Synthesis 1: Basic Chemistry used

The most used monomer is acrylic acid (AAc) that offers the possibility to influence the charge density via pH. The other important parameter of influence is the degree of crosslinking or the average length of the chains between two crossing points. Also of importance, but not easy to control, is the homogenity of the network and the existence of free dangling ends.

A typical reaction scheme for polyacrylic acid

Gel-Blocking, a typical problem of hydrogels in application

One important problem in applications in the general is the so called "gel-blocking". If the network flexibility ist not high enough, only the outer parts of the gel will swell and then block the inner region resulting in a drastical decreasesd swelling range or at least in an increased swelling time.
This Problem is more pronounced for bigger gel particles and for particles under stress because then the voids between the single particles can be blocked by deformation.

Therefore it is of highest importance for the application in an osmosis engine where we want fasst swelling times and high degrees of swelling, all under mechanical load.
To avoid these problem, we use specialized synthesis techniques, microfluidic and 3D-Printing, described in the pages Synthesis 2 and Synthesis 3, best accessible via the content information bar at the top of the page.