Search

Reported here is the study on various types of ESR spectra of the propagating radical in polystyrene. Spectrum simulation, analysis of the hyperfine coupling constant, and calculations of the conformation energy show that the propagating radical of styrene has two stable inner-rotation conformations R1 and R2. R1 corresponds to a 6-line spectrum which, in some special conditions, can appear as a 4-line or 3-line spectrum. R2 corresponds to an 8-line spectrum which, in some special conditions, appear as a 6-line spectrum. All the ESR spectra observed in the polymerization process can be regarded as the superposition of some of these spectra. The concentration ratio of R1 to R2 is affected by rotational interchange between R1 and R2, as well as the propagating reaction

The ammonium sulfate-iron oxide system treated at different temperatures has been characterized by ESR, IR and Mossbauer spectroscopy. Results show that during the heat treatment some interaction between ammonium sulfate and iron oxide takes place. As a result of this interaction a surface sulfato complex of iron is formed. The complex is involved in the sites responsible for activity for acid catalytic esterification. Above 573 K, the sulfato complex will gradually decompose with a further increase in temperature. A new structure scheme of the sulfato complex is proposed.