A. Babul Reddy

5-Fluorouracil Loaded Chitosan–PVA/Na+MMT Nanocomposite Films for Drug Release and Antimicrobial Activity

In the present study, chitosan and polyvinyl alcohol (PVA) were blended with different concentrations of sodium montmorillonite (Na+MMT) clay solution by a solvent casting method. X-ray diffraction and transition electron microscope results show that the film properties are related to the co-existence of Na+MMT intercalation/exfoliation in the blend and the interaction between chitosan–PVA and Na+MMT. 5-Fluorouracil (5-FU) was loaded with chitosan–PVA/Na+MMT nanocomposite films for in vitro drug delivery study. The antimicrobial activity of the chitosan–PVA/Na+MMT films showed significant effect against Salmonella (Gram-negative) and Staphylococcus aureus (Gram-positive), whereas 5-FU encapsulated chitosan–PVA/Na+MMT bio-nanocomposite films did not show any inhibition against bacteria. Our results indicate that combination of a flexible and soft polymeric material with high drug loading ability of a hard inorganic porous material can produce improved control over degradation and drug release. It will be an economically viable method for preparation of advanced drug delivery vehicles and biodegradable implants or scaffolds.

RETRACTED: Influence of alkali metal cations on the thermal, mechanical and morphological properties of rectorite/chitosan bio-nanocomposite films

The main theme of this work is to study the influence of ion-exchangeable alkali metal cations, such as: Li(+), Na(+), K(+), and Cs(+) on the thermal, mechanical and morphological properties. In this regard, a set of rectorite/chitosan (REC-CS) bio-nanocomposite films (BNCFs) was prepared by facile reaction of chitosan with ion-exchanged REC clay. The microstructure and morphology of BNCFs were investigated with XRD, TEM, SEM and AFM. Thermal and tensile properties of BNCFs were also investigated. As revealed from TEM and XRD results, the BNCFs featured a mixed morphology. Some intercalated clay sheets, together with nano-sized clay tactoids were obtained in LiREC/CS, NaREC/CS and KREC/CS of the BNCFs. From fractured surface study, via SEM, it was observed that the dispersion of chitosan polymer attaches to (and covers) the clay platelets. FTIR confirmed strong hydrogen bonds between clay and chitosan polymer. In addition, the thermal stabilities significantly varied when alkali metal cations varied from Li(+) to Cs(+). The BNCFs featured high tensile strengths (up to 84 MPa) and tensile moduli (up to 45 GPa). After evaluating these properties of BNCFs, we came to conclusion that these bio-nano composites can be used for packaging applications.

Hydrophobic/Hydrophilic Nanostructured Polymer Blends

It is the objective of this chapter to review the hydrophobically modified water-soluble and other hydrophilic nanostructured polymer systems and their biocompatibility for potential use in biomedical applications. The nanostructured polymer systems reviewed include block copolymers, amphilic copolymers, nanostructured polymer blends, and networks that exhibit hydrophilic/hydrophobic micro-/nanophase domain structures. Enhanced biocompatibility and mechanical strength appear to be a general characteristic of such systems as compared to single phase hydrophilic polymers. Fabrication of solid surfaces in terms of chemical affinity including hydrophilicity is a technology of importance in the development of various devices and functional materials. In particular, super-hydrophobic/super-hydrophilic patterning is crucial because it is applicable to the control of liquid flow and the immobilization of functional materials into specific areas. The ability to create superhydrophilic-superhydrophobic micro patterns and arrays on nanostructured polymer blends is essential for a variety of applications ranging from micro fluidics to cell microarrays. Despite a lot of research done on the development of new superhydrophobic and superhydrophilic surfaces on nanostructured polymer blend films, creating precise, and stable micro patterns of superhydrophilic and superhydrophobic areas has proved challenging. To the best of our knowledge, most of the existing methods are based on the surface modification of a rough superhydrophobic and or superhydrophilic substrate through a mask to reverse hydrophobicity of the exposed areas.

A potential utilization of end-of-life tyres as recycled carbon black in EPDM rubber

End-of-life (EOL) tyres and their decomposition present severe environmental concern due to their resistance to moisture, oxygen, natural degradation, etc. Pyrolysis is considered to be the most effective and sustainable process for recycling, due to its eco-friendly process. The current work studied the effect of recycled carbon black (rCB), obtained from the pyrolysis of EOL tyres, on the properties of ethylene propylene diene rubber (EPDM). The rCB was characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and chemical methods. rCB was incorporated solely, into a conventional EPDM formulation and also in combination with N550 carbon black. The physico-mechanical properties of the EPDM vulcanizates, before and after aging, were succinctly studied by SEM, TGA, Differential Scanning Calorimetry (DSC), tensile tests and cross-link density. The average particle size of rCB was observed to be 8 µm and the ash content was observed to be higher when compared to the conventional N550 carbon black, which was evident, by the TGA and SEM-EDX analyses. The reinforcing effect and the cross-link density of the rCB-filled vulcanizates were found to be marginally inferior in comparison to the conventional carbon black (N550). The morphology of the tensile- and tear-fractured surfaces were studied by SEM and it was observed that the breaking mechanism follows the rubber chain detachment from the surface mode.

Nanostructured Polymer Blends for Gas/Vapor Barrier and Dielectric Applications

This chapter describes the gas barrier and dielectric properties of nanostructure polymer blends. More particularly, it relates to the incorporation of nanostructured fillers such as polyhedral oligomeric silsesquioxane (POSS) and layered silicate clays in a polymer matrix. The resulting nanostructured polymers show improved gas barrier and dielectric properties. Such properties are useful in the production of lightweight transportation bodies in the automotive industry, high-performance in the packaging industry. The dispersion of nanoparticles into a fully intercalated state is dependent on the properties of the nanoparticles and the polymer matrix. The properties of ethylene-vinyl acetate (EVA) and polyamides, nanostructured blends of EVA, nanostructured polyamide blends and POSS-blended nanostructured polymer are discussed in detail.

Thermoplastic-Thermoset Nanostructured Polymer Blends

Polymer blends are presently attracting both scientific and industrial interest because of their potentials as economical alternatives to more expensive engineering polymers and non-polymeric materials. More importantly, nanostructure polymer blends could lead to the design and production of low-cost materials with valuable properties in comparison to conventional polymer blends. However, thermoplastics/thermosets blends are problematic because such blends naturally tend to phase separation on the macroscopic scale. Therefore, controlling the phase behavior and morphology by reducing phase size and improving interfacial adhesion become key factors in converting these immiscible blends into useful polymeric products. This can be achieved by adding some copolymers as compatibilizers. Also, addition of nanoparticles can reduce interfacial tension and improve miscibility between polymers and thus have significant effect on phase behavior of polymer blends. Some of the methods of blending are melt extrusion, higher shear processing, physical blending, and reactive blending.

Chapter 5 – Aerogels and Foamed Nanostructured Polymer Blends

Foamed polymer blend systems play a significant role in designing cellular materials. The foaming process also plays a crucial role in cellular properties. This chapter deals with the recent developments in the synthesis of foamed nanostructure and aerogel polymer blends. The combination of functional fillers and supercritical fluid foaming technology has great potential for the generation of a new class of materials that are lightweight, high strength, and multi-functional. This is followed by an extensive discussion regarding the role of nanoparticles in foam morphology and properties. The properties of these polymers depend, mostly, on the foaming process, gas used for dispersion (foaming), aerogels, and the nanofillers used for blending. This chapter also reviews the various foaming techniques that are used for developing a foamed polymer blend. We conclude with the current and future trends for foamed polymer blends in both industrial and biomedical applications.