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Taihorng Young - One of the best experts on this subject based on the ideXlab platform.
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study on the relationship between the ternary interaction parameter and the structure of water by the effect of aliphatic alcohols and phenol on the swelling behavior of poly ethylene co vinyl alcohol membrane in aqueous solution
European Polymer Journal, 2004Co-Authors: Liaoping Cheng, Kenyu Chang, Pingshan Lai, Taihorng YoungAbstract:Abstract The effect of very low concentrations of ethanol, 2-propanol and phenol on the swelling degree of poly(ethylene-co-vinyl alcohol) (EVAL) in water was investigated. The effect of phenol on the swelling degree of EVAL was remarkably large compared to that of ethanol and that of 2-propanol. Theoretical analysis on the basis of Flory–Huggins Theory using three binary interaction parameters could appropriately predict the EVAL swelling degree in ethanol/water and 2-propanol/water mixtures. However, the theoretical swelling degree of EVAL in phenol/water mixtures needed a ternary interaction parameter (χT) to match with experimental data points. An optimum value of χT for the water–phenol–EVAL system was found to be −3.3. The relationship between the ternary interaction parameter and the structure of water from observations of the effect of phenol on the EVAL swelling was discussed. Based on the analysis of low-frequency Raman spectroscopy reported by Suzuki et al. [J. Chem. Phys. 107 (1997) 5890], the contribution of χT to the EVAL swelling was attributed to the increase of the entropy in bulk water due to the effect of phenol on the disruption of the tetrahedral hydrogen-bonded networks of water molecules. This, in turn, induced an increase of water absorption in EVAL.
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phase behavior of poly ether imide in mixtures of n methyl 2 pyrrolidinone and methylene chloride
Polymer, 2003Co-Authors: Taihorng YoungAbstract:Abstract The phase behavior of poly(ether imide) (PEI) in solutions composed of N -methyl-2-pyrrolidone (NMP) and methylene chloride (MC) was studied at 25 °C. The pair of solvents used to dissolve PEI has been selected for the purpose to perform a cononsolvent system. From the observed phase behavior, PEI was soluble in either NMP or MC individually but liquid–liquid demixing was observed in mixtures of NMP and MC. However, no cononsolvency was found by the theoretical prediction on the basis of Flory–Huggins formalism including three binary interaction parameters. Therefore, attempts were made to correlate the phase behavior of a cononsolvent system with the modified Flory–Huggins Theory using a ternary interaction parameter. A good prediction was obtained when a composition-dependent ternary interaction parameter was included into calculations. In addition, the mechanism of cononsolvency and its relation with the ternary interaction parameter in the cononsolvent systems were discussed. Based on the analysis of IR spectroscopy, the ternary interaction parameter correlates well with a more intermolecular complexation of NMP with MC in the presence of PEI. Thus, the driving force for cononsolvency results from the formation of the NMP–MC complexes favoring over NMP–MC–PEI contacts, leading to exclude PEI segments in the vicinity of the NMP–MC complexes.
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formation of particulate microporous poly vinylidene fluoride membranes by isothermal immersion precipitation from the 1 octanol dimethylformamide poly vinylidene fluoride system
Polymer, 1999Co-Authors: Liaoping Cheng, Taihorng Young, Lin FangAbstract:Abstract Phase diagrams were determined for poly(vinylidene fluoride) (PVDF) and a terpolymer of vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene (VDF/HFP/TFE) in solutions composed of 1-octanol and dimethylformamide at 25°C. From the measured gelation and liquid–liquid phase separation data, binary interaction parameters were computed using a modified Flory–Huggins Theory. PVDF microporous membranes were then prepared by isothermal immersion precipitation processes in various doping conditions. The formed membrane exhibited a particulate morphology characterized by a uniform package of spherical particles of identical size. These particles were identified to be full spherulites of PVDF using scanning electron microscopy, differential scanning calorimetry and small angle light scattering techniques.
John M Prausnitz - One of the best experts on this subject based on the ideXlab platform.
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solubilities and diffusivities of water vapor in poly methylmethacrylate poly 2 hydroxyethylmethacrylate poly n vinyl 2 pyrrolidone and poly acrylonitrile
Polymer, 2003Co-Authors: John M Prausnitz, Oscar Rodriguez, Francesco Fornasiero, Alberto Arce, C J RadkeAbstract:Abstract Sorption and diffusion data were obtained for water vapor in four different polymers: poly (methylmethacrylate) (PMMA), poly (2-hydroxyethylmethacrylate) (PHEMA), poly (N-vinyl-2-pyrrolidone) (PVP) and poly (acrylonitrile) (PAN) at 35 °C using a gravimetric sorption method. Highest sorption was for PVP, followed by PHEMA. PMMA and PAN sorbed very little water. All the polymers exhibit a BET type III sorption isotherm; the large upturn at high activity for PVP and PHEMA is probably due to plasticization of the polymers by water vapor. Sorption data were interpreted using Flory–Huggins Theory and the Zimm and Lundberg cluster integral. Fickian diffusion is observed for PHEMA. For PVP, the fractional uptake Mt/M∞ is linear with the square root of the time up to Mt/M∞=0.6−0.8 for all water activities aw, but it shows a clear water sorption overshoot at aw=55.3% and aw=72.1%, probably due to macromolecular relaxation. PMMA sorption kinetics is also characterized by a maximum in the water uptake. The diffusion coefficient increases significantly with water concentration for PVP and PHEMA, weakly for PMMA, but it is independent of concentration for PAN.
