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Articles 1 - 12 of 12
Full-Text Articles in Polymer Science
Photopolymerization-Induced Crystallization And Phase Separation In Poly(Ethylene Oxide)/Triacrylate Blends, Soo Jeoung Park, Thein Kyu
Photopolymerization-Induced Crystallization And Phase Separation In Poly(Ethylene Oxide)/Triacrylate Blends, Soo Jeoung Park, Thein Kyu
College of Polymer Science and Polymer Engineering
The present article describes experimental and theoretical investigations of miscibility and crystallization behavior of blends of poly(ethylene oxide) (PEO) and triacrylate monomer (TA) using differential scanning calorimetry and optical microscopy. The PEO/TA blends manifested a single T(g) varying systematically with composition suggestive of a miscible character in their amorphous states. Moreover, there occurs melting point depression of PEO crystals with increasing TA. A phase diagram was subsequently established that exhibited a solid+liquid coexistence region bound by the liquidus and solidus lines, followed by an upper critical solution temperature (UCST) at a lower temperature. The emerging phase morphology was investigated to …
From Elastic Deformation To Terminal Flow Of A Monodisperse Entangled Melt In Uniaxial Extension, Yangyang Wang, Shi-Qing Wang
From Elastic Deformation To Terminal Flow Of A Monodisperse Entangled Melt In Uniaxial Extension, Yangyang Wang, Shi-Qing Wang
College of Polymer Science and Polymer Engineering
Using a well-entangled monodisperse styrene-butadiene random-copolymer (SBR) melt as a model system, we illustrate generic features of uniaxial extension behavior that may be shared by all well-entangled thermoplastic and elastomeric materials. Depending on the imposed extensional rate, the same sample may behave like a viscous liquid or an elastic "solid." Analogous to the recently revealed shear inhomogeneity, the SBR melt inevitably undergoes cohesive failure in the form of sample breakage whenever the Weissenberg number is much greater than unity, making it challenging to reach steady state. In the elastic deformation regime where the external deformation rate is faster than Rouse …
Partial Crystallinity In Alkyl Side Chain Polymers Dictates Surface Freezing, Shishir Prasad, Zhang Jiang, Sunil K. Sinha, Ali Dhinojwala
Partial Crystallinity In Alkyl Side Chain Polymers Dictates Surface Freezing, Shishir Prasad, Zhang Jiang, Sunil K. Sinha, Ali Dhinojwala
College of Polymer Science and Polymer Engineering
We have studied the structure of a novel crystalline surface monolayer on top of a disordered melt of the same material [poly(n-alkyl acrylate)s] using grazing incidence x-ray diffraction. The grazing incidence x-ray diffraction, surface tension, and bulk latent heat results show that side chains crystallize except the nine methylene units of the alkyl side chains closest to the polymer backbone. The partial crystallinity along with a thicker surface layer, due to the additional length of the linker group, explains why the difference between the surface order-to-disorder transition temperature and bulk melting temperature increases with a decrease in the length of …
Steady State Measurements In Stress Plateau Region Of Entangled Polymer Solutions: Controlled-Rate And Controlled-Stress Modes, Sham Ravindranath, Shi-Qing Wang
Steady State Measurements In Stress Plateau Region Of Entangled Polymer Solutions: Controlled-Rate And Controlled-Stress Modes, Sham Ravindranath, Shi-Qing Wang
College of Polymer Science and Polymer Engineering
Despite decades of efforts, reliable measurements of nonlinear flow behavior of well-entangled polymers in continuous shear have been challenging to obtain. The present work attempts to accomplish three important tasks: (A) overcome this challenge by adopting a strategy of decoupling theological measurements from the outer meniscus region in a cone-partitioned plate (C/PP) setup; (B) determine whether well-entangled solutions indeed undergo a flow transformation under creep that can be taken to phenomenologically define an entanglement-disentanglement transition (EDT); (C) provide the velocity profiles of such solutions undergoing either controlled-stress or controlled-rate shear by carrying out in situ particle-tracking velocimetric (PTV) measurements. Upon …
Universal Scaling Characteristics Of Stress Overshoot In Startup Shear Of Entangled Polymer Solutions, Sham Ravindranath, Shi-Qing Wang
Universal Scaling Characteristics Of Stress Overshoot In Startup Shear Of Entangled Polymer Solutions, Sham Ravindranath, Shi-Qing Wang
College of Polymer Science and Polymer Engineering
We have carried out conventional theological measurements to explore the well-known stress overshoot behavior in startup shear of eight entangled polybutadiene solutions. In the elastic deformation regime with (gamma)over dot tau(R)> 1, we have identified universal scaling features associated with the stress maximum sigma(max) for samples of different levels of entanglements per chain ranging from 27, 40 to 64. Specifically, at the moment t(max) of the peak stress sigma(max) where the applied strain is gamma(max) = (gamma)over dott(max): (a) sigma(max) varies linearly with gamma(max), (b) sigma(max) scales with t(max) as sigma(max)similar to(t(max))-1/2. The combination of (a) and (b) yields a …
Sticky Gecko Feet: The Role Of Temperature And Humidity, Peter H. Niewiarowski, Stephanie Lopez, Liehui Ge, Emily Hagan, Ali Dhinojwala
Sticky Gecko Feet: The Role Of Temperature And Humidity, Peter H. Niewiarowski, Stephanie Lopez, Liehui Ge, Emily Hagan, Ali Dhinojwala
College of Polymer Science and Polymer Engineering
