The reaction of acyl peroxides with 2,2,6,6-tetramethylpiperidinyl-1-oxy

Benzoyl ana lauroyl peroxides undergo induced decomposition by 2,2,6,6-tetramethylpiperidinyl-1-oxy to form acyloxy radicals and carboxylic acid in equimolar amounts. Formation of the carboxylic acid does not involve free acyloxy radicals.     

Replacement of benzene with regulators for the catalyzed polymerization of 1,3‐butadiene to high cis‐1,4‐polybutadiene

The polymerization regulators mesitylene and 1,3,5‐trimethoxybenzene were investigated as suitable substitutes for benzene in the cobalt(II) octanoate/diethylaluminum chloride/water‐catalyzed polymerization of 1,3‐butadiene to high cis‐1,4‐polybutadiene. The propagation rates were reduced by 50% with the inclusion of 18 mM mesitylene or 0.17 mM trimethoxybenzene. Mesitylene was found to be an inefficient polymerization regulator because it reduced the propagation rate by a combination of regulation and destruction of the active catalyst complex. Not only did trimethoxybenzene reduce the propagation rate by effective regulation at low concentration, it also increased the percentage activity of cobalt to 200%, indicating that two polymer chains were propagating simultaneously from each active center. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2244–2255, 2001     

Tailored polymer architectures by reversible addition‐frasmentation chain transfer

Living radical polymerization methods that allow the preparation of polymers with predetermined molecular weight, narrow molecular weight distribution and tailored architecture (e.g. block, graft, stars) are offering a vast range of new and advanced materials. With applications ranging from surfactants, dispersants, coatings and adhesives, to microelectronics, membranes, drug delivery, and biomaterials they have the potential of revolutionizing a large part of the polymer industry.     

A new method based on low background instrumental neutron activation analysis for major,trace and ultra-trace element determination in atmospheric mineral dust from polar ice cores

Dust found in polar ice core samples present extremely low concentrations, in addition the availability of such samples is usually strictly limited. For these reasons the chemical and physical analysis of polar ice cores is an analytical challenge. In this work a new method based on low background instrumental neutron activation analysis (LB-INAA) for the multi-elemental characterization of the insoluble fraction of dust from polar ice cores is presented. Thanks to an accurate selection of the most proper materials and procedures it was possible to reach unprecedented analytical performances, suitable for ice core analyses. The method was applied to Antarctic ice core samples. Five samples of atmospheric dust (μg size) from ice sections of the Antarctic Talos Dome ice core were prepared and analyzed. A set of 37 elements was quantified, spanning from all the major elements (Na, Mg, Al, Si, K, Ca, Ti, Mn and Fe) to trace ones, including 10 (La, Ce, Nd, Sm, Eu, Tb, Ho, Tm, Yb and Lu) of the 14 natural occurring lanthanides. The detection limits are in the range of 10⁻¹³–10⁻⁶ g, improving previous results of 1–3 orders of magnitude depending on the element; uncertainties lies between 4% and 60%.     

Tin-mediated synthesis of lyso-phospholipids

1-O-Acyl-sn-glycero-3-phosphocholine and 1-O-acyl-sn-glycero-3-phosphoric acid have been prepared selectively and with high yields from the corresponding diols, glycerophosphoryl choline and glycerol-3-phosphate. Starting from the diols, the activated tin ketals were prepared in 2-propanol by reaction with dialkyltin oxide. The intermediates were acylated in the same solvent with long-chain fatty acid chlorides, giving the corresponding 1-acyl-lyso-phospholipids in high yield and with complete regioselectivity. The catalytic nature of the tin-mediated acylation and the relevance of the solvent are discussed.     

