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Records with Subject: Materials
Showing records 133 to 157 of 158. [First] Page: 1 3 4 5 6 7 8 Last
Investigation of the Interaction between Benzene and SXFA Using DFT
Katherine M. E. Stewart, Ian P. Hamilton, Alexander Penlidis
July 31, 2018 (v1)
Subject: Materials
Keywords: benzene, Density Functional Theory (DFT), gas sensors, polymeric sensing material, sensing mechanisms
Density Functional Theory (DFT) studies were conducted to evaluate the sensing mechanism between benzene and a polymeric sensing material, referred to as SXFA, which contains trifluoro-groups and OH-groups. These studies were undertaken to improve the understanding of how benzene and SXFA mechanistically interact based on their chemistry, information which can be used to more efficiently design polymeric sensing materials. We find that benzene adsorbed onto the OH-groups in SXFA rather than the trifluoro-groups as previously proposed. Specifically, we find that sorption results from electrostatic attraction between the negative benzene ring and the positive hydrogens of the OH-groups of SXFA.
Computational Package for Copolymerization Reactivity Ratio Estimation: Improved Access to the Error-in-Variables-Model
Alison J. Scott, Alexander Penlidis
July 31, 2018 (v1)
Subject: Materials
Keywords: copolymer composition, copolymerization kinetics, design of experiments, error-in-variables-model (EVM), parameter estimation, polymer reaction engineering, reactivity ratios
The error-in-variables-model (EVM) is the most statistically correct non-linear parameter estimation technique for reactivity ratio estimation. However, many polymer researchers are unaware of the advantages of EVM and therefore still choose to use rather erroneous or approximate methods. The procedure is straightforward but it is often avoided because it is seen as mathematically and computationally intensive. Therefore, the goal of this work is to make EVM more accessible to all researchers through a series of focused case studies. All analyses employ a MATLAB-based computational package for copolymerization reactivity ratio estimation. The basis of the package is previous work in our group over many years. This version is an improvement, as it ensures wider compatibility and enhanced flexibility with respect to copolymerization parameter estimation scenarios that can be considered.
Effect of Alkane Chain Length on Crystallization in Emulsions during Supercooling in Quiescent Systems and under Mechanical Stress
Serghei Abramov, Kinza Shah, Lydia Weißenstein, Heike Petra Karbstein
July 31, 2018 (v1)
Subject: Materials
Keywords: aggregation, crystallization, crystallization index, dispersion, emulsion, melt emulsification, nucleation
Crystallization behavior of hexadecane (C16H34), octadecane (C18H38), eicosane (C20H42), and docosane (C22H46) dispersions of similar mean droplet diameter (x50.2 ≈ 15 µm) was investigated in quiescent systems and compared to crystallization under mechanical stress. In quiescent systems, the required supercooling decreased with increasing chain length of the alkanes to initiate crystallization. Crystallization of alkane dispersions under mechanical stress resulted in similar onset crystallization supercooling, as during quiescent crystallization. Increase of mechanical stress did not affect the onset crystallization supercooling within alkane dispersions.
On the Thermal Self-Initiation Reaction of n-Butyl Acrylate in Free-Radical Polymerization
Hossein Riazi, Ahmad Arabi Shamsabadi, Patrick Corcoran, Michael C. Grady, Andrew M. Rappe, Masoud Soroush
July 31, 2018 (v1)
Subject: Materials
Keywords: free-radical polymerization, n-butyl acrylate, reaction order, thermal self-initiation
This experimental and theoretical study deals with the thermal spontaneous polymerization of n-butyl acrylate (n-BA). The polymerization was carried out in solution (n-heptane as the solvent) at 200 and 220 °C without adding any conventional initiators. It was studied with the five different n-BA/n-heptane volume ratios: 50/50, 70/30, 80/20, 90/10, and 100/0. Extensive experimental data presented here show significant monomer conversion at all temperatures and concentrations confirming the occurrence of the thermal self-initiation of the monomer. The order, frequency factor, and activation energy of the thermal self-initiation reaction of n-BA were estimated from n-BA conversion, using a macroscopic mechanistic model. The estimated reaction order agrees well with the order obtained via our quantum chemical calculations. Furthermore, the frequency factor and activation energy estimates agree well with the corresponding values that we already reported for bulk polymerization of n-BA.
