Kwei Equation Research Articles

Comparison of specific interactions in P4VP/PSCA and PS4VP/PSCA blends and complexes

AbstractThe compatibilization of an immiscible polymer system polystyrene/poly(4‐vinylpyridine) has been induced by the introduction of carboxylic acid groups within the polystyrene chains. Poly(styrene‐co‐cinnamic acid), PSCA, copolymers were used to prepare blends and complexes with poly(4‐vinylpyridine), P4VP, and in a second time with poly(styrene‐co‐4‐vinylpyridine), PS4VP, copolymer in order to reduce the density of the interacting groups. The miscibility of the systems has been ascertained by DSC, which revealed that both blends and complexes exhibit a single glass transition temperature indicating their single phase nature. The Tgs of the complexes of PS4VP with PSCA15, containing 15 mol % of cinnamic acid content, were higher than those of the corresponding blends indicating that stronger interpolymer interactions were developed in the complexes. Furthermore, the application of the Kwei equation suggested that P4VP interacts more strongly with PSCA15 than does PS4VP. FTIR spectra revealed the development of hydrogen bonding within the PS4VP/PSCA system and both hydrogen bonding and ionic interaction in the P4VP/PSCA blends whereas the same interactions were expected in both systems. This observation confirmed the stronger ability of P4VP to interact with PSCA copolymer. The viscosimetric study showed both positive and negative deviations of the reduced viscosity of the blends from the additivity law confirming the presence of specific interactions within the blend solutions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Enhancement of bio‐compatibility via specific interactions in polyesters modified with a bio‐resourceful macromolecular ester containing polyphenol groups

Specific interactions and miscibility are demonstrated in a series of binary miscible blend comprising of bio-compatible/biodegradable polyesters, such as poly(epsilon-caprolactone) (PCL), poly(ethylene adipate) (PEA), or poly (butylene adipate) (PBA), and a macromolecular ester with polyphenol groups, tannic acid (TA). Thermal analysis and infrared spectroscopy were used for proving existence of favorable interactions, and polarized-light optical microscopy was used for characterizing the changes in crystal growth. The appearance of a single composition-dependent glass transition temperature (T(g)) observed by differential scanning calorimetry (DSC) indicated that TA is miscible with PCL, PBA, and PEA, respectively, over the entire range of compositions. Fourier transform infrared (FTIR) spectroscopy confirmed the presence of specific intermolecular hydrogen bonding interactions between the carbonyl groups of polyesters and the phenolic hydroxyl groups of TA. The blend T(g)'s generally exhibited various extents of positive-then-negative deviation from linearity with the compositions. The T(g)-composition relationships for three blend systems could all be fitted by the Kwei equation with large negative q values of -80 to -110 for different polyesters. Significant effects by TA on the spherulitic crystallization growth in the polyester/TA blends were also discussed to support the miscibility and strong interactions. Overall, the behavior of blends of polyesters with TA is similar to that of blends of polyesters with poly(vinyl p-phenol) (PVPh) that have been more widely studied and reported. However, TA is naturally bio-resourceful, bio-compatible, and bio-degradable but PVPh is not. Synergism of miscibility, natural bio-compatibility, and biodegradability in these blends by introducing naturally biodegradable macromolecules such as TA may offer greater potential in intended applications.

Miscibility with positive deviation in Tg–composition relationship in blends of poly(2-vinyl pyridine)- block-poly(ethylene oxide) and poly( p-vinyl phenol)

