Amphiphilic pentablock copolymers and their blends with PDMS for antibiofouling coatings

Well‐defined amphiphilic pentablock copolymers Siy‐(EGx‐FAz)₂ composed of polysiloxane (Si), polyethylene glycol (EG), and perfluorohexylethyl polyacrylate (FA) blocks are synthesized by ATRP of FA monomer starting from a difunctional bromo‐terminated macroinitiator. Diblock copolymers EGx‐FAz are also synthesized as model systems. The block copolymers are used, either alone or blended with a PDMS matrix in varied loadings, to prepare antibiofouling coatings. Angle‐resolved XPS and contact angle measurements show that the coating surface is highly enriched in fluorine content but undergoes reconstruction after contact with water. Protein adsorption experiments with human serum albumin and calf serum highlight that diblock copolymers resist protein adhesion better than do pentablock copolymers. Blending of the pentablock copolymer with PDMS results in increased protein adsorption. By contrast, the PDMS‐matrix coatings show high removal percentages of sporelings of the green fouling alga Ulva linza. © 2015 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 2015 , 53, 1213–1225     

Interpreting technical evidence from spectral imaging of paintings by Édouard Manet in the Courtauld Gallery

The paintings by Édouard Manet in The Courtauld Gallery Déjeuner sur l'herbe (1863–68), Marguerite de Conflans en Toilette de Bal (1870–1880), Banks of the Seine at Argenteuil (1874), and A Bar at the Folies–Bergère (1882) were investigated for the first time using a range of non-invasive in situ analyses. The aims of the study were to investigate the painting techniques and materials used for this group of works and to critically evaluate the technical evidence derived from the integrated use of imaging techniques and portable spectroscopic methods in this context. The paintings were investigated by means of macro X-ray fluorescence (MA-XRF), reflection spectral imaging, portable UV–Vis–NIR spectroscopy, portable Raman spectroscopy, and reflection FTIR. MA-XRF and reflection spectral imaging allowed visualising elements in the compositions that were not visible using traditional methods of technical study. For example, MA-XRF analysis of Déjeuner sur l'herbe revealed elements of the development of the composition that provided new evidence to consider its relationship to other versions of the composition. The study also highlighted questions about the interpretation of elemental distribution maps and spectral images that did not correspond to the reworking visible in X-radiographs. For example, in A Bar at the Folies–Bergère Manet made numerous changes during painting, which were not clearly visualised with any of the techniques used. The research has wider implications for the study of Impressionist paintings, as the results will support technical studies of works by other artists of the period who used similar materials and painting methods.     

A TEMPO-catalyzed oxidation–reduction method to probe surface and anhydrous crystalline-core domains of cellulose microfibril bundles

Cellulose - A modified TEMPO-catalyzed oxidation of the solvent-exposed glucosyl units of cellulose to uronic acids, followed by carboxyl reduction with NaBD4 to 6-deutero- and...     

Interpretation of graphs with logarithmic scales

Summary The use of logarithmic scales for the graphical presentation of experimental data can lead to errors in interpretation. Consideration is given to two examples in rheology, namely the viscosity — molecular weight relationship for a polymer system, and flow behaviour at low rates of shear.

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Zusammenfassung Die Verwendung logarithmischer Skalen bei der graphischen Darstellung experimenteller Ergebnisse kann zu Interpretationsfehlern führen. Dies wird an zwei Beispielen aus der Rheologie diskutiert, nämlich an der Viskositäts-Molekulargewichts-Beziehung von Polymersystemen und am Fließverhalten bei kleinen Schergeschwindigkeiten.

     

On the dynamic response of viscoelastic fluids

Summary To define the dynamic shear behaviour of a viscoelastic fluid we require two functions — one elastic and one viscous. There are two simple alternatives based on the Voigt and Maxwell concepts which are mathematically interrelated. Current practice interprets the dynamic response of fluids as a function of angular frequency () in terms of the storage (G) and loss (G) moduli: the loss function is commonly converted to a viscosity = G/. As is well known the parameters andG are the elements of a Voigt model whereas it is near universal practice to interpret steady flow in terms of the Maxwell model. This paper shows how the interpretation of dynamic experiments on fluids in terms of the apparent Maxwell parameters is more simple, more sensitive, more consistent with steady flow behaviour, and physically more realistic.