Development of Molecularly Imprinted Polymers to Target Polyphenols Present in Plant Extracts
Catarina Gomes, Gayane Sadoyan, Rolando C. S. Dias, Mário Rui P. F. N. Costa
July 31, 2018 (v1)
Subject: Materials
Keywords: adsorbents, amphiphilic materials, continuous processes, crosslinking polymerization, molecular imprinting, polyphenols, vegetable extracts
The development of molecularly imprinted polymers (MIPs) to target polyphenols present in vegetable extracts was here addressed. Polydatin was selected as a template polyphenol due to its relatively high size and amphiphilic character. Different MIPs were synthesized to explore preferential interactions between the functional monomers and the template molecule. The effect of solvent polarity on the molecular imprinting efficiency, namely owing to hydrophobic interactions, was also assessed. Precipitation and suspension polymerization were examined as a possible way to change MIPs morphology and performance. Solid phase extraction and batch/continuous sorption processes were used to evaluate the polyphenols uptake/release in individual/competitive assays. Among the prepared MIPs, a suspension polymerization synthesized material, with 4-vinylpyridine as the functional monomer and water/methanol as solvent, showed a superior performance. The underlying cause of such a significant outcome... [more]
Organic Polymers as Porogenic Structure Matrices for Mesoporous Alumina and Magnesia
Zimei Chen, Christian Weinberger, Michael Tiemann, Dirk Kuckling
July 31, 2018 (v1)
Subject: Materials
Keywords: mesoporous alumina, mesoporous magnesia, poly(dimethylacrylamide), poly(ethylene glycol), poly(N-(2-hydroxypropyl) methacrylamide), poly(vinyl alcohol)
Mesoporous alumina and magnesia were prepared using various polymers, poly(ethylene glycol) (PEG), poly(vinyl alcohol) (PVA), poly(N-(2-hydroxypropyl) methacrylamide) (PHPMA), and poly(dimethylacrylamide) (PDMAAm), as porogenic structure matrices. Mesoporous alumina exhibits large Brunauer⁻Emmett⁻Teller (BET) surface areas up to 365 m² g−1, while mesoporous magnesium oxide possesses BET surface areas around 111 m² g−1. Variation of the polymers has little impact on the structural properties of the products. The calcination of the polymer/metal oxide composite materials benefits from the fact that the polymer decomposition is catalyzed by the freshly formed metal oxide.
Selected Phenomena of the In-Mold Nodularization Process of Cast Iron That Influence the Quality of Cast Machine Parts
Marcin Stawarz, Krzysztof Janerka, Malwina Dojka
July 31, 2018 (v1)
Subject: Materials
Keywords: ductile iron, fayalite, forsterite, in-mold process, sulfides
This paper discusses a problem connected with the production process of ductile iron castings made using the in-mold method. The study results are presented showing that this method compromises the quality of the cast machine parts and of the equipment itself. Specifics of the nodularization process using the in-mold method do not provide the proper conditions for removal of chemical reaction products to the slag, i.e., the products stay in the mold cavity and they also decrease the quality of the casting. In this work, corrosion-type defects were diagnosed mostly on the surface of the casting and some compounds in the near-surface layer—i.e., fayalite (Fe₂SiO₄) and forsterite (Mg₂SiO₄)—which cause discontinuities in the metal matrix. The results presented here were selected based on experimental melts of ductile iron. The elements of the mold used in this study, the shape of the mixing chamber, charge materials, method of melting, temperature of liquid metal, etc. were directly relate... [more]
Thermal and Rheological Properties of Crude Tall Oil for Use in Biodiesel Production
Peter Adewale, Lew P. Christopher
July 31, 2018 (v1)
Subject: Materials
Keywords: biodiesel, crude tall oil, crystallization, melting, viscosity
