Showing papers on "Miscibility published in 2000"
TL;DR: In this paper, the Tg of chitosan (to be ca. 203°C) was observed by the direct and careful measurement of differential scanning calorimetry (DSC), which had been assumed not to be sensitive enough to detect it.
432 citations
ARCO1
TL;DR: In this paper, the miscibility, morphology, mechanical behaviour and other prominent characteristics of a representative number of blends and composites of PHB and PHBV copolymers are summarized.
Abstract: Poly(3-hydroxy)butyrate (PHB) and poly(3-hydroxybutyrate-hydroxyvalerate) (PHBV) copolymers are microbial polyesters presenting the advantages of biodegradability and biocompatibility over other thermoplastics with useful mechanical properties. However, their costs and performances must be adjusted by blending with suitable polymers. In this article the miscibility, morphology, mechanical behaviour and other prominent characteristics of a representative number of blends and composites of PHB and PHBV are summarized. In particular, blends with a few polyethers, polyesters, polyvinylacrylates and polysaccharides are illustrated. Furthermore, a brief paragraph deals with PHB/vegetal fiber composites. A wide range of properties emerges by blending with polymers having very different molecular structures and characteristics, such as crystallinity, glass transition and melting temperatures. The microstructure of the blends, resulting from thermodynamic and kinetic factors, is regarded as an important factor in controlling the mechanical and the biodegradation behaviours. Moreover, some considerations upon the nature of the “driving force” of the miscibility have been made in order to explain miscibility behaviour differences.
307 citations
TL;DR: In this article, a miscible homopolymer-copolymer pair viz., poly(ethyl methacrylate) (PEMA) and poly(styrene-co-butyl acrylate), was reported.
Abstract: A miscible homopolymer–copolymer pair viz., poly(ethyl methacrylate) (PEMA)–poly(styrene-co-butyl acrylate) (SBA) is reported. The miscibility has been studied using differential scanning calorimetry. While 1 : 1 (w/w) blends with SBA containing 23 and 34 wt % styrene (ST) become miscible only above 225 and 185 °C respectively indicating existence of UCST, those with SBA containing 63 wt % ST is miscible at the lowest mixing temperature (i.e., Tg's) but become immiscible when heated at ca 250 °C indicating the existence of LCST. Miscibility for blends with SBA of still higher ST content could not be determined by this method because of the closeness of the Tg's of the components. The miscibility window at 230 °C refers to the two copolymer compositions of which one with the lower ST content is near the UCST, while the other with the higher ST content is near the LCST. Using these compositions and the mean field theory binary interaction parameters between the monomer residues have been calculated. The values are χST-BA = 0.087 and χEMA-BA = 0.013 at 230 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 369–375, 2000
230 citations
TL;DR: In this article, a series of blends of polybenzimidazole (PBI) with sulfonated polysulfone (SPSF) at various sulfonation levels has been studied by dynamic mechanical analysis (DMA), FT-IR, and FT-Raman spectroscopy.
Abstract: Polybenzimidazole (PBI) and polysulfone (PSF) compose an immiscible polymer pair; the introduction however of functional groups such as sulfonate groups in the polymeric chain of PSF resulted in the formation of miscible blends with PBI. The miscibility behavior of a series of blends of PBI with sulfonated PSF (SPSF) at various sulfonation levels has been studied by dynamic mechanical analysis (DMA), FT-IR, and FT-Raman spectroscopy. DMA has shown that the sulfonation degree as well as blend composition controls the miscibility behavior of the studied system. In that respect, partially miscible or miscible blends were obtained when the sulfonation level is higher than 10 mol %. Since both polymers exhibit functional groups, which could participate in specific interactions, this possibility has been examined by FT-IR analysis. In absorption FT-IR spectra of PBI−SPSF specimens with high sulfonation degree and high PBI content, band shifts associated with the NH and sulfonate groups are accounted for the ind...
216 citations
TL;DR: In this paper, the phase structure of binary blends of poly[(S)-lactide with atactic poly[R, S)-3-hydroxybutyrate (ataPHB) of different molecular weights (M w =9400, 21,000 and 140,000) were investigated by the means of differential scanning calorimetry (DSC) and optical microscopy.
