|Yam, Kit Leith|
Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2009
Publication Date: 2/24/2009
Citation: Liang, S., Liu, L.S., Huang, Q., Yam, K.L. 2009. Preparation of single or double-network chitosan/poly(vinyl alcohol) gel films through selective cross-linking method. Carbohydrate Polymers. 77:718-724. Interpretive Summary: Multilayered membranes are promising in food packaging, because the membranes can be used in the controlled release of bioactive substances (BAS), and thus better regulate the interactions between their contents and the environment. Consequently, the membranes can better maintain food quality and reduce food loss due to long-term storage or environmental variations. The development of the matrix layer, the BAS carrier, is the key step in the creation of multilayered membranes, and has been a challenge in the design and synthesis of food packaging materials. Chitosan/poly(vinyl alcohol) (CPVA) films can serve as an ideal BAS carrier and can be easily sandwiched with films of pectin, or cellulose, or pectin and poly(lactic acid) composites via interfacial adhesion. This paper studies the effect of different cross-linking methods on the structures of single or double network CPVA matrices, by which BAS release profiles can be tailored to fit with the nature of foods and their storage conditions. The study is not only useful for food applications, but also explores the non-food uses for pectin and other agricultural products, and eventually will benefit US agribusiness.
Technical Abstract: A selective cross-linking method was developed to create single or double network chitosan/poly(vinyl alcohol) gel films. The cross-linking is based on the hydrogen bonding between PVA and borate and the strong electrostatic interaction between chitosan and tripolyphosphate. The resultant gel films were characterized for water vapor permeation rate (WVTR), mechanical properties, and surface morphology. The polymeric molecular interactions were studied by atomic force microscopy and ATR-FTIR spectroscopy. With the introduction of cross-linking structure, there is a large improvement in elastic modulus from 271 plus or minut 14.2 MPa to 551 plus or minus 14.7 MPa and a large decrease in WVTR from (5.41 plus or minus 0.21) ×10-7 g/mhPa to (3.12 plus or minus 0.24) ×10-7 g/mhPa of the chitosan/poly(vinyl alcohol) films. ATR-FTIR results indicate that strong interactions between the polymeric matrices and cross-linkers exist. The surface morphology of the cross-linked films exhibits a nanoparticle aggregation structure. The size and aggregation behavior of these nanoparticles are strongly dependant on the type of cross-linkers. This work provides a simple and fast way to prepare chitosan/PVA films with a controlled network structure.