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Alexander Penlidis - One of the best experts on this subject based on the ideXlab platform.
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computational package for copolymerization Reactivity Ratio estimation improved access to the error in variables model
Processes, 2018Co-Authors: Alison J Scott, Alexander PenlidisAbstract: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.
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Binary vs. ternary Reactivity Ratios: Appropriate estimation procedures with terpolymerization data
European Polymer Journal, 2018Co-Authors: Alison J Scott, Alexander PenlidisAbstract:Abstract There is a widely accepted analogy between copolymerization and terpolymerization mechanisms that has allowed researchers to use Reactivity Ratios obtained for binary pairs (from copolymerization experiments) in models dealing with terpolymerizations. However, binary Reactivity Ratios are not always applicable to terpolymerization systems; using the binary-ternary analogy (even as an approximation) requires making considerable assumptions about the system. When binary Reactivity Ratios are used to describe ternary systems, the consequences may include substantial differences in Reactivity Ratio estimates, poor composition prediction performance, and incorrect determination of product (terpolymer) characteristics. Experimental results and Reactivity Ratio estimation (via the error-in-variables-model) for the terpolymerization of 2-acrylamido-2-methylpropane sulfonic acid (AMPS), acrylamide (AAm) and acrylic acid (AAc) (and associated copolymers) are compared, all other conditions being equal.
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amps aam aac terpolymerization experimental verification of the evm framework for ternary Reactivity Ratio estimation
Processes, 2017Co-Authors: Alison J Scott, Niousha Kazemi, Alexander PenlidisAbstract: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 Reactivity Ratios: r12 = 0.66, r21 = 0.82, r13 = 0.82, r31 = 0.61, r23 = 1.61, r32 = 0.25.
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optimal design for Reactivity Ratio estimation a comparison of techniques for amps acrylamide and amps acrylic acid copolymerizations
Processes, 2015Co-Authors: Alison J Scott, Marzieh Riahinezhad, Alexander PenlidisAbstract:Water-soluble polymers of acrylamide (AAm) and acrylic acid (AAc) have significant potential in enhanced oil recovery, as well as in other specialty applications. To improve the shear strength of the polymer, a third comonomer, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), can be added to the pre-polymerization mixture. Copolymerization kinetics of AAm/AAc are well studied, but little is known about the other comonomer pairs (AMPS/AAm and AMPS/AAc). Hence, Reactivity Ratios for AMPS/AAm and AMPS/AAc copolymerization must be established first. A key aspect in the estimation of reliable Reactivity Ratios is design of experiments, which minimizes the number of experiments and provides increased information content (resulting in more precise parameter estimates). However, design of experiments is hardly ever used during copolymerization parameter estimation schemes. In the current work, copolymerization experiments for both AMPS/AAm and AMPS/AAc are designed using two optimal techniques (Tidwell-Mortimer and the error-in-variables-model (EVM)). From these optimally designed experiments, accurate Reactivity Ratio estimates are determined for AMPS/AAm (rAMPS = 0.18, rAAm = 0.85) and AMPS/AAc (rAMPS = 0.19, rAAc = 0.86).
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Design of Optimal Experiments for Terpolymerization Reactivity Ratio Estimation
Macromolecular Reaction Engineering, 2015Co-Authors: Niousha Kazemi, Thomas A. Duever, Alexander PenlidisAbstract:A model-based design of experiments is implemented for the problem of Reactivity Ratio estimation in terpolymerizations for the first time in the literature. Optimal terpolymerization feed compositions are calculated using a design criterion, based on the Error-in-Variables-Model (EVM) approach. The results show that there are three optimal feed compositions with their locations naturally dependent on the values of the Reactivity Ratios. However, the interesting observation is that in almost all cases the optimal feed compositions are located close to the corners of the terpolymerization composition triangular plot. In addition, the impact of the Reactivity Ratio values on the location of the optimal feed compositions is explored and “practical heuristics” are presented.
