Physical, Mechanical, and Antibacterial Properties of Chitosan/ PEO Blend Films Svetlana Zivanovic,* ,† Jiajie Li, † P. Michael Davidson, † and Kevin Kit ‡ Food Biopolymers Research Group, Department of Food Science and Technology, University of Tennessee, 2509 River Drive, Knoxville, Tennessee 37996, and Department of Material Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996 Received December 1, 2006; Revised Manuscript Received February 13, 2007 Films formed by blending of two polymers usually have modified physical and mechanical properties compared to films made of the individual components. Our preliminary studies indicated that incorporation of chitosan in polyethylene oxide (PEO) films may provide additional functionality to the PEO films and may decrease their tendency to spherulitic crystallization. The objective of this study was to determine the correlation between chitosan/ PEO weight ratio and the physical, mechanical, and antibacterial properties of corresponding films. Films with chitosan/PEO weight ratios from 100/0 to 50/50 in 10% increments were characterized by measuring thickness, puncture strength (PS), tensile strength (TS), elongation at break (%E), water vapor permeability (WVP), and water solubility (WS). Additionally, the films were examined by polarized microscopy, wide-angle X-ray diffraction (WAXD), and Fourier transform infrared (FTIR) spectroscopy, and their antibacterial properties were tested against Escherichia coli. The chitosan fraction contributes to antimicrobial effect of the films, decreases tendency to spherulitic crystallization of PEO, and enhances puncture and tensile strength of the films, while addition of the PEO results in thinner films with lower water vapor permeability. Films with 90/10 blend ratio of chitosan/PEO showed the most satisfactory PS, TS, %E, and antibacterial properties of all tested ratios. 1. Introduction There has been a growing interest over the past few years in the development of biopolymers partly because of their renew- able, sustainable, and biodegradable properties. As one of the candidates for such biopolymers, chitosan has attracted much attention mainly because of its antimicrobial and metal-binding properties. Chitosan is a cationic biopolymer obtained by a full or partial N-deacetylation of chitin, which is known to be the second most abundant biopolymer in nature and is the major component of the exoskeleton of crustaceans. 1 Chitosan may be regarded as a binary heteropolysaccharide containing (1- 4) linked 2-acetamido-2-deoxy--D-glucopyranose and 2-amino- 2-deoxy--d-glucopyranose residues. 2 Chitosan has been evalu- ated for various uses in the food, medical, pharmaceutical, agricultural, and chemical industries because of its nontoxic, biocompatible, mucoadhesive, and biodegradable properties. 2-4 Dissolved chitosan has antimicrobial and metal-binding proper- ties and has been used as an antimicrobial additive to bind metals from food-processing wastewaters. 5-7 In addition, because of its free amino groups, chitosan can be dissolved in acidic aqueous solutions and form gels, films, sutures, beads, and fibers. 2 Polyethylene oxide (PEO) is a synthetic uncharged polymer with a molecular formula (-CH 2 CH 2 O-) n . It is low-toxic, semicrystalline, bioadhesive, and mucoadhesive because of its water solubility, hydrophilicity, high viscosity, ability to form hydrogen bonds, and biocompatibility with other bioactive substance. PEO has been widely used in a variety of dosage forms in the pharmaceutical industry such as for the production of hot-melt extruded capsules. However, since PEO is a flexible- chain polymer, pure PEO films have relatively poor mechanical and physical characteristics and high water solubility which limit their application. A convenient and effective method to improve PEO film properties is blending PEO with other polymers. The films formed by blending two or more polymers usually result in modified physical and mechanical properties compared to films made of the individual components. It has been reported that starch-chitosan blend films exhibited a higher flexibility and improved the percentage elongation than films produced from single polymers. 8 The blend of chitosan and quaternized poly- (4-vinyl-N-butyl)pyridine showed stronger tensile strength and breaking elongation than films of pure chitosan. 9 Chitosan/PEO blend films may provide additional functional- ity compared to the pure polymer films. Chitosan may improve mechanical properties and decreased water solubility of the PEO films, while PEO may contribute to the formation of colorless films that are more flexible. Our preliminary data showed that films with chitosan content of more than 50% decreased the PEO tendency to spherulitic crystallization. Therefore, the objective of this research was to evaluate the physical, mechan- ical, and antibacterial properties of films composed of blends of low molecular weight chitosan and high molecular weight PEO. 2. Materials and Methods Materials. Chitosan of low molecular weight (∼150 kDa) with a degree of deacetylation above 85% and PEO of high molecular weight (∼900 kDa) were purchased from Aldrich Chemical Co. (Milwaukee, WI). Film Preparation. Mixtures of chitosan and PEO with different weight ratios (100/0, 90/10, 80/20, 70/30, 60/40, 50/50) were dissolved in 1% w/w acetic acid and were stirred overnight at room temperature. * To whom correspondence should be addressed. Tel.: 865-974-0844; fax: 865-974-7332; e-mail: lanaz@utk.edu. † Department of Food Science and Technology. ‡ Department of Material Science and Engineering. 1505 Biomacromolecules 2007, 8, 1505-1510 10.1021/bm061140p CCC: $37.00 © 2007 American Chemical Society Published on Web 03/28/2007