The primary objective of this work was to investigate the thermal and rheological properties of crude tall oil (CTO), a low-cost by-product from the Kraft pulping process, as a potential feedstock for biodiesel production. Adequate knowledge of CTO properties is a prerequisite for the optimal design of a cost-effective biodiesel process and related processing equipment. The study revealed the correlation between the physicochemical properties, thermal, and rheological behavior of CTO. It was established that the trans/esterification temperature for CTO was greater than the temperature at which viscosity of CTO entered a steady-state. This information is useful in the selection of appropriate agitation conditions for optimal biodiesel production from CTO. The point of interception of storage modulus (G′) and loss modulus (G′′) determined the glass transition temperature (40 °C) of CTO that strongly correlated with its melting point (35.3 °C). The flow pattern of CTO was modeled as a non... [more]
Radical Copolymerization Kinetics of Bio-Renewable Butyrolactone Monomer in Aqueous Solution
Sharmaine B. Luk, Robin A. Hutchinson
July 31, 2018 (v1)
Subject: Materials
Keywords: bio-renewable, depropagation, ionic strength, parameter estimation
The radical copolymerization kinetics of acrylamide (AM) and the water-soluble monomer sodium 4-hydroxy-4-methyl-2-methylene butanoate (SHMeMB), formed by saponification of the bio-sourced monomer γ-methyl-α-methylene-γ-butyrolactone (MeMBL), are investigated to explain the previously reported slow rates of reaction during synthesis of superabsorbent hydrogels. Limiting conversions were observed to decrease with increased temperature during SHMeMB homopolymerization, suggesting that polymerization rate is limited by depropagation. Comonomer composition drift also increased with temperature, with more AM incorporated into the copolymer due to SHMeMB depropagation. Using previous estimates for the SHMeMB propagation rate coefficient, the conversion profiles were used to estimate rate coefficients for depropagation and termination (kt). The estimate for kt,SHMeMB was found to be of the same order of magnitude as that recently reported for sodium methacrylate, with the averaged copolymeriz... [more]
Distribution of N-Methylimidazole in Ionic Liquids/Organic Solvents Systems
Milen G. Bogdanov, Ivan Svinyarov
July 31, 2018 (v1)
Subject: Materials
Keywords: interactions, ionic liquids, liquid-liquid extraction, N-methylimidazole, partition coefficient, separation, transfer
The partition coefficients, Kmim, of N-methylimidazole (mim) in two-component systems composed of ionic liquid (IL) and a series of organic solvents immiscible with ILs (butyl acetate, ethyl acetate, tert-butyl methyl ether, diethyl ether and cyclohexane) were determined by a shake-flask method. The influence of different factors such as temperature, solvent polarity, mim concentration, and water content on Kmim by using 1-butyl-3-methylimidazolium chloride {[C₄C₁im]Cl} as a model compound was comprehensively studied. The calculated thermodynamic functions of transfer (∆trG⁰, ∆trH⁰, ∆trS⁰) showed that the mim migration (IL→organic phase) is a thermodynamically unfavorable and enthalpy-determined process in the temperature range of 298.15 to 328.15K; however, the results suggested that mim partition toward the organic phase can be enhanced by the rational manipulation of the extraction conditions. Experiments conducted with other 1-alkyl-3-methylimidazolim chlorides (CnC₁im]Cl (n = 6, 8... [more]
Synthesis of Water-Soluble Group 4 Metallocene and Organotin Polyethers and Their Ability to Inhibit Cancer
Charles E. Carraher, Michael R. Roner, Jessica Frank, Alica Moric-Johnson, Lindsey C. Miller, Kendra Black, Paul Slawek, Francesca Mosca, Jeffrey D. Einkauf, Floyd Russell
July 31, 2018 (v1)
Subject: Materials
Keywords: anticancer, breast cancer, Group 4 metallocene polymers, Group 4 metallocenes, interfacial polycondensation, organotin polyethers, pancreatic cancer, poly(ethylene glycol), prostate cancer
Water-soluble metallocene and organotin-containing polyethers were synthesized employing interfacial polycondensation. The reaction involved various chain lengths of poly(ethylene glycol), and produced water-soluble polymers in decent yield. Commercially available reactants were used to allow for easy scale up. The polymers exhibited a decent ability to inhibit a range of cancer cell lines, including two pancreatic cancer cell lines. This approach should allow the synthesis of a wide variety of other water-soluble polymers.
