Peculiarities in the copolymerization of trioxane and epichlorohydrin under the influence of EtB⊖F3 A⊕lEt2

This study deals with the copolymerization of trioxane (TO) and 1-chloro-2, 3-epoxypropane (epichlorohydrin, ECH) catalyzed by EtB^?F₃ A^⊕lEt₂ in toluene. The rate of exhaustion of monomers during copolymerization was measured by gas chromatography. It was established that no homopolymers were formed. The copolymers obtained show a high alkali resistance, indicating a statistical distribution of the ECH in the polymer chain. During the first stages of the copolymerization the ECH is exhausted almost instantaneously, whereas TO is gradually exhausted, finally reaching a certain equilibrium depending both on the quantity of the initial ECH and on the temperature at which the process was carried out. Copolymerization is inhibited at increased ECH levels, and only homopolymerization occurs at a certain critical concentration of ECH.     

Dependence of the catalytic activity of organoaluminum compounds and some of their complexes on their composition

The influence of the acidity of organoaluminum compounds and their complexes on the catalytic activity in polymerization of trioxane has been studied. It is found that the catalytic activity of organoaluminum compounds of the type R_nALX_3?n depends on n as well as the nature of R or X. Catalytic activity of the complexes also depends on the type of cocatalyst used. The change of electroconductivity in the course of formation of some initiator complexes has been studied and an attempt has been made to determine the relation between conductivity and polymerization activity.     

Effects of different composition ratio on the dielectric relaxation and dynamic mechanical properties of poly(ω‐dodecalactam‐co‐ε‐caprolactam‐co‐propylene oxide) copolymers

The molecular dynamics of new poly (ω‐dodecalactam‐co‐ε‐caprolactam‐co‐propylene oxide) copolymers (DL/CL/PAC) has been investigated by using dynamic mechanical thermal analysis (DMTA) and dielectric relaxation spectroscopy (DRS) measurements. The copolymers were synthesized via anionic polymerization of relevant lactams activated with carbamoyl derivatives of telechelic hydroxyl terminated polypropylene oxide with isophorone diisocyanate (PAC). The calorimetric, X‐ray diffraction, and DMTA measurements were performed to recognize the influence of the composition ratio and the type of PAC on the physical, thermal, and mechanical properties of the synthesized copolymers. The DRS was used to study the frequency dependence of the dielectric permittivity of some isotherms from ?110 to 145 °C. Copolymerization of ε‐caprolactam with about 10 wt % ω‐dodecalactam results in a copolymer that has lower water absorption, a melting point close to that of polyamide 6 and has a high enough degree of crystallinity in respect to high storage modulus. Five dielectric relaxations have been observed in the dielectric spectra, three at lower temperature and two at higher temperature. The copolymers have two glass transition temperatures for polyamide segments and polyether blocks, indicating microphase separation in the copolymers. Other studies directed toward molecular dynamics of polyamide DL/CL/PAC copolymers have not been reported. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Densitometric TLC Analysis of Histamine in Fish and Fishery Products

JPC – Journal of Planar Chromatography – Modern TLC - A simple and rapid densitometric thin-layer chromatographic method, suitable for monitoring the histamine content of fish and...     

On the kinetics and mechanism of copolymerization of vinyl acetate and itaconic monomers

The introduction of anionic hydrophylic groups in the pendant chain of polyvinyl alcohol improves its surface and adhesive properties. For the purpose of synthesizing raw materials for preparation of modified polyvinyl alcohol with enhanced performance characteristics, the copolymerization of vinyl acetate with itaconic acid and diethyl itaconate at concentrations up to 9 mol % in methanol solution using azo-bis-isobutyronitrile and tert-butylcyclohexylperoxydicarbonate as initiators has been studied. The experiments were performed using two different methods of addition of the itaconic monomer—single, at the beginning of the process, and continuous. It was established that the process rate decreases as the quantity of the second comonomer increases. The reaction order in terms of itaconic acid ( ?2, 95) and reactivity ratios for both pairs vinyl acetate and itacinic acid (r₁ = 0.053 and r₂ = 31) and vinyl acetate and diethyl itaconate (r₁ = 0.125 and r₂ = 18) were determined. The products obtained were characterized by IR and NMR. It was confirmed that for the case of single addition at the beginning of the process a two-phase system is formed while the continuous addition resulted in random group distribution.     

