ISSN:
0449-2951
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
A study of the scope and limitations of the anionic polymerization of styrene and substituted styrenes under conditions in which a chain termination reaction is lacking was made. Under these conditions polymers of very narrow molecular weight distributions were obtained. Ultracentrifuge data are presented as evidence confirming the formation of narrow distributions. All reagents used were carefully purified and subsequently were not exposed to the atmosphere. Standard procedure was to conduct the polymerizations by adding monomer solution slowly to initiator solution. Deviations from this procedure were designed to study various reaction conditions. Monomers used were styrene, α-methylstyrene, and m- and p-vinyltoluene. Solvents used were tetrahydrofuran, tetrahydropyran, 2-methyl-tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether. Initiators used were sodium-naphthalene, sodium-biphenyl, sodium-α-methylstyrene, sodium-phenanthrene, and lithium-naphthalene. The choice of solvent had a great effect on the course of the polymerization and the temperature at which narrow distribution polymers could be produced. Solvents promoting rapid initiation and relatively slow propagation were best, and those promoting the reverse situation tended to give side reactions leading to termination and abroad distribution polymer. The order of promotion of rapid initiation and slow propagation for these solvents is dioxan 〉 tetrahydrofuran 〉 ethylene glycol dimethyl ether 〉 diethylene glycol dimethyl ether. In dioxane solutions monodisperse polymer was prepared under a wide range of conditions. Monodisperse polymer could not be prepared under the most favorable conditions in diethylene glycol dimethyl ether. These effects were interpreted in terms of ion pair separation. Other factors which might lead to broad distribution polymers were examined. The age of the initiator was found to be very important, order initiator solutions giving broad distribution polymers. Aged initiator solutions were found to evolve hydrogen when allowed to react with water; freshly prepared initiator solutions evolved on hydrogen. In the presence of toluene there was chain transfer to the methyl group giving a broad distribution polymer. Similar transfer to benzene at the ring gave termination before polymerization was complete. Rusty iron, Fe2O3, and Fe3O4 adversely effected the course of polymerizations giving broad distribution polymers. Hydrogen-reduced iron in the reaction mixture resulted in only minor deviation from narrow distribution.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1963.100010526
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