Rheology of Green Plasticizer/Poly(vinyl chloride) Blends via Time⁻Temperature Superposition
Roya Jamarani, Hanno C. Erythropel, Daniel Burkat, James A. Nicell, Richard L. Leask, Milan Maric
July 31, 2018 (v1)
Subject: Materials
Keywords: blends, extrusion, green plasticizers, poly(vinyl chloride) (PVC), rheology, time–temperature superposition
Plasticizers are commonly added to poly(vinyl chloride) (PVC) and other brittle polymers to improve their flexibility and processing properties. Phthalate plasticizers such as di(2-ethylhexyl phthalate) (DEHP) are the most common PVC plasticizers and have recently been linked to a wide range of developmental and reproductive toxicities in mammals. Our group has developed several replacement compounds that have good biodegradation kinetics, low toxicity profiles, and comparable plasticizer properties to DEHP. Knowledge of the rheology of PVC⁻plasticizer blends at elevated temperatures is crucial for understanding and predicting the behavior of the compounds during processing. In this work, the time⁻temperature profiles of PVC blended with our replacement green plasticizers—succinates, maleates, and dibenzoates, of varying alkyl chain length—are compared to blends prepared with DEHP and a commercially available non-phthalate plasticizer, di(isononyl cyclohexane-1,2-dicarboxylate) (Hexamo... [more]
Special Issue: Water Soluble Polymers
Alexander Penlidis
July 31, 2018 (v1)
Subject: Materials
This Special Issue (SI) of Processes on water soluble polymers (WSP), and the associated Special Issue reprint, contain papers that deal with this extremely popular area of scientific investigation in polymer science and engineering, both in academic and industrial environments.[...]
Comparison of Polymer Networks Synthesized by Conventional Free Radical and RAFT Copolymerization Processes in Supercritical Carbon Dioxide
Patricia Pérez-Salinas, Gabriel Jaramillo-Soto, Alberto Rosas-Aburto, Humberto Vázquez-Torres, María Josefa Bernad-Bernad, Ángel Licea-Claverie, Eduardo Vivaldo-Lima
July 31, 2018 (v1)
Subject: Materials
Keywords: hydrogels, polymer network homogeneity, RAFT polymerization, solubility in supercritical fluids, supercritical carbon dioxide
There is a debate in the literature on whether or not polymer networks synthesized by reversible deactivation radical polymerization (RDRP) processes, such as reversible addition-fragmentation radical transfer (RAFT) copolymerization of vinyl/divinyl monomers, are less heterogeneous than those synthesized by conventional free radical copolymerization (FRP). In this contribution, the syntheses by FRP and RAFT of hydrogels based on 2-hydroxyethylene methacrylate (HEMA) and ethylene glycol dimethacrylate (EGDMA) in supercritical carbon dioxide (scCO₂), using Krytox 157 FSL as the dispersing agent, and the properties of the materials produced, are compared. The materials were characterized by differential scanning calorimetry (DSC), swelling index (SI), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Studies on ciprofloxacin loading and release rate from hydrogels were also carried out. The combined results show that the hydrogels synthesized by FRP and RAFT are signif... [more]
Applications of Water-Soluble Polymers in Turbulent Drag Reduction
Wen Jiao Han, Yu Zhen Dong, Hyoung Jin Choi
July 31, 2018 (v1)
Subject: Materials
Keywords: aqueous polymer, drag reduction, gum, poly(ethylene oxide), polyacrylamide, turbulent flow
Water-soluble polymers with high molecular weights are known to decrease the frictional drag in turbulent flow very effectively at concentrations of tens or hundreds of ppm. This drag reduction efficiency of water-soluble polymers is well known to be closely associated with the flow conditions and rheological, physical, and/or chemical characteristics of the polymers added. Among the many promising polymers introduced in the past several decades, this review focuses on recent progress in the drag reduction capability of various water-soluble macromolecules in turbulent flow including both synthetic and natural polymers such as poly(ethylene oxide), poly(acrylic acid), polyacrylamide, poly(N-vinyl formamide), gums, and DNA. The polymeric species, experimental parameters, and numerical analysis of these water-soluble polymers in turbulent drag reduction are highlighted, along with several existing and potential applications. The proposed drag reduction mechanisms are also discussed based... [more]
Aqueous Free-Radical Polymerization of Non-Ionized and Fully Ionized Methacrylic Acid
