A Multifunctional Hydrogel with High-Conductivity, pH-Responsive, and Release Properties from Polyacrylate/Polyptrrole Jianming Lin, Qunwei Tang, Jihuai Wu, Qinghua Li Engineering Research Center of Environment-Friendly Functional Materials, Ministry of Education, China, The Key Laboratory for Functional Materials of Fujian Higher Education, China, Institute of Material Physical Chemistry, Huaqiao University, Quanzhou, 362021, China Received 28 May 2008; accepted 4 September 2008 DOI 10.1002/app.31642 Published online 4 January 2010 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: A simple, two-step aqueous polymerization was introduced to synthesize a polyacrylate (PAC)/poly- pyrrole (PPy) hydrogel. The hydrogel had a semi-inter- penetrating network (semi-IPN) structure with a loose, three-dimensional PAC network and a one-dimensional PPy conjugated chain. The presence of PPy led to a higher conductivity (9.1 mS/cm) for the PAC/PPy hydrogel. Because of the acrylate group on PAC and the imine group on PPy, the hydrogel showed typical pH sensitivity with two water absorption peaks at pH 4–6 and pH > 11. The loose semi-IPN structure endowed the hydrogel with good load and release functions. V C 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 1376–1383, 2010 Key words: adsorption; conducting polymers; hydrogels; interpenetrating networks (IPN); polypyrroles INTRODUCTION Superabsorbent polymers are structurally loosely crosslinked three-dimensional (3D) network hydro- philic polymers; 1 they are able to absorb consider- able amounts of liquid to form stable hydrogels and do not dissolve in the liquid. About 3 decades ago, 2 superabsorbent polymers were introduced into the agriculture and diaper industries, and then their applications were extended to other industries where excellent water-holding properties were emphasized. Recently, many researchers have focused their attention on superabsorbent polymers for the development of new applications, such as conducting materials, biomaterials, sensors, and release materials. 3–10 They expected to prepare mul- tifunctional soft matters from superabsorbents to meet application requirements by modification, grafting, copolymerizing, and other methods. Conducting hydrogels are novel functional materi- als that were recently developed. Conducting hydro- gels are often prepared by the copolymerization or doping of conducting materials with/to hydrophilic monomers/polymers. 11,12 Polypyrrole (PPy) is one of the most extensively studied conductive polymers because of its good conductivity, low cost, easy syn- thesis, and good environmental stability. 8,13 On the basis of the superabsorbent polymer polyacrylate (PAC) and the conducting PPy, a novel hydrogel with multifunctional properties is expected. In this study, we introduced a one-dimensional PPy conjugated chain into a 3D PAC network to form a novel hydrogel by a two-step aqueous poly- merization. We expected the obtained hydrogel to be a semi-interpenetrating network (semi-IPN). On the basis of the PPy conjugated chain, bifunctional groups of ANHA on PPy and ACOOH (or ACOO  ) on PAC, and the semipermeable membrane struc- ture of the PAC/PPy, a novel multifunctional hydro- gel with high-conductivity, pH-sensitive, drug-load- ing, and release properties was obtained. It could be used in fuel cells, supercapacitors, dye sensitive so- lar cells, rechargeable lithium batteries, conducting films, coatings, sensors, conducting fibers, and so on 4,14–20 because of to its high conductivity, colloidal stability, low cost, and simple preparation. EXPERIMENTAL Materials Acrylic acid (AA) and pyrrole (Py) monomers were distilled under reduced pressure before use. Potas- sium hydroxide (KOH) was used to neutralize the AA monomer to form acrylate (AC) monomer and Correspondence to: J. Wu (jhwu@hqu.edu.cn). Contract grant sponsor: National High Technology Research and Development Program of China; contract grant number: 2009AA03Z217. Contract grant sponsor: National Natural Science Foundation of China; contract grant numbers: 90922028 and 50842027. Journal of Applied Polymer Science, Vol. 116, 1376–1383 (2010) V C 2010 Wiley Periodicals, Inc.