Dear Lei Zhang, it depends on the polymer and the filler in question. Generally, two ways of preparing such compounds. Either by melt mixing or by solution mixing. The first way use internal mixers (such as Brabender), two roll-mill, extruders (single and twin screw), and orhers. Solution mixing use Solvent to solubilize first the polymer and after that the filler is added under mixing, once good didpersion is reached, the solvent is gradually evaporated.

Generally, good contact is achieved by the use of coupling agents, where silanes are the most widely used and studied. My Regards

As your question seems in general, below are the parameters to consider while selecting organic fillers to achieve good distribution within the matrix to ensure a strong & cohesive interface

• Consider adding fillers in stages during the gelation process to ensure optimal distribution.
• Applying mild heat during or after the gel curing to encourage the filler particles to redistribute and settle evenly in the matrix.
• Filler material should be optimized in the size and morphology for better dispersibility (Smaller, irregular shapes may provide more surface area for interaction with the matrix)
• By selecting hydrogel and organic filler that are chemically compatible to promote adhesion and reduce phase separation.
• Coating the surface of the fillers with compatible molecules that can form physical bond with hydrogel to enhance bonding with the hydrogel matrix.
• Using ultrasonication to achieve a uniform distribution of the filler throughout the hydrogel matrix before gelation.... Hope this helps you @Lei Zhang