Eric Jean Fischer, Giuseppe Storti, Danilo Cuccato
July 31, 2018 (v1)
Subject: Materials
Keywords: electrostatic interactions, electrostatic screening, free radical polymerization, kinetics, methacrylic acid, Modelling, NMR, propagation, termination
Water-soluble, carboxylic acid monomers are known to exhibit peculiar kinetics when polymerized in aqueous solution. Namely, their free-radical polymerization rate is affected by several parameters such as monomer concentration, ionic strength, and pH. Focusing on methacrylic acid (MAA), even though this monomer has been largely addressed, a systematic investigation of the effects of the above-mentioned parameters on its polymerization rate is missing, in particular in the fully ionized case. In this work, the kinetics of non-ionized and fully ionized MAA are characterized by in-situ nuclear magnetic resonance (NMR). Such accurate monitoring of the reaction rate enables the identification of relevant but substantially different effects of the monomer and electrolyte concentration on polymerization rate in the two ionization cases. For non-ionized MAA, the development of a kinetic model based on literature rate coefficients allows us to nicely simulate the experimental data of conversio... [more]
Polymerization Kinetics of Poly(2-Hydroxyethyl Methacrylate) Hydrogels and Nanocomposite Materials
Dimitris S. Achilias, Panoraia I. Siafaka
July 31, 2018 (v1)
Subject: Materials
Keywords: HEMA, in situ polymerization, nano-clays, nano-silica, nanocomposites, polymerization kinetics
Hydrogels based on poly(2-hydroxyethyl methacrylate) (PHEMA) are a very important class of biomaterials with several applications mainly in tissue engineering and contacts lenses. Although the polymerization kinetics of HEMA have been investigated in the literature, the development of a model, accounting for both the chemical reaction mechanism and diffusion-controlled phenomena and valid over the whole conversion range, has not appeared so far. Moreover, research on the synthesis of nanocomposite materials based on a polymer matrix has grown rapidly recently because of the improved mechanical, thermal and physical properties provided by the polymer. In this framework, the objective of this research is two-fold: to provide a kinetic model for the polymerization of HEMA with accurate estimations of the kinetic and diffusional parameters employed and to investigate the effect of adding various types and amounts of nano-additives to the polymerization rate. In the first part, experimental... [more]
Kinetics of the Aqueous-Phase Copolymerization of MAA and PEGMA Macromonomer: Influence of Monomer Concentration and Side Chain Length of PEGMA
Iñaki Emaldi, Shaghayegh Hamzehlou, Jorge Sanchez-Dolado, Jose R. Leiza
July 31, 2018 (v1)
Subject: Materials
Keywords: aqueous-phase copolymerization, ionization degree, polyethylene glycol methacrylate monomers, reactivity ratios, solids content
An in situ nuclear magnetic resonance spectroscopy (NMR) technique is used to monitor the aqueous-phase copolymerization kinetics of methacrylic acid (MAA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) macromonomers. In particular, the study analyses the effect of the number of ethylene glycol (EG) groups along the lateral chains of PEGMA and is carried out under fully ionized conditions of MAA at different initial monomer ratios and initial overall monomer concentrations (5⁻20 wt % in aqueous solution). The composition drift with conversion indicates that PEGMA macromonomer is more reactive than MAA. Individual monomer consumption rates show that the rates of consumption of both monomers are not first order with respect to overall concentration of the monomer. The reactivity ratios estimated from the copolymerization kinetics reveal, that for the short PEGMA, the reactivity ratios rMAA and rPEGMA increase with the solids content (SC). A totally different trend is obtaine... [more]
Biodegradable and Biocompatible PDLLA-PEG1k-PDLLA Diacrylate Macromers: Synthesis, Characterisation and Preparation of Soluble Hyperbranched Polymers and Crosslinked Hydrogels
Alan Hughes, Hongyun Tai, Anna Tochwin, Wenxin Wang
July 31, 2018 (v1)
Subject: Materials
Keywords: ">d,, ">l-lactide, biodegradable hydrogels, hyperbranched polymers, macromers, poly (ethylene glycol), triblock co-polymers
