Submitted to: Macromolecular Chemistry and Physics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/10/2009
Publication Date: 5/22/2009
Citation: Liang, S., Liu, L.S., Huang, Q., Yam, K.L. 2009. Microstructure and molecular interaction in glycerol plasticized chitosan/poly(vinyl alcohol) blending films. Macromolecular Chemistry and Physics. 210:(10):832-839. Interpretive Summary: The packaging material and technology market is several hundred billion dollars and growing at an annual rate of 4%. Various pectin based membranes and films have been developed in our laboratory for food packaging and wrapping. Multilayered membranes from pectin and other polymeric materials are under intensive study, because such membranes can play multiple functions simultaneously; therefore, can better protect foods from environmental factors, and thus prolong the shelf life, retain quality, and enhance the value of foods. Chitosan nanostructures are considered an ideal counter part to form multi-layered membranes with pectin via electrostatic interactions. However, little knowledge on the structure-function relationship of chitosan composites has been obtained. The present study filled this gap by altering the characteristics of chitosan, and then, investigating the resultant composites, laminated on a pectin matrix. A clear view of the nanostructure of chitosan composites and know how to make them provides materials for various applications of pectin/chitosan multilayered membranes. Eventually, it will expand the utility of pectin and benefit U.S. agribusiness.
Technical Abstract: Poly (vinyl alcohol) (PVA)/chitosan (CS) blended films plasticized by glycerol were investigated using mechanical testing, atomic force microscopy (AFM), differential scanning calorimetry (DSC) and FTIR spectroscopy, with primary emphasis on the effects of the glycerol content and the molecular weight of chitosan on the film structure and properties. Our results showed that both glycerol content and chitosan molecular weight can effectively change the film appearance, mechanical strength and water vapor permeation. All of the films containing glycerol exhibited a largely improved mechanical toughness compared to that without glycerol. The optimum glycerol content for the highest elastic modulus and the largest elongation at break of the films were obtained. AFM results indicated that these films were basically composed of spherical nanoparticles, which exhibited a different aggregation behavior closely related to the glycerol content and chitosan molecular weight. The strong hydrogen bonding interaction between glycerol molecules and the polymer matrix detected by FTIR analysis was considered as the main driving force that determines the film structure, thereby affecting the mechanical, water permeation and optical transparent properties of the films. Furthermore, DSC results showed the addition of glycerol could result in a continuous shift and change in the Tg and Tm of the PVA and chitosan components, suggesting that glycerol can effectively improve the miscibility of the films through this hydrogen bonding interaction. Therefore, the formation of a new hydrogen bonding network (cluster) by introducing glycerol is of great importance in controlling the structure and improving the performance of these blended films.