ISSN:
0449-2951
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
A study has been carried out on the molecular weights and their distribution for polystyrene prepared by means of ethyl and butyl lithium initiators, using benzene and tetrahydrofuran as solvents. Stringent high vacuum techniques were employed in order to minimize any destruction of initiator or termination of growing chains in these anionic polymerizations. Under these conditions, it was found that the stoichiometry corresponded to the formation of one chain from each initiator molecule. Furthermore, the molecular weight distribution could be made very narrow (M̄w/M̄n = 1.05 - 1.1) in these cases, where the initiation reaction was very rapid compared to the propagation step. In the case of the benzene systems, the initiation reaction was too slow, leading to a broadening of the molecular weight distribution, and this could be circumvented by a “seeding” technique whereby all the chain anions were pre-initiated before the main polymerization took place. The alkyl lithium initiators were found to react rapidly with THF at room temperature, but the styryl lithium apparently did not.
Zusätzliches Material:
6 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/pol.1963.100010140
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