K S V Srinivasan - One of the best experts on this subject based on the ideXlab platform.
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synthesis characterization and Reactivity Ratio studies on new sulfide copolymers containing ethylbenzene units
Polymer, 2003Co-Authors: Subramanian Sundarrajan, K Ganesh, K S V SrinivasanAbstract:Abstract Soluble new sulfide copolymers were synthesized readily by the polycondensation of ethylene dibromide (EDB) (or methylene dibromide (MDB)) with styrene dibromide (SDB) and sodium sulfide (Na2S) in the presence of phase transfer catalyst. The copolymers were characterized by using Fourier transform-infrared, 1H NMR, 13C NMR, gel permeation chromatography, and thermogravimetric analysis (TGA) techniques. The copolymer composition obtained from the 1H NMR spectra led to the determination of Reactivity Ratios. The analysis of Reactivity Ratios revealed that both EDB and MDB are more reactive than SDB towards Na2S, and copolymers formed are random in nature. Furthermore, it also gave an insight on the microstructure of the copolymers that both poly (ethylene sulfide-co-styrene sulfide) (p(ES-co-SS)), and poly(methylene sulfide-co-styrene sulfide) (p(MS-co-SS)) copolymers have more of blocky structure with increase in the concentRation of ethylene sulfide (ES) or methylene sulfide (MS) units in the respective copolymers. The TGA was used to find out the thermal stability of these polymers. The XRD data indicated an increase in the amorphous content of the copolymers with an increase in the concentRation of styrene sulfide (SS) units and thereby resulting in most of these copolymers being soluble in common organic solvents. The solubility and molecular weight of the polymers formed were dependent on the concentRation of SDB taken in the feed.
Niousha Kazemi - One of the best experts on this subject based on the ideXlab platform.
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amps aam aac terpolymerization experimental verification of the evm framework for ternary Reactivity Ratio estimation
Processes, 2017Co-Authors: Alison J Scott, Niousha Kazemi, Alexander PenlidisAbstract: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 Reactivity Ratios: r12 = 0.66, r21 = 0.82, r13 = 0.82, r31 = 0.61, r23 = 1.61, r32 = 0.25.
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Design of Optimal Experiments for Terpolymerization Reactivity Ratio Estimation
Macromolecular Reaction Engineering, 2015Co-Authors: Niousha Kazemi, Thomas A. Duever, Alexander PenlidisAbstract:A model-based design of experiments is implemented for the problem of Reactivity Ratio estimation in terpolymerizations for the first time in the literature. Optimal terpolymerization feed compositions are calculated using a design criterion, based on the Error-in-Variables-Model (EVM) approach. The results show that there are three optimal feed compositions with their locations naturally dependent on the values of the Reactivity Ratios. However, the interesting observation is that in almost all cases the optimal feed compositions are located close to the corners of the terpolymerization composition triangular plot. In addition, the impact of the Reactivity Ratio values on the location of the optimal feed compositions is explored and “practical heuristics” are presented.
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Reactivity Ratio Estimation in Radical Copolymerization: From Preliminary Estimates to Optimal Design of Experiments
Industrial & Engineering Chemistry Research, 2014Co-Authors: Niousha Kazemi, Thomas A. Duever, Benoît H. Lessard, Milan Marić, Alexander PenlidisAbstract:An error-in-variables-model (EVM) framework is presented for the optimal estimation of Reactivity Ratios in copolymerization systems. This framework consists of several sequential steps and practical prescriptions that can yield reliable and statistically correct Reactivity Ratio values. These steps include: (a) screening experiments for estimating preliminary Reactivity Ratios, (b) optimal design of experiments, (c) full conversion range experiments and estimation of optimal Reactivity Ratios, and if necessary, (d) design of sequentially optimal experiments and re-estimation of Reactivity Ratios and diagnostic checks. This complete methodology should become common practice for determining Reactivity Ratios with the highest possible level of confidence. The performance of this framework is verified experimentally with data from the controlled nitroxide-mediated copolymerization of 9-(4-vinylbenzyl)-9H-carbazole (VBK) and methyl methacrylate (MMA), a novel and largely unstudied copolymer system.
