Dow Water & Process Solutions

Gel vs. Macroporous Resins

Gel

Gel ion exchange resins are translucent and are composed of a polymer matrix which results in the formation of a homogeneous continuous phase throughout the bead.  The pore structure of gel resins depends on the degree of crosslinking (i.e. amount of DVB) which is usually up to ~10%.  These resins are non-functional in non-polar solvents since they effectively have no porosity in this kind of medium.

Macroporous

Macroporous resins are opaque due to the fact that they contain up to 20% DVB in the polymer matrix.  They are produced from a styrene-divinylbenzene copolymer to which has been added a non-polymerizable diluent that volatilizes leaving discrete macro pores throughout the bead.  These pores are considerably larger than those found in gel resins and, as such, allow the accessibility of large molecules.  Due to the increased amount of DVB in macroporous resins (i.e. higher degree of crosslinking), little volume change is exhibited in any solvent.  Therefore, they may be successfully used in non-polar solvents since the matrix is non-collapsible (i.e. does not shrink).  Macroporous resins are also frequently used where rigorous conditions are encountered since the increased crosslinkage permits resistance to resin degradation caused by such factors as osmotic shock and oxidation.

Macroporous vs. Gel Resin Comparison

	Gel	Macroporous	Comments
Capacity	+	-
Kinetics	+	-
Regeneration efficiency	+	-	The higher degree of crosslinkage in macroporous resins results in slower diffusion within the bead, reducing resin performance.
Attrition	+	+	Attrition is worst with macroporous resins due to their rough surface and more brittle nature.
Oxidation stability	-	+	Thermal or chemical degradation due to decrosslinking, NOT defunctionalization.
Swelling	-	+	Resistance to osmotic shock
Selectivity	-	+	Macroporous resins are more selective (based on size of hydrated ion) since swelling required by larger ions is opposed to a greater degree by increased crosslinkage.