Copolymerization of N‐tert‐Butylacrylamide with Ethylene Glycol Dimethacrylate

N‐tert‐butylacrylamide (NtBA) was copolymerized with ethylene glycol dimethacrylate (EDMA) in butanone solution over a wide composition and conversion range, using dibenzoyl peroxide (Bz₂O₂) as a free‐radical initiator. The copolymer composition was determined from the nitrogen content. Using only low conversion (≤20%) collected for the copolymerization reactions, monomer reactivity ratios were estimated using the Kelen‐Tüdos graphical method and were found to be r₁=0.26 (NtBA) and r₂=7.05 (EDMA). In order to get a better insight into the mechanism of nanoporous copolymers of NtBA with EDMA preparation by thermal degradation of copolymers of N‐acryl‐N,N′‐di‐tert‐butylurea (A‐DitBuU) with EDMA, nonporous copolymers (model compound), of the same chemical structure and composition, were prepared by performing copolymerization of NtBA with EDMA up to the high conversion of 97–100%. Thermal behavior of nanoporous and nonporous copolymers of NtBA with EDMA was studied.     

Advancements of thermal analysis and calorimetry in Central-Eastern Europe and Mediterranean region

Journal of Thermal Analysis and Calorimetry -     

Non-Stationary Abstract Friedrichs Systems

Inspired by the results of Ern et al. (Commun Partial Differ Equ 32:317–341, 2007) on the abstract theory for Friedrichs symmetric positive systems, we give the existence and uniqueness result for the initial- (boundary) value problem for the non-stationary abstract Friedrichs system. Despite the absence of the well-posedness result for such systems, there were already attempts for their numerical treatment by Burman et al. (SIAM J Numer Anal 48:2019–2042, 2010) and Bui-Thanh et al. (SIAM J Numer Anal 51:1933–1958, 2013). We use the semigroup theory approach and prove that the operator involved satisfies the conditions of the Hille–Yosida generation theorem. We also address the semilinear problem and apply the new results to a number of examples, such as the symmetric hyperbolic system, the unsteady div–grad problem, and the wave equation. Special attention was paid to the (generalised) unsteady Maxwell system.     

Structural Differences Between Copolymers of Acryl‐ and Methacryl‐dicyclohexylurea with Ethylene Glycol Dimethacrylate and their Thermal Degradation Products

The present paper describes structural characteristics of crosslinked copolymers of acryl‐dicyclohexylurea (A‐DCU) and methacryl‐dicyclohexylurea (MA‐DCU) with ethylene glycole dimethacrylate (EDMA). Both copolymers decompose when heated at temperatures between 180–250°C under the separation cyclohexylisocyanate (C₆H₁₁NCO) yielding nanoporous copolymers of poly(A‐CHA‐co‐EDMA) and poly(MA‐CHA‐co‐EDMA). The comparison was also made between structural characteristics of crosslinked nanoporous copolymers of poly(A‐CHA‐co‐EDMA) and poly(MA‐CHA‐co‐EDMA) and nonporous crosslinked model compounds poly(A‐CHA‐co‐EDMA) and poly(MA‐CHA‐co‐EDMA).     

Functions,equivalence relations,quotient spaces and subsets in fuzzy set theory

In the usual set theory, the power set of a set X is lattice isomorphicto 2^x. The theory of fuzzy sets, or fuzzy set theory, involves generalizing the lattice 2 = {0, 1} to a more general, usually non-Boolean, lattice. A ‘point’ in this lattice need not have Boolean properties. Thus proper generalizations must be based on notions which are defined without explicitly using points. In the light of this we give equivalent definitions of function, relation and quotient set involving the members of a power set but not specifically the singletons.A number of authors [1,2,5] have worked with generalizations of functions and quotient sets which are not strictly point free. It emerges that these are special cases of the ones we produce.     

Determination of very-long-chain fatty acids in plasma by a simplified gas chromatographic-mass spectrometric procedure

The concentration of very-long-chain fatty acids (VLCFA) (straight chain, more than 22 carbon atoms) in plasma or in cultured fibroblasts is one of the most important diagnostic criteria for the diagnosis of the peroxisomal disorders. A sensitive method for VLCFA assay in plasma, using small sample volume and a simplified procedure, is described. After adequate extraction and derivatization, methyl esters of VLCFA are separated, identificated and quantified by gas chromatography-mass spectrometry (GC-MS). The method is sensitive, reproducible, accurate and relatively simple. GC-MS equipment used for routine organic acid analysis can be used.     

Free-Radical-Initiated Polymerization of N(p-Phenoxy-phenyl)maleimide and Copolymerization with Styrene, α-Methylstyrene and β–Methylstyrene

Abstract

Synthesis and free-radical-initiated homopolymerization of phenoxy-phenylmaleimide (PhOPhMI) and copolymerization with styrene (St), (α-methylstyrene (αMeSt) and β–methylstyrene (β-MeSt) are described. It was found that alternating copolymers are formed under different monomer-to-monomer ratios in the feed and that the mechanism based on the participation of CT-complex best explains the formation of alternating copolymers. Equilibrium constants of CT-complexes are: K _PhOPhMI/St = 0.20 Lmol^?1; K_{PhOPhMI/αMeSt} = 0.05 Lmol^?1; K_{PhOPhMI/βMeSt} = 0.02 Lmol^?1. Homopolymer and co-polymers are film-forming materials, stable up to 350°C under TGA conditions. T_g s and higher transition temperatures are within the thermally stable region.     

Characterization of poly(ethylene oxide) modified with different phenyl hepta isobutyl polyhedral oligomeric silsesquioxanes

Journal of Thermal Analysis and Calorimetry - Poly(ethylene oxide)/polyhedral oligomeric silsesquioxanes (PEO/POSSs) composites were prepared by the melting method. The investigation of their...     

Spectrophotometric and polarographic investigation of the Ofloxacin-Cu(II) complexes

By means of spectrophotometric methods it was found that ofloxacin reacts with copper(II) ions to form complexes with molar ratios of ofloxacin: Cu(II) of 1:1 at pH 4.00, 2:1 at pH 7.02 and 3:1 at pH 8.30. The stability constants of the complexes were determined. The formation of ofloxacin:Cu(II) 1:1 and 3:1 complexes was confirmed by a polarographic method and the corresponding overall stability constant was evaluated.