Abstract
Opalescence of the aqueous solution of hydroxypropylmethylcellulose (HPMC) induced by heating has been studied in terms of the phase diagram and the phase separation dynamics. The cloud point curve and the sol-to-gel transition curve intersected with each other at about 55°C. Just above the cloud-point curve at which the spinodal curve has its minimum, a ring-like scattering pattern appeared corresponding to the spinodal decomposition. Temporal growth of the scattering function in the course of phase separation was studied by a time-resolved light scattering technique. The gelation pinned the phase separation (spinodal decomposition) of the aqueous HPMC solution.
Highlights
Phase separation of thermo-responsive water-soluble polymers is an intense research field in polymer science driven by promising technologies in a diverse range of fields, among biomedicine[1] and environmentally friendly materials.[2,3,4] Critical aspects to designing and screening such systems rely on a better understanding of the phase transition and the determination of well-characterized phase diagrams and phase transition solution temperatures since the latter temperatures are the main experimental data needed to further investigate the fundamentals of phase separation mechanisms and kinetics
The thermo-responsive phase separation of commercial hydroxypropylcellulose was investigated in a broad concentration range covering the dilute and semi-dilute regime by dynamic light scattering
Our results show that the fast and slow mode amplitudes undergo a sharp transition by increasing the temperature near the phase separation temperature
Summary
Phase separation of thermo-responsive water-soluble polymers is an intense research field in polymer science driven by promising technologies in a diverse range of fields, among biomedicine[1] and environmentally friendly materials.[2,3,4] Critical aspects to designing and screening such systems rely on a better understanding of the phase transition and the determination of well-characterized phase diagrams and phase transition solution temperatures since the latter temperatures are the main experimental data needed to further investigate the fundamentals of phase separation mechanisms and kinetics. In this article we are interested in exploring another approach to define the phase separation transition of a thermo-responsive water-soluble polymer in a broad range of concentrations based on Dynamic Light Scattering (DLS). In this article we show that the approach of HPC phase transition significantly impacts the fast and slow mode behaviors By following the latter modes up to the phase boundary, we demonstrate that it is possible to define the phase transition temperature with a remarkable accuracy. We show that DLS can be used to resolve the growth kinetics of HPC domains for concentrations as high as 5 % and thermal quenches of an amplitude such as the single exponential nature of g2(t) is preserved
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