ISSN:
0360-6376
Schlagwort(e):
Physics
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
Spiro[2,4]hepta-4,6-diene, a derivative of cyclopentadiene, was polymerized at -76°C with various triphenylmethyl salts as initiator. The polymer consists only of the 1,2- and 1,4-addition structures, and their contents can be determined by the relative area of the olefin proton peaks. The polymer structure changed characteristically with the polymerization conditions. The content of 1,4-structure decreased with increasing polarity of the medium from 45-70 in toluene to 25-30% in 7:3 CH2Cl2-CH3CN. In 1:1 CH2Cl2-toluene, the 1,4-structure content decreased from 70% to 40% with increasing radii of counteranions. These results were interpreted according to the model of the cationic propagation proposed earlier, as arising from the different tightness of the propagating ion pair. In the case of pentacoordinate counteranions, in particular SnCl5-, the 1,4-structure content was greater than expected from the anion size alone and decreased with increasing initiator concentrations, in contrast with the behavior of the other tetra- and hexacoordinate anions. This was attributed to the possibly facile aggregation of the pentacoordinate anion. However, the common ion effect was not observed.
Zusätzliches Material:
4 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/pol.1975.170131115
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