Poly(ethylene terephthalate)/attapulgite nanocomposites: Preparation, structure, and properties

Multifunctional cationic polymer decorated and drug intercalated layered silicate (NLS) for early gastric cancer prevention

A multifunctional compound that can prevent early gastric cancer is produced by intercalating 3.20% and 1.64% of 5-FU into the interlayer of montmorillonite (MMT) and attapulgite (At), respectively. A low molecular weight cationic polymer, polyethylenimine (PEI1200), is incorporated into the surface of the 5-FU-MMT and 5-FU-At to form the multifunctional layered silicate (NLS). The chemical structure and surface morphology of the NLS are characterized and the model drug of 5-FU is intercalated into the MMT and At. The cell viability determined by the MTT assay on the BGC-823 cell lines show that over 80% of the cells are live under the experimental conditions. The PEI-5-FU-MMT and PEI-5-FU-At can carry the report gene to the BGC-823 and COS-7 cell lines efficiently. Western blotting assay shows that the pTrail protein of the BGC-823 cell lines treated with PEI-5-FU-MMT/pTrail and PEI-5-FU-At/pTrail is up-regulated, whereas the cFLIP protein is down-regulated at 48 h compared to free 5-FU, PEI1200, MMT, and At, providing evidence that the NLS can increase the sensitivity of pTrail gene and improve the effects of pTrail gene therapy. Moreover, the Helicobacter pylori (HP) bacteria are adsorbed and immobilized efficiently on the surface of the NLS according to the LIVE/DEAD(®) BacLight™ Bacterial Viability Kit in the confocal fluorescence analysis. The histochemical analyses provide evidence that NLS/pTrail can prevent early gastric mucosa effectively.

Foams based on poly(ethylene terephthalate) nanocomposites with enhanced thermal stability

Novel poly(ethylene terephthalate) nanocomposites have been developed, incorporating commercial bottle grade polyester and modified organoclay, which exhibit enhanced thermal and dynamic-mechanical properties and improved foaming behavior. A benefit arising from the use of an organoclay is that this class of material is generally able to withstand the high processing temperatures of engineering polymers, such as poly(ethylene terephthalate), and not undergo decomposition. This offers a great advantage over the use of organic modifiers, whose volatile by-products are known to promote thermal degradation of the polymer matrix under such conditions.

In this work, a novel organoclay was obtained via intercalation of bis-(hydroxyethyl terephthalate) in sodium montmorillonite layers and then used to prepare poly(ethylene terephthalate)-clay nanocomposites via melt compounding by using a twin-screw extruder. Thermogravimetric analysis indicated that the onset decomposition temperatures of poly(ethylene terephthalate) nanocomposites incorporating this organoclay were higher than those of controls based on commercial organoclays. However, the inclusion of this new nanofiller also led to a drastic decrease of melt viscosity, which in turn suppressed foaming. In order to compensate for the effects of the viscosity reduction, pyromellitic dianhydride was used in the reactive extrusion process of poly(ethylene terephthalate) nanocomposites. Rheological analysis showed a strong improvement in viscosity of these poly(ethylene terephthalate)/pyromellitic dianhydride/organoclay nanocomposites, to levels of the same order of magnitude as reference commercial foaming grade poly(ethylene terephthalate), or higher. Samples were foamed using carbon dioxide as physical blowing agent in a batch foaming process. Comparison of sample morphology, performed by scanning electron microscopic analysis, indicated very good results in some samples in terms of cellular morphology and foam density.