Small-angle neutron scattering studies of polybutadiene/polystyrene blends as a function of pressure and microstructure: Comparison of experiment and theory

We study a Gibbs free energy model for describing the thermodynamics of compressible polymer blends in the case of nonpolar polymers. This model is a mean field model equivalent to the cell model of Prigogine et al. and close also to the model by Flory-Orvoll and Vrij. The model is expressed as a function of the interaction energies between monomer pairs (a, b, and c), the degrees of polymerization (X A and X B ), a close packing parameter q 0 , the temperature, and the pressure. We derive an analytical expression regarding blend miscibility. All the already observed phase behaviors are recovered: the occurrence of two kinds of upper critical solution transition (UCST): case-I and case-II UCST for which the pressure has a destabilizing or stabilizing effect, respectively, and lower critical solution transition; cases where the pressure have a non-monotonous effect on the UCST temperature; cases where the spinodal lines close up under high pressures; and the so-called hour-glass transition. The model allows for making explicit the effect of the different physical parameters on phase behavior. We calculate complete miscibility maps regarding the occurrence of the various possible kinds of transitions in the 2D space b/a and X A , for different values of ðc2 ffiffiffiffiffi ab p Þ=a, applied pressure P, and chain length ratios. This approach may come as a complement to already existing, more quantitative and elaborated approaches.

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“…. Similarly, it is possible to define an effective Flory‐Huggins parameter χ eff ( T , P ) in similar ways as those used for other models …”

Section: Discussionmentioning

confidence: 99%

Miscibility maps for polymer blends: Effects of temperature, pressure, and molecular weight

Masnada

Julien

Long

2013

J. Polym. Sci. Part B: Polym. Phys.

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“…The experimental results of Δ H M do not fit the theoretical curve obtained developing the LCT on the basis of the architectures that previous results18, 19 indicate as the most realistic for the repetition units of PS and PVME. The experimental trend is rather asymmetrical; this leads to the conclusion that strongly different architectures between the two polymers must be considered to have a good fitting of the theory with the experimental results. In a more recent paper36 Freed takes into consideration, for PS, a microstructure different from the one here used for the calculations.…”

Section: Resultsmentioning

confidence: 99%

“…The experimental trend is rather asymmetrical; this leads to the conclusion that strongly different architectures between the two polymers must be considered to have a good fitting of the theory with the experimental results. In a more recent paper36 Freed takes into consideration, for PS, a microstructure different from the one here used for the calculations.…”

Section: Resultsmentioning

confidence: 99%

Thermodynamic of polymer mixtures: The LCT applied to the poly(styrene)/poly(vinyl methylether) system

Vicini

Princi

Pedemonte

2008

J Polym Sci B Polym Phys

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In this article, the Lattice Cluster Theory developed by Freed and coworkers is applied to the poly(styrene)/poly(vinyl methylether) system by measuring the enthalpy and the volume variation associated with the mixing of the two homopolymers. It comes out that the chains architectures previously chosen for the two macromolecules based on the phase diagram and of the partition function developed by the theory correctly predicts the sign of both ΔHM and ΔVM. The foreseen trends as function of mixture composition fit the experimental data only for ΔVM; ΔHM is higher than predicted, asymmetrical and independent on the chain lengths of the components. The conclusion is that the theory needs some final touches in order to obtain a better agreement with experiments. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 791–797, 2008

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“…Most experiments under pressure have been performed to elucidate the effect of pressure on miscibility of polymer blends [10][11][12][13][14][15]. Almost no researches had been done on the details of nano-structures of PLA/PEG blends under pressure.…”

Section: Introductionmentioning

confidence: 98%

Influence of high pressure on higher-order structures of poly(oxyethylene) in its blend with poly(d,l-lactide)

2015

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The effect of high pressure on the higher-order structures of poly (oxyethylene) (PEG) crystallites in poly(d,l-lactide)/poly(oxyethylene) (PDLLA/PEG) blends during melting and recrystallization was investigated by in situ small-angle X-ray scattering (SAXS) measurements. It was found that melting temperature (T m ) increases at 50 MPa in accordance with the prediction by the Clausius-Clapeyron equation. However, T m at slightly pressurized state (5 MPa) surprisingly decreased, suggesting that the effect of pressure is not so straightforward. It may be due to an increase of the miscibility under higher pressure, causing the melting point depression. Meanwhile, an advantage of analyses of SAXS data enabled us to determine directly discrete distribution of lamellar thickness as a function of temperature under pressure. As a result, lamellar thickening was observed at 5 and 50 MPa as temperature approaches closer to the melting point, but the tendency of thickening was lesser as compared to that observed at ambient pressure.& Nguyen-Dung Tien

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Small-angle neutron scattering studies of polybutadiene/polystyrene blends as a function of pressure and microstructure: Comparison of experiment and theory

Cited by 22 publications

References 20 publications

Miscibility maps for polymer blends: Effects of temperature, pressure, and molecular weight

Miscibility maps for polymer blends: Effects of temperature, pressure, and molecular weight

Thermodynamic of polymer mixtures: The LCT applied to the poly(styrene)/poly(vinyl methylether) system

Influence of high pressure on higher-order structures of poly(oxyethylene) in its blend with poly(d,l-lactide)

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