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Phase behavior of polymer/nanoparticle blends near a substrate
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10.1063/1.2899329
/content/aip/journal/jcp/128/15/10.1063/1.2899329
http://aip.metastore.ingenta.com/content/aip/journal/jcp/128/15/10.1063/1.2899329
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Schematic of the model polymer/nanoparticle system. The polymers are freely jointed, hard sphere chains of length with segment diameters of and the nanoparticles are hard spheres with diameter .

Image of FIG. 2.
FIG. 2.

Surface free energy as a function of nanoparticle density for a system with , , and . The dark curve with the ×’s indicates stable configurations. The abrupt change in slope of this curve at is indicative of a first order phase transition. The light curve shows the solver continuations into the metastable and unstable regions. The dashed line indicates the free energy of a pure polymer system at the same bulk density.

Image of FIG. 3.
FIG. 3.

Density profiles for the system with , , and at the phase transition . Profile (a) was converged from a lower density profile, while profile (b) was converged from a higher density profile. The polymer (×’s) scale is along the left axis and the nanoparticle scale (+’s) is on the right axis.

Image of FIG. 4.
FIG. 4.

Plot of the pressure for a 100-mer blend at packing fraction, . The nanoparticle diameters were . The inset indicates the percentage difference between the pressure and the sum of the contact densities .

Image of FIG. 5.
FIG. 5.

Nanoparticle density at the phase transition as a function of chain length for blends with . The +’s and ×’s are for and , respectively.

Image of FIG. 6.
FIG. 6.

Transition density as a function of nanoparticle diameter for blends of 100-mers at packing fraction . The density of the transition saturates at larger diameters indicating that the particles are becoming more wall-like to the polymers. No transition was found for particles of diameter or below.

Image of FIG. 7.
FIG. 7.

Surface free energy as a function of nanoparticle density for a blend with packing fraction, , chains of length , and nanoparticles of size . The dark curve with the × markers indicates stable configurations. The layering transition takes place at . The continuations into meta- and unstable regions are indicated by the light curve. Note: The continuation curves are cut off to show the phase transition point more clearly.

Image of FIG. 8.
FIG. 8.

Density profiles converged from (a) below and (b) above the critical density, , for the layering transition for a blend of 100-mers with larger nanoparticles. The total packing fraction for the system was . The polymer (×’s) density scale is on the left axis and the nanoparticle (+’s) density scale is on the right axis. Note that the polymer is able to pass through the gaps between the large nanoparticles and thus resides near the wall.

Image of FIG. 9.
FIG. 9.

Surface free energy as a function of nanoparticle density for and . The dark curve with the ×’s indicates stable configurations. The abrupt changes in slope of this curve at and are indicative of first order phase transitions. The light curve shows the solver continuations into the metastable and unstable regions. The dashed line indicates the free energy of a pure polymer system at the same bulk density. Note that the last six branches of the metastable curve all intersect in the vicinity of the second phase transition.

Image of FIG. 10.
FIG. 10.

Density profiles for a with at one of the layering phase transitions . Profile (a) was converged from a lower density profile while profile (b) was converged from a higher density profile. The polymer (×’s) scale is along the left axis and the nanoparticle scale (+’s) is on the right axis.

Image of FIG. 11.
FIG. 11.

Density profile of a structure of a 100-mer/nanoparticle blend in the bulk at the surface transition concentration . The calculation was performed in a periodic cell, which was allowed to vary in length in steps of the mesh size (0.01). The configuration with the lowest overall free energy has a period of 2.93 monomer units. The packing fraction for the system is and the nanoparticle size is . The surface free energy for this system is 0.03% lower ( vs ) than that of a homogeneous blend.

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/content/aip/journal/jcp/128/15/10.1063/1.2899329
2008-04-16
2014-04-21
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Phase behavior of polymer/nanoparticle blends near a substrate
http://aip.metastore.ingenta.com/content/aip/journal/jcp/128/15/10.1063/1.2899329
10.1063/1.2899329
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