On many articles I found the following equation to measure porosity of hydrogels:
Percent porosity = (M2 - M1) / pV × 100
Where M1 and M2 are the mass of the hydrogel before and after immersion in absolute ethanol, respectively; p is the density of absolute ethanol and V represents the volume of the hydrogel.
The problem is that after immersion in ethanol, the hydrogel sample (alginate-based) weights less. Additionally it has lost elasticity, becoming very fragile.
Any suggestion on why this happens and how I can measure the porosity differently?
Virginia Clarizia
1. Hydrogel porosity is not an exact parameter. The hydrogel contains water. It gives it elasticity, but you don't know how much water is there before adding absolute ethanol. Therefore, the attitude towards this value depends on the reviewer.
2. The porosity of the xerogel is measured - this is a dry gel and the measured porosity is more accurate.
3. Absolute ethanol absorbs the water of the hydrogel and therefore the gel becomes brittle and lighter. Polymers are generally lighter than water.