Phase behavior and miscibility with positive deviation from linear T g–composition relationship in a copolymer/homopolymer blend system, poly(2-vinyl pyridine)- block-poly(ethylene oxide) (P2VP- b-PEO)/poly( p-vinyl phenol) (PVPh), were investigated by differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR) and solid-state 13C nuclear magnetic resonance ( 13C NMR), optical microscopy (OM), and scanning electron microscopy (SEM). Optical and electron microscopy results as well as NMR proton spin–lattice relaxation times in laboratory frame ( T 1 H ) all confirmed the miscibility as judged by the T g criterion using DSC. In comparison to the literature result on a homopolymer/homopolymer blend of P2VP/PVPh, fitting with the Kwei equation on the T g–composition relationship for the block-copolymer/homopolymer blend of P2VP- b-PEO/PVPh blend system yielded a smaller q value ( q = 120) for P2VP- b-PEO/PVPh than that for P2VP/PVPh blend ( q = 160). The FT-IR and 13C NMR results revealed hydrogen-bonding interactions between the pendant pyridine group of P2VP- b-PEO and phenol unit in PVPh, which is responsible for the noted positive deviation of the T g–composition relationship. Comparison of the shifts of hydroxyl IR absorbance band, reflecting the average strength of H-bonding, indicates a decreasing order of P2VP/PVPh > P2VP- b-PEO/PVPh > PEO/PVPh blends. The PEO block in the copolymer segment tends to defray the interaction strength in the P2VP- b-PEO/PVPh blends because of relative weaker interaction between PEO and PVPh than that between P2VP and PVPh pairs. A comparative ternary (P2VP/PEO)/PVPh blend was also studied as the controlling experiments for comparison to the P2VP- b-PEO/PVPh blend. The thermal behavior and interaction strength in (P2VP/PEO)/PVPh ternary blends are discussed with those in the P2VP- b-PEO/PVPh copolymer/homopolymer blend.

Achieving miscible ternary polymer blends with hydrogen bonding

AbstractPoly(vinyl phenol) (PVPh) has previously been found to be successful in making immiscible poly(methyl methacrylate) (PMMA)/poly(vinyl acetate) (PVAc) miscible. Poly(ethyl methacrylate) (PEMA) with one more methyl group than PMMA is also immiscible with PVAc. PEMA and PVAc are miscible with PVPh according to the literature. To determine whether PVPh can also cosolubilize PEMA/PVAc, PVPh samples of two different molecular weights have been mixed in this study with PEMA and PVAc to produce a ternary blend. On the basis of the calorimetry data, the ternary PEMA/PVAc/PVPh blend, regardless of the molecular weight of PVPh, has been determined to be miscible. The reason for the observed miscibility is probably that the interactions between PVAc and PVPh are similar in magnitude to those between PEMA and PVPh. A modified Kwei equation based on the binary interaction parameters proposed previously is used to describe the experimental glass‐transition temperature of the miscible ternary blend almost quantitatively well. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 643–652, 2006

Competitive specific interactions in miscible blends of poly(hydroxyether terephthalate ester) and poly(4‐vinyl pyridine)

AbstractThe miscibility of poly(hydroxyether terephthalate ester) (PHETE) with poly(4‐vinyl pyridine) (P4VP) was established on the basis of thermal analysis. Differential scanning calorimetry showed that each blend displayed a single glass‐transition temperature (Tg), which is intermediate between those of the pure polymers and varies with the composition of blend. The Tg‐composition relationship can be well described with Kwei equation with k = 1 and q = −30.8 (K), suggesting the presence of the intermolecular specific interactions in the blend system. To investigate the intermolecular specific interactions in the blends, the model compounds such as 1,3‐diphenoxy‐2‐propanol, 4‐methyl pyridine, and ethyl benzoate were used to determine the equilibrium constants, according to Coleman and Painter model, to account for the association equilibriums of several structural moieties, using liquid Fourier transform infrared difference spectroscopy. In terms of the difference in the association equilibrium constant, it is proposed that there are the competitive specific interactions in the blends, which were confirmed by means of Fourier transform infrared spectroscopy of the blends. It is observed that upon adding P4VP to the system, the ester carbonyls of PHETE that were H‐bonded with the hydroxyl groups were released because of the formation of the stronger interchain association via the hydrogen bonding between the hydroxyls of PHETE and tertiary nitrogen atoms of P4VP. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1618–1626, 2006

Preparation and characterization of poly(ether sulfone)/sulfonated poly(ether ether ketone) blend membranes

Polymer blends of sulfonated poly(ether ether ketone) (SPEEK) and poly(ether sulfone) (PES) in N-methyl-2-pyrrolidinone (NMP) were prepared by solution casting. The investigation on water uptake, methanol uptake, permeability and proton conductivity has been conducted. The spin-lattice relaxation time in the rotating frame ( T 1 ρ H ) of PES/SPEEK blend was obtained from the results of cross-polarization magic angle spinning (CP/MAS) solid state 13C NMR. SPEEK blended with PES resulted in increasing T 1 ρ H , indicating the molecular motion of polymer chain was reduced. The glass transition temperature of the PES/SPEEK blend membranes were predicted by the Kwei equation. PES plays an important role in the decreasing water uptake, methanol uptake and methanol permeability while enhancing the thermal stability of the blend membrane, which shows the feasibility for direct methanol fuel cell.

