Continuous Spin Fractionation: A large scale method to improve the performance of polymers

Abstract

Most technical polymers and many biopolymers contain very different molecular species (unlike chain length, molecular architecture and/or chemical composition) in contrast to pure low molecular weight compounds. This inconsistent constitution of macromolecules proves very adverse in many cases. An adequate fractionation of polydisperse polymers is therefore mandatory. Very efficient means are available for analytical purposes. However, these methods break down as soon as the required amount of product exceeds some ten grams. In order to gain access to large enough quantities of sufficiently uniform polymer samples, we have developed a special kind of extraction process called Continuous Spin Fractiona-tion (CSF). The better soluble macromolecular species are preferentially transferred from a feed phase (concentrated polymer solution) into a pickup phase (solvent of tai-lored thermodynamic quality). The main problem of the procedure lies in the high vis-cosities of reasonably concentrated polymer solutions, impeding the attainment of ther-modynamic equilibria. This hurdle could be cleared by means of spinning nozzles through which the feed is pressed into the pickup phase. CSF can be implemented to any soluble polymer and is likewise apt for the production of small and of large amounts of polymer samples with the required uniformity. This contribution explains how to customize CSF to the polymer of interest and presents a number of typical ex-amples.