Showing papers on "Miscibility published in 1991"

A monolayer phase miscibility comparison of long-chain fatty acids and their ethyl esters

Abstract: It has recently been confirmed by a number of independent studies that insoluble monolayers of several classes of amphiphilic compound at the air/water interface display complicated polymorphism. At least four of these phases are mesophases, in the sense that they show long-range orientational order but only short-range translational order

Development of miscible blends of polyamide-6 and manganese sulfonated polystyrene using specific interactions

Abstract: Polyamide-6 and a functionalized polystyrene containing 10.1 mol % manganese sulfonate groups were miscible over the entire range of composition as evidenced by a single, composition-depentent T g . The T g 's for the blends exhibited positive deviation from a weight average of the two component polymer T g 's. Interaction parameters were large and negative, indicating strong interactions between the component polymers. Infrared spectra confirmed that these specific interactions were hydrogen-bonding, ion-dipole, and complexation interactions involving the manganese sulfonate and amide groups

Miscible blends of cellulose and poly(vinylpyrrolidone)

Abstract: WAXS, FTIR, DSC, DMA and NMR results showed that blnds of cellulose with PVP are miscible over the whole composition rang and that the miscibilityis driven by hydrogen bond formation between the hydroxyl groups of cellulose and carbonyl groups of PVP. The plot of the measured T g versus composition is not a smooth function but shows a singularity at a blend composition of ca 60:40 w/w cellulose/PVP. This behavior is tentatively interpreted in relation to to the molar ratio of the repeating units of the polymers.

Blends of styrene/maleic anhydride copolymers with polymethacrylates

Abstract: The phase behavior of a series of styrene/maleic anhydride (SMA) copolymers with various polyacrylate and polymethacrylate homopolymers has been investigated using various techniques. None of the polyacrylates are miscible with SMA copolymers. Poly (methyl methacrylate) (PMMA) poly(ethyl methacrylate) (PEMA) and poly(n-propyl methacrylate) (PnPMA), are miscible with these copolymers over a certain range of maleic anhydride contents; whereas, the higher methacrylates apparently have no region of miscibility. For PEMA and PnPMA, the miscibility windows extend through 0% MA; hence, polystyrene is miscible with these polymethacrylates although the lower critical solution temperature is quite low. The exothermic heat of mixing styrene and ester analogs found here supports the observed miscibility of polystyrene with ethyl, n-propyl, and cyclohexyl (reported elsewhere) methacrylates. Lattice fluid interaction parameters for styrene-methacrylate obtained from the cloud points of these blends agree quite well with the Flory—Huggins parameters obtained from copolymer miscibility windows.

Effect of morphology, crosslink density, and miscibility on interpenetrating polymer network damping effectiveness

Abstract: The areas under the linear loss modulus versus temperature curves (loss area, LA) and tan δ versus temperature curves (TA) were evaluated for a number of acrylic, methacrylic, styrenic and butadiene based copolymers and interpenetrating polymer networks, IPNs, as a function of crosslink density and comliosition, and were compared with values predicted by group contribution analysis. The LAs of the sequential IPNs, cross-poly(n-butyl methacrylate)-inter-crosspolystyrene, were found to exhibit up to 30% larger LAs than the poly(n-butyl metacrylate-stat-styrene) copolymers, which had LAs slightly less than the values predicted from the group contribution analysis. At constant chemical composition (50% n-butyl methacrylate, 50% styrene), LA equals 14.4 GPa K for the IPN, attributed to a synergistic effect resulting from the IPN's microheterogeneous morphology, as compared with 10.7 GPa K for the single phase, miscible copolymer. Increases in the LA with increased concentration of polymer, network II were also observed for cross-poly(ethyl acrylate)-inter-crosspolystyrene and cross-polybutadiene-inter-cross-polystyrene IPNs. On the other hand, cross-polybutadiene-inter-cross-poly(methyl methacrylate) IPNs had LAs much lower than were predicted by the group contribution analysis, which were attributed to lower miscibility in this system relative to the other systems evaluated. In general, decreased crosslink densities and lower concentrations of network II increased TA. These findings demonstrate how the morphology of a multiphase polymeric material can affect LA and TA, with significant increases In damping capability over the average of the component polymer values.

