Fabrication and characterization of novel macroporous cellulose–alginate hydrogels Chunyu Chang, Bo Duan, Lina Zhang * Department of Chemistry, Wuhan University, Wuhan 430072, China article info Article history: Received 10 March 2009 Received in revised form 26 May 2009 Accepted 1 June 2009 Available online 6 June 2009 Keywords: Macroporous hydrogel Natural polymer Chemical cross-linking abstract Novel macroporous hydrogels were prepared by blending of cellulose and sodium alginate (SA) solution, and then cross-linking with epichlorohydrin. The resulting cellulose/SA hydrogels were characterized by solid-state 13 C NMR, wide-angle X-ray diffraction (WXRD), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), rheological measurement, dynamic mechanical analysis (DMA) and swelling test to evaluate their structure, interior morphology, gelation time, compressive modulus, and equilib- rium swelling ratio. Our findings revealed that the cellulose acted as backbone in the hydrogels, whereas SA contributed to the higher equilibrium swelling ratio. The combination of cellulose having semi-stiff chains and SA containing –COOH groups in the cross-linking hydrogel created the macroporous struc- ture. This work provided a new pathway for preparation of hydrogel with large porous structure through incorporation of stiff polymer as support of pore wall and acidic polysaccharide as expander of pore size because of high water-absorbency. Ó 2009 Published by Elsevier Ltd. 1. Introduction Hydrogels, attractive soft materials, have become the focus of intense activity due to the applications in the fields of food, phar- maceuticals, agriculture, personal care products, and electronics [1]. Especially, biodegradable hydrogels have potential applications as implantable carriers for drug delivery systems because of the high responsiveness to the stimulus and good biocompatibility [2,3]. Furthermore, the biodegradable hydrogels have been already proved to be safe in many medical applications [4]. Recently, several avail- able works dealing with the preparation of biodegradable hydrogels based on both biodegradable synthetic polymers such as poly(vinyl alcohol) [5] and poly(ethylene glycol) [6], and natural polymers such as chitosan [7,8] have been reported. Moreover, the biodegradable hydrogels have been prepared from synthetic polymers and natural polymers through semi-IPN strategy [9–11]. Exciting researches have been carried out on the materials derived from natural resource [12], and the presence of polysaccharides can induce the biocom- patibility, biodegradability and non-toxicity of these materials [13]. Cellulose is the most abundant natural polymer on earth [14], which is an almost inexhaustible source of raw material for the increasing demand for environmentally friendly and biocompatible products [15–17]. Therefore, cellulose based materials have become one of the most important bioresource materials in the 21st century. In our laboratory, cellulose solution has been prepared from NaOH/urea aqueous systems [18,19], and was used to fabricate cellulose membranes [18], novel fibers [20], films [21], and gels [22,23]. From the results of these works, we have discovered that cellulose can exhibit better mechanical properties than traditional water-soluble natural polymer in hydrogel matrix [24]. Sodium alginate (SA) is an acidic polysaccharide, composed of linear block copolymer of 1–4 linked b-D-mannuronic acid and a-L-guluronic acid. When metallic divalent cations such as Ca 2þ are added into SA solution, it is readily transformed into a hydrogel [25]. Many materials based on alginate have been reported through blending [26], grafting [27] and cross-linking [28]. However, studies on hydrogels prepared from cellulose and SA in NaOH/urea aqueous systems have been never published. It is well known that sodium alginate is a more hydrophilic polysaccharide than cellulose. Furthermore, cellulose exists as a wormlike chain in the NaOH/urea aqueous solution, suggesting character of stiffness. Therefore, we attempted to fabricate novel biodegradable hydrogel from cellulose as the backbone and SA as pore size expander. In this article, cellulose and SA were dissolved in NaOH/urea aqueous solution to construct macroporous hydro- gels through chemical cross-linking. To clarify the different roles of cellulose and SA, the hydrogels were fabricated from a mixture of both the solutions with different feed ratios. The structure and morphology of the hydrogels were characterized by solid-state 13 C NMR, wide-angle X-ray diffraction (WXRD), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), and dynamic * Corresponding author. Tel.: þ86 27 87219274; fax: þ86 27 68754067. E-mail address: lnzhang@public.wh.hb.cn (L. Zhang). Contents lists available at ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer 0032-3861/$ – see front matter Ó 2009 Published by Elsevier Ltd. doi:10.1016/j.polymer.2009.06.001 Polymer 50 (2009) 5467–5473