Carbohydrate Polymers 92 (2013) 23–32 Contents lists available at SciVerse ScienceDirect Carbohydrate Polymers jo u rn al hom epa ge: www.elsevier.com/locate/carbpol Multiresponsive macroporous semi-IPN composite hydrogels based on native or anionically modified potato starch Ecaterina Stela Dragan ∗ , Diana Felicia Apopei “Petru Poni” Institute of Macromolecular Chemistry, Aleea Grigore Ghica Voda 41 A, RO-700487 Iasi, Romania a r t i c l e i n f o Article history: Received 30 May 2012 Received in revised form 22 August 2012 Accepted 23 August 2012 Available online 30 August 2012 Keywords: Composites Hydrogels Interpenetrating network (IPN) Macroporous polymers Potato starch a b s t r a c t Macroporous semi-interpenetrating polymer networks (semi-IPN) composite hydrogels were synthe- sized by cross-linking polymerization of acrylamide (AAm) with N,N’-methylenebisacrylamide (BAAm) in the presence of potato starch (PS) or an anionic polyelectrolyte derived from PS (PA), below the freez- ing point of the reaction solution (-18 ◦ C). The composite cryogels have been further modified by the partial hydrolysis of the amide groups in poly(acrylamide) (PAAm) matrix, under alkaline conditions. The influence of the entrapped polymer on the properties of the composite gels, both before and after the hydrolysis, has been evaluated by the swelling kinetics, FT-IR spectroscopy, scanning electron microscopy, and external stimuli responsiveness. The potential of the anionic composite cryogels as intelligent hydro- gels has been evaluated by the investigation of the deswelling/reswelling kinetics as a function of solvent nature, ionic strength, and environment pH. Cryogels with fast responsivity at variation of the external stimuli, which withstood repeated deswelling/reswelling cycles, have been obtained at a low cross-linker ratio (one mole BAAm for 80 moles of AAm) and a monomer concentration around 3 wt%. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction Considerable interest has been focused last years on the ionic macroporous hydrogels due to the numerous applications in con- trolled delivery of drugs and proteins and separation processes of small ionic species (Baggiani, Baravalle, Giovanolli, Anfossi, & Giraudi, 2010; Dragan, Cazacu, & Nistor, 2009; Hajizadeh, Kirsebom, Galaev, & Mattiasson, 2010; Liu et al., 2011; Tekin, Uzun, S ¸ ahin, Bektas ¸ , & Denizli, 2011). For the preparation of such materials, some strategies have been widely used: cross-linking polymerization in the presence of a pore-forming agent (Wu, Hoffman, & Yager, 1992), porogen leaching (Pradny et al., 2003; Serizawa, Wakita, Kaneko, & Akashi, 2002), cross-linking in the presence of substances releasing porogen gases (Behravesh, Jo, Zygourakis, & Mikos, 2002; Kim & Park, 2004), lyophilization of the hydrogel swollen in water (Dragan et al., 2009; Kang, Tabata, & Ikada, 1999), and cryogelation (Burova et al., 2011; Kirsebom, Topggard, Galaev, & Yu Mattiasson, 2010; Lozinsky, Plieva, Galaev, & Mattiasson, 2001; Orakdogen, Karacan, & Okay, 2011; Ozmen, Dinu, Dragan, & Okay, 2007; Savina et al., 2011; Zhao, Sun, Lin, & Zhou, 2010; Zhao, Sun, Wu, & Lin, 2011). By cryogelation, the cross-linking polymerization reactions are conducted below the freezing point of the reaction solutions, when the most part of the solvent (water, in the case of hydrogels) forms crystals, the bound ∗ Corresponding author. E-mail address: sdragan@icmpp.ro (E.S. Dragan). water and the soluble substances (monomers, initiator, polymers) being concentrated in a non-frozen liquid microphase, where the gel is formed. Starting with Lozinsky et al. (Burova et al., 2011; Lozinsky et al., 2001), numerous research groups such as Galaev et al. (Kirsebom et al., 2010; Savina, Mattiasson, & Galaev, 2005; Savina et al., 2011), Okay et al. (Bilici, Karayel, Demir, & Okay, 2010; Orakdogen et al., 2011; Ozmen et al., 2007), Zhao et al. (Zhao et al., 2010, 2011) contributed to the fast development of this type of hydrogels. It is already established that, by their inter- connected pore structure, cryogels allow the unhindered diffusion of solutes or even colloidal particles, making them very attrac- tive in biomedicine and biotechnology including chromatographic materials, carriers for the immobilization of molecules and cells, matrices for cell separations, and cell culture (Baydemir et al., 2009; Burova et al., 2011; Dispinar, Van Camp, De Cock, De Geest, & Du Prez, 2012; Jain, Karande, & Kumar, 2011; Kathuria, Tripathi, Kar, & Kumar, 2009; Lozinsky et al., 2001; Savina et al., 2007). The mechanical properties and the diffusion of solutes in hydrogels can be further modulated by the preparation of multicomponent networks like semi-interpenetrating polymer networks (semi-IPN) or full-IPN. The biocompatibility and biodegradability of these multicomponent composite gels can be improved with biopoly- mers like polysaccharides, as components of the gel architecture (Baggiani et al., 2010; Jain et al., 2011; Kathuria et al., 2009; Liang, Liu, Huang, & Yam, 2009; Orakdogen et al., 2011; Van Vlierberghe, Dubruel, & Schacht, 2011). Lately, much attention has been given to anionic multi- component systems, these materials being appropriate for the 0144-8617/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.carbpol.2012.08.082