Highly dispersed clay-polyolefin nanocomposites free of compatibilizers, via the in situ polymerization of alpha-olefins by clay-supported catalysts

In situ polymerization by certain transition metal catalysts supported on and activated by acid-treated montmorillonite produces well-dispersed clay-polyolefin nanocomposites, without requiring either organic surfactants to be present in the clay phase or modification of the polyolefin structure.     

Preparation of Antibacterial Waterborne Polyurethane/silver Nanocomposite

Stable aqueous dispersions of silver (Ag) nanoparticles were prepared by reducing silver nitrate solutions with sodium borohydride (NaBH₄) in the presence of waterborne polyurethane as a stabilizing agent. WPU/Ag nanocomposites were obtained after evaporating water. Transmission electron microscope (TEM) shows nanoscale Ag particles are well dispersed in WPU matrix at a lower concentration, while particles exhibit a little aggregation at a higher concentration. UV‐visible spectra, X‐ray powder diffraction, and energy dispersive X‐ray spectrometer (EDS) confirm the existence of Ag particle in WPU matrix. The WPU/Ag composite films show good antibiotic ability.     

A designed glycoprotein analogue of Gc-MAF exhibits native-like phagocytic activity

Rational protein design has been successfully used to create mimics of natural proteins that retain native activity. In the present work, de novo protein engineering is explored to develop a mini-protein analogue of Gc-MAF, a glycoprotein involved in the immune system activation that has shown anticancer activity in mice. Gc-MAF is derived in vivo from vitamin D binding protein (VDBP) via enzymatic processing of its glycosaccharide to leave a single GalNAc residue located on an exposed loop. We used molecular modeling tools in conjunction with structural analysis to splice the glycosylated loop onto a stable three-helix bundle (alpha3W, PDB entry 1LQ7). The resulting 69-residue model peptide, MM1, has been successfully synthesized by solid-phase synthesis both in the aglycosylated and the glycosylated (GalNAc-MM1) form. Circular dichroism spectroscopy confirmed the expected alpha-helical secondary structure. The thermodynamic stability as evaluated from chemical and thermal denaturation is comparable with that of the scaffold protein, alpha3W, indicating that the insertion of the exogenous loop of Gc-MAF did not significantly perturb the overall structure. GalNAc-MM1 retains the macrophage stimulation activity of natural Gc-MAF; in vitro tests show an identical enhancement of Fc-receptor-mediated phagocytosis in primary macrophages. GalNAc-MM1 provides a framework for the development of mutants with increased activity that could be used in place of Gc-MAF as an immunomodulatory agent in therapy.     

Highly protein-resistant coatings from well-defined diblock copolymers containing sulfobetaines

Three well-defined diblock copolymers of poly(sulfobetaine methacrylate) [poly(SBMA)] and poly(propylene oxide) (PPO) were synthesized by the sequential addition of SBMA monomer to fixed amounts of PPO using an atom transfer radical polymerization method and varying poly(SBMA) lengths. These copolymers were characterized by 1H NMR and aqueous gel permeation chromatography. These copolymers were physically adsorbed onto a surface plasmon resonance (SPR) sensor surface covered by methyl-terminated self-assembled monolayers, followed by the in situ evaluation of protein adsorption on the adsorbed copolymers. It is found that the behavior of the protein adsorption depends on the molecular weight of the copolymers. Results show that the diblock copolymers containing poly(SBMA) can be highly protein resistant when surface SBMA densities are well controlled. Thus, copolymers containing zwitterionic groups are ideal for resisting protein adsorption when the surface density of zwitterionic groups is controlled.     

Selective patterning and scribing of Ti thin film on glass substrate by 532 nm picosecond laser

In this paper, the feasibility of Ti film coated on glass substrate scribed via a 532 nm picosecond laser is investigated. Laser irradiations from the film side and from the transparent substrate side are performed for comparison. Optical microscopy, SEM, surface stylus and contact resistance measurement reveal that the Ti film can be completely removed with no damage to the glass substrate, using optimized process parameters. The complete removal threshold for the film for front-side scribing is found at 120 mJ/cm², while the minimum laser fluence for complete scribing is 70 mJ/cm² in the case of back-side scribing. The lines scribed from the front side exhibit obvious thermal effects such as heat affected zones, burr and micro cracks. Back-side scribing exhibits non-thermal behavior, which also can increase the process speed for the scribing of a Ti film on glass to 1000 mm/s. This makes the back-side laser scribing of Ti film a promising technique.     

Correlation of thermodynamic modeling and molecular simulations for liquid-liquid equilibrium of ternary polymer mixtures based on a phenomenological scaling method

In our previous study [S.Y. Oh, Y.C. Bae, J. Phys. Chem. B 114 (2010) 8948-8953], we presented a new method to predict liquid-liquid equilibria in ternary simple liquid mixtures by using a combination of a thermodynamic model and molecular simulations. As a continuation of that effort, we extend our previously developed method to ternary polymer systems. In the simulations, we used the dummy atoms to calculate the pair interaction energy values between the polymer segments and the solvent molecules. Furthermore, a thermodynamic model scaling concept is introduced to consider the chain length dependence of the energy parameters. This method was applied to ternary mixtures incorporating low to high molecular weight polymers. The method presented here well described the experimental observations using one or no adjustable parameters.     

An off‐axis magnetron‐sputtering system for in situ studies of artificial superlattices growth by synchrotron radiation scattering

A sputtering chamber for the growth of artificial superlattices of oxide‐based materials is described. The chamber is designed to fit into a standard Huber eight‐circle diffractometer. The chamber serves for investigation with synchrotron radiation of growth characteristics of oxide‐based artificial superlattices in situ. Two Be windows of large area in the vacuum chamber enable measurement of reflections of X‐rays at entrance and exit angles up to ～50°. Large perpendicular momentum transfers are practical with this apparatus. The possibility of investigating X‐ray scattering in situ is demonstrated by observation of the effects of the modulation length and the stacking period on the growth characteristics of BaTiO₃/LaNiO₃ artificial superlattices.     

Synthesis and ion‐sensing phenomena of two new helical conjugated oligomers containing 1,10‐phenanthroline and oligo‐alkylthiophene

Two new 1,10‐phenanthroline (Phen) containing conjugated oligomers, oligo‐3,8‐bis(4‐octylthiophene‐2‐yl)‐1,10‐phenanthroline) (PDTPh) and oligo‐3,8‐bis‐(4‐octyl‐5‐(4‐ctylthiophene‐2‐yl)thiophene‐2‐yl)‐1,10‐phenanthroline) (PTTPh), as well as their corresponding monomers (OTPhOT and OTOTPhOTOT) were prepared and their metal ion‐sensing properties were investigated. The oligomers showed high thermal stability, good proccessibility, and gave varied color when reacted with different metal ions. Oligomers also showed distinct responses toward metal ions when compared with their corresponding monomers, suggesting that the ionochromic responses were determined by not only the coordinating ability of Phen unit but also the conformation of oligomer chains. Moreover, the differences in the ion‐sensing behaviors between OTPhOT and OTOTPhOTOT also suggested that the coordination ability of Phen depends on its substituents. The oligo‐alkylthiophene moieties in PDTPh and PTTPh acted as spacers to reorganize the conformation of the oligomer chains, as well as the electron donating groups to adjust the coordination ability of the Phen. These findings provide a clue for designing Phen‐containing ion‐sensors for specified ion‐sensing applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1586–1597, 2008