Gecko adhesion is expected to be temperature insensitive over the range of temperatures typically experienced by geckos. Previous work is limited and equivocal on whether this expectation holds. We tested the temperature dependence of adhesion in Tokay and Day geckos and found that clinging ability at 12 degrees C was nearly double the clinging ability at 32 degrees C. However, rather than confirming a simple temperature effect, our data reveal a complex interaction between temperature and humidity that can drive differences in adhesion by as much as two-fold. Our findings have important implications for inferences about the mechanisms underlying the …
Large Amplitude Oscillatory Shear Behavior Of Entangled Polymer Solutions: Particle Tracking Velocimetric Investigation, Sham Ravindranath, Shi-Qing Wang
Large Amplitude Oscillatory Shear Behavior Of Entangled Polymer Solutions: Particle Tracking Velocimetric Investigation, Sham Ravindranath, Shi-Qing Wang
College of Polymer Science and Polymer Engineering
Large amplitude oscillatory shear (LAOS) has been employed widely to probe the nonlinear behavior of complex fluids. Typically, the system undergoing LAOS has been assumed to experience homogeneous shear in each cycle so that material functions can be introduced to analyze the nonlinear dependence of these functions on the amplitude and frequency. Using particle-tracking velocimetric technique, we have carried a more systematic investigation on four different entangled polybutadiene (PBD) solutions with the number of entanglements per chain Z=13, 27, 64 and 119, extending well beyond the initial observations of shear banding in entangled PBD solutions under LAOS [Tapadia , Phys. …
Thermal Damage Approach Of Concrete: Application To Specimens Subjected To Combined Compressive And High Temperature Loads, Abdellah Menou, Ghassan Mounajed, Hocine Boussa, Christian La Borderie, Khalid Lafdi
Thermal Damage Approach Of Concrete: Application To Specimens Subjected To Combined Compressive And High Temperature Loads, Abdellah Menou, Ghassan Mounajed, Hocine Boussa, Christian La Borderie, Khalid Lafdi
Chemical and Materials Engineering Faculty Publications
Within the framework of study of concrete structures subjected to fire, .a theoretical and experimental work was conducted. The aim of this study was to investigate and to model the damage mechanisms of concrete after their exposure to high temperatures. The multiphase Digital Concrete Model as well as the damage model, MOD EV, which were both implemented on the finiteelem~ rit software package, SYMPHONIE, were used simμltaneously to assess the thermal damage of the concrete. In order to validate the thermal damage model, an experimental investigation was performed. The mechanical characteristics of 5 cementitious materials, which included cement paste, mortar, …
Electrical, Structural, And Chemical Properties Of Semiconducting Metal Oxide Nanofiber Yarns, A. F. Lotus, E. T. Bender, E. A. Evans, R. D. Ramsier, Darrell Hyson Reneker
Electrical, Structural, And Chemical Properties Of Semiconducting Metal Oxide Nanofiber Yarns, A. F. Lotus, E. T. Bender, E. A. Evans, R. D. Ramsier, Darrell Hyson Reneker
College of Polymer Science and Polymer Engineering
The electrical, structural, and chemical properties of twisted yarns of metal-oxide nanofibers, fabricated using a modified electrospinning technique, are investigated in this report. In particular, synthesized zinc oxide and nickel oxide yarns having diameters in the range of 4-40 mu m and lengths up to 10 cm were characterized, whose constituent nanofibers had average diameters of 60-100 nm. These yarns have one macroscopic dimension for handling while retaining some of the properties of nanofibers. (C) 2008 American Institute of Physics.
Structure Property Relationships In Electron Donating Systems For Potential Photovoltaic Applications., Jonathan Moghal
Structure Property Relationships In Electron Donating Systems For Potential Photovoltaic Applications., Jonathan Moghal
Doctoral
Conjugated polymers are considered to be one-dimensional semiconductors. In conjugated polymers single and double bonds alternatively bond the carbon atoms along the polymer chain. The loosely bound electrons determine the electronic properties of conjugated polymers. In order to utilise the properties of conjugated polymers in terms of a photovoltaic (PV) device application an acceptor material must be added. The acceptor material used in this study is used in buckminsterfullerence (C60). C60 was selected for this purpose due to its size and the fact that it can accept up to six additional electrons. Ultrafast charge transfers from a conducting polymer onto …
Plasma Medicine, Mounir Laroussi, Alexander Fridman
Plasma Medicine, Mounir Laroussi, Alexander Fridman
Electrical & Computer Engineering Faculty Publications
Recent demonstrations of plasma technology in the treatment of living cells, tissues, and organs are creating a newfield at the intersection of plasma science and technology with biology and medicine - Plasma Medicine.
Sublethal And Killing Effects Of Atmospheric-Pressure, Nonthermal Plasma On Eukaryotic Microalgae In Aqueous Media, Ying Zhong Tang, Xin Pei Lu, Mounir Laroussi, Fred C. Dobbs
Sublethal And Killing Effects Of Atmospheric-Pressure, Nonthermal Plasma On Eukaryotic Microalgae In Aqueous Media, Ying Zhong Tang, Xin Pei Lu, Mounir Laroussi, Fred C. Dobbs
OES Faculty Publications
In-depth studies on the interaction of nonthermal plasmas with microorganisms usually focus on bacteria; only little attention has been given to their effects on more complex eukaryotic cells. We report here nonthermal plasma's effects on cell motility, viability staining, and morphology of eukaryotic microalgae, with three marine dinoflagellates and a marine diatom as major targets. The effects on motility and viability staining depended on the time of exposure to plasma and the species of microalgae. We observed a strong pH decrease in aqueous samples (marine and freshwater algal cultures, their culture media, and deionized water) after exposure to plasma, and …