Hello Torben,

I think reading this article would be useful

Study of ion–solvent interactions and activation energy of LiBr in DMSO, H2O and DMSO–H2O mixtures at various temperatures

Ionics

August 2007, Volume 13, Issue 4, pp 245–255

Hope it helps

Amin

The Mechanism of dissolution of e.g, cellulose in DMSO in presence of LiBr - is very similar to that- in case of dissolution of (thermally untreated) Kevlar in concentrated H2SO4.

Namely- the main role in both the cases play voluminous anions of Br-  and  Cl-  which move the chains apart and prevent them from approaching each other.

See also: Nancy D Hann, 'Effects of lithium bromide on the gel-permeation chromatography of polyester-based polyurethanes in dimethylformamide' Journal of Polymer Science: Polymer Chemistry Edition Volume 15, Issue 6, 1331–1339 (June 1977)  DOI: 10.1002/pol.1977.170150604

Basically, as I understand it,  the LiBr bridges between high MW polymers taking the place of hydrogen bonding and thus increasing the resolution by separating these entities.

Thanks, Amin, Leonid, and Alan;

after reading the papers and with the descriptions you, Leonid and Alan, provided, I think I'm getting somewhere. Thanks.

I am still a little bit flustered by how the LiBr in such small concentrations (0.05M) is able to effectively break appart the polymer associations (of e.g. PE-based PUs) in solution and whether the LiBr more (1) directly affects the polymer chains (by associating to them, if yes how strong might such an association to an uncharged polymer be) or the (2) changes the characteristics of the solvent (DMF in that case) so it better screens the polar molecules from each other.

though, for now, that was all I was looking for and thanks for your answers.

@ Torben Well done in reading the replies and going to the literature. The LiBr does not have to physically break associations - it simply separates them where otherwise the loose associations would appear to be larger in size/MW.