A series of PDLLA-PEG1k-PDLLA tri-block co-polymers with various compositions, i.e., containing 2⁻10 lactoyl units, were prepared via ring opening polymerisation of d,l-lactide in the presence of poly (ethylene glycol) (PEG) (Mn = 1000 g·mol−1) as the initiator and stannous 2-ethylhexanoate as the catalyst at different feed ratios. PDLLA-PEG1k-PDLLA co-polymers were then functionalised with acrylate groups using acryloyl chloride under various reaction conditions. The diacrylated PDLLA-PEG1k-PDLLA (diacryl-PDLLA-PEG1k-PDLLA) were further polymerised to synthesize soluble hyperbranched polymers by either homo-polymerisation or co-polymerisation with poly(ethylene glycol) methyl ether methylacrylate (PEGMEMA) via free radical polymerisation. The polymer samples obtained were characterised by ¹H NMR (proton Nuclear Magnetic Resonance), FTIR (Fourier Transform Infra-red spectroscopy), and GPC (Gel Permeation Chromatography). Moreover, the diacryl-PDLLA-PEG1k-PDLLA macromers were used for t... [more]
Simultaneous Monitoring of the Effects of Multiple Ionic Strengths on Properties of Copolymeric Polyelectrolytes during Their Synthesis
Aide Wu, Zifu Zhu, Michael F. Drenski, Wayne F. Reed
July 31, 2018 (v1)
Subject: Materials
Keywords: ACOMP, copolymeric polyelectrolytes, light scattering, online monitoring, viscosity
A new Automatic Continuous Online Monitoring of Polymerization reactions (ACOMP) system has been developed with multiple light scattering and viscosity detection stages in serial flow, where solution conditions are different at each stage. Solution conditions can include ionic strength (IS), pH, surfactants, concentration, and other factors. This allows behavior of a polymer under simultaneous, varying solution conditions to be monitored at each instant of its synthesis. The system can potentially be used for realtime formulation, where a solution formulation is built up additively in successive stages. It can also monitor the effect of solution conditions on stimuli responsive polymers, as their responsiveness changes during synthesis. In this first work, the new ACOMP system monitored light scattering and reduced viscosity properties of copolymeric polyelectrolytes under various IS during synthesis. Aqueous copolymerization of acrylamide (Am) and styrene sulfonate (SS) was used. Poly... [more]
Poly(Poly(Ethylene Glycol) Methyl Ether Methacrylate) Grafted Chitosan for Dye Removal from Water
Bryan Tsai, Omar Garcia-Valdez, Pascale Champagne, Michael F. Cunningham
July 31, 2018 (v1)
Subject: Materials
Keywords: chitosan, dye, grafting, nitroxide-mediated polymerization, PEGMA, Wastewater
As the demand for textile products and synthetic dyes increases with the growing global population, textile dye wastewater is becoming one of the most significant water pollution contributors. Azo dyes represent 70% of dyes used worldwide, and are hence a significant contributor to textile waste. In this work, the removal of a reactive azo dye (Reactive Orange 16) from water by adsorption with chitosan grafted poly(poly(ethylene glycol) methyl ether methacrylate) (CTS-GMA-g-PPEGMA) was investigated. The chitosan (CTS) was first functionalized with glycidyl methacrylate and then grafted with poly(poly(ethylene glycol) methyl ether methacrylate) using a nitroxide-mediated polymerization grafting to approach. Equilibrium adsorption experiments were carried out at different initial dye concentrations and were successfully fitted to the Langmuir and Freundlich adsorption isotherm models. Adsorption isotherms showed maximum adsorption capacities of CTS-g-GMA-PPEGMA and chitosan of 200 mg/g a... [more]
AMPS/AAm/AAc Terpolymerization: Experimental Verification of the EVM Framework for Ternary Reactivity Ratio Estimation
Alison J. Scott, Niousha Kazemi, Alexander Penlidis
July 31, 2018 (v1)
Subject: Materials
Keywords: 2-acrylamido-2-methylpropane sulfonic acid, acrylamide, acrylic acid, error-in-variables-model, polymerization kinetics, reactivity ratio estimation, terpolymerization
The complete error-in-variables-model (EVM) framework, consisting of both design of experiments and parameter estimation stages, is applied to the terpolymerization of 2-acrylamido-2-methylpropane sulfonic acid (AMPS, M₁), acrylamide (AAm, M₂) and acrylic acid (AAc, M₃). This water-soluble terpolymer has potential for applications in enhanced oil recovery, but the associated terpolymerization kinetic characteristics are largely unstudied. In the current paper, EVM is used to design optimal experiments (for the first time in the literature), and reactivity ratios are subsequently estimated based on both low and medium-high conversion data. The results from the medium-high conversion data are more precise than those from the low conversion data, and are therefore used next to predict the terpolymer composition trajectory over the full course of conversion. Good agreement is seen between experimental data and model predictions, which confirms the accuracy of the newly determined ternary r... [more]
