Synthesis and characterization of poly(acrylamidoglycolic acid) grafted onto chitosan and its polyelectrolyte complexes with hydroxyapatite K.S.V. Krishna Rao, Ildoo Chung * , Chang-Sik Ha * Department of Polymer Science and Engineering, Pusan National University, Pusan 609-735, Republic of Korea Received 20 October 2007; received in revised form 6 February 2008; accepted 11 February 2008 Available online 20 February 2008 Abstract Graft copolymerization of acrylamidoglycolic acid (AGA) onto chitosan (CS) was carried out via a free radical initi- ation mechanism using a redox initiation system. Grafting ratio (%), efficiency, and conversion (%) were all found to depend on the content of potassium persulfate and AGA as well as on reaction temperature and time. Evidence of grafting was obtained by FTIR, 13 C NMR spectra, differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy. Hydroxyapatite (HA) polyelectrolyte complexes (PEC) were prepared by in situ addition of HA to the poly- merization medium under optimal reaction conditions. Complexes were prepared using different ratios of HA with respect to CS-g-PAGA graft copolymers. The synthesized PECs were evaluated in swelling studies in phosphate-buffered saline. A mechanism for the free radical grafting and HA complexation were proposed. Ó 2008 Elsevier Ltd. All rights reserved. Keywords: Chitosan; Acrylamidoglycolic acid; Hydroxyapatite; Graft copolymers; Polyelectrolyte complex; Radical polymerization 1. Introduction Graft copolymerization of vinyl monomers onto chitosan (CS) and other natural polymers using free radical initiation has attracted the interest of many scientists over the last two decades. This technique enables the production of new polymer materials with desired properties. 1(4) 2-Amino-2-deoxy-D- glucan (CS) is a polyaminosaccharide of an acid-sol- uble deacetylated derivative of chitin, and it is obtained from N-deacetylation of chitin using a strong alkali [1]. The polysaccharide chitin occurs naturally in the shells of crustacea and insects, and in bacterial cell walls. Chitosan and chitin have a wide range of applications in biomedicine, pharma- cology, agriculture, and as flocculants [2]. Graft polymers have been synthesized to improve physicochemical properties of synthetic/natural polymers for applications in agriculture, biomedi- cine, and other fields. Natural polymers are preferred over synthetic ones for biomedical applications. Var- ious techniques have been used for grafting, includ- ing chemical initiators, c-radiation, and microwave 1381-5148/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.reactfunctpolym.2008.02.002 * Corresponding authors. Tel.: +82 51 510 2407; fax: +82 51 514 4331. E-mail addresses: idchung@pusan.ac.kr (I. Chung), csha@ pusan.ac.kr (C.-S. Ha). Available online at www.sciencedirect.com Reactive & Functional Polymers 68 (2008) 943–953 www.elsevier.com/locate/react REACTIVE & FUNCTIONAL POLYMERS