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

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 * style="background-color: #EEE"|[[Image:owwnotebook_icon.png|128px]] LAOS study on physical gelation
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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

Frequency Sweep
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
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.

Objectives
Effect of molecular weights

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

Instruments
ARES Rheometer

Frequency Sweep
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
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%.

Objectives
Effect of molecular weights

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

Instruments
ARES Rheometer

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

FT-Rheology
Fig. 6.

Objectives
Effect of molecular weights

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

Instruments
ARES Rheometer

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

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


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