I.N. Topchieva

Mono- and bifunctional 2,4-dinitrophenyl derivatives of polyethylene oxide☆

Mono- and bifunctional 2,4-dinitrophenyl derivatives of polyethylene oxide (PEO) are synthesized by two methods, i.e. by ionic polymerization of ethylene oxide and subsequent deactivation of the “living” polymers with appropriate reagents, and also by substitution of the OH groups of commercial polyethylene glycol (PEG). Polymers of M=900−102,000 are identified by UV spectroscopy, chemical analysis methods, and from the molecular mass characteristics. Comparison of the two methods of synthesis shows that the first results in higher final 2,4-dinitrophenyl functionality. The synthesized polymers have immunogenic properties.

Spin-labelled polymer catalysts prepared from polyoxyethylene

Spin-labelled polymer catalysts were synthesized from polyxyethylene samples having molecular weights 15,000 and 40,000 and N-(2,2′,5,5′-tetramethyl-3-carboxypyrrolidine-1-oxyl)histidine (POIG-15 and POIG-40) and hydrolysis of p-nitrophenylacetate (NPA) in their presence examined. The nature of the relation between induction periods and the rate of hydrolysis of NPA catalysed by POBG-15 indicates the equilibrium, active “monomer” → inactive associate. From an analysis of this relation the number of macromolecules contained in the associate was determined. From a study of EPR spectra and the electrophoretic mobility of POIG-15 abd POIG-40 preparations it was assumed that the imidazole group in the molecule of a mono-substituted compound is inside the polymer globule.

A kinetic study of polyoxyethylene glycol cyclization under conditions of the Pfitzner-Moffat reaction

Abstract The kinetics was studied of the polyoxyethylene glycol cyclization in the presence of dicyclohexylcarbodiimide, dimethyl sulfoxide and ortho -phosphoric acid in CCl 4 at room temperature (the Pfitzner-Moffat reaction). For polymers of various molecular mass, the rate constants of this reaction were determined by IR-spectroscopy. The rate constant of oxidation of a low-molecular mass monofunctional analogue (ethanol) was determined by GLC. It was found that in all cases the constants have similar values, in the range (4–7) × 10 −6 sec −1 . The polymer cyclization rate appears to be limited by the hydroxyl group oxidation to aldehyde.

Conformational models of mono- and disubstituted polyoxyethylene ethers of n-benzoylhistidine

A study was made of the electrophoretic behaviour of polyoxyethylene ethers of N-benzoylhistidine (POBH) with molecular weights of 15,000 and 40,000. It is shown that in both cases the polymer separates into two fractions: a mixture of monosubstituted POBH and unreacted polyoxyethylene (POE), of low electrophoretic mobility, and disubstituted POBH of relatively high electrophoretic mobility. The reaction of modification of imidazole groups of the mono- and disubstituted POBH of these compounds with bromoacetic acid was investigated. It is shown that no modification of imidazole groups of the monosubstituted compounds takes place, but that the disubstituted POBH are catalytically active and can be modified with the bromoacetic acid. The pK values of imidazole groups of the monosubstituted POBH were determined by the potentiometric titration method. On comparing pK values for the imidazole of the mono- and disubstituted molecules it is concluded that H bonds play a major role in stabilizing the structure of the monosubstituted POBH samples.

Catalysts used in hydrolysis of esters prepared from associating macromolecules

Abstract A study was made of new properties of polymer-polymer catalytic adsorption systems in which parts combining the substrates and catalytically active groups belong to different polymers. An investigation was made of polyoxyethylene ester-N-benzoylhistidine-polyacrylic (or polymethacrylic) acid systems in hydrolysis of neutral and positively charged substrates. It was shown that the catalytic efficiency of polyoxyethylene ester of N-benzoylhistidine in hydrolysis of p -nitrophenylacetate, a neutral substrate, remains practically unchanged, while hydrolysis of a positively charged substrate— p -dimethylaminophenylacetate iodomethylate in the presence of polyoxyethylene ester of N-benzoylhistidine, is considerably accelerated on adding poly acid. It is assumed from kinetic results that a polyoxythylene ester complex of N-benzoylhistidine-poly-acid is formed. The catalytic behaviour of polyoxyethylene ester of N-benzoylhistidine was examined in hydrolysis of a polymer substrate—a copolymer of acrylic acid with p -nitrophenyl ester of p -vinylbenzoic acid.