( on. A swirled or schlieren pattern ...)Acrylamide Polymerization A Practical Approach

Polymerization Profile
As acrylamide polymerizes, UV-absorbing double bonds are eliminated. The progress of a reaction can therefore be followed by monitoring absorbance at 260 nm. As the reaction proceeds, the UV absorbance drops. Absorbance increases with the amount of unreacted monomer.

Figure 1 shows a UV profile of chemical polymerization for 2 samples of acrylamide polymerized under identical conditions in a quartz cuvette. Sample A was an enzyme grade acrylamide with a conductivity (50% w/w) of 3.75 S. Sample B was Bio-Rads electrophoresis-purity acrylamide with a conductivity of 0.56 S. As the figure shows, polymerization is largely complete after about 90 min, even though the reaction proceeds to a small extend beyond that time. While sample A began to polymerize faster, sample B polymerized more completely, as indicated by the lower final UV absorbance.

Contaminants in acrylamide may be accelerators or inhibitors of polymerization. Therefore, initiation of polymerization, as indicated by reduced absorbance, may be faster with crude acrylamide than with highly refined acrylamide. However, the most important consideration is the completeness of polymerization. Polymerization of highly refined acrylamide may be initiated more slowly, but conversion of monomer to polymer, as indicated by the low final absorbance, is more complete. Therefore, less residual monomer remains. Complete polymerization is critical for reproducibility in ge
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