Phase behavior and a modified Kwei equation for ternary polymer blends containing stereoregular PMMA

Previously, poly(methyl methacrylate) (PMMA) was found to be almost immiscible with poly(vinyl acetate) (PVAc) regardless of tacticity of PMMA and casting solvent. Poly(vinyl phenol) (PVPh) was found successful previously in making immiscible atactic PMMA/PVAc miscible. In this investigation, tacticity effect of PMMA on a ternary composed of PMMA, PVAc and PVPh was studied. Isotactic PMMA ternary was shown to be miscible in all the studied compositions on the basis of single T g observation. However, syndiotactic PMMA ternary demonstrated immiscibility at ca. 25% PVPh and miscibility was observed at higher PVPh concentrations. A modified Kwei equation based on the binary interaction parameters was proposed to describe the experimental T g of the miscible ternary almost quantitatively.

An Unusual, Completely Miscible, Ternary Hydrogen-Bonded Polymer Blend of Phenoxy, Phenolic, and PCL

We have investigated the miscibility and hydrogen-bonding behavior of ternary blends of phenoxy, phenolic, and poly(e-caprolactone) (PCL) by using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy. On the basis of DSC analyses, we observed a rare totally miscible ternary hydrogen-bonded polymer blend in the amorphous phase: all compositions of this ternary blend display a single glass transition temperature. In addition, these single glass transition temperatures can be predicted well by extending the Kwei equation from the binary polymer blend to this ternary polymer blend. The infrared spectra indicate that the intermolecular hydrogen bonding of each pair of binary components still exists in the ternary polymer blend. We used the ternary totally miscible blend to determine the interassociation equilibrium constant between the hydroxyl groups of phenolic and the hydroxyl groups of phenoxy indirectly from the fraction of hydrogen-bonded carbonyl groups of PCL. Quantitati...

Relations between Glass Transition Temperatures in Miscible Polymer Blends and Composition: From Volume to Mass Fractions

AbstractThe use of volume fractions in the empirical mixing laws to predict the glass transition temperatures (Tg) of polymer blends provides good agreement with experimental values, even for polymer systems with different densities. No adjustment parameter is therefore required whereas Gordon‐Taylor and Kwei equations based on weight fractions need the use of a fitting parameter which has to be determined from experimental data. This assumption was validated from Tg measurements through DSC experiments conducted on PMMA /PVDF blends which have significantly different densities.

Determination of the Glass-Transition Temperature of a Coal Extract, Using a Polymer Blend Methodology

The glass-transition temperature (Tg) of pyridine-soluble extracts obtained from Upper Freeport (UPF) coal was investigated. Previous studies have suggested that such a transition, if it exists, might occur at high temperatures and is probably masked by other transition processes. In this study, we used differential scanning calorimetry (DSC) experiments to calculate that the glass transition of the UPF coal extract occurs at ∼194 °C. This Tg value was obtained using an extrapolation of observed Tg values of miscible blends of the coal extract and poly(4-vinylpyridine) (P4VPy). UPF extract/P4VPy blends were prepared as a series that had a UPF extract content of 10−85 wt %. DSC thermograms of all blends exhibited a single Tg value at a temperature higher than that of pure P4VPy. The Tg values of the blends were dependent on the composition of the coal extract. Using the Kwei equation, which describes the relationship between blend composition and Tg, the Tg value of the coal extract was calculated.

