Separation according to branching
Although technically very important, the development and understanding of high performance polymers with specific branch architecture is currently limited due to the lack of adequate characterization and separation techniques for branched polymers. The multiple distributions in molar mass, branching topology and chemical structure forced us to search for a new methodology for effective clarification of the composition of branched polymers.
Our first attempts involved the systematic identification of branching using liquid chromatography under critical conditions performed in collaboration with DKI Darmstadt (now Fraunhofer LBF) which was financially supported by the Dutch Polymer Institute. A series of well-defined polyesters in chemical composition, molar mass and branching was prepared for this purpose. In this way separation according to dendritic type of branching was performed for the first time. Further development on the basis of two-dimensional liquid chromatography shows that this approach even leads to quantitative separation and determination of branching. Recent efforts are focused on the robust application of this technique to industrially relevant hyperbranched polymers.
Simultaneously, we are searching for novel approaches capable to identify and separate the different types of branching. Recent investigations were focused on phase distribution chromatography (PDC) used initially for the separation of polymers by their molecular weight. The separation principle is based on the different distribution coefficients of the different species within the stationary phase. We used non-crosslinked, ultra high molecular weight polystyrene (UHPS) as a stationary phase. At the theta conditions of the UHPS, different distribution equilibrium between mobile and stationary phase of the linear and branched polymers is expected. The difference in the thermodynamic parameters between linear and star polystyrene enables the separation according to branching by PDC
The research activities of our group on the systematic development of branching separation techniques led to the formation and coordination of strong scientific consortium on an international level. Leading European scientists with outstanding expertise in the field of branched polymers, like Peter Schoenmakers (University of Amsterdam), Tom McLeish (University of Durham), an Australian scientist, Bob Gilbert (University of Queensland) together with leading industrial enterprises in this area joined in to work together on a proposal in the frame of the FP7.
M. Al Samman et al. Retention Behaviour of Linear, Branched and Hyperbranched Polyesters in Interaction Liquid Chromatography, Macromolecules 2010, 43, 3215-3220
S. Boye et al. Separation of Linear and Star-Shaped Polystyrenes by Phase Distribution Chromatography J. Sep. Sci. 2010, 33, 35843594
S. Boye et al. Solution Properties of Selectively Modified Hyperbranched Polyesters Polymer 2010, 51, 4110-4120