Analytical technique used to characterise polymers, gels and nanoparticles

Thermal field flow fractionation has been successfully used to elucidate the core microstructure, morphology and chain arrangement of self-assembling block copolymers

A study conducted by a research group at the Department of Chemistry and Polymer Science, University of Stellenbosch (South Africa) has used thermal field flow fractionation to elucidate the core microstructure, morphology and chain arrangement of self-assembling block copolymers (BCPs).

The measurements for this study were performed using a Postnova Analytics TF2000 thermal field-flow fractionation system coupled in series to MALS and RI detectors, and Malvern Instruments Zetasizer Nano system. 

“Thermal FFF data has proved invaluable in advancing our research,” said Professor Pasch, head of the research group. “It allows us to separate and understand polymer species that we otherwise would not be able to, adding a new dimension to our analytical capability.”

Thermal field flow fractionation is a technique that is ideally suited to the characterisation of polymers, gels and nanoparticles using different organic solvents and to get additional chemical information about the polymers. Different from the other field flow fractionation sub-techniques, thermal field flow fractionation can separate polymers not only by molar mass but also by chemical composition at the same time. Thus, thermal field flow fractionation can separate two polymer fractions of different material but same molecular weight into independent peaks.

The correlation of BCP microstructure and the structure of the resulting self-assemblies requires advanced analytical methods. However, traditional bulk characterisation techniques are limited in the quest to provide detailed information regarding molar mass (Mw), hydrodynamic size (Dh), chemical composition and morphology for these self-assemblies. 

The researchers were able to successfully separate, using ThFFF, micelles prepared from BCPs of similar PS and PBd block sizes. Furthermore, it was established that for the vesicles and homopolymers of similar surface chemistry and Dh, ThFFF was sensitive towards the inherent differences in morphology and chain arrangement, enabling the two polymeric species to be successfully separated.