Poly (1,4-dioxan-2-one)/montmorillonite Nanocomposites: Preparation, Structures And Properties

In recent years, polymer-clay nanocomposites have attracted great interests from scientists since they frequently exhibit unexpected hybrid properties synergistically derived from the two components. In most cases, the new and improved properties are derived when the dimensions of dispersion clay are ca. 1nm and many techniques have been attempted for the ultrafine dispersion of clay into the polymer matrix. This is due, in great part, to the recent developments of new functionalization of smectic clays, especially Na-montmorillonite (MMT-Na). Montmrillonite (MMT), a smectic clay, is the hydrous alumina silicate mineral, which lamellae is constructed from two silica tetrahedral sheet fused to an edge-shared octahedral silica sheet of either aluminum or magnesium hydroxide, and exhibits a net negative charge on the lamellar surface and causes then to attach by sorbed cations (Na+ or Ca2+). In that case, the interlayer is incorporated with sodium cation, and the hydrophilic properties must be enhanced which in turn leads to high degree of water swelling. Therefore, these phenomena can possibly provide an effective method for the preparation of hybrid composite intercalated with polymer in the layered silicate if an aqueous system is involved in the intercalation procedure. According, in previous research work, many polymer-montmorillonite nanocomposites have been successfully synthesized by intercalation process. In this paper, we prepared PPDO/MMT nanocomposites by in situ ring-opening polymerization of p-dioxanone (PDO) and three types of montmorillonites (MMT-Na, MMT-1831 and MMT-OH) in the presence of triethylaluminum. The influence of montmorillonite on the polymerization rate of PDO was researched, and the structure and properties of PPDO/MMT nanocomposites have been researched by XRD, DSC, TGA and POM, and the mechanical properties, biodegradable properties and rheology properties were also be tested . The conclusion may be presented as follows: PPDO nanocomposites have been prepared by polymerization of p-dioxanone initiated by triethylaluminum in the presence of MMT-Na, MMT-1831 and MMT-OH. Intercalated structures are formed in the three samples as assessed by XRD analysis. It was found that the reaction rate increased with the addition of MMT into the polymerization system, and a viscosity-average molecular weight of 44,900 can be reached in half an hour. From the DSC and POM, all three montmorillonites can increase the crystallization temperatures, melting temperature and the glass transition temperature, especially the crystallization temperatures was increased from 40.6°C to 58.4°C. The crystallization rate of PPDO/MMT nanocomposites are faster than the neat PPDO. According to the graph of TGA, all the PPDO/montmorillonite nanocomposites are degraded at higher temperature than the bulk polymer, the onset temperature of degradation were increased by around 13-15°C. Compared with the neat PPDO, the biodegradable properties, mechanical properties and rheology properties of PPDO/MMT nanocomposites were improved greatly. We also prepared successfully the film of PPDO/MMT nanocomposites.