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lattice thermodynamics for aqueous salt polymer two phase systems
Journal of Applied Polymer Science, 1998Co-Authors: T Hino, John M PrausnitzAbstract:A lattice model is presented to compute salt-induced liquid–liquid phase separation in aqueous polymer solutions. The Gibbs energy of mixing contains an electrostatic contribution given by Pitzer's extension of the Debye–Huckel function, and the extended Flory–Huggins Theory that uses empirical functions of temperature and composition as binary interaction parameters. Our Flory–Huggins Theory assumes complete dissociation of salt into ions, but it does not distinguish between cation and anion; our Theory represents the water–salt–polymer mixture as an incompressible ternary system consisting of water, ion, and polymer. In the extended Flory–Huggins Theory, the binary interaction parameter between water and ion, and that between water and polymer, are obtained by correlating the observed activity of water in each of the two relevant binary systems. The electrostatic contribution does not contain adjustable parameters. We show that the electrostatic contribution to the Gibbs energy of mixing is responsible for inducing salt–polymer aqueous two-phase systems. Calculated phase diagrams are compared with experiment for aqueous solutions containing polyethylene glycol and a single salt at room temperature. The efficiency of a salt to form salt–polymer aqueous two-phase systems is discussed in terms of ion valence and the interaction parameter between ion and polymer. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci Inc. J Appl Polym Sci 68: 2007–2017, 1998
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molecular thermodynamics for volume change transitions in temperature sensitive polymer gels
Polymer, 1998Co-Authors: John M Prausnitz, Toshiaki HinoAbstract:Abstract A molecular-thermodynamic model is presented to predict volume change transitions in temperature-sensitive polymer gels. The model uses an extended Flory-Huggins Theory as a mixing contribution and a new interpolated affine model suggested by Birshtein as an elastic contribution. The Flory χ parameter is given by the product of a temperature-dependent and a composition-dependent term. Our model also differs from those presented previously because the temperature-dependent term is given by the incompressible lattice-gas model by ten Brinke and Karasz that accounts for specific interactions such as hydrogen bonding. Following conventional practice, the van't Hoff equation is introduced to represent the effect of a small number of ionizable segments in the network chain. Calculated swelling-ratio curves for neutral and weakly ionized aqueous N -isopropylacrylamide gels use molecular parameters obtained from phase-equilibrium data for (non-crosslinked) polymer solutions. In agreement with experiment, the calculated volume-transition temperature of the gel is about 1°C higher than the lower critical solution temperature of the (non-crosslinked) polymer solution.
Gavin Andrews - One of the best experts on this subject based on the ideXlab platform.
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probing the effects of experimental conditions on the character of drug polymer phase diagrams constructed using flory huggins Theory
Pharmaceutical Research, 2015Co-Authors: Conor Donnelly, Yiwei Tian, Catherine B Potter, David S Jones, Gavin AndrewsAbstract:Purpose Amorphous drug-polymer solid dispersions have been found to result in improved drug dissolution rates when compared to their crystalline counterparts. However, when the drug exists in the amorphous form it will possess a higher Gibb’s free energy than its associated crystalline state and can recrystallize. Drug-polymer phase diagrams constructed through the application of the Flory Huggins (F-H) Theory contain a wealth of information regarding thermodynamic and kinetic stability of the amorphous drug-polymer system. This study was aimed to evaluate the effects of various experimental conditions on the solubility and miscibility detections of drug-polymer binary system.
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construction of drug polymer thermodynamic phase diagrams using flory huggins interaction Theory identifying the relevance of temperature and drug weight fraction to phase separation within solid dispersions
Molecular Pharmaceutics, 2013Co-Authors: Yiwei Tian, David S Jones, Jonathan Booth, Elizabeth Meehan, Shu Li, Gavin AndrewsAbstract:Amorphous drug–polymer solid dispersions have the potential to enhance the dissolution performance and thus bioavailability of BCS class II drug compounds. The principle drawback of this approach is the limited physical stability of amorphous drug within the dispersion. Accurate determination of the solubility and miscibility of drug in the polymer matrix is the key to the successful design and development of such systems. In this paper, we propose a novel method, based on Flory–Huggins Theory, to predict and compare the solubility and miscibility of drug in polymeric systems. The systems chosen for this study are (1) hydroxypropyl methylcellulose acetate succinate HF grade (HPMCAS-HF)–felodipine (FD) and (2) Soluplus (a graft copolymer of polyvinyl caprolactam–polyvinyl acetate–polyethylene glycol)–FD. Samples containing different drug compositions were mixed, ball milled, and then analyzed by differential scanning calorimetry (DSC). The value of the drug–polymer interaction parameter χ was calculated fr...
