Chemical Engineering Commons^™

Semiflexible Oligomers Crystallize Via A Cooperative Phase Transition, Pierre Kawak, Dakota S. Banks, Douglas R. Tree

Faculty Publications

Semicrystalline polymers are ubiquitous, yet despite their fundamental and industrial importance, the theory of homogeneous nucleation from a melt remains a subject of debate. A key component of the controversy is that polymer crystallization is a non-equilibrium process, making it difficult to distinguish between effects that are purely kinetic and those that arise from the underlying thermodynamics. Due to computational cost constraints, simulations of polymer crystallization typically employ non-equilibrium molecular dynamics techniques with large degrees of undercooling that further exacerbate the coupling between thermodynamics and kinetics. In a departure from this approach, in this study, we isolate the near-equilibrium nucleation …

Approaching Disorder-Tolerant Semiconducting Polymers, Xinwen Yan, Miao Xiong, Xin Yu Deng, Kai Kai Liu, Jia Tong Li, Xue Qing Wang, Song Zhang, Nathaniel Prine, Zhuoqiong Zhang, Wanying Huang, Yishan Wang, Jie Yu Wang, Xiaodan Gu, Shu Kong So, Jia Zhu, Ting Lei

Faculty Publications

Doping has been widely used to control the charge carrier concentration in organic semiconductors. However, in conjugated polymers, n-doping is often limited by the tradeoff between doping efficiency and charge carrier mobilities, since dopants often randomly distribute within polymers, leading to significant structural and energetic disorder. Here, we screen a large number of polymer building block combinations and explore the possibility of designing n-type conjugated polymers with good tolerance to dopant-induced disorder. We show that a carefully designed conjugated polymer with a single dominant planar backbone conformation, high torsional barrier at each dihedral angle, and zigzag backbone curvature is highly …

Nanoparticles For Targeted Drug Delivery To Cancer Stem Cells: A Review Of Recent Advances, Yavuz Nuri Ertas, Keyvan Abedu Dorcheh, Ali Akbari, Esmaiel Jabbari

Faculty Publications

Cancer stem cells (CSCs) are a subpopulation of cells that can initiate, self-renew, and sustain tumor growth. CSCs are responsible for tumor metastasis, recurrence, and drug resistance in cancer therapy. CSCs reside within a niche maintained by multiple unique factors in the microenvironment. These factors include hypoxia, excessive levels of angiogenesis, a change of mitochondrial activity from aerobic aspiration to aerobic glycolysis, an upregulated expression of CSC biomarkers and stem cell signaling, and an elevated synthesis of the cytochromes P450 family of enzymes responsible for drug clearance. Antibodies and ligands targeting the unique factors that maintain the niche are utilized …

Establishing Independent Tunability Of The Mechanical And Transport Properties Of Polymer Gels, Lucas Rankin

Master’s Theses

Polymer gels can be used in the fabrication of materials for filtering liquid and gaseous media, solid-state electrolytes, and transdermal medical patches. This diverse range of applications primarily relies on the transport and mechanical properties of polymer gels. Both sets of properties have shown excellent tunability, but typically in a coupled fashion. Establishing the independent tunability of the transport and mechanical properties of polymer gels (using simple, cost-effective methods) is paramount if polymer gels are to be used to their full potential. Specifically, block copolymer gels self-assemble into organized nanoscale networks within the gel solvent, which allows for facile control …

Methods For Film Coating Electrospun Fibers, Kristopher Dejean

Williams Honors College, Honors Research Projects

Electrospinning uses high voltages to form polymer nanofiber membranes. These membranes have potential for use in filtration, tissue engineering, drug delivery, and catalysis. The nonwoven fiber mat is malleable but has a low tensile strength compared to a solid film of the same polymer. Joining the fibers with a thin film is desired to balance the strength and flexibility. Three methods of producing a film on fiber membrane were tested. The techniques are spraying then melting, spin coating, and dip coating. Electrospinning setup conditions, solvent ratios, damage to fibers, and spin coating speeds were determined. Research was abruptly stopped and …

Decorative Articles Based On Polymeric Materials, Bassant Hussein, Yaser M. Asal, M. A. Radwan, M. A. Sadek, Hany A. Elazab

Chemical and Biochemical Engineering Faculty Research & Creative Works

The aim of the research is to create decorative articles based on polymeric materials, study the effects of fillers and the type of moulds that it can cope with the exothermic reaction nature of resin to create a scientific background on the usage of the resins in daily life products. The polymeric materials that will be concentrated on are the unsaturated polyester resins and epoxy resins. The unsaturated polyester is of many types and chemical constituents, the used experimentally is a general-purpose type and the epoxy also have different types and the used is a commercially 3D floor coating type. …

