Oligo(vinylidene fluoride) Langmuir-Blodgett films studied by spectroscopic ellipsometry and the density functional theory

Thin films of amphiphilic vinylidene fluoride oligomers prepared by Langmuir-Blodgett deposition on silicone substrates were investigated by comparing experimental and theoretical mid-infrared (IR) spectra. The experimental spectra were obtained using infrared spectroscopic ellipsometry. Theoretical spectra were calculated using density functional theory. Excellent correspondence of major IR bands in both data sets shows that the molecular backbone is oriented with the long axis normal to the substrate plane. This is in contrast to poly(vinylidene fluoride) LB films, in which the polymer chains are parallel to the substrate.     

Interaction of supercritical CO2 with alkyl-ammonium organoclays: changes in morphology

This paper investigates the influence of supercritical carbon dioxide on the morphology and surface chemistry of three organic modified montmorillonite species. Alkyl based quaternary ammonium surfactants with differing numbers of chains attached, were chosen to vary the degree of CO(2)-philicity exhibited by the organoclay. In a high pressure batch vessel, the different organoclays were suspended in the supercritical solvent at temperatures of 50 and 200 degrees C and pressures of 7.6 and 9.6 MPa and then removed after de-pressurization at 0.2 or 4.8 MPa/s. The structures of these treated clays were characterized by X-ray diffraction (XRD), differential scanning microscopy (DSC), and thermogravimetric analysis (TGA), and their chemical properties were analyzed by various methods including atomic absorption spectroscopy, and water uptake measurement. Solute-solvent interactions plasticized the organic medium while suspended in the supercritical fluid, which resulted in greater chain mobility and further cation exchange. The results indicate that intercalated surfactants exhibiting a paraffin complex arrangement were most likely to experience significant basal expansion, provided the tilt angle was not already close to being perpendicular to the silicate surface. At the lower processing temperature condition, the chemistry of the clay surface was notably altered by the CO(2) associations with the Lewis acid/base sites, which significantly reduced the moisture adsorption capacity of the material. For those organoclays demonstrating basal expansion, it was noted that the resulting particle size was increased due to enhanced porosity.     

Arene Selectivity by a Flexible Coordination Polymer Host

The coordination polymers [Ag₄(O₂CCF₃)₄(phen)₃] ? phen ? arene ( 1? phen ? arene) (phen=phenazine; arene=toluene, p‐xylene or benzene) have been synthesised from the solution phase in a series of arene solvents and crystallographically characterised. By contrast, analogous syntheses from o‐xylene and m‐xylene as the solvent yield the solvent‐free coordination polymer [Ag₄(O₂CCF₃)₄(phen)₂] ( 2 ). Toluene, p‐xylene and benzene have been successfully used in mixed‐arene syntheses to template the formation of coordination polymers 1? phen ? arene, which incorporate o‐ or m‐xylene. The selectivity of 1? phen ? arene for the arene guests was determined, through pairwise competition experiments, to be p‐xylene>toluene≈benzene>o‐xylene>m‐xylene. The largest selectivity coefficient was determined as 14.2 for p‐xylene:m‐xylene and the smallest was 1.0 for toluene:benzene.     

Hematocrit analysis through the use of an inexpensive centrifugal polyester-toner device with finger-to-chip blood loading capability

Hematocrit (HCT) measurements are important clinical diagnostic variables that help physicians diagnose and treat various medical conditions, ailments, and diseases. In this work, we present the HCT Disc, a centrifugal microdevice fabricated by a Print, Cut and Laminate (PCL) method to generate a 12-sample HCT device from materials costing <0.5 USD (polyester and toner or PeT). Following introduction from a drop of blood (finger stick), whole blood metering and cell sedimentation are controlled by centrifugal force, only requiring a CD player motor as external hardware and, ultimately, a cell phone for detection. The sedimented volume from patient blood in the HCT Disc was analyzed using a conventional scanner/custom algorithm for analysis of the image to determine a hematocrit value, and these were compared to values generated in a clinical laboratory, which correlated well. To enhance portability and assure simplicity of the HCT measurement, values from image analysis by a cell phone using a custom application was compared to the scanner. Fifteen samples were analyzed with cell phone image analysis system and were found to be within 4% of the HCT values determined in the clinical lab. We demonstrate the feasibility of the PeT device for HCT measurement, and highlight its uniquely low cost (<0.5 USD), speed (sample-to-answer <8 min), multiplexability (12 samples), low volume whole blood requirement (<3 μL), rotation speeds (<4000 rpm) needed for effective measurement as well as the direct finger-to-chip sample loading capability.     

