Molecular free volume and viscosity changes in non-Newtonian fluids probed with molecular rotors

MOspace/Manakin Repository

Breadcrumbs Navigation

Molecular free volume and viscosity changes in non-Newtonian fluids probed with molecular rotors

Please use this identifier to cite or link to this item: http://hdl.handle.net/10355/2233

[-] show simple item record

dc.contributor.author Wilson, Joseph P. en
dc.contributor.author Haidekker, Mark A., 1963- en
dc.date 2005 en
dc.date.accessioned 2009-08-13T20:30:50Z en
dc.date.available 2009-08-13T20:30:50Z en
dc.date.issued 2005 en
dc.identifier.uri http://hdl.handle.net/10355/2233 en
dc.description Abstract only available en
dc.description.abstract An empirical relationship between molecular free volume and viscosity has been established (Doolittle AK, J Appl. Phys. 1952; 23: 236-9). Non-Newtonian fluids hold much importance to scientific study because of their ubiquity in nature - from gelatins to starches to blood. The purpose of this study was to examine the relationship between molecular free volume and viscosity in non-Newtonian fluids under shear-thinning conditions. Molecular rotors are fluorescent probes for free volume. After photoexcitation, these molecules can decay from their singlet state either through radiation (fluorescence) or torsional relaxation (intramolecular rotation). In environments with low free volume, intramolecular rotation is hindered, and the radiative deexcitation pathway becomes dominant. This behavior is accompanied by a measurable increase in fluorescence intensity. Molecular rotors have been used successfully as viscosity probes in various fluids and polymers. Two molecular rotors, CCVJ (9-(2-carboxy-2-cyano)-vinyl-julolidine) and CCVJ-TEG (CCVJ-triethyleneglycol ester), were dissolved at 10µM in an aqueous solution of KelcoGelF (gellan gum) and subjected to shear forces both in a tube shear apparatus for fluorescence measurements and in a Haake VT-550 rheometer to determine the shear-thinning behavior. The gellan solution exhibited power-law behavior with an exponent n=0.48. In spite of this strong shear-thinning behavior, no change in rotor emission intensity was observed. Additionally, a novel behavior of some molecular rotors, a sensitivity towards fluid flow (Haidekker MA et al, Sensor Lett. 2005; 3: 42-8), was exploited to observe shear-thinning behavior by probing flow velocity in a tube. Under application of sufficiently high shear rates to cause shear thinning, molecular rotors revealed no change in free volume as observed with fluorescence intensity. This preliminary study suggests that molecular free volume and shear thinning are independent properties. Further studies will be needed to corroborate that the free volume of a fluid is not related to its viscosity in shear-thinning environments. en
dc.description.sponsorship NSF-REU Program in Biosystems Modeling and Analysis en
dc.language en_US en
dc.language.iso en_US en
dc.publisher University of Missouri--Columbia. Office of Undergraduate Research en
dc.relation.ispartof 2005 Summer Undergraduate Research and Creative Achievements Forum (MU) en
dc.source.uri http://undergradresearch.missouri.edu/forums-conferences/abstracts/abstract-detail.php?abstractid= en
dc.subject non-Newtonian fluids en
dc.subject molecular rotors en
dc.subject molecular free volume and viscosity en
dc.subject shear-thinning en
dc.title Molecular free volume and viscosity changes in non-Newtonian fluids probed with molecular rotors en
dc.type Presentation en
dc.contributor.meetingname Summer Undergraduate Research and Creative Achievements Forum (2005 : University of Missouri--Columbia) en
dc.contributor.corporatename University of Missouri-Columbia. Office of Undergraduate Research en
dc.relation.ispartofcommunity University of Missouri-Columbia. Office of Undergraduate Research. Undergraduate Research and Creative Achievements Forum


This item appears in the following Collection(s)

[-] show simple item record