2007-08-212007-08-211998Chen, Bing-Hung. "Rates of solubilization of triolein and triolein/fatty acid mixtures and dissolution processes of neat surfactants." (1998) Diss., Rice University. <a href="https://hdl.handle.net/1911/19248">https://hdl.handle.net/1911/19248</a>.https://hdl.handle.net/1911/19248Videomicroscopy was used to measure rates of solubilization of triolein drops injected into thin, rectangular glass cells containing solutions of nonionic surfactants and their mixtures with alcohols at various temperatures. In most cases the solubilization rate per unit area was independent of time and of initial drop size. This indicates that processes occurring at the interface control the rate of solubilization. The solubilization rate can be increased by increasing the flexibility of the surfactant films either by adding short-chain alcohols or by using a surfactant mixture with a thinner and less ordered hydrocarbon chain region. Videomicroscopy was also used to investigate the mechanisms and rates of dissolution of neat, liquid nonionic surfactants in water. A microinjection technique was used to produce drops of pure C$\sb{12}$E$\sb5$ and C$\sb{12}$E$\sb6,$ which dissolved rapidly at temperatures below their cloud points. The results indicated that the process was diffusion controlled. Estimates of effective binary diffusion coefficients in the intermediate liquid crystalline phase(s) which formed were obtained by combining their measured growth rates in one-dimensional experiments where neat surfactant contacted water with measured dissolution times of surfactant drops. Drops of the commercial nonionic surfactants Neodol 25-7 and Tergitol 15-S-7 required considerable time for complete dissolution at temperatures just below their cloud points. Considerable spontaneous emulsification of water in the surfactant drops was also observed. Moreover, the final small drops frequently became elongated and sometimes formed conical projections that emitted jets. Similar behavior was seen for the model system C$\sb{12}$E$\sb8$/n-decanol/water and occurs because the more hydrophilic component dissolves more rapidly. At 30$\sp\circ$C a compact mass of viscous myelinic figures developed when a drop of C$\sb{12}$E$\sb4$ was injected into water. However, complete dissolution occurred when 5 wt% of small SDS crystals was added to the drop. Here too considerable spontaneous emulsification, elongation, and some jetting were observed. Complete dissolution also occurred when C$\sb{12}$E$\sb4$ drops were injected into dilute SDS solutions. However, dissolution was much slower when the SDS concentration was large enough that hexagonal and cubic intermediate phases formed in addition to the lamellar phase which was seen in all cases.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.Physical chemistryChemical engineeringThesisTHESIS CH.E. 1998 CHEN