Showing papers on "Miscibility published in 2006"
TL;DR: The thermodynamics of API-polymer systems can be modeled using solution based theories and can contribute towards providing an understanding of the compatibility between API and polymer and the mechanisms of physical stabilization in such systems.
Abstract: Crystallization of drugs formulated in the amorphous form may lead to reduced apparent solubility, decreased rate of dissolution and bioavailability and compromise the physical integrity of the solid dosage form. The purpose of this work was to develop thermodynamic approaches, both practical and theoretical, that will yield a better understanding of which factors are most important for determining the ability of polymers to stabilize amorphous active pharmaceutical ingredients (API). Lattice based solution models were used to examine miscibility criteria in API-polymer blends. Different methods were used to estimate the Flory‐Huggins interaction parameter for model API-polymer systems consisting of felodipine or nifedipine with poly(vinylpyrrolidone) (PVP). These were melting point depression and determination of solubility parameters using group contribution theory. The temperature and enthalpy of fusion of crystalline API alone and the fusion temperature of the API in the presence of the polymer were measured by differential scanning calorimetry. The resultant thermal data were used to estimate the reduced driving force for crystallization and the solubility of the API in the polymer. Flory‐Huggins theory predicts that, for typical API-polymer systems, the entropy of mixing is always favorable and should be relatively constant. Due to the favorable entropy of mixing, miscibility can still be achieved in systems with a certain extent of unfavorable enthalpic interactions. For the model systems, interaction parameters derived from melting point depression were negative indicating that mixing was exothermic. Using these interaction parameters and Flory‐Huggins theory, miscibility was predicted for all compositions, in agreement with experimental data. A model was developed to estimate the solubility of the API in the polymer. The estimated solubility of the model APIs in PVP is low suggesting that kinetic rather than thermodynamic stabilization plays a significant role in inhibiting crystallization. The thermodynamics of API-polymer systems can be modeled using solution based theories. Such models can contribute towards providing an understanding of the compatibility between API and polymer and the mechanisms of physical stabilization in such systems.
513 citations
TL;DR: In this paper, agreed plasticizers for food contact were melt mixed with L-PLA and then, the glass transition, melting, crystallization and mechanical properties of the blends were investigated.
317 citations
TL;DR: In this paper, the morphology of blends of PS/PMMA, PC/SAN24, and PMMA/EVA was compared with and without modified organoclay cloisite 20A or Cloisite 6A clays, and it was proposed that in-situ grafts were forming on the clay surfaces during blending and the grafts then had to be localized at the interfaces.
Abstract: We have studied the morphology of blends of PS/PMMA, PC/SAN24, and PMMA/EVA and compared the morphologies with and without modified organoclay Cloisite 20A or Cloisite 6A clays. In each case we found a large reduction in domains size and the localization of the clay platelets along the interfaces of the components. The increased miscibility was accompanied in some cases, with the reduction of the system from multiple values of the glass transition temperatures to one. In addition, the modulus of all the systems increased significantly. A model was proposed where it was proposed that in-situ grafts were forming on the clay surfaces during blending and the grafts then had to be localized at the interfaces. This blending mechanism reflects the composition of the blend and is fairly nonspecific. As a result, this may be a promising technology for use in processing recycled blends where the composition is often uncertain and price is of general concern.
303 citations
TL;DR: Although the presence of phase separation at a microscopic level was detected for these membranes, pronounced interactions between components were confirmed and obtained results shown that some membranes prepared under optimized processing conditions had a partially miscible structure.
222 citations
TL;DR: In this paper, phase-inversion process was used in membrane preparation from polysulfone (PSF) casting solution with poly(ethylene glycol) introduction by using the method of viscosity measurement and triangle phase diagram.
147 citations
TL;DR: In this paper, new types of poly(ethylene oxide) (PEO)-based composite composite polymer electrolyte membranes, prepared by adding succinonitrile (SN) as a solid plasticizer, and lithium bis-trifluoromethanesulphonimide (LiTFSI), as a salt, are discussed.
