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Microrheology, microstructure, and aging of physically cross-linked poly(vinyl alcohol)/poly(ethylene glycol) blends
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10.1122/1.4708603
/content/sor/journal/jor2/56/4/10.1122/1.4708603
http://aip.metastore.ingenta.com/content/sor/journal/jor2/56/4/10.1122/1.4708603
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Mean square displacements of 110 nm microspheres measured from dynamic light scattering experiments in water (filled circles), 10% PVA solution (diamonds) and 10% PVA/PEG blends with PEG concentrations of 3% (squares), 5% (circles) and 7% (triangles). The dynamic light scattering experiments were performed 1 h after each sample was prepared. The dashed line has a slope of 1.

Image of FIG. 2.
FIG. 2.

The filled circles show the microscopic viscosity , computed from the data of Fig. 1 at short lag times. The local elasticity obtained from the plateau of in Fig. 1 is plotted as open squares. Both are plotted as a function of PEG concentration.

Image of FIG. 3.
FIG. 3.

for dynamic light scattering experiments using microspheres of different sizes in (a) a 10% PVA solution and (b) a 10% PVA/7% PEG blend. The sample age in both cases was 1 day. Scaled data for 110 nm and 210 nm microspheres in water are also shown in (a) for comparison (circles).

Image of FIG. 4.
FIG. 4.

Mean square displacements of 110 nm microspheres measured from dynamic light scattering experiments in a 10% PVA/7% PEG blend at different aging times as indicated. The dashed line has a slope of 1. The line segments with slopes , and schematically represent the behavior of at short, intermediate, and long lag times, respectively.

Image of FIG. 5.
FIG. 5.

(a) Mean square displacement at three different lag times as a function of aging time for 110 nm tracer particles in a 10% PVA/7% PEG blend. The error bars are based on the uncertainty in the light scattering measurements; where not shown they are smaller than the plotted symbols. (b) The logarithmic slopes at short, intermediate, and long lag times as a function of aging time for tracer particles in a 10% PVA/7% PEG blend. The lines are to guide the eye.

Image of FIG. 6.
FIG. 6.

The effective microscopic viscous modulus (dashed lines) and elastic modulus (solid lines) calculated from the data shown in Fig. 1 using Eqs. (7) and (8) for fresh samples of (a) 10% PVA solution, (b) 10% PVA/3% PEG, (c) 10% PVA/5% PEG, and (d) 10% PVA/7% PEG. + and × are the bulk values of and , respectively, measured using small-amplitude oscillatory shear with a rheometer.

Image of FIG. 7.
FIG. 7.

The open symbols show the crossover frequencies and at which , obtained from the data in Fig. 6. The solid symbols show , the minimum value of the , and , the microelastic modulus at the same frequency. The lines are to guide the eye.

Image of FIG. 8.
FIG. 8.

The effective microscopic viscous modulus (dashed lines) and elastic modulus (solid lines) calculated from the data shown in Fig. 4 for a 10% PVA/7% PEG blend. The sample ages are (a) 0 day, (b) 1 day, (c) 8 days, and (d) 27 days. + and × are the bulk values of and , respectively, measured with a rheometer using small amplitude oscillatory shear.

Image of FIG. 9.
FIG. 9.

Mean square displacements of 110 nm microspheres measured from video-based particle tracking experiments in freshly prepared samples of: 10% PVA (diamonds), 10% PVA with 3% PEG (squares), 10% PVA with 5% PEG (circles), and 10% PVA with 7% PEG (triangles). The dashed line has a slope of one.

Image of FIG. 10.
FIG. 10.

(a) Mean square displacements of individual 110 nm tracer particles in the 10% PVA solution. The measurements were performed 1 h after the sample was prepared. The dashed lines are for particles with nearly diffusive motion and the solid lines for particles that are strongly subdiffusive at short τ. (b) Distribution of particle displacements at a lag time of 1 s for the particles labeled (i)–(iii) in (a). (c) The particle displacement distributions averaged over all particles at lag times (squares) and (circles). The dashed lines in (b) and (c) are fits to Gaussian functions. (d) Trajectories of particles (i)–(iii).

Image of FIG. 11.
FIG. 11.

(a) Mean square displacements of individual 110 nm tracer particles in the 10% PVA/7% PEG blend. The measurements were performed 1 h after the sample was prepared. The solid lines are for particles that are subdiffusive at short τ, while the dotted-dashed lines are for particles, whose curves are nearly flat over all the accessible times. (b) Distribution of particle displacements at a lag time of 1 s for the particles labeled (iv) and (v) in (a). (c) The particle displacement distributions averaged over all particles at lag times (squares) and (circles). The dashed lines in (b) and (c) are fits to Gaussian functions. (d) Trajectories of particles (iv) and (v).

Image of FIG. 12.
FIG. 12.

Elasticity as a function of aging time for (a) particles which show dynamic confinement effects (group 2) and (b) particles which show permanent confinement (group 3). is estimated from the plateau of measured in the video particle tracking experiments. The uncertainties include those from the temperature fluctuation, the probe-size polydispersity, and the mean squared displacement measurements in the particle tracking experiments. Note that there are no particles in group 3 in the pure PVA solution at age 0.

Image of FIG. 13.
FIG. 13.

Effective microscopic viscous (open symbols) and elastic moduli (filled symbols) calculated from video particle tracking data for particles in a 10% PVA sample. (a)–(d) are for particles in group 2, which show dynamic confinement, and (e)–(g) are for group 3, which show permanent confinement. The different plots are for different aging times: (a) 0 day; (b) and (e) 1 day; (c) and (f) 4 days; (d) and (g) 10 days. There are no permanently confined particles in the pure PVA solution at age 0. The solid lines in (c) are fits to a Maxwell model.

Image of FIG. 14.
FIG. 14.

Effective viscous (open symbols) and elastic moduli (filled symbols) calculated from video particle tracking data for particles in a 10% PVA/7% PEG blend. (a)–(d) are for particles in group 2, which show dynamic confinement, and (e)–(g) are for group 3, which show permanent confinement. The different plots are for different aging times: (a) and (e) 0 day, (b) and (f) 1 day, (c) and (g) 4 days, and (d) and (h) 10 days.

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/content/sor/journal/jor2/56/4/10.1122/1.4708603
2012-05-09
2014-04-23
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Microrheology, microstructure, and aging of physically cross-linked poly(vinyl alcohol)/poly(ethylene glycol) blends
http://aip.metastore.ingenta.com/content/sor/journal/jor2/56/4/10.1122/1.4708603
10.1122/1.4708603
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