Poly(methacrylic acid-ran-2-vinylpyridine) Statistical Copolymer and Derived Dual pH-Temperature Responsive Block Copolymers by Nitroxide-Mediated Polymerization
Milan Marić, Chi Zhang, Daniel Gromadzki
July 31, 2018 (v1)
Subject: Materials
Keywords: nitroxide-mediated polymerization, poly(ampholytes), stimuli-responsive polymers
Nitroxide-mediated polymerization using the succinimidyl ester functional unimolecular alkoxyamine initiator (NHS-BlocBuilder) was used to first copolymerize tert-butyl methacrylate/2-vinylpyridine (tBMA/2VP) with low dispersity (Đ = 1.30⁻1.41) and controlled growth (linear number average molecular Mn versus conversion, Mn = 3.8⁻10.4 kg·mol−1) across a wide composition of ranges (initial mol fraction 2VP, f2VP,0 = 0.10⁻0.90). The resulting statistical copolymers were first de-protected to give statistical polyampholytic copolymers comprised of methacrylic acid/2VP (MAA/2VP) units. These copolymers exhibited tunable water-solubility due to the different pKas of the acidic MAA and basic 2VP units; being soluble at very low pH < 3 and high pH > 8. One of the tBMA/2VP copolymers was used as a macroinitiator for a 4-acryloylmorpholine/4-acryloylpiperidine (4AM/4AP) mixture, to provide a second block with thermo-responsive behavior with tunable cloud point temperature (CPT), depending on the... [more]
From Single Microparticles to Microfluidic Emulsification: Fundamental Properties (Solubility, Density, Phase Separation) from Micropipette Manipulation of Solvent, Drug and Polymer Microspheres
Koji Kinoshita, Elisa Parra, Abdirazak Hussein, Anders Utoft, Prasad Walke, Robin de Bruijn, David Needham
July 30, 2018 (v1)
Subject: Materials
Keywords: drug dissolution, encapsulation, ibuprofen, microfluidic emulsification, microparticle, micropipette manipulation, PLGA
The micropipette manipulation technique is capable of making fundamental single particle measurements and analyses. This information is critical for establishing processing parameters in systems such as microfluidics and homogenization. To demonstrate what can be achieved at the single particle level, the micropipette technique was used to form and characterize the encapsulation of Ibuprofen (Ibp) into poly(lactic-co-glycolic acid) (PLGA) microspheres from dichloromethane (DCM) solutions, measuring the loading capacity and solubility limits of Ibp in typical PLGA microspheres. Formed in phosphate buffered saline (PBS), pH 7.4, Ibp/PLGA/DCM microdroplets were uniformly solidified into Ibp/PLGA microparticles up to drug loadings (DL) of 41%. However, at DL 50 wt% and above, microparticles showed a phase separated pattern. Working with single microparticles, we also estimated the dissolution time of pure Ibp microspheres in the buffer or in detergent micelle solutions, as a function of th... [more]
Extending Emulsion Functionality: Post-Homogenization Modification of Droplet Properties
Long Bai, David Julian McClements
July 30, 2018 (v1)
Subject: Materials
Keywords: electrostatic deposition, emulsions, homogenization, hydrogels, nanoemulsions, post-homogenization, solid lipid nanoparticles
Homogenizers are commonly used to produce oil-in-water emulsions that consist of emulsifier-coated oil droplets suspended within an aqueous phase. The functional attributes of emulsions are usually controlled by selecting appropriate ingredients (e.g., surfactants, co-surfactants, oils, solvents, and co-solvents) and processing conditions (e.g., homogenizer type and operating conditions). However, the functional attributes of emulsions can also be tailored after homogenization by manipulating their composition, structure, or physical state. The interfacial properties of lipid droplets can be altered using competitive adsorption or coating methods (such as electrostatic deposition). The physical state of oil droplets can be altered by selecting an oil phase that crystallizes after the emulsion has been formed. The composition of the disperse phase can be altered by mixing different kinds of oil droplets together to induce inter-droplet exchange of oil molecules. The local environment of... [more]
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