142 citations
TL;DR: In this paper, a mixture of chitosan with two cellulose ethers-hydroxypropylmethylcellulose and methylcelluloses-was cast from acetic acid solutions, and it was shown that although weak hydrogen bonding exists between the polymer functional groups the blends are not fully miscible in a dry state.
121 citations
TL;DR: In this article, the authors investigated the miscibility of polyvinyl chloride (PVC) with polymethyl methacrylate (PMMA) by using various analytical methods: determination of the Vicat softening temperature, a viscometry method based on the α criterion of polymerpolymer miscibility, differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR).
110 citations
TL;DR: In this paper, two different molecular weights of poly(methyl methacrylate) (PMMA) and PMMA containing polyhedral oligomeric silsesquioxane (POSS) homopolymers have been prepared via the atom transfer radical polymerization (ATRP) technique.
Abstract: Two different molecular weights of poly(methyl methacrylate) (PMMA) and PMMA containing polyhedral oligomeric silsesquioxane (PMMA-POSS) homopolymers have been prepared via the atom transfer radical polymerization (ATRP) technique. The miscibility and specific interaction behaviors of PMMA-POSS and PMMA with phenolic resin were investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). FTIR results reveal that at least three competing equilibriums are present in the phenolic/PMMA-POSS blend: self-association of phenolic (hydroxyl-hydroxyl), hydroxyl-siloxane inter- association between phenolic and POSS, and hydroxyl-carbonyl interassociation between phenolic and PMMA. Among these blends, single and higher Tgs of these phenolic/PMMA-POSS blends were observed than the corresponding phenolic/PMMA blends at same composition, revealing that a stronger interassociation interaction of hydroxyl-siloxane than the hydroxyl-carbonyl interaction. Furthermore, we also found the screening effect in phenolic/LPMMA-POSS blends that tends to significantly decrease the hydrogen bond formation of the hydroxyl-carbonyl interassociation.
106 citations
TL;DR: In this article, the authors investigated the molecular modeling simulation approaches for understanding the blend compatibility/incompatibility of poly( l -lactide), PLL and poly(vinyl alcohol), PVA.
105 citations
TL;DR: In this article, poly( l -lactide (PLLA) was melt blended with poly(methyl methacrylate) (PMMA) using a two-roll mill.
TL;DR: In this article, a blend film obtained from an 80/20 mixing ratio of konjac glucomannan and chitosan derivate showed the highest miscibility and blend homogeneity.
TL;DR: A tribological evaluation of room temperature ionic liquids (RTILs) compatible lubricant additive was reported in this paper. But this was performed on a steel/Cu-Sn alloy sliding pair.
Abstract: In this paper, we report on the first tribological evaluation of the room temperature ionic liquids (RTILs) compatible lubricant additive. Benzotriazole (BTA) was chosen for study in that it shows good miscibility with imidazole ionic liquids because of similar molecular structure. BTA can greatly improve the tribological behaviors of ionic liquids carrying hexafluorophosphate anions for Steel/Cu–Sn alloy sliding pair mainly because of the alleviation of corrosion. The worn surface of the bronze was investigated by X-ray photoelectron spectroscopy (XPS), which revealed complex tribochemical reactions during the sliding process. A protective film comprised of [Cu(–C6H5N3)] and Cu2O is formed. Strong interaction between benzotriazole and the surface of Cu alloy was proposed to account for the excellent anti-wear and anti-corrosion improvement capability.
TL;DR: In this paper, the elastomer particle morphology in ternary blends of maleated and non-maleated ethylene-based elastomers with polyamides has been examined.
TL;DR: By modifying the chain length of either one of the two lipids, it is shown that it is possible to control their miscibility and thus the intervals of temperature and composition where spontaneous alignment is observed in a magnetic field.
TL;DR: The aqueous phase behavior of a series of complex salts, containing cationic surfactants with polymeric counterions, has been investigated by visual inspection and small-angle X-ray scattering, finding that the attraction between oppositely charged surfactant aggregates and polyions decreases with decreasing surfACTant chain length, and with decreasing polyion length, resulting in an increased miscibility with water.