Novel use of glow discharge optical emission spectroscopy (GDOES) to study corrosion of AA2024‐T3 in the presence and absence of inhibitors – part 3: investigating the effects of various proportions of inhibitor in the coating matrix or in nanocontainers

Elemental depth profiling by glow discharge optical emission spectroscopy has been used to characterize the corrosion products on AA2024‐T3. In previous work, the aluminium, oxygen and copper depth profiles were shown to provide information regarding surface roughening, the thickness of corroded layers and extent of copper de‐alloying/relocation. Nitrogen, sulfur, phosphorus and chromium depth profiles were examined in the hope of detecting inhibitor species within the corroded/altered layers after 5 h of exposure to a corrosive solution. In the present work, the study is extended to longer exposure time. The work presents a further study of the leaching of benzotriazole from the coating matrix or from nanocontainers during various times of exposure to a corrosive environment. Copyright © 2016 John Wiley & Sons, Ltd.     

Capillary zone electrophoresis tandem mass spectrometry detects low concentration host cell impurities in monoclonal antibodies

We have evaluated CZE‐ESI‐MS/MS for detection of trace amounts of host cell protein impurities in recombinant therapeutics. Compared to previously published procedures, we have optimized the buffer pH used in the formation of a pH junction to increase injection volume. We also prepared a 5‐point calibration curve by spiking 12 standard proteins into a solution of a human mAb. A custom CZE‐MS/MS system was used to analyze the tryptic digest of this mixture without depletion of the antibody. CZE generated a ～70‐min separation window (～90‐min total analysis duration) and ～300‐peak capacity. We also analyzed the sample using ultra‐performance LC‐MS/MS. CZE‐MS/MS generated approximately five times higher base peak intensity and more peptide identifications for low‐level spiked proteins. Both methods detected all proteins spiked at ～100 ppm level with respect to the antibody.     

Effects of Active‐Site Modification and Quaternary Structure on the Regioselectivity of Catechol‐O‐Methyltransferase

Catechol‐O‐methyltransferase (COMT), an important therapeutic target in the treatment of Parkinson's disease, is also being developed for biocatalytic processes, including vanillin production, although lack of regioselectivity has precluded its more widespread application. By using structural and mechanistic information, regiocomplementary COMT variants were engineered that deliver either meta‐ or para‐methylated catechols. X‐ray crystallography further revealed how the active‐site residues and quaternary structure govern regioselectivity. Finally, analogues of AdoMet are accepted by the regiocomplementary COMT mutants and can be used to prepare alkylated catechols, including ethyl vanillin.     

Searching for globally optimal functional forms for interatomic potentials using genetic programming with parallel tempering

Molecular dynamics and other molecular simulation methods rely on a potential energy function, based only on the relative coordinates of the atomic nuclei. Such a function, called a force field, approximately represents the electronic structure interactions of a condensed matter system. Developing such approximate functions and fitting their parameters remains an arduous, time-consuming process, relying on expert physical intuition. To address this problem, a functional programming methodology was developed that may enable automated discovery of entirely new force-field functional forms, while simultaneously fitting parameter values. The method uses a combination of genetic programming, Metropolis Monte Carlo importance sampling and parallel tempering, to efficiently search a large space of candidate functional forms and parameters. The methodology was tested using a nontrivial problem with a well-defined globally optimal solution: a small set of atomic configurations was generated and the energy of each configuration was calculated using the Lennard-Jones pair potential. Starting with a population of random functions, our fully automated, massively parallel implementation of the method reproducibly discovered the original Lennard-Jones pair potential by searching for several hours on 100 processors, sampling only a minuscule portion of the total search space. This result indicates that, with further improvement, the method may be suitable for unsupervised development of more accurate force fields with completely new functional forms.     

Aggregation, adsorption, and surface properties of multiply end-functionalized polystyrenes

The properties of polystyrene blends containing deuteriopolystyrene, multiply end-functionalized with C8F17 fluorocarbon groups, are strikingly analogous to those of surfactants in solution. These materials, denoted FxdPSy, where x is the number of fluorocarbon groups and y is the molecular weight of the dPS chain in kg/mol, were blended with unfunctionalized polystyrene, hPS. Nuclear reaction analysis experiments show that FxdPSy polymers adsorb spontaneously to solution and blend surfaces, resulting in a reduction in surface energy inferred from contact angle analysis. Aggregation of functionalized polymers in the bulk was found to be sensitive to FxdPSy structure and closely related to surface properties. At low concentrations, the functionalized polymers are freely dispersed in the hPS matrix, and in this range, the surface excess concentration grows sharply with increasing bulk concentration. At higher concentrations, surface excess concentrations and contact angles reach a plateau, small-angle neutron scattering data indicate small micellar aggregates of six to seven F2dPS10 polymer chains and much larger aggregates of F4dPS10. Whereas F2dPS10 aggregates are miscible with the hPS matrix, F4dPS10 forms a separate phase of multilamellar vesicles. Using neutron reflectometry (NR), we found that the extent of the adsorbed layer was approximately half the lamellar spacing of the multilamellar vesicles. NR data were fitted using an error function profile to describe the concentration profile of the adsorbed layer, and reasonable agreement was found with concentration profiles predicted by the SCFT model. The thermodynamic sticking energy of the fluorocarbon-functionalized polymer chains to the blend surface increases from 5.3kBT for x = 2 to 6.6kBT for x = 4 but appears to be somewhat dependent upon the blend concentration.