Miscibility and Intermolecular Specific Interactions in Blends of Poly(hydroxyether sulfone) and Poly(N‐vinylpyrrolidone)

AbstractSummary: The blends of poly(hydroxyether sulfone) (PHES) with poly(N‐vinylpyrrolidone) (PVPy) were investigated by means of differential scanning calorimetry (DSC) and FTIR spectroscopy. The miscibility of the blend system was established on the basis of the thermal analysis results. DSC showed that the PHES/PVPy blends prepared by casting from N,N‐dimethylformamide (DMF) possessed single, composition‐dependent glass transition temperatures, indicating that the blends are miscible in the entire composition. The experimental glass transition temperatures have higher values than those calculated on the basis of additive behavior; the variation of the glass transition temperatures of the blends was accounted for by the Kwei equation. FTIR studies indicate that competitive hydrogen bonding interactions exist upon addition of PVPy to the system, which were involved in the self‐ and cross‐association, i.e., OH···OS, OH···OH of PHES and OH···OC< of PVPy. The FTIR spectra in the range of the sulfonyl stretching vibrations showed that the hydroxyl‐associated sulfonyl groups are partially “set free” upon addition of PVPy to the system. The IR spectroscopic investigation of both the model compounds and the PHES/PVPy blends suggests that the strength of the hydrogen bonding interactions in the blend system increases in the following order: OH···OS, OH···OH and OH···OC<.Plot of glass transition temperature for PHES/PVPy blends as a function of weight fraction of PVPy. The prediction of the Kwei equation yields the values of k = 1 and q = 122.magnified imagePlot of glass transition temperature for PHES/PVPy blends as a function of weight fraction of PVPy. The prediction of the Kwei equation yields the values of k = 1 and q = 122.

Miscibility behavior and hydrogen bonding in blends of poly(vinyl phenyl ketone hydrogenated) and poly(2‐ethyl‐2‐oxazoline)

AbstractThe miscibility behavior of poly(2‐ethyl‐2‐oxazoline) (PEOx)/poly(vinyl phenyl ketone hydrogenated) (PVPhKH) blends was studied for the entire range of compositions. Differential scanning calorimetry and thermomechanical analysis measurements showed that all the PEOx/PVPhKH blends studied had a single glass‐transition temperature (Tg). The natural tendency of PVPhKH to self‐associate through hydrogen bonding was modified by the presence of PEOx. Partial IR spectra of these blends suggested that amide groups in PEOx and hydroxyl groups in PVPhKH interacted through hydrogen bonding. This physical interaction had a positive influence on the phase behavior of PEOx/PVPhKH blends. The Kwei equation for Tg as a function of the blend composition was satisfactorily used to describe the experimental data. Pure‐component pressure–volume–temperature data were also reported for both PEOx and PVPhKH. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 636–645, 2004

Hydrogen‐Bonding Interaction and Crystalline Morphology in the Binary Blends of Poly(ε‐caprolactone) and Polyphenol Catechin

AbstractThe specific intermolecular hydrogen‐bonding interaction between the ester carbonyl groups of poly(ε‐caprolactone) (PCL) and the phenolic hydroxyl groups of catechin has been studied by Fourier‐transform infrared spectroscopy (FT‐IR) and differential scanning calorimetry (DSC). According to quantitative curve‐fitting analysis of the FT‐IR spectra of PCL/catechin blends, it was found that the fraction of hydrogen‐bonded carbonyl groups of PCL increased with catechin content, while that of hydrogen‐bonded hydroxyl groups of catechin decreased. The calculated crystallinity of PCL in the binary blends, based on the curve‐fitting results, suggested that the crystallization of PCL was restrained in the blends with catechin. Only single glass transition temperature, Tg, was observed over the whole range of blend compositions, which was between those of the pure components. The melting point, Tm, depressed and Tg increased, indicating also the existence of strong intermolecular association. The blend composition dependence of Tg could be predicted very well by the Kwei equation with a positive ‘q’ value of 124. With the aid of small angle X‐ray scattering measurement, the segregation of catechin was investigated. It was found that the extent of extra‐lamellar segregation increased with catechin content. It was suggested that the crystal growth rate played the dominant role in the formation of morphology. With decreasing crystal growth rate of PCL component in the blends, enough time has been given to catechin molecules to diffuse into extra‐lamellar region. magnified image

