Reference : Microdynamics of reverse micelles of ω- and α,ω-metal sulfonato polystyrene in toluene
Scientific journals : Article
Engineering, computing & technology : Materials science & engineering
Physical, chemical, mathematical & earth Sciences : Chemistry
http://hdl.handle.net/2268/15706
Microdynamics of reverse micelles of ω- and α,ω-metal sulfonato polystyrene in toluene
English
Vanhoorne, Pierre [University of Liège (ULg) > Department of Chemistry > Center for Education and Research on Macromolecules (CERM) > >]
Grandjean, Jean mailto [University of Liège (ULg) > Department of Chemistry > Laboratoire de Chimie Fine aux Interfaces > >]
Jérôme, Robert mailto [University of Liège (ULg) > Department of Chemistry > Center for Education and Research on Macromolecules (CERM) > >]
18-May-1995
Macromolecules
Amer Chemical Soc
28
10
3553-3561
Yes (verified by ORBi)
International
0024-9297
Washington
[en] halatotelechelic polymer
[en] Reverse micelles of omega- and alpha,omega-metal sulfonato polystyrenes in toluene have been investigated by Li-6, Li-7, and pulsed field gradient NMR. Micelles are found to be of a narrow size distribution and to consist of roughly spherical ionic cores shielded from the solvent by a polystyrene shell. The nature of the ion pair is found to influence significantly the micellar size. The correlation time characteristic of lithium relaxation is faster than the reorientational correlation time of the aggregates, which means that lithium relaxation essentially takes place within the ionic cores. The effective relaxation mechanism is consistent with a fast exchange of lithium ions between different coordination sites within the aggregates. In concentrated solutions, the equilibrium between aggregated polymer chains and unassociated chains is essentially shifted toward the aggregated species. This tendency is reversed upon dilution. Below a critical micellar concentration of ca. 0.01 g/dL, only ''free'' chains persist in solution. Temperature has no significant effect on the position of the aggregation equilibrium. The aggregates are dissociated by the addition of a polar cosolvent, such as methanol, which solvates the ion pairs. The MeOH/Li+ molar ratio must, however, be higher than 100 to perturb significantly the ion pair aggregation. Up to a MeOH/Li+ ratio of 10 000, part of the chains remain aggregated, and the lithium spin-lattice relaxation is dominated by the aggregates. Above a MeOH/Li+ ratio of 10 000, the aggregates are almost completely disrupted. Self-diffusion coefficients of the difunctional chains are not dramatically smaller compared to the monofunctional counterparts, even when solutions of difunctional compounds form a gel. This behavior might be explained by the percolation model applied to the aggregation process, with the pulsed field NMR experiment probing only the selfdiffusion of the clusters in the sol phase of the gel.
Center for Education and Research on Macromolecules (CERM)
Politique Scientifique Fédérale (Belgique) = Belgian Federal Science Policy ; Fonds de la Recherche Scientifique (Communauté française de Belgique) - F.R.S.-FNRS
Researchers
http://hdl.handle.net/2268/15706
10.1021/ma00114a008
http://pubs.acs.org/doi/pdf/10.1021/ma00114a008

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