Strategy for Better Ordering in Diblock Copolymer Based Nanocomposites

A simple approach to improve the structural ordering in block copolymer/nanoparticle nanocomposites is presented. It is to blend a small molecular weight homopolymer with the composites, which can uniformly swell the preferred domain where the nanoparticles locate and increase the conformational entropy of the domain. Consequently, the interfaces between the block copolymer domains become smooth that improves the long range order in the nanocomposites. Furthermore, the uniform swelling of the preferred domain by the homopolymer will allow higher loading of nanoparticles without adversely affecting the long range order.

     

Kinetic study of chitosan‐tripolyphosphate complex reaction and acid‐resistive properties of the chitosan‐tripolyphosphate gel beads prepared by in‐liquid curing method

Chitosan gel beads were prepared using an in‐liquid curing method by the ionotropic crosslinking with sodium tripolyphosphate. Crosslinking characteristics of the chitosan‐TPP beads were improved by the modification of in‐liquid curing mechanism of the beads in TPP solution. Chitosan gel beads cured in pH value lower than 6 were really ionic‐crosslinking controlled, whereas chitosan gel beads cured in pH values higher than 7 were coacervation‐phase inversion controlled accompanied with slightly ionic‐crosslinking dependence. According to the result, significantly increasing the ionic‐crosslinking density of chitosan beads could be achieved by transferring the pH value of the curing agent, TPP, from basic to acidic. The swelling behavior of various chitosan beads in acid appeared to depend on the ionic‐crosslinking density of the chitosan‐TPP beads that were deeply affected by the curing mechanism of the beads. The mechanism of chitosan‐TPP beads swollen in weak acid was chain‐relaxation controlled, while the mechanism of chitosan‐TPP beads swollen in strong acid seem to be not only chain‐relaxation but also chain‐scission controlled. Chitosan‐TPP beads prepared in acidic TPP solution decreased the chain‐scission ability due to the increase of ionic crosslinking density of the beads. By the transition of curing mechanism, the swelling degree of chitosan‐TPP beads was depressed, and the disintegration of chitosan‐TPP beads would not occur in strong acid. The mechanism of ionic‐crosslinking reaction of chitosan beads could be investigated by an unreacted core model, and the curing mechanism of the chitosan beads is mainly diffusion controlled when higher than 5% of chitosan was employed. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1551–1564, 1999     

Development of α‐Gal–Antibody Conjugates to Increase Immune Response by Recruiting Natural Antibodies

Cancer treatment with antibodies (Abs) is one of the most successful therapeutic strategies for obtaining high selectivity. In this study, α‐gal–Ab conjugates were developed that dramatically increased cellular cytotoxicity by recruiting natural Abs through the interaction between α‐gal and anti‐gal Abs. The potency of the α‐gal–Ab conjugates depended on the amount of α‐gal conjugated to the antibody: the larger the amount of α‐gal introduced, the higher the level of cytotoxicity observed. The conjugation of antibodies with an α‐gal dendrimer allowed the introduction of large amounts of α‐gal to the Ab, without loss of affinity for the target cell. The method described here will enable the re‐development of Abs to improve their potency.     

Strain‐Enhanced Metallic Intermixing in Shape‐Controlled Multilayered Core–Shell Nanostructures: Toward Shaped Intermetallics

Controlling the surface composition of shaped bimetallic nanoparticles could offer precise tunability of geometric and electronic surface structure for new nanocatalysts. To achieve this goal, a platform for studying the intermixing process in a shaped nanoparticle was designed, using multilayered Pd‐Ni‐Pt core–shell nanocubes as precursors. Under mild conditions, the intermixing between Ni and Pt could be tuned by changing layer thickness and number, triggering intermixing while preserving nanoparticle shape. Intermixing of the two metals is monitored using transmission electron microscopy. The surface structure evolution is characterized using electrochemical methanol oxidation. DFT calculations suggest that the low‐temperature mixing is enhanced by shorter diffusion lengths and strain introduced by the layered structure. The platform and insights presented are an advance toward the realization of shape‐controlled multimetallic nanoparticles tailored to each potential application.     

Highly active heterogeneous palladium nanoparticle catalysts for homogeneous electrophilic reactions in solution and the utilization of a continuous flow reactor

A highly active heterogeneous Pd-nanoparticle catalyst for the intramolecular addition of phenols to alkynes was developed and employed in a continuous flow reaction system. Running the reaction in flow mode revealed reaction kinetics, such as the activation energy and catalyst deactivation, and provides many potential practical advantages.     

Similarity solutions of a class of laminar three-dimensional boundary layer equations of power law fluids

An analysis of the possibility of finding similarity solutions to the three-dimensional, steady, incompressible, boundary layer equations in rectangular coordinates for a power law fluid is investigated. It is found that, in general, the two components of the mainstream flow must differ by at most a multiplicative constant and that these components are powers or exponentials of the x'-coordinate.

By assuming small cross-flows, the cross flow component may be generalized and found to be representable by a polynomial in the through flow variable, x'.     

PdSi based ohmic contact on n-InP

The electrical and microstructural properties of the PdSi based ohmic contacts on n-InP are discussed in the research. A low specific contact resistance of 2.25 × 10⁻⁶ Ω cm² is obtained on Au/Si/Pd/n-InP contact after rapid thermal annealing (RTA) at 450 °C for 30 s. The low contact resistance can be maintained at the order of 10⁻⁶ Ω cm² even up to 500 °C annealing. From the Auger analysis, it is found that both the outdiffusion of In and the indiffusion of Si into the InP surface occurred at the ohmic contact sample. The formation of the Pd₃Si compound lowered the barrier of the contact. The reactions between Pd and InP of the contact, forming In vacancies, and leading the doping of Si to the InP contact interface.