Synthesis and swelling behavior of poly(vinyl alcohol)/poly(acrylic acid)/hydroxyapatite superabsorbent composites

A novel poly(vinyl alcohol)/poly(acrylic acid)/hydroxyapatite (PVA/PAA/HA) superabsorbent composite was synthesized through aqueous solution polymerization of partially neutralized acrylic acid (AA), poly(vinyl alcohol) (PVA) and hydroxyapatite (HA), using ammonium persulfate (APS) as an initiator and N, N′-methylenebisacrylamide (MBA) as a crosslinker. The effect of PVA content on water absorbency was studied. The swelling behaviors in various pH solutions and swelling kinetics in 2 mmol/L NaCl and CaCl2 saline solutions were also systematically investigated. Results show the introduction of proper amount of PVA into the polymeric network can improve water absorbency of the superabsorbent. Swelling behaviors reveal that the superabsorbent composites retain high water absorbency over a wide pH range of 4~11, and the swelling kinetics of the superabsorbent composite hydrogel in CaCl2 solution exhibits a remarkable overshooting phenomenon.