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Zusammenfassung Zur Festlegung des dynamischen Scherverhaltens einer viskoelastischen Flüssigkeit benötigt man zwei Funktionen, eine für das elastische und eine für das viskose Verhalten. Dafür gibt es zwei einfache, mathematisch miteinander verknüpfte Alternativen, die entweder auf dem Voigtschen oder dem Maxwellschen Konzept gründen. Die übliche Praxis beschreibt das dynamische Verhalten der Flüssigkeiten als Funktion der Winkelgeschwindigkeit durch den SpeichermodulG und den VerlustmodulG bzw. die zugeordnete Viskosität = G/. Die Parameter undG sind bekanntlich die Elemente eines Voigt-Modells, wohingegen es nahezu allgemein üblich ist, das stationäre Fließen durch ein Maxwell-Modell zu beschreiben. Diese Arbeit zeigt nun, daß die Beschreibung dynamischer Versuche mit Hilfe von apparenten Maxwell-Parametern einfacher, empfindlicher, mit dem stationären Verhalten konsistenter und in physikalischer Hinsicht realistischer ist.

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Paper presented at British Society of Rheology conference. Rheometry: Methods of measurement and analysis of results, Shrivenham, April 8–11, 1975.

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With 13 figures and 2 tables     

ToxML,a data exchange standard with content controlled vocabulary used to build better (Q)SAR models

Development of accurate quantitative structure–activity relationship (QSAR) models requires the availability of high quality validated data. International regulations such as REACH in Europe will now accept (Q)SAR-based evaluations for risk assessment. The number of toxicity datasets available for those wishing to share knowledge, or to use for data mining and modelling, is continually expanding. The challenge is the current use of a multitude of different data formats. The issues of comparing or combining disparate data apply both to public and proprietary sources. The ToxML project addresses the need for a common data exchange standard that allows the representation and communication of these data in a well-structured electronic format. It is an open standard based on Extensible Markup Language (XML). Supporting information for overall toxicity endpoint data can be included within ToxML files. This makes it possible to assess the quality and detail of the data used in a model. The data file model allows the aggregation of experimental data to the compound level in the detail needed to support (Q)SAR work. The standard is published on a website together with tools to view, edit and download it.     

Novel,highly polarizable thiophene derivatives for use in nonlinear optical applications

The synthesis of a variety of thiophene-containing materials for use in electro-optic devices requiring highly birefringent materials is reported. The refractive indices were measured with the use of an Abbé refractometer, and from these results the optical anisotropies, polarizabilities and order parameters were determined. The replacement of a phenyl ring by thiophene leads to large enhancements of polarizability. The most significant increases in polarizability anisotropy were observed when the rigid core was a collinear 5,5′-disubstituted-2,2′-dithienyl unit. The changes in the optical properties are discussed in terms of the structural units (thiophene, phenyl, isothiocyanate, nitrile, butylsulfanyl, alkoxy and alkyl moieties) used and their positions with respect to the molecular core.     

The structure of poly-2,5-benzoxazole (ABPBO) and poly-2,6-benzothiazole (ABPBT) fibers by X-ray diffraction

The determination of the crystalline structure of oriented fibers of poly-2,5-benzoxazole (ABPBO) and poly-2,6-ben-zothiazole (ABPBT) is described. Both unit cells are metrically orthorhombic, with the parameters: a = 6.061 (17), b = 3.384 (13), c (fiber axis) = 11.575 (6) Å for ABPBO; and a = 6.044 (6), b = 3.417 (7), c (fiber axis) = 12.194 (18) Å for ABPBT. The fiber repeat consists in each structure of two fused ring groups arranged in a planar, zigzag conformation. The conformational torsion angle and orientation of chains within the unit cells are derived from a linked-atom least squares refinement technique. Polymer chains pack laterally through van der Waals interactions. A plausible disorder model which involves defects in chain direction is presented. Refinement of a static disorder model for ABPBO in which 50% of the chains have their chain directions reversed leads to a lower R residual and sum of constraints.