Synthesis and Viscoelastic Properties of Smart Hydrogel
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OLYMER GELS
Synthesis and Viscoelastic Properties of Smart Hydrogel H. Hosseinia,b,* and B. Shirkavand Hadavandc a
b
Department of Chemical Engineering, Abadan Branch, Islamic Azad University, Abadan, Iran Laboratory of Polymer Chemistry, Faculty of Chemistry, University of Helsinki, Helsinki, Finland c Department of Resin and Additives, Institute for Color Science and Technology, Tehran, Iran *e-mail: [email protected] Received December 11, 2019; revised February 14, 2020; accepted March 27, 2020
Abstract—Here we report the synthesis and viscoelastic properties of smart hydrogels based on N-isopropylacrylamide, cationic (3-acrylamidopropyl)trimethylammonium chloride and nanoclay. Hydrogels were prepared by aqueous free radical polymerization. The effect of some salts, N,N '-methylenebisacrylamide, (3-acrylamidopropyl)trimethylammonium chloride and nanoclay content on the viscoelastic properties was studied. Also volume phase transition temperature and thermal behavior of the prepared hydrogels were investigated. Synthetic nanoclay and anionic groups of the bind to the cationic co-monomer units and significantly affected the viscoelasticity and thermal properties of the hydrogels. DSC measurements showed that the volume phase transition temperature of hydrogels depended on nanoclay content. By introducing of co-monomer, 250 mM solution of NaCl 15 mM bis(trif luoromethane)sulfonimide lithium salt (LiNTF2) and laponite nanoclay, a 10, 4, and 3.8 fold increase in elastic module was obtained, respectively, compared to that of the homopolymer PNIPAM hydrogel. With a temperature change from 20 to 45°C for the homopolymer PNIPAM hydrogel in 15 mM LiNTF2, the elastic module grew 5 times larger. DOI: 10.1134/S1560090420040053
INTRODUCTION Hydrogels are network polymers that with absorbing water or biofluids are swelled, which then gain high flexibility [1]. Hydrogels have been used for agricultural and horticultural purposes for many years, but due to their other properties gradually they have found other uses [2, 3]. These materials exist in nature (gelatin and agar) or are prepared synthetically [4]. Depending on the structure of the hydrogels, these materials are sensitive to physical (temperature, pressure, light, and electric field), chemical (pH, glucose and oxidants) and biochemical (antigen, enzyme) factors [5]. These properties of hydrogels have made them widely used in medical, pharmacology, agricultural, sensors, elimination of environmental pollutants and for many other applications [5]. Synthesis of hydrogels is usually done using hydrophilic monomers having carbon-carbon double bonds by radical polymerization. In the manufacture of hydrogels, cross-links are also formed with an appropriate amount of cross-linking agent. Another method of preparing hydrogels is to modify polymers by grafting or functionalizing them with hydrophilic portions [6, 7]. Hydrogels are cross-linked physically and chemically. Physical cross-linkage may occur by hydrogen bonds, from amphiphilic graft and block
polymers, by cryst
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