ISSN:
0025-116X
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The polymerization of methylthiirane in homogeneous phase initiated by bis(isopropylcysteinato)cadmium is a living process. For low conversions, oligomers (essentially heptamers and octamers) are formed, apparently using one valency of cadmium, the main propagation taking place by using the other one. However, the size of the oligomers may still grow for higher conversions. The mechanism of the oligomer formation depends on the temperature. A “normal” insertion of the monomer is observed at -23°C, whereas at 20°C a disulfide bond is formed. The preferential choice of a different enantiomer in the main propagation reaction may depend on the presence of a particular type of oligomer, in the vicinity of cadmium, linked to the cysteine group. However, stereospecificity (stereoselection and stereoelection) appears only with molecular weights higher than 6000 and also depends on the temperature of propagation: with decreasing temperature, the stereoregularity increases and the stereoelection can be inverted (for a definite oligomer structure).
Additional Material:
5 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/macp.1984.021850705
Permalink