195 citations
TL;DR: In this article, the authors investigate poly(methyl methacrylate) (PMMA)-modified epoxy thermoset based on DGEBA before and after curing of the epoxy with various aromatic amines by means of different techniques: Differential Scanning Calorimetry (DSC), Size Exclusion Chromatography (SEC), Infra-Red Spectroscopy (FT-IR), Dynamic Mechanical Analysis (DMA) and Transmission Electron Microscopy (TEM).
148 citations
TL;DR: In this article, copolymers of a fluorinated acrylate and styrene were synthesized to enhance the viscosity of liquid carbon dioxide, and the phase behavior of mixtures of these polymers with carbon dioxide was measured at 295 K and pressures from 6.70 to 48.28 MPa.
Abstract: Copolymers of a fluorinated acrylate and styrene were synthesized to enhance the viscosity of liquid carbon dioxide. The phase behavior of mixtures of these polymers with carbon dioxide was measured at 295 K and pressures from 6.70 to 48.28 MPa. Miscibility pressures decreased with a decrease in the styrene content and increased as molecular weight increased. These polymers were also found to significantly enhance the viscosity of carbon dioxide, by a factor of ca. 5 to 400 at concentrations from 1 to 5 wt %. The optimal composition for viscosity enhancement was 29 mol % styrene−71 mol % fluoroacrylate.
122 citations
TL;DR: In this paper, the phase separation in unsaturated polyester resins with an increase of styrene concentration is investigated and the dependence of the glass transition temperature of the UP resin on the styrene content is complex and reflects a balance of elastic forces of the network and the immiscibility of polystyrene and UP.
102 citations
TL;DR: In this article, the second-order Moller−Plesset perturbation theory and density functional theory were applied to determine the hydrogen bonding interaction energies in pyridine−water and in a set of methyl-substituted Pyridine-water complexes, and the results showed that methyl substitution stabilizes the hydrogen bond and the degree of stabilization varies with the number and position of methyl groups.
Abstract: Density functional theory (DFT) and second-order Moller−Plesset perturbation theory (MP2) are applied to determine the hydrogen bonding interaction energies in pyridine−water and in a set of methyl-substituted pyridine−water complexes. The results show that methyl substitution stabilizes the hydrogen bond and the degree of stabilization varies with the number and the position of methyl groups. It is demonstrated that the MP2 method yields more reliable relative stabilities for these complexes than does the applied DFT method, which does not take proper account of the dispersion interactions between water and the methyl groups in ortho positions. The comparison of the order of the computed association energies of methyl-substituted pyridine−water complexes with the experimentally observed sequence of the ease of miscibility of these molecules with water shows that there is no simple relationship between the miscibility behavior and the strength of hydrogen bond formed between water and methyl derivatives o...
102 citations
TL;DR: In this article, phase equilibria in the binary polymer-gas systems polyethyleneglycol (PEG)−propane, PEG−nitrogen and PEG-carbon dioxide have been investigated.
Abstract: Phase equilibria in the binary polymer–gas systems polyethyleneglycol (PEG)–propane, PEG–nitrogen and PEG–carbon dioxide have been investigated. The experiments were performed for PEG with molecular weights of 200, 1500, 4000 and 8000 g/mol in a temperature range of 50 to 120°C and a pressure range from 5 to 300 bar using a static-analytical method. It was found that carbon dioxide dissolves much better in PEG than does propane or nitrogen. With rising temperature the PEG–carbon dioxide miscibility gap increases, whereas the miscibility gaps of the PEG–propane and the PEG–nitrogen systems decrease. The influence of the polymer molecular weight on the gas solubility is almost negligible for PEG 1500 to PEG 8000. The behaviour of the small PEG 200 deviates significantly due to strong endgroup influence. The gas solubilities in the polymers are correlated with the SAFT equation of state. The influence of temperature and of PEG molecular weight is represented satisfactorily.
92 citations
TL;DR: In this paper, a combination of DSC and hot stage polarised optical microscopy was used to study the crystallisation of the mixture of polypropylene and polyethylene.