Tejraj M Aminabhavi - One of the best experts on this subject based on the ideXlab platform.
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functionalized graphene sheets embedded in chitosan nanocomposite membranes for ethanol and isopropanol dehydration via pervaporation
Industrial & Engineering Chemistry Research, 2014Co-Authors: Suhas P Dharupaneedi, Raghu V Anjanapura, Jeong M Han, Tejraj M AminabhaviAbstract:Pervaporation is an important alternative membrane separation process compared to the distillation technique, and a relatively high separation factor is required to lower the energy demand. Solution processable nanocomposite membranes prepared by incorporating functionalized graphene sheets (FGS) loaded in various concentrations into the chitosan matrix have been employed for the pervaporative dehydration of ethanol and isopropanol. Incorporation of FGS leads to an increase of surface hydrophilicity of the chitosan membranes along with an increase in membrane tortuosity that was favorable to the selective permeation of water molecules. The nanocomposite membrane containing 2.5 wt % FGS gave the highest selectivities of 7781 and 1093 for isopropanol–water and ethanol–water mixtures, respectively, when tested for 10 wt % water-containing feed mixture. Membranes were characterized by wide-angle XRD, SEM, contact angle, and optical profilometry techniques. The Flory–Huggins Theory was employed to estimate the...
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graphene loaded sodium alginate nanocomposite membranes with enhanced isopropanol dehydration performance via a pervaporation technique
RSC Advances, 2013Co-Authors: D P Suhas, Anjanapura V Raghu, Han Mo Jeong, Tejraj M AminabhaviAbstract:Graphene-loaded sodium alginate (NaAlg) nanocomposite membranes have been prepared to enhance the pervaporation (PV) dehydration of isopropanol. The effect of graphene loading on the physico-chemical properties, micro-morphology and barrier performance of the derived nanocomposite membranes was investigated as a function of temperature and feed water composition of the isopropanol mixture. The interaction of graphene with the NaAlg matrix as well as water and isopropanol seems to influence the thermal, kinetic and Arrhenius activation energy parameters. At the lowest concentration of graphene, the membrane performance was optimum with a permeance value of 3122 GPU and a selectivity of 4623 for a 10 wt.% water containing feed mixture at 30 °C. Flory–Huggins Theory could explain the polymer–solvent interaction as well as equilibrium swelling; both of these affected the membrane performance.
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pervaporation separation of water 2 propanol mixtures by use of the blend membranes of sodium alginate and hydroxyethyl cellulose roles of permeate membrane interactions zeolite filling and membrane swelling
Industrial & Engineering Chemistry Research, 2005Co-Authors: Boya Vijaya Kumar Naidu, Tejraj M AminabhaviAbstract:In an effort to improve membrane performance of pristine sodium alginate (NaAlg) for 2-propanol dehydration, blend membranes of NaAlg with (hydroxyethyl)cellulose (HEC) (5, 10, and 20 mass %) were prepared. Membranes were prepared by solution casting and cross-linked by a two-stage process as confirmed by Fourier transform infrared spectroscopy. The blend membrane of NaAlg with 10 mass % HEC gave the highest selectivity of 63 000 for 5 mass % water in feed mixture (highest selectivity achieved so far in the literature) by removing 99.97% of water, giving a flux of 0.04 kg/m2·h. Incorporation of ZSM-5(40) zeolite in the blend membrane increased flux without affecting selectivity. Swelling results are used to study the membrane−solvent interactions. Sorption and diffusion selectivity values were computed from experimental data, which were comparable with the theoretically calculated values obtained from thermodynamic treatment based on Flory−Huggins Theory.
Seung Soon Jang - One of the best experts on this subject based on the ideXlab platform.
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molecular modeling approach to determine the flory huggins interaction parameter for polymer miscibility analysis
ChemPhysChem, 2018Co-Authors: Connor P Callaway, Kayla Hendrickson, Nicholas Bond, Seung Min Lee, Parveen Sood, Seung Soon JangAbstract:In this work, we present a thorough procedure for estimating the Flory-Huggins χ-parameter for use in atomistic and mesoscale molecular simulations in computational materials science. In particular, we propose improvements upon traditional Flory-Huggins Theory by implementing a Connolly volume normalization (CVN). We apply this technique to several test systems, including a blend of poly (epichlorohydrin) and poly (methyl acrylate), a blend of polyethylene glycol and poly (methyl methacrylate), a blend of polystyrene and deuterated polystyrene, and three molecular-weight variants (monomer, dimer, and trimer) of a triblock copolymer for use in multicompartment micelle applications. Our results demonstrate that the newly developed procedure offers high accuracy and efficiency in predicting the Flory-Huggins χ-parameter for miscibility analysis compared to traditional experimental and computational methods. There are still several factors that cause the magnitude of the χ-parameter to vary between simulations performed on molecular species with the same identity but different degrees of polymerization; although we discuss possible explanations for these factors, this is nonetheless a primary focus for further exploration into this new methodology.