Abstract: The aqueous phase behavior of a series of complex salts, containing cationic surfactants with polymeric counterions, has been investigated by visual inspection and small-angle X-ray scattering (SAXS). The salts were alkyltrimethylammonium polyacrylates, C(x)TAPA(y), based on all combinations of five surfactant chain lengths (C-6, C-8, C-10, C-12, and C-16) and two lengths of the polyacrylate chain ( 30 and 6 000 repeating units). At low water contents, all complex salts except C(6)TAPA(6000) formed hexagonal and/or cubic Pm3n phases, with the hexagonal phase being favored by lower water contents. The aggregate dimensions in the liquid crystalline phases changed with the surfactant chain length. The determined micellar aggregation numbers of the cubic phases indicated that the micelles were only slightly aspherical. At high water contents, the C(6)TAPA(y) salts were miscible with water, whereas the other complex salts featured wide miscibility gaps with a concentrated phase in equilibrium with a ( sometimes very) dilute aqueous solution. Thus, the attraction between oppositely charged surfactant aggregates and polyions decreases with decreasing surfactant chain length, and with decreasing polyion length, resulting in an increased miscibility with water. The complex salt with the longest surfactant chains and polyions gave the widest miscibility gap, with a concentrated hexagonal phase in equilibrium with almost pure water. A decrease in the attraction led to cubic-micellar and micellar-micellar coexistence in the miscibility gap and to an increasing concentration of the complex salt in the dilute phase. For each polyion length, the mixtures for the various surfactant chain lengths were found to conform to a global phase diagram, where the surfactant chain length played the role of an interaction parameter.
TL;DR: The phase behavior of methnol-triolein system was determined experimentally at 6.0, 8.0 and 10.0 MPa in the temperature range of 353.2 −463.2 K.
TL;DR: In this paper, a new type of A−B/C blend, formed between poly(methyl methacrylate-b-vinylpyrrolidone) and poly(vinylphenol) that displays unusual phase behavior was investigated.
Abstract: We have investigated a new type of A−B/C blend, formed between poly(methyl methacrylate-b-vinylpyrrolidone) and poly(vinylphenol) (PMMA-b-PVP/PVPh), that displays unusual phase behavior. In this blend, the PMMA (A) and PVP (B) blocks within the PMMA-b-PVP (A−B) copolymer are miscible; although PVPh (C) experiences attractive interactions (ξ ≤ 0) through hydrogen bonding, with both the PVP and PMMA blocks, its interaction with the former block is significantly stronger than that with the latter (ξBC ≫ ξAC). We investigated the miscibility and phase behavior of this novel A−B/C blend through the use of FTIR spectroscopy, DSC, 13C CP/MAS solid-state NMR spectroscopy, and TEM. The proton spin−lattice relaxation time in the rotating frame (T1ρH), which we determined using 13C NMR spectroscopy, indicates that phase separation occurs for blends containing ca. 20−60 wt % PVPh. TEM images indicated clearly that the morphology of phase separation consists of a matrix of homogeneous mixed PVP/PVPh and micellar domai...
TL;DR: In this article, the authors have evaluated the geometry factor γ and hydrodynamic interaction parameter α and found α is a suitable parameter in predicting the miscibility window in SAN/PMMA blends.
TL;DR: In this article, the authors used solvent evaporation techniques to obtain PVP/HPMC and PVP-Chitosan polymer blends by using the solvent-evaporation technique and found that both blends are completed miscible in the entire composition range since only one glass transition temperature was detected.
Abstract: In the present study PVP/HPMC and PVP/Chitosan polymer blends were prepared by using the solvent evaporation technique. From DSC studies were revealed that both blends are completed miscible in the entire composition range since only one glass transition temperature was detected. Miscibility can be attributed to the strong interactions evolved between the carbonyl group of PVP, which acts as strong proton acceptor, with hydroxyl and amino-groups of HPMC and Chitosan, which are proton donors. Thus hydrogen bonds are easily formed, as was verified by FTIR, producing miscible blends. However, the extent of interactions depends from polymer composition and mainly from the ratio and the kind of reactive groups. In PVP/HPMC blends a negative variation of Tg is recorded while in PVP/Chitosan the variation has a sigma form. The miscibility of these systems creates matrixes with completely different physical properties in order to use as effective drug carriers. PVP/HPMC blends can be used as pulsatile chronotherapeutics systems adjusting exactly the time of the drug release while PVP/Chitosan blends can be used to control the release profile of a poorly water soluble drug. In these blends HPMC and Chitosan respectively are the control factors for the corresponding applications.
