Thermosensitive hard spheres.

Journal of colloid and interface science

PubMedID: 17931641

Clements M, Pullela SR, Mejia AF, Shen J, Gong T, Cheng Z. Thermosensitive hard spheres. J Colloid Interface Sci. 2008;317(1):96-100.
We demonstrate an extension of a UV-Vis spectroscopy method to determine the phase boundaries for thermosensitive colloids as an alternative to the time-consuming sedimentation method. The Bragg attenuation peak from colloidal crystallites was monitored during the quasi-equilibrium colloidal crystal melting. The melting and freezing boundaries of the coexistence region were determined via a blue shift of Bragg's peak and the disappearance of peak area. We confirm this method using poly(N-isopropylacrylamide) (PNIPAM) particles at different charge densities and temperatures far below the lower critical solution temperature. At low pH, the particles behave as thermosensitive hard spheres.