Thermal behavior and specific interaction in high glass transition temperature PMMA copolymer

A series of high glass transition temperature copolymers based on poly(methyl methacrylate) (PMMA) were prepared by free radical copolymerization of methacrylamide and methyl methacrylate monomers in dioxane solvent. The thermal properties and hydrogen-bonding interactions of these poly(methacrylamide-co-methyl methacrylate) (PMAAM-co-PMMA) copolymers with various compositions were investigated by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, and solid-state nuclear magnetic resonance (NMR) spectroscopy. A large positive deviation in the behavior of Tg, based on the Kwei equation from DSC analyses, indicates that strong hydrogen bonding exists between these two monomer segments. The FTIR and solid-state NMR spectroscopic analyses give positive evidence for the hydrogen-bonding interaction between the carbonyl group of PMMA and the amide group of PMAAM (e.g. by displaying significant changes in chemical shifts). Furthermore, the proton spin–lattice relaxation time in the rotating frame (T1ρ(H)) has one single value over the entire range of compositions of copolymers, and gives a value shorter than the average predicted. The proton relaxation behavior indicates the rigid nature of the copolymer.

Epoxy resin/poly(ethylene oxide) (PEO) and poly(?-caprolactone) (PCL) blends cured with 1,3,5-trihydroxybenzene: miscibility and intermolecular interactions

Epoxy resin (ER)/poly(ethylene oxide) (PEO) and/or poly(e-caprolactone) (PCL) blends cured with 1,3,5-trihydroxybenzene (THB) were prepared via the in situ curing reaction of epoxy monomers in the presence of PEO and/or PCL, which started from the initially homogeneous mixtures of DGEBA, THB and PEO and/or PCL. The miscibility and the intermolecular specific interactions in the thermosetting polymer blends were investigated by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The two systems displayed single and composition-dependant glass transition temperatures (Tgs), indicating the full miscibility of the thermosetting blends. The experimental Tgs of the blends can be well accounted for by Gordon-Taylor and Kwei equations, respectively. The Tg-composition behaviors were compared with those of poly(hydroxyether of bisphnol A) (Phenoxy) blends with PEO and PCL. It is noted that the formation of crosslinked structure has quite different effects on miscibility and intermolecular hydrogen bonding interactions for the thermosetting polymer blends. In ER/PEO blends, the strength of the intermolecular hydrogen bonding interactions is weaker than that of the self-association in the control epoxy resin, which is in marked contrast to the case of Phenoxy/PEO blends. This suggests that the crosslinking reduces the intermolecular hydrogen bonding interactions, whereas the intermolecular hydrogen bonding interactions were not significantly reduced by the formation of the crosslinking structure in ER/PCL blends.

Thermal properties and hydrogen bonding in polymer blend of polybenzoxazine/poly( N-vinyl-2-pyrrolidone)

The thermal properties and hydrogen bonding behavior of B-a type polybenzoxazine (PBZZ)/PVP blends were investigated by DSC and FTIR. The DSC result shows a single T g over the entire compositions and a large positive deviation based on Kwei equation was observed in the T g versus composition diagram, implying that strong hydrogen bonding interaction exists between PBZZ and PVP segments. The strength of hydrogen bonding interaction is in the order of inter-association between the hydroxyl group of PBZZ and the carbonyl group of PVP (K A =594 L mol −1) >self-association between the hydroxyl group of pure PBZZ (K B =72.6 L mol −1) >inter-association between the hydroxyl and the Mannich-based bridge of pure PBZZ (K C <10 L mol −1). Good correlation between DSC and FTIR analysis were observed.

Effects of Inert Diluent Segment and Hydrogen Bonding in Poly(styrene-co-methacrylamide) Copolymers

A series of random poly(styrene-co-methacrylamide) (PS-co-PMAAM) copolymers were prepared by free radical polymerization of styrene and methacrylamide monomers. The PS and PMAAM units of the copolymer do not have any specific interaction based on the Kwei equation and the infrared spectroscopy result, indicating that the styrene plays strictly as an inert diluent segment on the PMAAM main chain. This result offers an opportunity to enhance the miscibility and specific interaction between the amide group of PMAAM and the functional group of second polymer by reducing the strong self-association of the PMAAM.

