and ionization in multilayers

B. P. Binks*, P. D.I. Fletcher, J. S. Phipps, R. M. Richardson

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

5 Citations (Scopus)

Abstract

We have investigated the properties of insoluble monolayers and Langmuir-Blodgett (LB) multilayers of a preformed derivative of an α-olefin maleic anhydride copolymer. The polymer repeat unit contained a hexadecyl hydrophobic group and two carboxylic acid moieties in the hydrophilic headgroup. Using X-ray reflectivity we have determined the floating monolayer structure and the adsorption of cadmium ions from the subphase as a function of pH at a fixed surface pressure. The tailgroup thickness is 14 Å, much less than the all-trans length of the hexadecyl chains. The headgroup layer thickness is approximately 8 Å. Both thickness are independent of pH. Cadmium ion binding to the carboxylic acid headgroups occurs with a 1:2 stoichiometry and a pK of 5.7. Using attenuated total reflectance IR spectroscopy, the ionization of the corresponding LB multilayers deposited on germanium was also measured. The pH of 50% ionization is approximately 5, in reasonable agreement with the pK for cadmium ion binding to the floating monolayer.

Original languageEnglish
Pages (from-to)280-287
Number of pages8
JournalThin Solid Films
Volume209
Issue number2
DOIs
Publication statusPublished - 30 Mar 1992

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