User:Andrew Sun/Notebook/LAOS study on physical gelation/2009/05/07

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LAOS Experiment of PAAc/Fe(III) Gels

Objectives

Find the critical gel point

Samples

Gels from 5 wt% PAAc solution (Mv=51100): f=1.30e-3 (f=[Fe(III)]/[COOH])

Instruments

ARES Rheometer

Results

Frequency Sweep

Fig. 1
The sample is close to the critical gel point as shown in Fig. 1 1st run. But it underwent an obvious dissociation as indicated by frequency sweeps before and after LAOS experiment (Fig. 1).

FT-Rheology

Fig. 2

The sample exhibit much larger values of 3rd harmonics compared with sample f=2.30e-3, while the manner I3/1 increases with strain amplitudes are similar, as shown in Fig. 2.

LAOS Experiment of PAAc/Fe(III) Gels

Objectives

Effect of molecular weights

Samples

Gels from 5 wt% PAAc solution (Mv=22400): f=1.30e-3

Instruments

ARES Rheometer

Results

Frequency Sweep

Fig. 3

Frequency sweep result (Fig. 3 1st run) shows that the sample is close to critical gel point. Comparison with frequency sweep after LAOS experiments indicates that the extend of dissociation was minor.

FT-Rheology

Fig. 4

The nonlinearity of the sample was comparatively obvious. The 3rd harmonic appeared since the strain amplitude exceeded 500% (Fig. 4), and the 5th harmonic appeared at the strain amplitude 1900%.

LAOS Experiment of PAAc/Fe(III) Gels

Objectives

Effect of molecular weights

Samples

Gels from 5 wt% PAAc solution (unknown molecular weight): f=1.30e-3

Instruments

ARES Rheometer

Results

Frequency Sweep

Fig. 5

The sample was below the critical gel point. Dissociation occurred after LAOS experiment. See Fig. 5.

FT-Rheology

Fig. 6

Fig. 6.

LAOS Experiment of PAAc/Fe(III) Gels

Objectives

Effect of molecular weights

Samples

Gels from 5 wt% PAAc solution (Mv=22900): f=1.30e-3

Instruments

ARES Rheometer

Results

Frequency Sweep

Fig. 7

The sample was below the critical gel point (Fig. 7).

FT-Rheology

No higher harmonic observed up to strain amplitude of 1900%.