Effect of grafted polymer species on particle monolayer structure at the air-water interface

We have studied poly(methyl methacrylate)-grafted(PMMA) particle monolayer systems at the air-water interface. In previous papers, we reported that PMMA chains grafted from particles (silica particle and polystyrene latex) were extended on water surfaces. Through observing deposited particle monolayers on substrates using SEM, we have confirmed that PMMA of large molecular weights were either dispersed or arrayed in structure with long inter-particle distances approximately 500 nm. In contrast, low molecular weight PMMA were observed to aggregate upon deposition. We speculated that the difference in morphology in deposited particle monolayers would be attributed to the affinity between the grafted polymer and the substrate. To examine the effect of this affinity three new polymer-grafted silica particles were synthesized with a fairly high graft density of about 0.14 approximately 0.43 nm(-2). As well as PMMA-grafted silica particles (SiO2-PMMA), poly(2-hydroxyethyl methacrylate) and poly(t-butyl methacrylate)--grafted silica particles (SiO2-PHEMA and SiO2-PtBuMA) were also prepared and subjected to pi-A isotherm measurements and SEM observations. These pi-A isotherms indicated that polymer-grafted silica formed monolayer at the air-water interface, and the onset area of increasing surface pressure suggests that the polymer chains are extended on a water surface. However, the morphology of the deposited monolayer is highly dependent on polymer species: SiO2-PHEMA showed that the dispersed particle monolayer structure was independent of grafted molecular weight while SiO2-tBuMA showed an aggregated structure that was also independent of grafted moleculer weight. SiO2-PMMA showed intermediate tendencies: dispersed structure was observed with high grafted molecular weight and aggregated structure was observed with low grafted molecule weight. The morphology on glass substrate would be explaiened by hydrophilic interaction between grafted polymer and hydrophilic glass substrate.     

Functionalized imidazolium ionic liquids as electrolyte components of lithium batteries

Some basic properties and compatibility toward lithium electrode for electrolytes based on substituted imidazolium ionic liquid have been investigated. The ionic liquids having imidazolium cation substituted by methylcarboxyl or cyano group suffers from low conductivity. However, reversible lithium deposition–dissolution process was observed in electrolytes based on these electrolytes. In particular, lithium salt solution in cyanomethyl-substituted imidazolium ionic liquid provided similar cycle efficiency to conventional organic solvent electrolyte at constant-current condition. The mixed ionic liquid electrolyte containing the cyanomethyl-substituted ionic liquid also provided good cycle performance despite of containing large amount of 1-ethyl-3-methyl imidazolium (EMI)-based ionic liquid. Such mixed electrolyte system serves both the stability of lithium electrode process and valid conductivity for practical use.     

Calpain inhibitor nanocrystals prepared using Nano Spray Dryer B-90

ABSTRACT: The Nano Spray Dryer B-90 offers a new, simple and alternative approach for the production of drug nanocrystals. Among attractive drugs, calpain inhibitor that inhibits programmed cell death "apoptosis" is candidate for curing apoptosis-mediated intractable disease such as Alzheimer's and Parkinson's disease. In this study, the preparation of calpain inhibitor nanocrystals by Nano Spray Dryer B-90 was demonstrated. The particle sizes were controlled by means of selecting mesh aperture sizes. The obtained average particle sizes were in the ranges of around 300 nm to submicron meter.     

Ion and water transport properties of cation exchange membranes prepared by heavy-ion-track grafting technique

ABSTRACT

For high-performance electrodialysis of saline water, cation exchange membranes (CEMs) that actively transport Na⁺ and restrict water permeation are required. In this study, we prepared novel CEMs by a heavy-ion-track grafting technique and measured their membrane resistance and water permeation flux as transport properties. The prepared nanostructured CEMs exhibited lower resistance and lower water flux than the commercial CEM. Na⁺ ions were efficiently transported through their unique one-dimensional ion channels (low resistance), while water transport was suppressed due to the very low water uptake of the CEMs. These results demonstrated the high potential of these nanostructured CEMs for use in practical saline water electrodialysis.     

Amorphous phase and crystalline morphology in blend of two polymorphic polyesters: Poly(hexamethylene terephthalate) and poly(heptamethylene terephthalate)

Crystalline/crystalline blends of two polymorphic aryl-polyesters, poly(hexamethylene terephthalate) (PHT) and poly(heptamethylene terephthalate) (PHepT), were prepared and the crystallization kinetics, polymorphism behavior, spherulite morphology, and miscibility in this blend system were probed using polarized-light optical microscopy (POM), differential scanning calorimetry (DSC), temperature-resolved wide-angle X-ray diffraction (WAXD), and small angle X-ray scattering (SAXS). The PHT/PHepT blends of all compositions were proven to be miscible in the melt state or quenched amorphous glassy phase. Miscibility in PHT/PHepT blend leads to the retardation in the crystallization rate of PHT; however, that of PHepT increases, being attributed to the nucleation effects of PHT crystals which are produced before the growth of PHepT crystals. In the miscible blend of polymorphic PHT with polymorphic PHepT, the polymorphism states of both PHT and PHepT in the blend are influenced by the other component. The fraction of the thermodynamically stable β-crystal of PHT in the blend increases with increasing PHepT content when melt-crystallized at 100 °C. In addition, when blended with PHT, the crystal stability of PHepT is altered and leads to that the originally polymorphic PHepT exhibits only the β-crystal when melt-crystallized at all T_c's. Apart from the noted polymorphism behavior, miscibility in the blend also shows great influence on the spherulite morphology of PHT crystallized at 100 °C, in which the dendritic morphology corresponding to the β-crystal of PHT changes to the ring-banded in the blend with higher than 50 wt% PHepT. In blends of PHT/PHepT one-step crystallized at 60 °C, PHepT is located in both PHT interlamellar and interfibrillar region analyzed using SAXS, which further manifests the miscibility between PHT and PHepT.