Coatings On Mammalian Cells: Interfacing Cells With Their Environment, Kara A. Davis, Pei-Jung Wu, Calvin F. Cahall, Cong Li, Anuhya Gottipati, Brad J. Berron

Chemical and Materials Engineering Faculty Publications

The research community is intent on harnessing increasingly complex biological building blocks. At present, cells represent a highly functional component for integration into higher order systems. In this review, we discuss the current application space for cellular coating technologies and emphasize the relationship between the target application and coating design. We also discuss how the cell and the coating interact in common analytical techniques, and where caution must be exercised in the interpretation of results. Finally, we look ahead at emerging application areas that are ideal for innovation in cellular coatings. In all, cellular coatings leverage the machinery unique to …

Hydrogels For Cell Delivery, Esmaiel Jabbari

Faculty Publications

No abstract provided.

Marangoni Flows During Nonsolvent Induced Phase Separation, Douglas R. Tree, Tatsuhiro Iwama, Kris T. Delaney, Joshua Lee, Glenn H. Fredrickson

Faculty Publications

Motivated by the much discussed, yet unexplained, presence of macrovoids in polymer membranes, we explore the impact of Marangoni flows in the process of nonsolvent induced phase separation. Such flows have been hypothesized to be important to the formation of macrovoids, but little quantitative evidence has been produced to date. Using a recently developed multifluid phase field model, we find that roll cells indicative of a solutal Marangoni instability are manifest during solvent/nonsolvent exchange across a stable interface. However, these flows are weak and subsequently do not produce morphological features that might lead to macrovoid formation. By contrast, initial conditions …

A Constitutive Model For Entangled Polydisperse Linear Flexible Polymers With Entanglement Dynamics And A Configuration Dependent Friction Coefficient. Part I: Model Derivation, David W. Mead, Saman Monjezi, Joontaek Park

Chemical and Biochemical Engineering Faculty Research & Creative Works

A new polydisperse "toy" constitutive model is derived and developed from fundamental principles and ideas governing the nonlinear rheology of linear flexible polymers [Mead et al., J. Rheol. 59, 335-363 (2015)]. Specifically, the new model is comprised of four fundamental pieces. First, the model contains a simple differential description of the entanglement dynamics of discrete entanglement pairs. Second, the model contains a differential description of the ij entanglement pair orientation tensor dynamics. Third, following a similar development by Mead and Mishler [J. Non-Newtonian Fluid Mech. 197, 61-79 and 80-90 (2013).], a diluted stretch tube is constructed to describe the relative …

Enhanced Energy Storage And Conversion Applications By Porous Carbon And Atomic Layer Deposition, Yomna H. Abdelmoaty

Theses and Dissertations

The design and synthesis of porous materials attracted great attention recently because of their potential use in many fields like clean energy and environmental protection. Herein, we introduced new synthetic approaches for the preparation for porous carbons and organic polymers for selective CO₂ and iodine capture application. Regarding CO₂ capture application, Two new

series of porous carbons (PYDCs) and (TRI-Ps) were synthesized by thermally activating Pyrazole and Triazolo Pyridine monomers respectively using KOH as a catalyst, which leads to porous carbon. PYDCs exhibit high surface area according to Brunauer–Emmett–Tellertheory (SA_BET = 1266–2013 m² g⁻¹), …

Impedance Biosensors And Deep Crater Salivary Gland Scaffolds For Tissue Engineering, Robert Arthur Schramm

Legacy Theses & Dissertations (2009 - 2024)

The salivary gland is a complex, branching organ whose primary biological function is the production of the fluid critical to alimentary function and the lubrication and maintenance of the oral cavity, saliva. The most frequent disruption of the salivary organ system is one in which the rate of supply of saliva into the oral cavity is diminished, and this may vary from a minor reduction, to near cessation. Regenerative medicine is a field which seeks to find ways to overcome the symptoms of organ malfunction or damage by inducing regrowth, repair and replacement of partial or whole organ function. Historically, …

The Kinetics Of Drug Dissolution In Polymers During Hot-Melt Extrusion, Huayang Fang