TL;DR: Modulated temperaturedifferential scanning calorimetry (MTDSC) was shown to be a useful technique incharacterizing the interactions between some commonly used pharmaceutical polymers.
Abstract: Purpose. To assess the miscibility and phase behavior of binary blendsof hydroxypropylmethyl cellulose (HPMC) with hydroxypropylcellulose (HPC), methylcellulose (MC), and polyvinylpyrrolidone (PVP).
TL;DR: In this paper, the miscibility of Bionolle (BN) with CTA is investigated and it was found that BN molecules in the CTA matrix do not form a crystalline state, but forms an amorphous state.
TL;DR: The dynamic mechanical and thermal properties of natural rubber/poly (methyl methacrylate) blends with and without the addition of graft copolymer (NR-g-PMMA) have been investigated in this article.
Abstract: The dynamic mechanical and thermal properties of natural rubber/poly (methyl methacrylate) blends (NR/PMMA) with and without the addition of graft copolymer (NR-g-PMMA) have been investigated. Dynamic mechanical spectroscopy is used to examine the effect of compatibilizer loading on storage modulus (E′), loss modulus (E″) and loss tangent (tan δ) at different temperatures and at different frequencies. The morphology of the blends indicates that the size of the dispersed phase decreased by the addition of a few percent of the graft copolymer followed by a leveling off at higher concentrations. This is an indication of interfacial saturation. Attempts have been made to correlate morphology with dynamic mechanical properties. Various models have been used to fit the experimental viscoelastic results. Differential scanning calorimetry has been used to analyze the glass-transition temperatures of the blends. The thermal stability of the blends has been analyzed by thermogravimetry. Compatibilized blends are found to be more thermally stable than uncompatibilized blends. Finally the miscibility and mechanical properties of the blends annealed above Tg are evaluated. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 525–536, 2000
TL;DR: In this paper, the phase separation process during the cure of unsaturated polyester resins with thermoplastic additives was investigated by optical microscopy, and a shrinkage control mechanism at low temperature cure was proposed.
TL;DR: In this article, pyrrole monomer was dispersed in polyvinyl alcohol (PVA) solvents, which were previously mixed with an iron chloride solution, and the resulting mixtures were coated on substrates.
TL;DR: In this paper, an autocatalytic mechanism was observed for the epoxy/polyphenylene oxide (PPO) blends and the neat epoxy, and it was also found that the Epoxy/PPO blends react faster than the neat Epoxy.
Abstract: Cure behavior, miscibility, and phase separation have been studied in blends of polyphenylene oxide (PPO) with diglycidyl ether of bisphenol A (DGEBA) resin and cyanate ester hardener. An autocatalytic mechanism was observed for the epoxy/PPO blends and the neat epoxy. It was also found that the epoxy/PPO blends react faster than the neat epoxy. During cure, the epoxy resin is polymerized, and the reaction-induced phase separation is accompanied by phase inversion upon the concentration of PPO greater than 50 phr. The dynamic mechanical measurements indicate that the two-phase character and partial mixing existed in all the mixtures. However, the two-phase particulate morphology was not uniform especially at a low PPO content. In order to improve the uniformity and miscibility, triallylisocyanurate (TAIC) was evaluated as an in situ compatibilizer for epoxy/PPO blends. TAIC is miscible in epoxy, and the PPO chains are bound to TAIC network. SEM observations show that adding TAIC improves the miscibility and solvent resistance of the epoxy/PPO blends.
TL;DR: Freeze-concentration separates some combinations of proteins and nonionic polymers into different amorphous phases in a frozen solution, which is important in designing protein formulations.
Abstract: Purpose. To study the miscibility of proteins and polymer excipients in frozen solutions and freeze-dried solids as protein formulation models.
Methods. Thermal profiles of frozen solutions and freeze-dried solids containing various proteins (lysozyme, ovalbumin, BSA), nonionic polymers (Ficoll, polyvinylpyrrolidone [PVP]), and salts were analyzed by differential scanning calorimetry (DSC). The polymer miscibility was determined from the glass transition temperature of maximally freeze-concentrated solute (Tg′) and the glass transition temperature of freeze-dried solid (Tg).
