Controlling the size and the stability of magnetic clusters formed in polyacrylamide hydrogels via Cobalt-anionic fluoroprobe interactions

Polyacrylamide (PAAm)-Cobalt(II)acetate (Co) composite materials were synthesized with and without pyranine (8-hydroxypyrene-1, 3,6-trisulfonic acid, trisodium salt; POH) anionic fluoroprobe having a reactive group, OH, and three ionic groups, SO-₃ , as peripheral. Magnetization and fluorescence measurements showed that addition of POH molecules into the pregel solution results in stable clusters between Co⁺² ions and POH molecules via ionic interactions. The cluster formation, which decreases magnetization of the composites considerably, can occur only during the polymerization. When the POH molecules are diffused into the PAAm- Co gel after the preparation, no change in the magnetization is observed. But, they behave like flocculants and decrease the average size of the Co-clusters by dispersing them via attractive electrostatic interactions. Change in the fluorescence spectra of POH molecules gives direct information about the cluster formation and the stability of the clusters. SEM images showed that the size of the clusters formed in composites depends roughly on Co-POH composition. POLYM. ENG. SCI., 50:843-850, 2010.