Behavior of Hydrogel Microparticles Based on Acrylamide and 2-HEMA Obtained By Inverse Emulsion
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Behavior of Hydrogel Microparticles Based on Acrylamide and 2-HEMA Obtained By Inverse Emulsion Raymundo Sanchez-Orozco1, Salomon R. Vasquez-Garcia2, Nelly Flores-Ramirez3 and Lada Domratcheva3 1 Universidad Politecnica de Atlacomulco, Estado de México 50450, Mexico 2 Faculty of Chemical Engineering, Universidad Michoacana de San Nicolas de Hidalgo (UMSNH), Morelia 58030, Mexico 3 Faculty of Wood Engineering and Technology, UMSNH, Morelia 58030, Mexico ABSTRACT Poly(acrylamide-co-2-hydroxyethyl methacrylate), hydrogel microparticles were prepared by free radical copolymerization of acrylamide (AAm) and 2-hydroxyethyl methacrylate (2-HEMA) using an inverse emulsion polymerization technique, employing ethylene glycol dimethylacrylate (EGDMA) as crosslinker in the presence of w/o emulsifiers span-80 and span-85 (sorbitol mono-oleate) above the lower critical solution temperature. Water absorption capacity and characteristics of the hydrogel microparticles were analyzed by Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). Thus, microparticles were submitted to a gravimetric study on their ability to absorb and to retain distilled water at 25°C. One gram of microparticles absorbed at least 15 g of water. By varying the relative ratio between the continuous phase (hexane and emulsifiers) and the dispersed phase (monomers, initiator and crosslinker), non-agglomerated dispersed particles with nearly spherical shape were obtained having a narrow size distribution in the range from 10 to 20 μm. At a constant value of the emulsifier, and as a result of increasing the stirring rate, a particle size reduction was observed from 13 to 7 μm. The PAAm and PHEMA structures of synthesized hydrogel were confirmed using FTIR analysis. Additionally, through thermal analysis the P(AAm-HEMA) hydrogel showed an increase of water retention and thermal stability due to PAAm addition. INTRODUCTION Hydrogels are water swollen polymer, which has been used in medical applications, waste water purification, bioengineering, biotechnology, agriculture, food industry, photographic technology and other fields. The hydrophilicity of hydrogels is due to the presence of polar groups [1]. Acrylamide (AAm) and 2-hydroxyethyl methacrylate (HEMA) have these groups and both can be polymerized to form hydrogels of P(AAm-HEMA) which are biocompatible and nontoxic hydrogel for living organisms. PAAm and its derivatives are the most preferred polymers to obtain hydrogels, mainly to recover waste oil [2-4]. In the other hand, PHEMA has been widely used for several applications including controlled release of biomacromolecular therapeutics [5]. This polymer that is inert to normal biological processes shows resistance to degradation and is not absorbed by the body. Typical swelling properties of P(AAm-HEMA)
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hydrogels are dependent upon their preparation methods such as polymer volume fraction, degree of crosslinking, temperature and swelling agent [6,7]. However, s
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