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Cheng, Hsin-Ling (2009) SPREADING AND JAMMING PHENOMENA OF PARTICLE-LADEN INTERFACES. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Partially wettable particles tend to adsorb irreversibly at interfaces of two immiscible fluids. The fluid-fluid interface can be the oil-water interface such as in an emulsion, or the polymer-polymer interface such as in a binary polymer blend. This work aims to have fundamental understanding on two interface-attributed phenomena and then to demonstrate the applications.A spreading event against the direction of gravity of particle-fluid films, termed as film-climbing, occurs as a result of drop coalescence in an unstable Pickering emulsion. We study the generality of this phenomenon, confirm the film structure, and investigate effects of substrate hydrophobicity and prewetting. The calculation and measurement of surface pressure, as well as a wall-coverage calculation are provided to support the proposed mechanism.We develop the spinning drop tensiometer method to conduct a systematic study on interfacial-tension-driven jamming. Specific interfacial area is correlated to a particle packing model. We identify the important characteristics for jamming such as hysteresis and dynamics-dependence. The difference between jamming of polar-nonpolar and nonpolar-nonpolar fluid interfaces is contrasted.For applications of jamming, we first demonstrate that the interfacial jamming can stabilize a bicontinuous morphology. Hand-blending a partially miscible system of polyisoprene (PI) and polyisobutylene (PIB) produces an evolving bicontinuous morphology. Interfacially-active particles are added to affect the domain coarsening rate. A bicontinuous, jammed structure (a.k.a. bijel) is realized.Interfacial jamming also affects the morphology of a droplet-matrix blend of PI and polydimethylsiloxane (PDMS). We use the drop coalescence induced by shear flow to generate elongated drops. Particle jamming on drop surface affects the relaxing kinetics of elongated drops. We utilize rheology as the tool to trace the drop relaxation and drop size change, as well as the elastic recovery of blends after cessation of shear flow. Another focus of PI/PDMS blends is the observation of particle-assisted network structures as we increase particle loading. The stabilization of network structures is attributed to interfacial effect.With these examples on polymer blends, we show the applications of jamming on creating particle-polymer composite materials of desired morphologies.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Cheng, Hsin-Linghsc12@pitt.eduHSC12
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairVelankar, Sachin Svelankar@pitt.eduVELANKAR
Committee MemberGao, Digaod@pitt.eduGAOD
Committee MemberKumta, Prashant Npkumta@pitt.eduPKUMTA
Committee MemberGaroff,
Committee MemberFederspiel, William Jfederspielwj@upmc.eduWFEDERSP
Date: 25 September 2009
Date Type: Completion
Defense Date: 10 July 2009
Approval Date: 25 September 2009
Submission Date: 17 July 2009
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Chemical Engineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: bicontinuous morphology; bijel; Pickering emulsion; polymer blend; rheology; fluid interface; interfacial jamming
Other ID:, etd-07172009-162249
Date Deposited: 10 Nov 2011 19:51
Last Modified: 19 Dec 2016 14:36


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