Physicochemical Properties of Hydrophobically Modified Polymeric Betaines and of Their Langmuir-Blodgett Films

Abstract

Summary: Polymeric betaines containing long alkyl chains (C12H25, C13H27, C14H29, C16H33 and C18H37) were synthesized by Michael addition reaction of alkylaminocrotonates and methacrylic acid. They were characterized by FTIR, 13C NMR, DLS, TEM, viscometry and zeta-potential measurements. In aqueous KOH and DMSO solutions the hydrophobically modified polymeric betaines behave polyelectrolyte character. The average hydrodynamic size and zeta potential of diluted aqueous solutions of hydrophobic polybetaines containing tetradecyl- and octadecyl groupswere studied as a function of pH. Anomalous low values of the isoelectric point (IEP) of amphoteric macromolecules were found to be in the range of pH 2.7–3.4. The TEM results revealed that in both aqueous KOH and DMSO media the nano- and microsized micelles and vesicles are existed. The structural organization of micelles and vesicles in water and water DMSO mixture is discussed. Langmuir-Blodgett (LB) monolayers on the water-air interface were obtained by spreading of hydrophobic polybetaines containing tetradecyl- and octadecyl groups dissolved in THF on the subphase surface. The LB films on the subphase surface are characterized by the specific areas of 0.6 0.05nm2 monomeric unit 1 at collapsed state. In the spectra of Langmuir- Blodgett filmthe absorption band with the maximumat 255 and 270nmwas observed.