1. Introduction 20642. Synthesis of Magnetic Nanoparticles 20662.1. Classical Synthesis by Coprecipitation 20662.2. Reactions in Constrained Environments 20682.3. Hydrothermal and High-TemperatureReactions20692.4. Sol-Gel Reactions 20702.5. Polyol Methods 20712.6. Flow Injection Syntheses 20712.7. Electrochemical Methods 20712.8. Aerosol/Vapor Methods 20712.9. Sonolysis 20723. Stabilization of Magnetic Particles 20723.1. Monomeric Stabilizers 20723.1.1. Carboxylates 20733.1.2. Phosphates 20733.2. Inorganic Materials 20733.2.1. Silica 20733.2.2. Gold 20743.3. Polymer Stabilizers 20743.3.1. Dextran 20743.3.2. Polyethylene Glycol (PEG) 20753.3.3. Polyvinyl Alcohol (PVA) 20753.3.4. Alginate 20753.3.5. Chitosan 20753.3.6. Other Polymers 20753.4. Other Strategies for Stabilization 20764. Methods of Vectorization of the Particles 20765. Structural and Physicochemical Characterization 20785.1. Size, Polydispersity, Shape, and SurfaceCharacterization20795.2. Structure of Ferro- or FerrimagneticNanoparticles20805.2.1. Ferro- and Ferrimagnetic Nanoparticles 20805.3. Use of Nanoparticles as Contrast Agents forMRI20825.3.1. High Anisotropy Model 20845.3.2. Small Crystal and Low Anisotropy EnergyLimit20855.3.3. Practical Interests of Magnetic NuclearRelaxation for the Characterization ofSuperparamagnetic Colloid20855.3.4. Relaxation of Agglomerated Systems 20856. Applications 20866.1. MRI: Cellular Labeling, Molecular Imaging(Inﬂammation, Apoptose, etc.)20866.2.

Magnetic Iron Oxide Nanoparticles: Synthesis, Stabilization, Vectorization, Physicochemical Characterizations, and Biological Applications

A review on polymer–layered silicate nanocomposites

Poly(lactic acid) crystallization

Plastic waste is currently generated at a rate approaching 400 Mt year–1. The amount of plastics accumulating in the environment is growing rapidly, yet our understanding of its persistence is very...

Degradation Rates of Plastics in the Environment

Because of its fundamental importance in many branches of science, hydrogen bonding is a subject of intense contemporary research interest. The physical and chemical properties of hydrogen bonds in the ground state have been widely studied both experimentally and theoretically by chemists, physicists, and biologists. However, hydrogen bonding in the electronic excited state, which plays an important role in many photophysical processes and photochemical reactions, has scarcely been investigated.Upon electronic excitation of hydrogen-bonded systems by light, the hydrogen donor and acceptor molecules must reorganize in the electronic excited state because of the significant charge distribution difference between the different electronic states. The electronic excited-state hydrogen-bonding dynamics, which are predominantly determined by the vibrational motions of the hydrogen donor and acceptor groups, generally occur on ultrafast time scales of hundreds of femtoseconds. As a result, state-of-the-art femtos...

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Hydrogen Bonding in the Electronic Excited State

Biodegradable polymeric blends are expected to be widely used by industry due to their environmental friendliness and comparable mechanical and thermal properties. Poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) are such biodegradable polymers which aim to replace commodity polymers in future applications. Since cost and brittleness of PLA is quite high, it is not economically feasible to use it alone for day to day use as a packaging material without blending. In this study, blends of PLA and PBS with various compositions were prepared by using a laboratory-scale twin-screw extruder at 180oC. Morphological, thermal, rheological and mechanical properties were investigated on the samples obtained by compression molding to explore suitability of these compositions for packaging applications. Morphology of the blends was investigated by scanning electron microscopy (SEM). Morphology showed a clear phase difference trend depending on blend composition. Modulated differential scanning calorimetry (MDSC) thermograms of the blends indicated that the glass transition temperature ( ) of PLA did not change much with the addition of PBS, but analysis showed that for PLA/PBS blend of up to 80/20 composition there is partial miscibility between the two polymers. The tensile strength and modulus were measured by the Instron Universal Testing Machine. Tensile strength, modulus and percentage (%) elongation at break of the blends decreased with PBS content. However, tensile strength and modulus values of PLA/PBS blend for up to 80/20 composition nearly follow the mixing rule. Rheological results also show miscibility between the two polymers for PBS composition less than 20% by weight. PBS reduced the brittleness of PLA, thus making it a contender to replace plastics for packaging applications. This work found a partial miscibility between PBS and PLA by investigating thermal, mechanical and morphological properties.

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Compatibility of biodegradable poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) blends for packaging application

Poly(lactic acid) (PLA) has great potentials to be processed into films for packaging applications. However, film production is difficult to carry out due to the brittleness and low melt strength of PLA. In this investigation, linear PLA (L-PLA) was plasticized with poly(ethylene glycol) (PEG) having MW of 1000 g mol−1 in various PEG concentrations (0, 5, 10, 15, and 20 wt%). In relation to plasticizer content, the impact resistance and crystallinity of L-PLA was increased, whereas a decrease in glass transition temperature and lower stiffness was observed. Nevertheless, the phase separation has been found in samples which contained PEG greater than 10 wt%. The dynamic and shear rheological studies showed that the plasticized PLA possessed lower viscosity and more pronounced elastic properties than that of pure PLA. Both storage and loss moduli decreased with PEG loading at all frequencies while storage modulus exhibited weak frequency dependence with increasing PEG content. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers

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Properties of linear poly(lactic acid)/polyethylene glycol blends

Morphology, electromagnetic properties and electromagnetic interference shielding performance of poly lactide/graphene nanoplatelet nanocomposites

Dielectric properties and electromagnetic interference shielding effectiveness of graphene-based biodegradable nanocomposites

Nanocomposites of ethylene-vinyl acetate copolymer (EVA) with 28 wt.% vinyl acetate content (EVA28) was prepared by melt intercalation with different loadings of organically-modified bentonite clay. The microstructure and morphology of the nanocomposites were examined by X-ray diffraction (XRD) and electron microscopy. XRD and transmission electron microscopy (TEM) indicated that EVA28 nanocomposites had predominantly exfoliated morphologies. The dynamic and steady shear rheological properties of the nanocomposites showed remarkable differences in comparison to that of pure EVA28 copolymer. Linear viscoelastic parameters were enhanced at all frequencies investigated and indicated the presence of a percolated network structure. Steady shear measurements revealed that the elasticity of EVA28 nanocomposites were dependent on the silicate loading at high shear stresses. Uniaxial extensional viscosities were found to increase with silicate loading and in general exhibited strain hardening behavior. Beyond a critical strain, nanocomposite extensional viscosities were almost identical with that of the unfilled EVA28, suggesting that at high strains, silicates have little effect on the extensional viscosities. An attempt has been made to propose a possible mechanism that describes the influence of clay layers on the uniaxial extensional flow field. Images obtained from transmission electron microscopy (TEM) and an environmental scanning electron microscopy (ESEM) were used to support the proposed mechanism.

Sati N. Bhattacharya

Papers

Compatibility of biodegradable poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) blends for packaging application

Properties of linear poly(lactic acid)/polyethylene glycol blends

Morphology, electromagnetic properties and electromagnetic interference shielding performance of poly lactide/graphene nanoplatelet nanocomposites

Dielectric properties and electromagnetic interference shielding effectiveness of graphene-based biodegradable nanocomposites

Shear and extensional rheology of EVA/layered silicate-nanocomposites