Spinodal Line and Critical Point of an Acrylamide Gel

Abstract

We present direct evidence for the existence of the critical point in an acrylamide gel, the gel consisting of a covalently cross-linked polymer network immersed in an acetone-water mixture. We determined the spinodal line for the gel from the measurements of the scattered light intensity. The spinodal line has a maximum at $T=(10\ifmmode\pm\else\textpm\fi{}1)\ifmmode^\circ\else\textdegree\fi{}$C and a network volume concentration of (18\ifmmode\pm\else\textpm\fi{}3)%. This corresponds to the critical point.