isomerism

The paramagnetic probe method with the use of free radicals of different dimensions (2,2,6,6-tetramethyl-1-piperidinyloxy and 4-benzoate-2,2,6,6-tetramethyl-1-piperidinyloxy) has been employed to study the effect of the isomeric composition of butadiene units in polybutadienes and butadiene–acrylonitrile copolymers on the number and dimensions of ordered structures. The nature of density fluctuations and defective regions, that is, the regions in which the radicals are sorbed, has been ascertained.

Chain microstructures and supramolecular structures of nitrile- butadiene rubbers are studied by ESR spectroscopy. On the temperature dependences of the rotational mobility (correlation time τc) of paramagnetic probe 2,2,6,6-tetramethylpiperidine-1-oxyl, relaxation transitions are observed. It is shown that there is a correlation between the Arrhenius parameters of rotational mobility of radical and the copolymer composition and that different brands of rubbers differ in microstructure and supramolecular structure.