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In this research, influence of incorporating LiClO4 salt on the crystallization, conformation, and ionic conductivity of poly(ethylene oxide) (PEO) in its miscible blend with poly(methyl methacrylate) (PMMA) is studied. Differential scanning calorimetry showed that the incorporation of salt ions into the blend suppresses the crystallinity of PEO. The X-ray diffraction revealed that the unit-cell parameters of the crystals are independent of the LiClO4 concentration despite of the existence of ionic interactions between PEO and Li cations. In addition, the complexation of the Li+ ions by oxygen atoms of PEO is investigated via Fourier transform infrared spectroscopy. The conformational changes of PEO segments in the presence of salt ions are studied via Raman spectroscopy. It is found that PEO chains in the blend possess a crown-ether like conformation because of their particular complexation with the Li+ ions. This coordination of PEO with lithium cations amorphize the PEO and is accounted for suppressed crystallinity of PEO in the presence of salt ions. Finally, electrochemical impedance spectroscopy is used to characterize the ionic conductivity of PEO in the PEO/PMMA/LiClO4 ternary mixture at various temperatures. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Complex coacervation driven by associative electrostaticinteractionswas studied in mixtures of exfoliated sodium-montmorillonite (Na+MMT) nanoplatelets and fish gelatin, at a specific mixingratio and room temperature. Structural and viscoelastic propertiesof the coacervate phase were investigated as a function of pH by meansof different complementary techniques. Independent of the techniqueused, the results consistently showed that there is an optimum pHvalue at which the coacervate phase shows the tightest structure withhighest elasticity. The solid-like coacervates showed an obvious shear-thinningbehavior and network fracture but immediately recovered back intotheir original elastic character upon removal of the shear strain.The nonlinear mechanical response characterized by single step stressrelaxation experiments revealed the same trend for the yield stressand isochronal shear modulus of the coacervates as a function of pHwith a maximum at pH 3.0 and lower values at 2.5 and 3.5 pHs, followedby a very sharp drop at pH 4.0. Finally, small-angle X-ray scattering(SAXS) data confirmed that at pHs lower than 4.0 the coacervate phaseswere dense and structured with a characteristic length scale (ξSAXS) of ∼7–9 nm. Comparing the ξSAXSwith rheological characteristic length (ξrheol)estimated from low-frequency linear viscoelastic data and networktheory, it was concluded that both the strength of the electrostaticinteractions and the conformation of the gelatin chains before andduring of the coacervation process are responsible for the structureand rigidity of the coacervates. [ABSTRACT FROM AUTHOR]

Polymer-silicate nanocomposites based on poly (ethylene oxide), PEO, poly(methyl methacrylate), PMMA, and sodium montmorillonite clay were fabricated and characterized to investigate the effect of nanolayered silicates on segmental dynamics of PEO/PMMA blends. X-ray results indicate the formation of an exfoliated morphology in the nanocomposites. At low silicate contents, an enhancement in segmental dynamics of blend nanocomposites and also PEO, minor component in blend, is observed at temperature region below blend glass transition. This result can be attributed to the improvement of the confinement effect of rigid PMMA matrix on the PEO chains by introducing a low amount of layered silicates. On the other hand, at high silicate contents, an enhancement in segmental dynamics of blend nanocomposites and PEO is observed at temperature region above blend glass transition. This behavior could be interpreted based on the reduction of monomeric friction between two polymer components, which can facilitate segmental motions of blend components in nanocomposite systems. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 [ABSTRACT FROM AUTHOR]

Gelatin nanoparticles, cross-linked by a mixture of a water soluble carbodiimide (CDI) and N-hydroxysuccinimide (NHS) as a non-toxic cross-linking system, was prepared. The conventional two step desolvation method with acetone as the non-solvent was used. The mean size and size distribution as well as the morphology of the formed nanoparticles were evaluated and compared with those of nanoparticles cross-linked by glutaraldehyde (GA) as the most commonly used cross-linking agent. Furthermore, intrinsic viscosities of the nanoparticles cross-linked by CDI/NHS and GA were measured and compared under various conditions. The results showed the formation of smoother and more homogeneous nanoparticles with smaller size when CDI/NHS used as cross-linking agent under the same synthesis condition. Moreover, nanoparticles encapsulating paracetamol as a model drug were produced by the two different cross-linking agents and were characterized for drug entrapment and loading efficiencies and in vitro drug release. Both drug entrapment and loading efficiencies was higher in the CDI/NHS cross-linked nanoparticles; however, the release kinetics was comparable to that of nanoparticles cross-linked with GA. The differences in the characteristics of CDI/NHS and GA cross-linked nanoparticles were attributed to the different nature of network structures formed by the two cross-linking agents. On the whole, these results suggested that CDI/NHS cross-linked nanoparticles have high potential to be used for drug delivery application in preference to the nanoparticles synthesized by toxic cross-linking agents.