Hydrophobic or Micellar Behavior of 2-butyl and 2-pentyl-2-(hydroxymethyl)-1,3-propaneDiol in Water. Volumes and Osmotic Coefficients

✍ Scribed by Robert Coudert; Jacky Paris; An Cao

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 216 KB
• Volume: 163
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1994.1084

✦ Synopsis

(n)-butyl-2 and (n)-pentyl-2-(hydroxymethyl)-1,3-propanediol, named (\mathrm{OT}) and (\mathrm{NT}), respectively, have been examined in aqueous solutions at 30,40 , and (50^{\circ} \mathrm{C}) for (\mathrm{NT}) and at (40^{\circ} \mathrm{C}) for (\mathrm{OT}), using density and vapor pressure osmometry techniques. OT does not form true micelles but rather hydrophobic aggregates at the critical hydrophobic interaction concentration (CHIC). (\mathrm{CHIC}=) (0.68 \mathrm{~mol} \mathrm{~kg}^{-1}) for this compound. NT gives micellar association and the CMC has been determined at these temperatures. The values obtained are (0.247\left(30^{\circ} \mathrm{C}\right)) and (0.239\left(40\right.) and (\left.50^{\circ} \mathrm{C}\right) \mathrm{mol}) (\mathrm{kg}^{-1}) using density measurements, and (0.260\left(30^{\circ} \mathrm{C}\right), 0.273) (\left(40^{\circ} \mathrm{C}\right)), and (0.276\left(50^{\circ} \mathrm{C}\right) \mathrm{mol} \mathrm{kg}^{-1}) using vapor pressure osmometry data. The volume changes during micellization are 3.81 (\left(30^{\circ} \mathrm{C}\right), 3.74\left(40^{\circ} \mathrm{C}\right)), and (3.75\left(50^{\circ} \mathrm{C}\right) \mathrm{cm}^{3} \mathrm{~mol}^{-3}). The concentration dependence of properties such as the osmotic coefficient, the molal activity coefficient, the nonideal Gibbs energy of the solute, and the relative chemical potential are also studied in the temperature range explored. The aggregation numbers of NT micelles (n=11.7\left(30^{\circ} \mathrm{C}\right), 12.0\left(40^{\circ} \mathrm{C}\right)), and (15.8\left(50^{\circ} \mathrm{C}\right)), with an accuracy (\pm 0.2), have bcen calculated using the phaseseparation model. Results are discussed and compared to those obtained from the 1,2,3-alkane triol series. (1994 Academic Press, Inc.