Heats of mixing of strongly interacting model compounds and miscibility of the corresponding polymers

Abstract: The miscibility between polystyrene polymers that contain potential hydrogen bond, or proton, donor groups and other polymers that are good hydrogen bond, or proton, acceptors is investigated. The thermodynamics of mixing of low molecular weight model compounds is studied. The proton donor groups include SO 3 H, CO 2 H, phenol, alcohol and hexafluoroisopropyl alcohol. The acceptor molecules are poly (N,N-dimethylacrylamide)) and poly(methyl methacrylate) The results for the model compounds are shown to be useful in predicting the probability of miscibility occurring between the corresponding polymers

Surface studies of polymer blends. 4. An ESCA, IR, and DSC study of the effect of homopolymer molecular weight on crystallinity and miscibility of poly(iε-caprolactone)/poly(vinyl chloride) homopolymer blends

Abstract: Les resultats montrent que la composition superficielle des melanges est gouvernee par la cristallinite et la masse moleculaire des polymeres

Tacticity effects on polymer blend miscibility

Abstract: Etude de melanges de polystyrenes (PS) atactiques de masses moleculaires differentes avec des poly(methyl vinyl ether) (PVME) isotactiques et heterotactiques. Les mesures de point de troubles montrent que le PVME isotactique est moins miscible avec le PS atactique que le PVME heterotactique

Characterization of semicrystalline polymers by inverse gas chromatography. 2. A blend of poly(vinylidene fluoride) and poly(ethyl methacrylate)

Abstract: The IGC method was found to be capable of detecting the melting point depression of a polymer blend containing a crystallizable homopolymer. Ther thermodynamics of PVF2-PEMA miscibility obtained from the melting point depression are discussed. The values of the PVF2-PEMA interaction parameter and the energy parameter obtained from the IGC method are in excellent agreement with the values obtained by the calorimetric method. Comparisons are made for the interaction parameters obtained from the melting point depression using the IGC and the calorimetric method

Microstructure Effects on the Lower Critical Solution Temperature Phase Behavior of Deuterated Polybutadiene and Protonated Polyisoprene Blends Studied by Small-Angle Neutron Scattering

Abstract: The miscibility of a blend of protonated polyisoprene (HPI) with the 3,4-linkage microstruc- ture in the range 7-15% and of deuterated polybutadiene (DPB) with the 1,Qlinkage microstructure in the range 12-28% was studied by small-angle neutron scattering (SANS). It was found that all blends studied here show lower critical solution temperature (LCST) type phase behaviors; i.e., the phase separation occurs by raising the temperature. It was also found that the miscibility is quite senaitive to the microstructures of the polydienes used. The effective thermodynamic interaction parameter xen per segment between two polymers was determined by fitting SANS data in the single-phase state with a theoretical scattering curve obtained on the basis of the random-phase approximation. The temperature dependence of xen showed a systematic change with the microstructure. For a given HPI, the xeff values decreased, and therefore, the blends became more miscible, with an increase in the vinyl content (Le., lI2-linkage content) in DPB. On the contrary, for a given DPB, the values increased, and therefore, the blends became more immiscible, with an increase in the vinyl content (Le., 3,4-linkage content) in HPI. We proposed an alternative explanation for the LCST phase behavior based on treatment for the random copolymer blends.

A study of the miscibility of bile components in mixed monolayers at the air-liquid interface. I, Cholesterol, lecithin, and lithocholic acid

Abstract: Experimental isotherms, obtained by compressing monomolecular layers formed by a number of compounds involved in gallstone formation (cholesterol, L-α-phosphatidylcholine, and lithocholic acid), are studied. Mixed monolayers consisting of pairs of these substances are also analyzed. The additivity rule for molecular areas is used for characterizing the possible interactions between such components. Applying the phase rule to the surface systems studied in conditions of extended/condensed liquid equilibrium allows the miscibility of the components in both phases to be determined. Some hypotheses are given regarding the kind of molecular rearrangements that take place when each system suffers a phase transformation. The general conclusion reached is that, at the experimental conditions used (pH=6.00 and T =298 K), significant interactions occur between the molecules of the compounds studied.