Crystal growth, defect structure and magnetism of new Li3N-derived lithium nitridocobaltates

New nitridocobaltates Li(3-x-y)Co(x)N are revealed to contain significant Li(+) vacancies (y approximately 0.45) disordered within lithium-nitrogen planes and to exist as partially delocalised spin systems as a result of increased covalency through infinite -N-(Li,Co)-N- chains.     

Anionic copolymerization of hexanelactam with functionalized polyisoprene

Block copolymers of the A‐B‐C‐B‐A type were synthesized for the first time via the activated anionic polymerization of hexanelactam (HL) with Na‐HL as an initiator and macroactivators [or polymeric activators (PACs)] as elastificators for nylon‐6. The PACs were prepared by the functionalization of telechelic hydroxyl‐terminated poly(ethylene oxide)–polyisoprene–poly(ethylene oxide) copolymers with different diisocyanates. Hexamethylene diisocyanate (1,6‐diisocyanatohexane) and isophorone diisocyanate (5‐isocyanate1‐isocyanatomethyl‐1,3,3‐trimetylcyclohexane) were used as functionalizing agents. This article reports on the effects that the various central elastomeric PAC blocks (type, content, and molecular weight) had on the polymerization kinetics and on the structure and molecular weights of the multiblock copolymers obtained. The copolymers were characterized spectroscopically. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 487–496, 2003     

Copolymerization of trioxane with phenylglycidylether

This study deals with the regularities and peculiarities of the copolymerization of trioxane (TO) and phenylglycidylether (PhGE) in nitrobenzene catalyzed by the cationic initiator BF₃Et₂O. The additions of PhGE were varied in wide bounds from 5 up to 50 mol %. No data were found about the course of copolymerization process, as well as about the influence of the polymerization conditions on the rate of exhaustion of the monomers and the composition of the copolymer. The effect of the polymerization conditions on the rate of exhaustion of comonomers was established. The kinetics of the process has been followed; the following equation is proposed: The activation energy was determined to be E_α = 15.3 kcal/mol. The course of copolymerization of TO/PhGE was compared with those of TO/DO, TO/EO, TO/St, and TO/ECH. The variation of comonomer concentrations was measured by gas chromatographic methods. The copolymers were characterized by elemental analysis, IR-, and NMR-spectroscopy, as well as by their molecular weights (M _v).     

Arsenic speciation patterns in freshwater fish

Muscle of 16 freshwater fish (9 different species belonging to 4 different families) was analysed for arsenic species using HPLC separation (anion and cation exchange) followed by on-line UV-decomposition, hydride generation and AFS detection. The main arsenic compounds found in the extracts were arsenobetaine (AsB), which accounted for 92–100% of extractable arsenic in species of salmonids (Salmo marmoratus, Oncorhynchus mykiss, Salmo trutta m. fario), and dimethylarsinic acid (DMAA), which accounted for 75% of extractable arsenic in burbot (Lota lota). AsB was also found in lower concentrations in almost all other fish species analysed (Silurus glanis, L. lota, Barbus barbus, Rutilus pigus virgo, Chondrostoma nasus). Arsenite (As(III)) and trimethylarsine oxide (TMAO) were detected in low concentrations in some representatives of Cyprinidae only (R. pigus virgo, C. nasus). Except in salmonids, an unknown cationic compound was present in most of the samples in relatively low concentrations. Cluster analysis of the generated data seems to indicate that there is a correlation between fish family and the arsenic speciation pattern. This is especially clear for the salmonids which show a completely separate cluster and thus a very distinct arsenic speciation pattern.