Synthesis of Microporous pH-sensitive Polyacrylic Acid/Poly (ethylene glycol) Hydrogels Initiated by Potassium Diperiodatocuprate (III)

Acopolymer hydrogel of polyacrylic acid poly(ethylene glycol) was prepared by potassium diperiodatocuprate (III). In this work we considered many reaction conditions which can affect the conversion and hydrogel efficiency, such as reaction time, concentration of initiator, reactants and cross-linking agent. In the optimal conditions, temperature was 35ºC, concentration of potassium diperiodatocuprate (III) was 1.76 ×10-3 mol/L, the weight ratio of polyacrylic acid-poly(ethylene glycol) was 5:1 with reaction time of 80 min, cross-linker was 0.1 mg/mL, hydrogel efficiency (HE) could reach 0.90 and total conversion was 0.98. At the same time the effects of pH, poreforming agent of the hydrogel and cross-linker on swelling ratio were also investigated. The maximum swelling ratio of the hydrogel was obtained at pH 7 while the pore-forming agent was 0.08 mg/mL, the weight ratio of polyacrylic acid-poly(ethylene glycol) was 25:1, and the cross-linker was 0.05 mg/mL. The hydrogel was synthesized successfully as confirmed by infrared spectroscopy, and the experimental result indicated that potassium diperiodatocuprate (III)/poly(ethylene glycol) redox system was an efficient initiator for this reaction. Meanwhile, we also used scanning electron microscope (SEM) to study the structure of the hydrogel. SEM showed that there are many microporesformed in the microporous hydrogel compared to the traditional hydrogel, whichobviously improved the swelling capacity.