Critical point, 263 polyacrylamide

According to the modern solution thermodynamics, most linear polymers dissolve into their solvent endothermically which means that the solubility of the polymer increases on heating the solvent and/or the polymer solution. On the contrary to this, however, some polymers lose their solubility into water at higher temperatures above a critical point but regain the solubility on cooling the solvents and or the polymer solutions below the critical condition. In this work, a series of N-substituted polyacrylamides and polymethacrylamides were prepared and, among those,PNiPAM and PNiPMAM were studied in more details as an typical example of such a new family of water soluble polymers. 

Although the properties of polyacrylamide gels are less critical in isoelectric focusing than in gel electrophoresis, particularly when low molecular weight proteins are separated, restrictiveness may become a major factor when isoelectric points under equilibrium conditions are to be determined or in work with larger proteins. In standard 5 % T, 3 2 gels, polymerized in the presence of... 

Liquid chromatography at the critical adsorption point (LC LCS) was investigated. The solubility of macromolecules, the sensitivity of LC LCS to such variables as the injection volume, concentration injected, mobile phase flow rate and mixing between the injection zone, were investigated, using polymethyl methacrylate (PMMA) and polyacrylamide standards. It is proposed that using tetrahydrofuran and n-hexane as eluents for PMMA, at the LC LCS, limited polymer insolubility or even local precipitation is combined with the size exclusion of macromolecules. 12 refs. 

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