Theses

Extrusion has been a most important and widely used continuous process in polymer processing for over one hundred and fifty years. However, it has only been recently applied and adopted by the pharmaceutical industry to prepare solid oral dosage formulations with increased bioavailability for the poorly-water soluble drugs and controlled release characteristics for the water-soluble drugs. In pharmaceutical Hot-melt extrusion poorly water soluble drug particulates are mixed with water soluble polymer excipient particulates and fed in the extruder, where the polymer is melted, after which the drug particulates begin to dissolve into the polymer melt. Extrusion-generated mixing accelerates dissolution process. …

The Odijk Regime In Slits, Douglas R. Tree, Wesley F. Reinhart, Kevin D. Dorfman

Faculty Publications

De Gennes’ blob theory has been remarkably successful at describing weakly confined polymers in both slits and channels, and comparable results surround Odijk’s theory of deflection segments for strongly confined wormlike polymers in nanochannels. However, given the success of Odijk’s theory in channels, it is remarkable that there is no comprehensive theory for the simple case of a wormlike polymer strongly confined between two parallel plates. We propose such a theory by drawing inspiration from the existing literature on ideal wormlike chains in slits and Daoud and de Gennes’ idea of mapping a slit-confined chain to a two-dimensional chain. We …

Interplay Between Chain Stiffness And Excluded Volume Of Semiflexible Polymers Confined In Nanochannels, Abhiram Muralidhar, Douglas R. Tree, Yanwei Wang, Kevin D. Dorfman

Faculty Publications

The properties of channel-confined semiflexible polymers are determined by a complicated interplay of chain stiffness and excluded volume effects. Using Pruned-Enriched Rosenbluth Method (PERM) simulations, we study the equilibrium properties of channel-confined polymers by systematically controlling chain stiffness and excluded volume. Our calculations of chain extension and confinement free energy for freely jointed chains with and without excluded volume show excellent agreement with theoretical predictions. For ideal wormlike chains, the extension is seen to crossover from Odijk behavior in strong confinement to zero-stretching, bulk-like behavior in weak confinement. In contrast, for self-avoiding wormlike chains, we always observe that the linear …

Modeling The Construction Of Polymeric Adsorbent Media: Effects Of Counter-Ions On Ligand Immobilization And Pore Structure, Enrico Riccardi, Jee-Ching Wang, Athanasios I. Liapis

Chemical and Biochemical Engineering Faculty Research & Creative Works

Molecular dynamics modeling and simulations are employed to study the effects of counter-ions on the dynamic spatial density distribution and total loading of immobilized ligands as well as on the pore structure of the resultant ion exchange chromatography adsorbent media. The results show that the porous adsorbent media formed by polymeric chain molecules involve transport mechanisms and steric resistances which cause the charged ligands and counter-ions not to follow stoichiometric distributions so that (i) a gradient in the local nonelectroneutrality occurs, (ii) non-uniform spatial density distributions of immobilized ligands and counter-ions are formed, and (iii) clouds of counter-ions outside the …

Aging Of A Polymer Core Composite Conductor Under Combined Ozone And Temperature Conditions, James M. Middleton

Electronic Theses and Dissertations

The next generation High Temperature Low Sag Polymer Core Composite Conductors (HTLS PCCC) can experience harsh in-service environments including high temperature and highly concentrated ozone. In some extreme cases, it is possible that the conductors will experience temperatures of up to 180°C and ozone concentrations as high as 1% (10,000 ppm). Therefore, the primary goal of this research was to determine the most damaging aging conditions which could negatively affect the in-service life of the conductors. This included characterizing the aging in ozone and at high temperature of the HTLS PCCC hybrid composite rods and neat resin. It was found …

Plasma Processes And Polymers Special Issue On: Plasma And Cancer, Mounir Laroussi, Michael Keidar

Electrical & Computer Engineering Faculty Publications

During the last two decades, research efforts on the application of low temperature plasmas in biology and medicine have positioned nonequilibrium lowtemperature plasmas as a technology that has the potential of revolutionizing healthcare.[1,2] Low temperature plasmas can be applied in direct contact with living tissues to inactivate bacteria,[3] to disinfect wounds and accelerate wound healing,[4] and to induce damage in some cancer cells.[5–11]

Polymers Functioning As Artificial Muscles, Nicholas Stanonis, William Pitt

Journal of Undergraduate Research

Current research in the field of polymers has led to the development of synthetic muscles that function similar to biological muscles. Scientists have engineered polymers to contract up to one thousand times their original volume when exposed to changes in light, temperature, voltage, or pH. The ability to contract and relax makes these polymers ideal artificial muscles. Currently, artificial muscles are being applied in the field of robotics. NASA is in the process of developing a dust wiper for their planetary rovers that operates with an artificial muscle. A common goal that many scientists are working towards is the implementation …

