Acta Phys. -Chim. Sin. ›› 2004, Vol. 20 ›› Issue (08): 837-842.doi: 10.3866/PKU.WHXB20040811

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A Study on Interactions between α-cyclodextrin and a Series of New Kind of Surfactants in Aqueous Solutions by Microcalorimetry

Wang Shi-Bing;Song Ming-Zhi;Wei Xi-Lian;Yin Bao-Lin;Sun De-Zhi   

  1. Department of Chemistry, Liaocheng University, Liaocheng 252059
  • Received:2004-01-09 Revised:2004-03-30 Published:2004-08-15
  • Contact: Sun De-Zhi

Abstract: The interactions between α-cyclodextrin (α-CD) and 3-alkoxyl-2-hydroxypropyl trimethyl ammonium bromides (CnNBr), new surfactants synthesized in this laboratory, in aqueous solutions have been investigated with titration microcalorimetry at 298.15 K. Stoichiometric ratio of the host-guest complex changes from 1:1 to 2:1 as the number of carbon atoms(n) in hydrophobic chain, CnH2n+1O, increases from 8 to 14. All the complexes are quite stable with the apparent experiential stability constants beingβ1=1.95×103 dm3•mol-1, β1=2.62×103 dm3•mol-1, β2=3.06×106 dm6•mol-2, β2=13.75×106 dm6•mol-2, respectively for n=7, 8, 12, 14. All the complexation processes are proved to be enthalpy beneficial but entropy unfavorable, and the absolute value of enthalpy changes(ΔHΘ) increases, while entropy change (ΔSΘ) decreases, with the enlarging of the number of methylene in the hydrophobic chain. The results are discussed in the light of hydrophobic interaction of α-CD with CnNBr and the iceberg structure formed by water molecules existing around the hydrophobic tail of surfactant.

Key words: α-cyclodextrin, CnNBr, Microcalorimetry, Host-guest complex