TL;DR: In this paper, a tensile strength test, Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were performed on the mixture of polyvinyl alcohol and sodium alginate.
Abstract: Blend films of poly(vinyl alcohol) (PVA) and sodium alginate (NaAlg) were prepared by casting from aqueous solutions. This blend films were characterized by tensile strength test, Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The miscibility in the blends of PVA and NaAlg was established on the basis of the thermal analysis results. DSC showed that the blends possessed single, composition‐dependent glass transition temperatures (Tgs), indicating that the blends are miscible. FT‐IR studies indicate that there is the intermolecular hydrogen bonding interactions, i.e. –OH…−OOC– in PVA/NaAlg blends. The blend films also exhibited the higher thermal stability and their mechanical properties improved compared to those of homopolymers.
TL;DR: Although the gamma-radiation treatment of solid polymeric blends was found to be inefficient, successful cross-linking was achieved by addition of N,N'-methylenebis(acrylamide) and the possibility of radiation cross- linking of these materials has been demonstrated.
TL;DR: In this article, a mixture of poly(butadiene-co-acrylonitrile) elastomer (NBR) and polyaniline dodecylbenzenesulfonate (PAni), with electrical conductivities up to 10−2 ǫ s cm−1, have been prepared by solution mixing and casting.
TL;DR: In this article, the phase behavior of two crystalline polymers with closely spaced Tg's was investigated, and the authors further extended the range of polyesters that can be miscible with PEO.
TL;DR: In this paper, a mixture of poly(ethylene succinate) and polypropylene succinate (PPSu) was used to obtain a single composition dependent glass transition temperature over the entire range of composition, indicating that the system is miscible.
Abstract: New binary blends composed of poly(ethylene succinate) and poly(propylene succinate) or poly(ethylene succinate) and poly(butylene succinate) were prepared. Both PESu/PPSu and PESu/PBSu systems belong to semicrystalline/semicrystalline pairs. The miscibility and crystallization behavior was investigated using differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), and polarizing light microscopy (PLM). Blends of PESu and PPSu exhibited a single composition dependent glass transition temperature over the entire range of composition, indicating that the system is miscible. The melting point depression of the high melting temperature component, PESu, was analyzed according to the Nishi-Wang equation. A negative polymer–polymer interaction parameter was obtained, indicating that the blends are thermodynamically miscible in the melt. The two components crystallized sequentially when the blends were cooled rapidly to a low temperature. DSC traces of PESu/PBSu blends after quenching showed two distinct composition dependent glass transition temperatures between those of the neat polymers, showing that the polymers are partially miscible. The amorphous PESu/PBSu blends in the intermediate compositions showed three cold-crystallization peaks, indicating the influence of mixing. The crystallization rates of PBSu were reduced and those of PESu were increased. WAXD showed reduced crystallinity and peak broadening in the patterns of the blends of intermediate compositions, while no spherulites could be detected by PLM. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 584–597, 2006
TL;DR: In this paper, the issue of recycling of poly(ethylene terephtalate) (PET) by melt blending with polycarbonate (PC) was addressed, and PET/PC blends containing various amounts of the immiscible polymers were prepared in a twin-screw extruder.