Is Dna A Good Model Polymer?, Douglas R. Tree, Abhiram Muralidhar, Patrick S. Doyle, Kevin D. Dorfman

Faculty Publications

The details surrounding the crossover from wormlike-specific to universal polymeric behavior has been the subject of debate and confusion even for the simple case of a dilute, unconfined wormlike chain. We have directly computed the polymer size, form factor, free energy, and Kirkwood diffusivity for unconfined wormlike chains as a function of molecular weight, focusing on persistence lengths and effective widths that represent single-stranded and double-stranded DNA in a high ionic strength buffer. To do so, we use a chain-growth Monte Carlo algorithm, the pruned-enriched Rosenbluth method (PERM), which allows us to estimate equilibrium and near-equilibrium dynamic properties of wormlike …

Improving The Efficiency Of P3ht:Icba Organic Solar Cells By Modifying The Photoactive Solution Preparation Step, Matthew Blaine Samson

Electrical & Computer Engineering Theses & Dissertations

Organic solar cells (OSCs) are a promising alternative to conventional silicon solar cells. These organic devices offer the promise of facile low cost large scale solution based processing on lightweight, flexible, plastic substrates. At the present state of the technology, however, OSCs exhibit relatively low power conversion efficiencies. To improve these efficiencies, new materials are constantly being developed.

One such material is the fullerene indene-C₆₀ bisadduct (ICBA). When implemented in a poly(3-hexylthiophene-2, 5-diyl) (P3HT) : ICBA bulk heterojunction solar cell, these devices exhibit open circuit voltages exceeding 0.8 V, a value much higher than the devices made implementing phenyl-C …

Measuring Acoustic Attenuation Of Polymer Materials Using Drop Ball Test, Yi Zhang

Doctoral Dissertations and Master's Theses

Polymers are often used for vibration damping and energy absorption. The effect of a material in reducing the strength of sound waves traveling through it is called acoustic attenuation. In the past, attenuation has mostly been evaluated in the MHz frequency range, using a pulse generator and transmitting transducer as the wave source. However, most real acoustic activities occur at frequencies up to a few hundred kHz. Here, a simple drop ball mechanism is used to generate acoustic source waves in the kHz range, and the attenuation capacities of several solid materials are measured. The recorded waveforms substantially differ between …

Stochastic Simulation Of Entangled Polymeric Liquids In Fast Flows: Microstructure Modification, Joontaek Park, David W. Mead, Morton M. Denn

Chemical and Biochemical Engineering Faculty Research & Creative Works

We have modified the full-chain stochastic tube (XDS) model developed by Xu et al. [J. Rheol. 50, 477-494 (2006)] to simulate the rheology of entangled melts and solutions of linear monodisperse polymers. The XDS model, which has a single adjustable parameter that is equivalent to the Rouse time, successfully describes steady and transient shear and normal stress data at low to moderate rates, but the results deviate systematically from experimental data at high rates. The algorithm for re-entanglement was revised, and a configuration- dependent friction coefficient (CDFC), as originally proposed by Giesekus, was incorporated to account for microstructural change of …

Resolution Limit For Dna Barcodes In The Odijk Regime, Yanwei Wang, Wes F. Reinhart, Douglas R. Tree, Kevin D. Dorfman

Faculty Publications

We develop an approximation for the probability of optically resolving two fluorescent labels on the backbone of a DNA molecule confined in a nanochannel in the Odijk regime as a function of the fluorescence wavelength, channel size, and the properties of the DNA (persistence length and effective width). The theoretical predictions agree well with equivalent data produced by Monte Carlo simulations of a touching wormlike bead model of DNA in a high ionic strength buffer. Although the theory is only strictly valid in the limit where the effective width of the nanochannel is small compared with the persistence length of …

Investigation Of Solid-State Shear Pulverization Processing Parameters For Polyethylene-Clay Nanocomposites , Ben Aldrich

Honors Theses

Investigates multiple processing parameters, includingpolymer type, filler type, processing technique, severity of SSSP (Solid-state shear pulverization)processing, and postprocessing, of SSSP. HDPE and LLDPE polymers with pristine clay and organo-clay samples are explored. Effects on crystallization, high-temperature behavior, mechanicalproperties, and gas barrier properties are examined. Thermal, mechanical, and morphological characterization is conducted to determine polymer/filler compatibility and superior processing methods for the polymer-clay nanocomposites.