Results. Frozen Ficoll or PVP 40k solutions showed Tg′ at −22°C, while protein solutions did not show an apparent Tg′. All the protein and nonionic polymer combinations (5% w/w, each) were miscible in frozen solutions and presented single Tg′s that rose with increases in the protein ratio. Various salts concentration-dependently lowered the single Tg′s of the proteins and Ficoll combinations maintaining the mixed amorphous phase. In contrast, some salts induced the separation of the proteins and PVP combinations into protein-rich and PVP-rich phases among ice crystals. The Tg′s of these polymer combinations were jump-shifted to PVP's intrinsic Tg′ at certain salt concentrations. Freeze-dried solids showed varied polymer miscibilities identical to those in frozen solutions.
Conclusions. Freeze-concentration separates some combinations of proteins and nonionic polymers into different amorphous phases in a frozen solution. Controlling the polymer miscibility is important in designing protein formulations.
TL;DR: In this article, the melting and cold crystallization behavior of two bacterial polyester/poly(epichlorohydrin- co -ethylene oxide) (PECH-EO) blend systems were studied.
TL;DR: In this article, a mixture of O-carboxymethylated chitosan and alginate was coagulated in aqueous solution with 5 wt % CaCl2, and then by treating with 1 wt% HCl in order to obtain high tensile strength and low permeation.
Abstract: The blend membranes were satisfactorily prepared by coagulating a mixture of O-carboxymethylated chitosan (CM-chitosan) and alginate in aqueous solution with 5 wt % CaCl2, and then by treating with 1 wt % HCl aqueous solution. Their structure and miscibility were characterized by scanning electron micrograph, X-ray diffraction, infrared spectra, differential thermal analysis, and atomic absorption spectrophotometer. The results indicated that the blends were miscible, when the weight ratio of CM-chitosan to alginate was in the range from 1 : 1 to 1 : 5. The polymers interpenetration including a Ca2+ crosslinked bridge occurred in the blend membrane, and leads to high separation factor for pervaporation separation of alcohol/water and low permeation. The tensile strength in the wet state (σb = 192 kg cm−2 for CM-chitosan/alginate 1 : 1) and thermostability of the blend membranes were significantly superior to that of alginic acid membrane, and cellulose/alginate blend membranes, owing to a strong electrostatic interaction caused by —NH2 groups of CM-chitosan with —COOH groups of algic acid. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 610–616, 2000
TL;DR: In this article, the miscibility of polybenzimidazole and polyimide blends were studied by FT-IR spectroscopy, thermal and thermomechanical methods, and by measuring vapour absorption at an ambient temperature.
TL;DR: In this article, the demixing data (in the form of P-T curves for a given concentration, or as P-x diagrams at a given T) and the density isotherms are presented for solutions of two polymer samples with different molecular weights at several concentrations in the range from 0.05 to 10 mass % over a temperature range from 302-425 K.
Abstract: Miscibility conditions and volumetric properties of solutions of poly(dimethylsiloxane) in supercritical carbon dioxide have been determined as a function of polymer molecular weight, polymer concentration, temperature, and pressure. Measurements have been conducted in a variable volume view cell equipped with an LVDT sensor to identify the position of a movable piston and thus the internal volume of the cell and consequently the density of the solution at a given pressure and temperature. The demixing data (in the form of P-T curves for a given concentration, or as P-x diagrams at a given T) and the density isotherms are presented for solutions of two polymer samples with different molecular weights (Mw = 38,600; Mw/Mn = 2.84 and Mw = 94,300; Mw/Mn = 3.01) at several concentrations in the range from 0.05 to 10 mass % over a temperature range from 302–425 K. Solution densities corresponding to the demixing points also have been identified. Representation of the demixing densities on the density isotherms, i.e., pressure-density plots is a new methodology that gives a direct assessment of the volumetric expansion the solution must undergo before phase separation. The temperature–composition diagrams generated at selected pressures show that the poly(dimethylsiloxane) + CO2 solutions display both lower critical solution and upper critical solution type behavior. The lower critical solution temperature moves to lower temperatures and the upper critical solution temperature moves to higher temperatures with decreasing pressure and they eventually merge together at lower pressures forming an hourglass-shaped region of immiscibility. This behavior is linked to the solvent quality of supercritical carbon dioxide that changes with pressure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1397–1403, 2000
TL;DR: In this paper, a fullerene (C 60 )-end-capped poly(ethylene oxide) (FPEO) has been prepared by the cycloaddition reaction of monoazido-terminated poly(methylene oxide), with C 60.