Abstract: The article addresses the issue of recycling of poly(ethylene terephtalate) (PET) by melt blending with polycarbonate (PC). PET/PC blends containing various amounts of the immiscible polymers were prepared in a twin-screw extruder. Selected compositions were also prepared in the presence of an Sn-based catalyst to assess the influence of transesterification during melt mixing. The degree of miscibility in the blends was studied using differential scanning calorimetry, scanning electron microscopy, and mechanical testing. PET/PC blends exhibit enhanced tensile properties in comparison to neat components for compositions of PET higher than 50% and these properties are improved by the addition of a transesterification catalyst. The PET/PC blend containing 20 wt% of PC, prepared with stannous octoate, shows the smallest size of the dispersed phase because of transesterification reactions that generate copolymer molecules at the interface between the immiscible polymers. The melting temperature of PET is decreased with the increase of the PC content in blends extruded in the presence of the catalyst. Also, the temperatures of the cold crystallization of PET are higher than those of similar blends without added catalyst. Both features give rise to better molding properties because of a shortening of the cooling time in the range of 50–90 wt% of PET. POLYM. ENG. SCI. 46:1378–1386, 2006. © 2006 Society of Plastics Engineers
TL;DR: In this paper, the effect of guar gum content on the miscibility, morphology and physical properties of the blend films is investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, density measurements, differential scanning calorimetry, dynamic mechanical thermal analysis, thermogravimetric analysis, water sensitivity measurements, solvent-swelling and tensile tests.
TL;DR: In this article, a semi-interpenetrating polymer network (semi-IPN) was synthesized from 6-O-carboxymethylchitosan (6-OCC) and waterborne polyurethanes (WPU) with ester or ether soft segments.
TL;DR: In this article, the poly(acrylic acid)/poly(ethylene oxide) (PAA/PEO) complexes with different stoichiometric ratio were obtained from aqueous solutions.
Abstract: The poly(acrylic acid)/poly(ethylene oxide) (PAA/PEO) complexes with different stoichiometric ratio were obtained from aqueous solutions. The chemical structure of these blends in solid state and the interactions between components has been studied using mainly FT-IR spectroscopy. The miscibility of components was proved also by differential scanning calorimetry (DSC). The films of both pure polymers and their blends at different compositions were UV-irradiated ( λ = 254 nm) in air atmosphere. The course of photochemical transformations has been monitored by absorption spectroscopy (FT-IR, UV–vis), DSC, X-ray diffraction and thermogravimetry, which was also applied for estimation of the thermal properties of samples studied. It was found that photooxidative degradation is less efficient in PAA/PEO complexes than that in PAA and PEO exposed separately. The most photostable was PAA/PEO (50/50) blend. PAA disturbs crystallization PEO in the blends but changes in crystallinity degree of PEO/PAA during UV-radiation were negligible. Thermal stability of PAA/PEO complexes is lower comparing to pure components but UV-irradiation does not cause significant changes in thermal resistance of blends studied.
TL;DR: In this article, the mixture of deuterated polystyrene (dPS) and sulfonated poly(styrene-ran- styrenesulfonate) (P(S-SS)) is examined by using forward recoil spectrometry (FRES) to probe the intermixing of bilayer films.
Abstract: The blend miscibilities of deuterated polystyrene (dPS) and sulfonated poly(styrene-ran- styrenesulfonate) (P(S-SS)) are examined by using forward recoil spectrometry (FRES) to probe the intermixing of bilayer films. This method directly determined the equilibrium coexistence compositions for dPS:P(S-SSx) blends where the degree of sulfonation (x) ranged from 0.2 to 2.6 mol %. In the temperature range 150-190 °C, FRES profiles reveal full miscibility for x e 0.2 mol % and complete immiscibility for x g 2.6 mol %. Partial miscibility exists in dPS:P(S-SSx) blends with x ) 0.7, 1.0, and 1.2 mol %, where between 150 and 190 °C the coexisting compositions show upper critical solution temperature (UCST) phase behavior. Blend interaction parameters, � blend, are calculated using the Flory-Huggins theory and the coexisting compositions of the partially miscible bilayers. The copolymer blend theory estimates the styrene-styrenesulfonate segmental interaction parameter to be extraordinarily large, � S/SS g 25. While the applicability of mean-field approaches is limited in this profoundly incompatible system, recent theories about random copolymers have established criteria for "self- demixing" due to their inherent compositional variations. Our estimate of the monomer-monomer interaction parameter suggests the potential for demixing in P(S-SSx) random copolymers that possess even a narrow distribution of compositions.