Measuring the gel fraction is important in determining the monomer conversion in polymerization processes. The gel fraction is defined as the fraction of the polymerized material that has formed a three-dimensional network, which is insoluble in the solvent used for polymerization.

It is important to note that the gel fraction can be affected by various factors, such as the type and amount of initiator used, the temperature and pressure conditions, and the molecular weight of the polymer. Therefore, it is important to carefully control these variables and standardize the measurement procedure to ensure accurate and reproducible results.

Geir Bjorklund Is it possible to measure gel fraction over time?

We conduct gel fraction by first rinsing the gel briefly to rid of unpolymerised monomer and blotting dry. We dry the gel in a vacuum oven until equilibrium weight is achieved- this weight is recorded as dry weight. Then we place the gel in physiological buffer (as our unpolymerised material is soluble in this solvent) or whichever solvent will help to leach out unpolymerised parts from your gel. This solution is changed daily until the weight change of the gel is stable- this weight is recorded as weight swollen.

Finally, the gel is re-dried in a vacuum oven until equilibrium weight which is recorded as weight re-dry. The % gel fraction can be calculated as follows:

Gel fraction (%)= (Re-dry weight/ Initial dry weight)*100

If I had a task to determine the conversion of a monomer (and not the amount of gel fraction), I would determine the content of residual monomers in the polymer by instrumental methods. If we consider the gel fraction as a cross-linked polymer, then the monomer in it is already embedded in the polymer. If the gel fraction is an undesirable formation during polymerization, it is necessary to maintain the conditions of the polymerization reaction at the "flawless" level.