A Molecular Dynamics Study On The Transport Of A Charged Biomolecule In A Polymeric Adsorbent Medium And Its Adsorption Onto A Charged Ligand, Enrico Riccardi, Jee-Ching Wang, Athanasios I. Liapis

Chemical and Biochemical Engineering Faculty Research & Creative Works

The transport of a charged adsorbate biomolecule in a porous polymeric adsorbent medium and its adsorption onto the covalently immobilized ligands have been modeled and investigated using molecular dynamics modeling and simulations as the third part of a novel fundamental methodology developed for studying ion-exchange chromatography based bioseparations. To overcome computational challenges, a novel simulation approach is devised where appropriate atomistic and coarse grain models are employed simultaneously and the transport of the adsorbate is characterized through a number of locations representative of the progress of the transport process. The adsorbate biomolecule for the system studied in this work changes …

Electrical And Structural Studies Of Polyacrylonitrile (Pan) Complexed With Inorganic Salts., Khairul Bahiyah Md Isa

Student Works (2010-2019)

In the present study, polymer electrolyte films composed of polyacrylonitrile (PAN) as a host polymer, ethylene carbonate (EC) as the plasticizer and lithium triflate (LiCF3SO3) and sodium triflate (NaCF3SO3) as dopant salts were prepared by the solution cast technique. Five systems of polymer electrolytes films have been prepared; these systems are the plasticized-PAN system i.e. PAN-EC system, two salted-PAN systems i.e. PAN-LiCF3SO3 and PAN-NaCF3SO3, and two plasticized-salted PAN systems i.e. PAN-EC-LiCF3SO3 and PAN-EC-NaCF3SO3. The pure PAN film was prepared as a reference. The ionic conductivity for each system is characterized using impedance spectroscopy. The room temperature conductivity of the pure …

A Rapid Method For Flow-Ready Cylindrical Microchannel Fabrication, Kimberly H. Henthorn

Chemical and Biochemical Engineering Faculty Research & Creative Works

Most current methods of microchannel fabrication are expensive and time consuming or result in noncylindrical channels, which is undesirable for many applications. A rapid inexpensive method for the fabrication of flow-ready cylindrical polymer microchannels from polydimethylsiloxane (PDMS) is presented here. In this method, cylindrical needles are used as molds for the channels and also function as flow delivery devices after fabrication. Validation of channel function and smoothness can be accomplished by comparing experimental data to theoretical models. One model was previously developed by the author to predict the incipient motion of a glass sphere in contact with a perfectly smooth …

Application Of The Thermal Flash Technique For Low Thermal Diffusivity Micro/Nanofibers, Michael T. Demko, Zhenting Dai, Han Yan, William P. King, Miko Cakmak, Alexis R. Abramson

College of Polymer Science and Polymer Engineering

The thermal flash method was developed to characterize the thermal diffusivity of micro/nanofibers without concern for thermal contact resistance, which is commonly a barrier to accurate thermal measurement of these materials. Within a scanning electron microscope, a micromanipulator supplies instantaneous heating to the micro/nanofiber, and the resulting transient thermal response is detected at a microfabricated silicon sensor. These data are used to determine thermal diffusivity. Glass fibers of diameter 15 mu m had a measured diffusivity of 1.21x10(-7) m(2)/s; polyimide fibers of diameters 570 and 271 nm exhibited diffusivities of 5.97x10(-8) and 6.28x10(-8) m(2)/s, respectively, which compare favorably with bulk …

Stress-Strain Behavior Of Perfluorosulfonic Acid Membranes At Various Temperatures And Humidities: Experiments And Phenomenological Modeling, Ahmet Kusoglu, Yaliang Tang, Michael Santare, Anette M. Karlsson, Simon Cleghorn, William B. Johnson

Mechanical Engineering Faculty Publications

The constitutive response of perfluorinated sulfonic acid (PFSA) membranes based on tensile testing is investigated, and a phenomenological constitutive model for the elastoplastic flow behavior as a function of temperature and humidity is proposed. To this end, the G'Sell–Jonas (1979, “Determination of the Plastic Behavior of Solid Polymers at Constant True Strain Rate,” J. Mater. Sci., 14, pp. 583–591) constitutive model for semicrystalline polymers is extended by incorporating, in addition to temperature, relationships between the material constants of this model and the measured relative humidity. By matching the proposed constitutive model to the experimental stress-strain data, useful material constants …