Interfacial Rheological Properties of a Series of Bolaamphiphilic Poly(fluorooxetane)s
| Autor: | Vernon M. Russell, Charles M. Kausch, Richard R. Thomas, Yongsin Kim, Robert E. Medsker |
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| Rok vydání: | 2003 |
| Předmět: |
Aqueous solution
Marangoni effect Thermodynamics Marangoni number Surfaces and Interfaces Strain rate Condensed Matter Physics Surface tension chemistry.chemical_compound chemistry Pulmonary surfactant Rheology Electrochemistry Organic chemistry General Materials Science Fluorosurfactant Spectroscopy |
| Zdroj: | Langmuir. 19:7354-7361 |
| ISSN: | 1520-5827 0743-7463 |
| DOI: | 10.1021/la0342518 |
| Popis: | Interfacial rheological studies were performed on a series ofbolaamphiphilic α,ω-(diammonium disulfato)-poly(fluorooxetane)s of several perfluoroalkyl chain lengths. Similar measurements were performed on a small-molecule, anionic fluorosurfactant with a -C 8 F 1 7 perfluoroalkyl group that is known to be an effective flow and leveling aid in aqueous coatings. Dilational viscoelasticities were measured for the fluorosurfactants as a function of concentration and oscillation rate. Elasticities were found to increase with increasing perfluoroalkyl chain length. All elasticities exhibited a strain rate dependence indicative of the influence of diffusional relaxation on elasticity values. Phase angles were found to be in the range for diffusional relaxation and decreased with increasing concentration and strain rate. Using interfacial rheological data, characteristic fluid dynamics numbers were calculated for the fluorosurfactants. Among these was the Marangoni number. Calculated Marangoni numbers for the poly(fluorooxetane)s were of the same order of magnitude as that for the small-molecule, long perfluoroalkyl chain surfactant. The poly(fluorooxetane)s all have equilibrium surface tensions greater than that of the small-molecule, long perfluoroalkyl chain surfactant, yet show similar abilities to aid in flow and leveling in aqueous coatings at comparable concentrations. Rheological measurements demonstrate that equilibrium surface tension alone is not enough to explain the fluid dynamics processes occurring during flow and leveling. |
| Databáze: | OpenAIRE |
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