Synthesis and physical properties of highly branched perfluorinated polymers from AB and AB2 monomers

Highly branched perfluorinated aromatic polyether copolymers were prepared from the polycondensation of the AB₂ monomer, 3,5‐bis[(pentafluorobenzyl)oxy]benzyl alcohol with a variety of fluoroaryl and alkyl bromide AB comonomers. The structures and comonomer distribution of the resulting polymers were characterized in detail. ¹H NMR data from kinetic trials illustrated that perfluoroaryl AB comonomer distribution correlated to AB comonomer sterics. ¹⁹F NMR data revealed that fluorinated AB monomers and 3‐bromo‐1‐propanol AB monomers were distributed within the AB₂ polymer backbone, while longer alkyl bromide AB monomers, 6‐bromo‐1‐hexanol, were mostly distributed along hyperbranched polymer chain ends. In general, as AB comonomer incorporation increased for nonsterically hindered copolymers, thermal decomposition onset increased and glass transition temperatures decreased. The combined data demonstrated the effect of comonomer distribution and sterics on physical properties of AB₂‐based polymer systems. The resulting materials were used to cast thin polymer films for measurement of contact angle, which were shown to be directly related to comonomer content. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1880–1894     

Correspondence between de Saint-Venant and Boussinesq. 1: Birth of the Shallow–Water Equations

The Shallow–Water Equations (SWEs), also referred to as the de Saint-Venant equations, constitute the current governing mathematical tool for free-surface water flows. These include, e.g., flood flows in rivers and in urban zones, flows across hydraulic structures as dams or wastewater facilities, flows in the environmental fields, glaciology, or meteorology. Despite this attractiveness, the system of two partial differential equations has an exact mathematical solution only for a limited number of problems of practical relevance.This historical work on the SWEs is based on a correspondence between two 19th-century scientists, de Saint-Venant and Boussinesq. Their well-known papers are thus commented from the point of development of their theory; the input of both scientists is evidenced by their writings, and comments of both to each other that led to what is commonly known as the SWEs. Given the age difference of the two of 45 years, the experienced engineer de Saint-Venant, and the mathematician Boussinesq, two eminent researchers, met to discuss not only problems in hydraulics, but in physics generally. In addition, their correspondence embraced also questions in ethics, religion, history of sciences, and personal news.The results of the SWEs cease to hold if streamline curvature effects dominate; this includes breaking waves, solitary and cnoidal waves, or non-linear waves in general. In most other cases, however, the SWEs perfectly apply to typical flows in engineering practice; they are considered the fundamental system of equations describing open channel flows. This work thus provides a background to its birth, including lots of comments as to its improvement, physical meanings, methods of solution, and a discussion of the results. This paper also deals with the steady flow equations, gives a short account on the main persons mentioned in the Correspondence, and provides a summary of further developments of the SWEs until 1920.     

Poly[N‐(10‐oxo‐2‐vinylanthracen‐9(10H)‐ylidene)cyanamide] as a novel cathode material for li‐organic batteries

Redox‐active polymers draw significant attention as active material in secondary batteries during the last decade. A new anthraquinone‐based redox‐active monomer was designed, which electrochemical behavior was tailored by mono‐modification of one keto group. The monomer exhibits two one‐electron redox reactions and has a low molar mass, resulting in a high theoretical capacity of 207 mAh/g. The polymerization of the monomer was optimized by variation of solvent and initiator. Moreover, the electrochemical behavior was studied using cyclic voltammetry and the polymer was used as active material in a composite electrode in lithium organic batteries. The polymer reveals a cell potential of 2.3 V and a promising capacity of 137 mAh/g. During the first 100 cycles, the capacity drops to 85% of the initial value. The influence of the charging speed on the charging/discharging properties of the batteries was further investigated. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2517–2523     

Reply to the Comment by S. J. Kowalski,TIPM 40, 113, 2000

Transport in Porous Media -     

Synthesis and characterization of polymethacrylates containing conjugated oligo(phenylene ethynylene)s as side chains

In order to form suitable systems designed for resonance energy transfer, a series of monodisperse methacrylate‐based monomers containing rigid π‐conjugated oligo(phenylene ethynylenes) with different sizes of the conjugated systems ( M1 – M3 ), and therefore different optoelectronic properties, were synthesized and subsequently polymerized using the reversible addition–fragmentation chain transfer polymerization technique ( P1 – P3 ). In addition, these oligomers were also copolymerized with methyl methacrylate. The obtained polymers were characterized by ¹H NMR spectroscopy, size exclusion chromatography, and analytical ultracentrifugation. The photophysical properties of the polymers were studied by UV–vis absorption and emission spectroscopy in diluted solutions as well as in thin films and compared to the photophysics of the corresponding monomers. Thereby, changes going from monomeric to polymeric systems could be detected in fluorescence quantum yields and lifetimes pointing to energy trapping, e.g., energy transfer. Donor–acceptor copolymers containing different numbers of monomeric units within the side chain exhibit differences in the emission spectra, indicating that energy trapping in polymers is very sensitive to structural properties such as the chain length. UV–vis absorption spectroscopy as well as time‐resolved lifetime studies indicate intrapolymer and interpolymer energy transfer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

A theorem and a question about epicomplete archimedean lattice-ordered groups

An archimedean ?-group is called epicomplete (or universally σ-complete, or sequentially inextensible) if it is divisible, σ-complete and laterally σ-complete. Various characterizations of such G are known in case the G have weak order units. The “theorem” of the title is a characterization of such G which have no weak order unit; it involves the requirement that G have a certain kind of representation. The “question” of the title is whether every epicomplete G has such a representation.     

Stability in the presence of degeneracy and error estimation

Received February 10, 1997 / Revised version received June 6, 1998 Published online October 9, 1998     

Non-Glycosidic Azides of D-Altro- and D-Gulopyranose

ABSTRACT

Starting with methyl 2-O-cyclohexylcarbamoyl-3,4-O-(2,2,2-trichloroethylidene)-α-D-altropyranoside (1), methyl 4-O-cyclohexylcarbamoyl-2,3-O-(2,2,2-trichloroethylidene)-β-D-gulopyranoside (12), and methyl 6-O-cyclohexylcarbamoyl-2,3-O-(2,2,2-trichloroethylidene)-β-D-gulopyranoside (21), the 6-azido-6-deoxyaltroses 4, 6, 11, the 6-azido-6-deoxy-D-gulose 14, the 4-azido-4,6-dideoxy-D-gulose 20, and the 4-azido-4-deoxy-D-gulose 26 were synthesised via iodinated or tosylated precursors. Additionally, two gluco-configured azides, the 3-azido-3,6-dideoxy-D-glucose (19) and the 3-azido-3-deoxy-D-glucose (25), were obtained besides the desired 4-azido-4-deoxy-D-gulosides 20 and 26, when methyl 6-deoxy-4-O-tosyl-β-D-gulopyranoside (18) and methyl 6-O-cyclohexylcarbamoyl-4-O-tosyl-β-D-gulopyranoside, respectively, were reacted with sodium azide. An X-ray analysis is presented for methyl 2,4-di-O-acetyl-3-azido-3,6-dideoxy-zl-D-glucose (19).