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design of experiments for Reactivity Ratio estimation in multicomponent polymerizations using the error in variables approach
Macromolecular Theory and Simulations, 2013Co-Authors: Niousha Kazemi, Thomas A. Duever, Alexander PenlidisAbstract:Model-based design of experiments using the error-in-variables model (EVM) is explored. The fundamental differences between DOE in the traditional nonlinear regression versus the EVM context are discussed, and it is pointed out that for cases where there are errors in all variables, using the EVM design criterion is the only appropriate approach. In addition, the implementation of the EVM design criterion and its characteristics for both initial and sequential design schemes are discussed. The main application is the implementation of the EVM criterion to design optimal trials for reliable estimating Reactivity Ratios for typical copolymerization systems, along with prescriptions for the practitioner.
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a powerful estimation scheme with the error in variables model for nonlinear cases Reactivity Ratio estimation examples
Computers & Chemical Engineering, 2013Co-Authors: Niousha Kazemi, Thomas A. Duever, Alexander PenlidisAbstract:Abstract This paper gives an overview of the error-in-variables-model (EVM) procedure for parameter estimation with nonlinear models. It is shown that the nested-iterative EVM algorithm, used in this work, is efficient and powerful, since it provides both true values of the variables and the best estimates of the parameters. The step by step illustRation along with evaluation techniques for results, are followed by further discussion about the importance and advantages of combining EVM with design of experiments strategies. With the focus on the performance of the EVM algorithm, an illustrative example of Reactivity Ratio estimation in copolymerization is included, with single-response (composition data) and multi-response (triad fraction data) scenarios.
Thomas A. Duever - One of the best experts on this subject based on the ideXlab platform.
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Parameter Estimation for an Inverse Nonlinear Stochastic Problem: Reactivity Ratio Studies in Copolymerization
Macromolecular Theory and Simulations, 2017Co-Authors: Hector Budman, Thomas A. DueverAbstract:A generalized polynomial chaos (gPC)-based methodology is developed to estimate the Reactivity Ratio in copolymerization, where the Reactivity Ratio is assumed to be stochastic unknown and determined by comparing model predictions with limited experimental data. The estimation step is formulated as a stochastic inverse problem of finding the distributional stochastic Reactivity Ratio parameters with a maximum likelihood function. The results show that the gPC-based Reactivity Ratio estimation is efficient and powerful, since it simultaneously provides the best estimates and their corresponding variances. Beyond achieving accurate estimation results, it is shown that the computational cost of the gPC-based methodology is significantly lower than Markov chain Monte Carlo simulations, thus demonstrating the potential of the gPC method for dealing with other more complicated nonlinear problems.
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Reactivity Ratio estimation in non linear polymerization models using markov chain monte carlo techniques and an error in variables framework
Macromolecular Theory and Simulations, 2015Co-Authors: Manoj Mathew, Thomas A. DueverAbstract:Reactivity Ratio estimation was carried out in various nonlinear models using Markov Chain Monte Carlo (MCMC) technique and an error-in-variables (EVM) regression model. The implementation steps for three different polymerization case studies are discussed in detail and the results from this work are compared to previously used approximation methods. Approximation techniques that rely on linear regression theory are shown to produce inaccurate joint confidence regions (JCRs). Therefore, in this paper, we explore MCMC techniques that can be used to produce JCRs with correct shape and probability content. In addition, the paper illustrates how an EVM model can be used in tackling any type of regression problem, including multi-response problems.
