کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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611871 | 880687 | 2008 | 5 صفحه PDF | دانلود رایگان |

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.
Phase diagram of the PNIPAM-co-acrylic acid microgel dispersions at pH 2.8 measured via UV–Vis spectroscopy. At room temperature, the fluid–crystal transition width normalized to the freezing transition concentration is approximately 7%.Figure optionsDownload as PowerPoint slide
Journal: Journal of Colloid and Interface Science - Volume 317, Issue 1, 1 January 2008, Pages 96–100