Thermal transitions of osmotically dehydrated tomato by modulated temperature differential scanning calorimetry

Modulated temperature differential scanning calorimetry (MTDSC) was employed to examine thermal transitions of osmotically dehydrated tomato ( Lycopersicon esculentum, var. Deborah). Tomato halves, soaked in sucrose solution (60% sucrose), sodium chloride (10% NaCl) and mixtures of salt–sucrose solution (60% sucrose–10% NaCl/40% sucrose–15% NaCl) for 3 h at 40 °C, were comminuted, freeze-dried for 48 h and kept in desiccator over saturated salt solutions at 25 °C until equilibrium was reached. A MTDSC 2920 (TA Instruments) was used in all tests. A cyclic modulation of ±0.5 °C/40 s was superimposed on a constant scanning ramp of 2.5 °C/min. Thermo-analytical curves of both osmotically dehydrated and untreated tomato allowed the determination of the glass transition data and the plot of state diagrams. Furthermore, a peak of enthalpy relaxation in the glass transition region that partially disappears on rescanning was detected. Structural recovery was modelled by Williams–Watts equation and glass transition temperature by Gordon and Taylor and Kwei equations.

Reexamination of the miscibility of stereoregular poly(methyl methacrylate) with poly(vinyl phenol)

AbstractPreviously, isotactic, atactic, and syndiotactic poly(methyl methacrylates) (PMMAs) (designated as iPMMA, aPMMA, and sPMMA) were mixed with poly(vinyl phenol) (PVPh) separately in tetrahydrofuran (THF) to make three polymer blend systems. According to calorimetry data, iPMMA was found to be miscible with PVPh; however, partial miscibility or immiscibility was found between aPMMA (or sPMMA) and PVPh. According to the article by C. J. T. Landry and D. M. Teegarden, Macromolecules, 1991, 24, 4310, THF is the reason for causing aPMMA and PVPh to phase separate, but 2‐butanone instead produces miscible blends. Therefore, in this article these three polymer systems were investigated again using 2‐butanone as solvent. Films were prepared under specific conditions to minimize the effect of aggregation in PMMA. The formation of hydrogen bonding between PMMA and PVPh and the attendant changes in the aggregation of PMMA segments were determined in the solid states by means of FTIR. Based on the results of calorimetry, iPMMA and aPMMA were found to be miscible with PVPh. For iPMMA/PVPh blends, different degrees of hydrogen bonding were observed based on DSC data and FTIR spectra when compared to previous study. An elevation of the glass transition temperatures (Tgs) of aPMMA/PVPh blends above weight average was detected and the Tg values were fitted well by the Kwei equation. But partial miscibility was still found between sPMMA and PVPh on account of the observation of two Tgs in most compositions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1425–1431, 2002

Study of hydrogen‐bonding strength in poly(ϵ‐caprolactone) blends by DSC and FTIR

AbstractThe hydrogen‐bonding strength of poly(ϵ‐caprolactone) (PCL) blends with three different well‐known hydrogen‐bonding donor polymers [i.e., phenolic, poly(vinyl‐phenol) (PVPh), and phenoxy] was investigated with differential scanning calorimetry and Fourier transform infrared spectroscopy. All blends exhibited a single glass‐transition temperature with differential scanning calorimetry, which is characteristic of a miscible system. The strength of interassociation depended on the hydrogen‐bonding donor group in the order phenolic/PCL &gt; PVPh/PCL &gt; phenoxy/PCL, which corresponds to the q value of the Kwei equation. In addition, the interaction energy density parameter calculated from the melting depression of PCL with the Nishi–Wang equation resulted in a similar trend in terms of the hydrogen‐bonding strength. Quantitative analyses on the fraction of hydrogen‐bonded carbonyl groups in the molten state were made with Fourier transform infrared spectroscopy for all systems, and good correlations between thermal behaviors and infrared results were observed. © 2001 John Wiley &amp; Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1348–1359, 2001