Abstract: A fullerene (C 60 )-end-capped poly(ethylene oxide) (FPEO) has been prepared by the cycloaddition reaction of monoazido-terminated poly(ethylene oxide) with C 60 . The majority of the FPEO sample is the mono-adduct as shown by thermogravimetry and X-ray photo-electron spectroscopy. Most electronic characteristics of C 60 are retained in the polymer as shown by its UV-visible absorption spectrum. The incorporation of C 60 reduces the extent of crystallinity of PEO by 17%. The miscibility behavior of FPEO with poly(p-vinylphenol) (PVPh) was studied. Similar to PEO, FPEO is miscible with PVPh over the entire composition range. The hydrogen-bonding interaction between FPEO and PVPh is a strong as that between PEO and PVPh as shown by Fourier-transform infrared spectroscopy.
TL;DR: In this paper, a model involving percolation was proposed to predict the mechanical properties of PHB and PHO blends, taking both linear and nonlinear mechanical behaviors into account and allowing for the effect of lack of adhesion between material domains and/or breakage of one of the component.
Abstract: Blends of bacterial poly(hydroxybutyrate) (PHB) with poly(hydroxyoctanoate) (PHO) were prepared by co-dissolving the two polyesters in chloroform and casting the mixture. To probe the question of blend miscibility, scanning electron microscopy (SEM) observations and differential scanning calorimetry (DSC) spectra were collected for the blends and blend components as well. It has been observed that PHB shows no miscibility at all with PHO, resulting in two-phase systems in which the nature of the continuous phase is composition-dependent. Dynamic mechanical analysis and tensile properties of these materials were also investigated. The morphology of the blend strongly influences the mechanical behavior. The mechanical properties of these materials have been predicted from a model involving the percolation concept. It takes both linear and nonlinear mechanical behaviors into account and allows for the effect of the lack of adhesion between material domains and/or breakage of one of the component.
TL;DR: The chemical characterization of the newly synthesized beta-CDC(6) and its ability to form mixed structures with dimyristoylphosphatidylcholine (DMPC) are reported and it is demonstrated that the beta-cyclodextrin derivative is partially miscible to the phospholipid.
TL;DR: In this article, the properties of three binary blends of 1-octene copolymer (EOC) were investigated to elucidate miscibility and phase behavior, and it was shown that the melt rheology appeared to influence the mechanical and film properties in the solid state.
Abstract: The rheological and morphological behaviors of commercially available three binary blends of ethylene 1-octene copolymer (EOC) regarding the melt index (MI), density and comonomer contents, one component made by the Ziegler–Natta and the other by the metallocene catalysts, were investigated to elucidate miscibility and phase behavior. Miscibility of the EOCs blend in a melt state was related to the value of the MI, density, and comonomer content. If the comonomer contents are similar, then the melt viscosity is weight average value, otherwise it is positively or negatively deviated. The microtomed surface prepared by two different cooling processes—one is fast cooling and the other is slow cooling—indicated that all the blends were not homogenous regardless the density, MI, and comonomer content. The Ziegler–Natta catalyzed EOCs exhibited bigger spherulitic diameter and larger ring space than those of the metallocene EOCs prepared by a cooling process. The blends consisting of similar MI showed banded spherulites with different diameter, whereas the blend consisting of different MI and density takes place of explicit phase separation and phase inversion at 1 : 1 blend composition. The melt rheology appeared to influence the mechanical and film properties in the solid state. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1950–1964, 2000
TL;DR: In this article, the thermal properties of PEO/Carbopol blends were investigated by thermal analysis (DSC, TGA) and infrared spectroscopy (FTIR).
TL;DR: In this paper, the presence of attractive forces among the polymers was evaluated according to the Sun theory by determination of the α parameter from the viscosimetric data and thermal analyses were performed based on the depression of the melting temperature.