Synthesis and characterization of thermosensitive hydrogel with improved mechanical properties
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Chenyu Wu College of Materials Science and Engineering, Chongqing University, Chongqing 400044, People’s Republic of China
Xuejiao Sun, Fengjun Jia, and Yueqin Yua) State Key Laboratory Base of Eco-chemical Engineering, College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042, People’s Republic of China (Received 2 May 2015; accepted 22 July 2015)
Semi-interpenetrating polymer network (semi-IPN) and fully interpenetrating polymer network (full-IPN) hydrogels composed of sodium alginate (SA) and N-isopropylacrylamide (NIPAAm) were prepared with Ca21 and N,N9-methylenebisacrylamide (BIS) as the cross-linkers, respectively. The influence of the SA content and crosslinking degree of alginate on thermosensitive, swelling, mechanical, morphological, and thermal properties was investigated in detail. The hydrogels obtained exhibited obvious thermosensitivity and rapid swelling rate. The presence of Ca21 contributed to the improvement of mechanical properties obviously, without altering the thermosensitivity and network porosity of the hydrogels significantly. The compressive strength of full-IPN hydrogel was improved considerably, while the tensile strength was increased by 308.5% than semi-IPN hydrogel. The Tg of full-IPN dried hydrogel ran up to 142.9 °C with respect to 97.3 °C of pure PNIPAAm, and the improvement indicated that hydrogel with more compact structure was prepared.
Contributing Editor: Linda S. Schadler a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2015.233
temperature above the LCST.3 This hydrophilic–hydrophobic transition has been widely studied. In spite of the unique behavior, the poor mechanical property, biocompatibility, and biodegradability of PNIPAAm hydrogel are the main limitation for its biomedical application. In our previous work,10–12 we dedicated to solving these problems effectively by adding biocompatible and biodegradable materials in hydrogels. In the past decade, they developed various biodegradable materials as cross-linkers applied in synthesis of hydrogels, which gave rise to the improvement of the biocompatibility and biodegradability of hydrogel obviously. The purpose of this study was to solve another limitation-developing the mechanical property of the hydrogel by means of the preparation of interpenetrating networks (IPN), while keeping its thermosensitivity and biocompatibility. In this article, sodium alginate (SA) was incorporated into the PNIPAAm backbone to keep the biocompatibility and biodegradability of the hydrogel. SA is a biocompatible, natural polymer with pH-sensitive gel-forming ability. It has been used as a matrix for the entrapment and delivery of drugs, which benefits its dissolution and biodegradation under normal physiological conditions.7 Carboxylic acid groups of the alginate play an important role of ionic interaction with divalent ions such as Ca21, Ba21 leading to a three-dimensional network.13 In this
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Ó Materials Research Society 2015
I. INTRODUCTION
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