In situ observation of heat- and pressure-induced gelation of methylcellulose by fluorescence measurement

In situ observation of heat- and pressure-induced gelation of methylcellulose (MC) aqueous solution has been studied by using dynamic viscoelastic and fluorescence measurements. The storage modulus G′ decreased gradually first on heating, and then leveled off in the temperature range from 25 °C to 75 °C. Methylcellulose solutions were subjected to pressures up to 450 MPa by using a high pressure cell. It was indicated that the microviscosity showed a dramatic change in the vicinity of the phase transition point. The T vs. P phase diagram of methylcellulose aqueous solution was constructed, and it indicated that the melting point was an increasing function of pressure. In situ microscopic observation of pressure-induced gelation of methylcellulose aqueous solution was also performed with a microscope, and it could be seen that gel phase of the sample disappeared and sol formed gradually. Pressure-released study by fluorescence measurement also showed that the phase transition of MC solution was reversible.

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