An Arm‐First Approach to Cleavable Mikto‐Arm Star Polymers by RAFT Polymerization

Redox‐cleavable mikto‐arm star polymers are prepared by an “arm‐first” approach involving copolymerization of a dimethacrylate mediated by a mixture of macroRAFT agents. Thus, RAFT copolymerization of the monomers BMA, DMAEMA, and OEGMA, with the disulfide dimethacrylate cross‐linker (DSDMA), bis(2‐methacryloyl)oxyethyl disulfide, mediated by a 1:1:1 mixture of three macroRAFT agents with markedly different properties [hydrophilic, poly[oligo(ethylene glycol) methacrylate]—P(OEGMA)_8–9; cationizable, poly[2‐(dimethylamino)ethyl methacrylate]—P(DMAEMA); hydrophobic, poly(n‐butyl methacrylate)—P(BMA)] provides low dispersity mikto‐arm star polymers. Good control (Đ < 1.3) is observed for the target P(DMAEMA)/P(OEGMA)/P(BMA) (3:3:1) mikto‐arm star, a double hydrophilic P(DMAEMA)/P(OEGMA) (3:3) mikto‐arm star and a hydrophobic P(BMA) homo‐arm star. However, Đ for the target mikto‐arm stars increases with an increase in either the ratio [DSDMA]:[total macroRAFT] or the fraction of hydrophobic P(BMA) macroRAFT agent. The quaternized mikto‐arm star in dilute aqueous solution shows a monomodal particle size distribution and an average size of ≈145 nm.

     

Physical and Chemical Characterization of Cellulose Based Textiles Modified by Periodate Oxidation

Conversion of dihydroxyl groups to dialdehyde by periodate oxidation is a useful method widely used in derivatization of cellulose to activate the polymer to further reactions as grafting polymerization. To investigate the cellulose behavior at different level of oxidation and to better understand the influence of the crystallinity on the effects induced by oxidative reactions on different cellulose materials, linen and cotton textiles have been oxidized with periodate solutions in different conditions. Oxidized cellulose samples have been characterized by several techniques: solid-state ¹³C NMR, Wide Angle X-Ray diffraction, and SEM. Moreover the mechanical properties of the untreated and oxidized yarns have been evaluated by means of tensile tests, the oxidation degree has been measured by means of the hydroxylamine hydrochloride method.     

Characterisation by high-performance liquid chromatography-multiple mass spectrometry of intermediate compounds formed from mepanipyrim photoinduced degradation

Mepanipyrim, a widely used pyrimidinic fungicide, has been photocatalytically degraded in aqueous solution on TiO2. The purpose of this study is to artificially produce degradation compounds similar to those formed in the environment. Numerous intermediates have been identified and characterised through a MSn spectra analysis, allowing us to give insight into the early steps of the degradation process. Several concomitant pathways occur concerning both reductive and/or oxidative attacks; the main steps involve the cleavage of triple bond, mono and bihydroxylation of the parent molecule, loss of benzene moiety and/or propynylic chain. All these structures are easily degraded themselves, so that the only species recognised to endure in the investigated times is guanidine. A mechanism of transformation accounting for the identified intermediates is proposed.     

Donor–acceptor rod–coil block copolymers comprising poly[2,7‐(9,9‐dihexylfluorene)‐alt‐bithiophene] and fullerene as compatibilizers for organic photovoltaic devices

The successful synthesis is described for a donor–acceptor rod–coil block copolymer comprising blocks of poly[2,7‐(9,9‐dihexylfluorene)‐alt‐bithiophene] (F6T2) and polystyrene functionalized with fullerene (PS(C₆₀)) (F6T2‐b‐PS(C₆₀)). This new material was obtained by combining Suzuki polycondensation with radical addition fragmentation chain transfer. The block copolymer was characterized by nuclear magnetic resonance, gel permeation chromatography, and optical spectroscopy methods. Photophysical data for (F6T2‐b‐PS(C₆₀)) and a related block copolymer (F6T2‐b‐PS(PCBM)) (PCBM, phenyl‐C61‐butyric acid methyl ester) are reported and their performance as compatibilizers in bulk heterojunction organic solar cells is assessed. It is demonstrated that the addition of the rod–coil block copolymers to the active layer extends the operational stability of organic photovoltaic devices. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 888–903