“Novel hydrogels based on zwitterionic monomer [3-(methacrylamido)propyl] dimethyl (3-sulfopropyl)
ammonium hydroxide (MPDSAH) and a strong acid monomer (2-acrylamido-2-methylpropane
sulfonic acid, AMPS) were synthesized through solution polymerization under normal conditions
to achieve nearly quantitative gel yield. The structure of the gels was confirmed using infrared
spectroscopy. Thermal properties were simultaneously studied by differential scanning calorimetry
and thermogravimetric analysis (DSC/TGA). The effects of the polymerization variables on the
swelling capacity of the products were investigated. It was found that, in a certain range of the
monomers mol ratio, increase of AMPS content was surprisingly accompanied with swelling reduction.
The swelling exhibited lower sensitivity to the crosslinker concentration (range 0.6-1.2 wt%)
compared with the conventional superabsorbents. However, in contrast with the conventional
acrylic acid-based superabsorbents, the neutralization degree of AMPS part of the new gels had
only a small enhancing effect on their swelling capacity. The effect of total monomer concentration
on the hydrogel absorbency was also studied. The fully ionic hydrogels showed an unusual pHindependency
behavior, so that their absorbency was nearly unchanged in a wide range of pH.
Such unexpected behavior was also observed for the swelling in the ionic environments with various
ionic strengths. Copyright # 2005 John Wiley & Sons, Ltd.”

By:
Kourosh Kabiri 1, Sara Faraji-Dana 2 3, Mohammad J. Zohuriaan-Mehr 1 *
1Superabsorbent Hydrogel Division, Department of Paint, Resin and Surface Coatings, Iran Polymer and Petrochemical Institute (IPPI), P. O. Box 14965-115, Tehran, Iran
2Department of Chemistry, Sharif University of Technology, P.O. Box 11365-9516, Tehran, Iran
3R&D Division, Rahab Resin Co., P.O. Box 14185-458, Tehran, Iran

email: Mohammad J. Zohuriaan-Mehr (m.zohuriaan@ippi.ac.ir mjzohuriaan@yahoo.com)

*Correspondence to Mohammad J. Zohuriaan-Mehr, Superabsorbent Hydrogel Division, Department of Paint, Resin and Surface Coatings, Iran Polymer and Petrochemical Institute (IPPI), P. O. Box 14965-115, Tehran, Iran.

Summary:
Super swelling due to cross linked hydrophphilic structure. Conventially it is though that superabsobents are preapred from non-ioni-anionic monomers.

The water absorbance is usually decreased substantially when the gel is put into an ionic medium. However some lightly crosslinked amphoteric polyelectrolytes and polyzwitterions have potential to swell more in salt solution than in pure water.

(i.e from 1-vinyl-3-sulfopropylimidazolium hydroxide inner salt imbibe 91% of 1M NaCl. whilst in deionised water gel absorbed only 46%)

With a breif review of literature hydrogels, sulfobetaines are exnteisvely used in industries with textiles, adhesives, coatings, flocculants

AMPS and like derivatives where the monomer 2-acrylamido-2-methylpropanesulfonic acid is copolymerized with other conventional arcylic monomers creating a hydrogel. ( acrylic acid, acrylamide, N,N-dimethylacrylamide and n-dodecyl poly(oxyethylene) maleate)

Suggested used of AMPS with acrylic monomer are skin contact electrodes, support carrier in biomedical engineering and drug delivery applications.

AMP mixed with copolmer to create superabsorbent hydrogels.

Literature has no dictated polymers of sulfobetaine-type monomer and AMPS.

Variables affecting swelling
comonomer ratio
crosslinker content
total monomer concentration
neutralization degree of AMPs on swelling behaviour of the gels which have been investigated