Synthesis and characterization of bead-like particles based on chitosan and vinyl polymers
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ORIGINAL PAPER
Synthesis and characterization of bead-like particles based on chitosan and vinyl polymers N. Preda & M. Enculescu
Received: 9 May 2012 / Accepted: 13 August 2012 / Published online: 24 August 2012 # Springer Science+Business Media B.V. 2012
Abstract Styrene, methyl methacrylate and glycidyl methacrylate vinyl monomers were grafted onto chitosan by surfactant-free emulsion copolymerization using potassium persulfate as initiator. The grafted compounds were characterized by X-ray diffraction, FTIR spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and zeta potential measurements. X-ray diffraction showed changes in the crystallinity pattern of chitosan after the copolymerization reaction. Evidence of grafting was confirmed by FTIR spectroscopy. From zeta potential measurements it is found that the surfaces of graft copolymers latex particles have positive charges resulting from the cationic chitosan molecules. The morphology evaluated by SEM, TEM and AFM proves that in the absence of chitosan, latexes of vinyl homopolymers contain quasi-monodispersed spheres with average diameter of about 400 nm or 250 nm while the graft copolymers latexes are formed by clustered irregular beads with average diameter around 100 nm. Keywords Chitosan . Surfactant-free emulsion copolymerization . Graft vinyl copolymers . FTIR spectroscopy . Scanning electron microscopy
Introduction Chitosan is a linear polysaccharide derived from chitin, the second most abundant organic compound next to cellulose in the nature. Chitin can be found in the shells of marine invertebrates (crabs, crustaceans, etc.), fungi, insects and yeasts. N. Preda (*) : M. Enculescu National Institute of Materials Physics, Magurele Bucharest, P.O. Box MG-7, 077125, Romania e-mail: [email protected]
Depending on the source, it generally functions as an exoskeleton, providing structural integrity, commonly embedded in a matrix of proteins, minerals and at times various other polysaccharides. Chitin is a homopolymer comprised of 2acetamido-2-deoxy-β-D-glucopyranose units; however, some units exist in the deacetylated form as 2-amino-2-deoxy-β-Dglucopyranose. When chitin is deacetylated to at least 50 %, it is referred to as chitosan, in other words this is essentially the N-deacetylated derivative of chitin. Chitosan has many interesting biological and chemical properties. The excellent features such as biocompatibility, ecologically safe biodegradability (degradation products of chitosan are non-toxic, non-immunogenic and noncarcinogenic) and low toxicity with versatile biological activities (chitosan has antimicrobial activity and low immunogenicity) recommends this biopolymer for applications in biomedicine [1–5]. In addition, chitosan is very efficient for interaction with the anionic solutes including dyes in acidic solutions due to the reactive groups, such as –OH and –NH2. This property has been widely used for the removal of the water-soluble dyes, as an alternative to the conve
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