K. Meißner and B. A. Wolf
"Continuous Polymer Fractionation - How does it function and how can it be applied to celluloses?"
Das Papier 1998, 52, 749-755.
Abstract: For basic research as well as for some technical applications it is often mandatory to have access to sufficient amounts of polymers with narrow molecular weight distribution. In case such products cannot be synthesized they must be obtained by fractionation. A method called CPF (Continuous Polymer Fractionation) allows the separation of the starting materials in their short chain and in their long chain constituents on a technical scale. This procedure consists in a continuous counter-current extraction; its successive application yields products with desired molecular weights and molecular weight distributions.So far CPF has been successfully applied to approximately two dozens of synthetic polymers. Cellulose, however could up to now only be fractionated in its derivatized form. Hydroxyethylcellulose did not show any particular difficulties. To prepare cellulose with narrow molecular weight distribution, CPF was also performed with trimethylsilylcellulose (where the substituents can be easily removed); here, however it turned out necessary to overcome several problems which are particularities of the system. In order to get easier access to such products we are presently checking whether there exist mixed solvents for cellulose which are suited for CPF.

preprint number: 181