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Design of Optimal Experiments for Terpolymerization Reactivity Ratio Estimation
Macromolecular Reaction Engineering, 2015Co-Authors: Niousha Kazemi, Thomas A. Duever, Alexander PenlidisAbstract:A model-based design of experiments is implemented for the problem of Reactivity Ratio estimation in terpolymerizations for the first time in the literature. Optimal terpolymerization feed compositions are calculated using a design criterion, based on the Error-in-Variables-Model (EVM) approach. The results show that there are three optimal feed compositions with their locations naturally dependent on the values of the Reactivity Ratios. However, the interesting observation is that in almost all cases the optimal feed compositions are located close to the corners of the terpolymerization composition triangular plot. In addition, the impact of the Reactivity Ratio values on the location of the optimal feed compositions is explored and “practical heuristics” are presented.
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Reactivity Ratio Estimation in Radical Copolymerization: From Preliminary Estimates to Optimal Design of Experiments
Industrial & Engineering Chemistry Research, 2014Co-Authors: Niousha Kazemi, Thomas A. Duever, Benoît H. Lessard, Milan Marić, Alexander PenlidisAbstract:An error-in-variables-model (EVM) framework is presented for the optimal estimation of Reactivity Ratios in copolymerization systems. This framework consists of several sequential steps and practical prescriptions that can yield reliable and statistically correct Reactivity Ratio values. These steps include: (a) screening experiments for estimating preliminary Reactivity Ratios, (b) optimal design of experiments, (c) full conversion range experiments and estimation of optimal Reactivity Ratios, and if necessary, (d) design of sequentially optimal experiments and re-estimation of Reactivity Ratios and diagnostic checks. This complete methodology should become common practice for determining Reactivity Ratios with the highest possible level of confidence. The performance of this framework is verified experimentally with data from the controlled nitroxide-mediated copolymerization of 9-(4-vinylbenzyl)-9H-carbazole (VBK) and methyl methacrylate (MMA), a novel and largely unstudied copolymer system.
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design of experiments for Reactivity Ratio estimation in multicomponent polymerizations using the error in variables approach
Macromolecular Theory and Simulations, 2013Co-Authors: Niousha Kazemi, Thomas A. Duever, Alexander PenlidisAbstract:Model-based design of experiments using the error-in-variables model (EVM) is explored. The fundamental differences between DOE in the traditional nonlinear regression versus the EVM context are discussed, and it is pointed out that for cases where there are errors in all variables, using the EVM design criterion is the only appropriate approach. In addition, the implementation of the EVM design criterion and its characteristics for both initial and sequential design schemes are discussed. The main application is the implementation of the EVM criterion to design optimal trials for reliable estimating Reactivity Ratios for typical copolymerization systems, along with prescriptions for the practitioner.
Mitsuo Sawamoto - One of the best experts on this subject based on the ideXlab platform.
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cyclopolymerization of cleavable acrylate vinyl ether divinyl monomer via nitroxide mediated radical polymerization copolymer beyond Reactivity Ratio
ACS Macro Letters, 2017Co-Authors: Yuki Kametani, Marina Nakano, Taizo Yamamoto, Makoto Ouchi, Mitsuo SawamotoAbstract:Cyclopolymerization of a divinyl monomer, where two different vinyl groups, that is, acrylate and vinyl ether, are connected via an ester bond, was performed under diluted condition with nitroxide-meditated radical polymerization (NMP). Both vinyl groups were consumed at almost same rate under suitable condition, although the inherent cross-propagation ability between the two vinyl groups are pretty low in radical copolymerization. Furthermore, the polymerization was controlled to some extent to give polymers of unimodal molecular weight distributions. The results obviously differed from copolymerization and homopolymerization with vinyl monomers that constitutes the divinyl monomer, 2-methoxyethyl acrylate and 2-acetoxyethyl vinyl ether. Structural analyses indicated formation of the cyclopolymer but the cyclo-efficiency was imperfect indicating that some units of olefinic dangling were incorporated. Eventually, the ester bonds of the cyclo units were cleaved to convert into the copolymer consisting of a...
