Research - Analytical Chemistry Laboratory
Service&Research Group
The Group provides analysis and molecular characterization of polymer materials by advanced instrumental methods for all departments of the Institute. To fulfill the mission, the group members also participate in the theoretical and practical development of the methods applicable in macromolecular science.
Novel controlled polymerization techniques produce polymeric materials with unprecedented complex molecular architecture. At the same time, various functionalized monomers are being used in smart applications of polymers. High fidelity of prepared materials is a must, starting with the monomers. The analytical chemistry and molecular characterization are indispensable in this respect.
Except elemental analysis, which gives the averaged content of chemical elements in the sample, the methods implemented by the Group are of separation nature – components of the sample are separated according to a certain physico-chemical property.
Gas chromatography (GC) is suitable for analysis of low-molecular-weight compounds. Thus, the information on polymer composition may be obtained only after degradation in a pyrolyzer. Usually, GC is used for purity check of commercial monomers and for verification of newly synthesized ones as well as in polymerization kinetic studies. Head-space analysis is employed in the identification of low-molecular-weight additives such as stabilizers and plasticizers.
We used GC with head-space sampling for analysis of volatiles released from wood, i.e. from a natural polymeric material. We detected harmful, irritant, and toxic compounds released from scorched wood; however, volatiles composition corresponded to intact wood after treating the surface of the scorched wood with a jet of dry-ice microparticles. The dry-ice micro-abrasion cleaning method proved to be suitable for restoration of wood elements and artefacts damaged by fire.
Size exclusion chromatography (SEC). SEC is a variant of liquid chromatography, in which the sample components equilibrate between the flowing solvent and the solvent immobilized in micropores of the packing material according to molecular dimensions. A chromatogram can be transformed into the molecular-weight distribution using calibration or directly, if a suitable detector is used. As the molecular dimensions depend also on the molecular architecture, the information on branching etc. can be obtained from SEC as well.
Experimental chromatograms are determined not only by the distribution of molecular dimensions of the sample, but also by number of other factors. We have developed a general chromatographic model, which allowed us to explain the effect of sample concentration on the chromatogram shape.
Asymmetrical flow field-flow fractionation (A4F) is a method related to SEC. A4F is more challenging experimentally, but with some clear advantages, from which the most important one is a much larger separation range 1—1000 nm. Consequently, A4F in aqueous solvents is mostly used for characterization of nanoparticles synthetized for applications such as drug delivery.
Another advantage of A4F is the absence of anomalies observed with SEC of high-molecular branched polymers. We explained the difference of these two methods by presenting the theoretical model of branched molecules separation in SEC.
Mass spectrometry (MS) separates charged particles according to the mass/charge ratio. Standard MS, accompanied with molecular fragmentation, gives information on the molecular structure and is frequently combined with chromatographic methods – specifically GC. Soft ionization techniques such as MALDI MS give molecular weight of intact molecules and are suitable for characterization of macromolecules. Due to the extraordinary precision, the nature of end groups, copolymer composition, or dendrimer quality can be inferred from MALDI MS results.
Gradient copolymers in which the content of one monomer increases intramolecularly along the chain are of a great interest in recent years. Nevertheless, no satisfactory detection method of intramolecular compositional gradient has been proposed so far. We have shown that MALDI MS may be such a method as it separates and identifies prematurely terminated molecules. These correspond to “time capsules” in which the information on the composition evolution during live copolymerization is preserved.
Cooperation
University of Chemistry and Technology, Prague, Department of Polymers
Charles University, Prague, Faculty of Science, Department of Physical & Macromolecular Chemistry
Pohang University of Science and Technology, Korea, Department of Chemistry
Laboratory Services
On contractual basis, the Group provides analytical laboratory services also to third-party customers. Elemental analysis is offered together with techniques outlined above. Feel free to inquire for details and availability at +420 296809360.