Ring‐opening polymerization of cyclic esters promoted by phosphido‐diphosphine pincer group 3 complexes

Phosphido‐diphosphine Group 3 metal complexes 1–4 [(o‐C₆H₄PR₂)₂P‐M(CH₂SiMe₃)₂; R = Ph, 1 : M = Y, 2 : M = Sc; R = iPr, 3 : M = Y, 4 : M = Sc] are very efficient catalysts for the ring‐opening polymerization (ROP) of cyclic esters such as ε‐caprolactone (ε‐CL), L ‐lactide, and δ‐valerolactone under mild polymerization conditions. In the ROP of ε‐CL, complexes 1–4 promote quantitative conversion of high amount of monomer (up to 3000 equiv) with very high turnover frequencies (TOF) (～4 × 10⁴ mol_CL/mol_I h) showing a catalytic activity among the highest reported in the literature. The immortal and living ROP of ε‐CL and L ‐lactide is feasible by combining complexes 1–4 with 5 equiv of 2‐propanol. Polymers with controlled molecular parameters (M_n, end groups) and low polydispersities (M_w/M_n = 1.05–1.09) are formed as a result of fast alkoxide/alcohol exchange. In the ROP of δ‐valerolactone, complexes 1–4 showed the same activity observed for lactide (L ‐ and D ,L ‐lactide) producing high molecular weight polymers with narrow distribution of molar masses. Complexes 1–4 also promote the ROP of rac‐β butyrolactone affording atactic low molecular weight poly(hydroxybutyrate) bearing unsaturated end groups probably generated by elimination reactions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Effect of UV activation on acid and catalytic properties of zeolite-containing catalysts in conversion of gas-condensate straight-run gasolines to high-octane gasolines

Effect of activation by UV radiation with different wavelengths on the acid and catalytic properties of the N-TsKE-G zeolite catalyst in conversion of straight-run gasolines from the gas condensate of the Myl’dzhinskoe deposit to high-octane components of motor fuels was studied.     

Poly‐2‐oxazoline‐derived polyurethanes: A versatile synthetic approach to renewable polyurethane thermosets

2‐Nonyl‐2‐oxazoline and 2‐(9‐decenyl)‐2‐oxazoline have been copolymerized in different proportions by cationic ring‐opening polymerization to obtain a series of random linear copolymers with tailored molecular weight and double bond functionality in the side chains. Thiol‐ene addition of 2‐mercaptoethanol has been used to produce a set of polyoxazoline–polyols under mild conditions and with quantitative double bond transformation. The polyols obtained in this way were reacted with methylene‐bis(phenylisocyanate) to yield a series of amorphous and semicrystalline polyurethane networks. The thermal stability and the thermomechanical properties of these thermosets have been studied and related with the structure of the parent polyols. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Food authentication in real life: How to link nontargeted approaches with routine analytics?

In times of increasing globalization and the resulting complexity of trade flows, securing food quality is an increasing challenge. The development of analytical methods for checking the integrity and, thus, the safety of food is one of the central questions for actors from science, politics, and industry. Targeted methods, for the detection of a few selected analytes, still play the most important role in routine analysis. In the past 5 years, nontargeted methods that do not aim at individual analytes but on analyte profiles that are as comprehensive as possible have increasingly come into focus. Instead of investigating individual chemical structures, data patterns are collected, evaluated and, depending on the problem, fed into databases that can be used for further nontargeted approaches. Alternatively, individual markers can be extracted and transferred to targeted methods. Such an approach requires (i) the availability of authentic reference material, (ii) the corresponding high-resolution laboratory infrastructure, and (iii) extensive expertise in processing and storing very large amounts of data. Probably due to the requirements mentioned above, only a few methods have really established themselves in routine analysis. This review article focuses on the establishment of nontargeted methods in routine laboratories. Challenges are summarized and possible solutions are presented.     

Acidic Proteases from Monterey Sardine (Sardinops sagax caerulea) Immobilized on Shrimp Waste Chitin and Chitosan Supports: Searching for a By-product Catalytic System

Solid wastes generated from the seafood industry represent an important environmental pollutant; therefore, utilization of those wastes for the development of processing biochemical tools could be an attractive and clean solution for the seafood industry. This study reports the immobilization of semi-purified acidic proteases from Monterey sardine stomachs onto chitin and chitosan materials extracted from shrimp head waste. Several supports (chitosan beads, chitosan flakes, and partially deacetylated flakes) were activated either with genipin or Na-tripolyphosphate and evaluated as a mean to immobilize acidic proteases. The protein load varied within the 67–91 % range on different supports. The immobilization systems based on chitosan beads achieved the highest protein loads but showed the lowest retained catalytic activities. The best catalytic behavior was obtained using partially deacetylated chitin flakes activated either with genipin or Na-tripolyphosphate. According to results, the immobilization matrix structure, as well as acetylation degree of chitin–chitosan used, has considerable influence on the catalytic behavior of immobilized proteases. Partially deacetylated chitin flakes represent a suitable option as support for enzyme immobilization because its preparation requires fewer steps than other supports. Two abundant seafood by-products were used to obtain a catalytic system with enough proteolytic activity to be considered for biotechnological applications in diverse fields.     

Solitons generated by self-organization in bismuth germanium oxide single crystals during the interaction with laser beam

We present here the experimental, theoretical, and numerical investigations of Kerr solitons generated by self-organization in black and yellow high quality bismuth germanium oxide (Bi₁₂GeO₂₀) single crystals. A picosecond laser beam of increasing power induces competing cubic and quintic nonlinearities. The numerical evolution of two-dimensional complex cubic-quintic nonlinear Schrödinger equation with measured values of nonlinearities shows the compensation of diffraction by competing cubic and quintic nonlinearities of opposite sign, i.e., the self-generation and stable propagation of solitons. Experiments as well as numerical simulations show higher nonlinearity in the black Bi₁₂GeO₂₀ than in the more transparent yellow one.     

Exchangeless magnetoelectric magnons: A new class of mixed hybrid dipole waves

A layer of an easy-axis antiferromagnet with antisymmetry center is considered. It is shown that the combination of magneto- and electric-dipole mechanisms of the indirect spin–spin interactions gives rise to the previously unknown class of hybrid dipole waves such as exchangeless magnetoelectric magnons and to the spin–spin and spin–dipole resonances accompanying them. The conditions for the formation of these waves are determined.