The preparation of perfluorinated esters of fluorine containing tertiary alcohols

The reaction of an aromatic lithium reagent, LiR, with a perfluoroacid anhydride (RfCO)₂O, in ether solution at low temperatures, produces esters of composition

in addition to the expected ketone

. Mixed esters of composition

may be prepared by starting with a ketone

and reacting with a lithium reagent LiR followed by perfluoroacid anhyride (RfCO₂O. Hydrolysis of the esters provide a convenient route to trertiary alcohols of composition Rf(R) ₂COH.     

On crystallization and phase separation phenomena in PEN/PHBA copolyesters

Two different etching techniques that reveal the semicrystalline morphology of polyesters have been developed and applied to an analysis of the phase structure of copolyesters made by reacting poly(hydroxybenzoic acid) (PHBA), and poly(ethylene naphtha-lene-dicarboxylate) (PEN). One technique is based on oxidation with acidic permanganate solutions and is used to study the macroscopic distribution of different phases. The other is based on sa-ponification with alkaline reagents and reveals more detailed structure within the various phases. Etching and electron microscopic examinations have been carried out for three different PEN-co-PHBA compositions. Three different types of solid phase are revealed: (1) a phase rich in PEN; (2) a phase containing roughly equal proportions of the two components, liquid crystalline at high temperatures; (3) a solid phase of crystalline HBA-rich molecules, which segregate into laminar regions. These observations are consistent with the previously published thermal, x-ray, and dynamic mechanical analyses of these materials.     

Diffusion of single adatoms of platinum,iridium and gold on platinum surfaces

Diffusion of single adatoms of platinum iridium and gold on platinum surfaces has been studied experimentally using field ion microscopy and theoretically using Morse potentials to describe the adatom bonding. The order of increasing activation energies for the surfaces studied was (111), (113), (011), (133), (001) and calculated activation energies agreed satisfactorily with the experimental values. On (113) and (011) platinum the activation energies for the adsorbates increased in the order Au, Pt, Ir. The calculations show that this variation arises largely from differences in the adsorbate binding energy, with the differences in adatom size having little effect. Diffusion of Au on (011) platinum occurred only along the direction of the surface channels, as is to be expected from the surface structure. In contrast, Pt and Ir adatoms were found to diffuse in two dimensions on (011). Since direct inter-channel jumps by adatoms should require large activation energies, it is proposed that the observed inter-channel adatom transfers proceed by a surface vacancy mechanism.     

Crystallization of propylene–ethylene random copolymers

Of the three melting peaks typical of a propylene–ethylene random copolymer (with 5.1 wt % ethylene) crystallized between 110 and 140 °C, the two higher peaks result from primary and secondary isothermal crystallization, whereas the material crystallized on cooling gives the lowest peak. In contrast to polypropylene homopolymers, which show strong morphological changes developing from the center of a spherulite, copolymer specimens are uniformly crosshatched. The highest melting peak is related to an open crosshatched framework of primary lamellae, and the next lower peak is related to later forming subsidiary lamellae filling the intervening space. The origin and nature of these double peaks are discussed in terms of the fractional crystallization and the ensuing constraints placed on isothermal lamellar thickening as a result of the exclusion of the comonomer from the polypropylene lattice. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3318–3332, 2004     

Electrical tuning of single nitrogen-vacancy center optical transitions enhanced by photoinduced fields

We demonstrate precise control over the zero-phonon optical transition energies of individual nitrogen-vacancy (NV) centers in diamond by applying multiaxis electric fields, via the dc Stark effect. The Stark shifts display surprising asymmetries that we attribute to an enhancement and rectification of the local electric field by photoionized charge traps in the diamond. Using this effect, we tune the excited-state orbitals of strained NV centers to degeneracy and vary the resulting degenerate optical transition frequency by >10 GHz, a scale comparable to the inhomogeneous frequency distribution. This technique will facilitate the integration of NV-center spins within photonic networks.     

Lung assist device technology with physiologic blood flow developed on a tissue engineered scaffold platform

There is no technology available to support failing lung function for patients outside the hospital. An implantable lung assist device would augment lung function as a bridge to transplant or possible destination therapy. Utilizing biomimetic design principles, a microfluidic vascular network was developed for blood inflow from the pulmonary artery and blood return to the left atrium. Computational fluid dynamics analysis was used to optimize blood flow within the vascular network. A micro milled variable depth mold with 3D features was created to achieve both physiologic blood flow and shear stress. Gas exchange occurs across a thin silicone membrane between the vascular network and adjacent alveolar chamber with flowing oxygen. The device had a surface area of 23.1 cm(2) and respiratory membrane thickness of 8.7 ± 1.2 μm. Carbon dioxide transfer within the device was 156 ml min(-1) m(-2) and the oxygen transfer was 34 ml min(-1) m(-2). A lung assist device based on tissue engineering architecture achieves gas exchange comparable to hollow fiber oxygenators yet does so while maintaining physiologic blood flow. This device may be scaled up to create an implantable ambulatory lung assist device.     

Crystallization of polyethylene at elevated pressures

The crystallization from the melt of three sharp polyethylene fractions has been studied at 5 kbar. It has been shown that the thickness of so-called extended-chain lamellae is a function of time, temperature, and molecular weight. There is by no means just the fully extended molecular configuration present. Crystallization is qualitatively similar to that of chain-folded crystals at 1 bar, giving an optimum lamellar thickness which increases with time and decreasing supercooling. Fractional crystallization is widespread and is a major cause of disparate lamellar thickness. Isothermal thickening of lamellae during crystallization has been established directly. Morphological detail suggests further that layers can increase their thickness tenfold over their initial size.