Polymers are never as simple as one would like them to be. Naturally occurring polymers vary in structure depending upon their biological source, while the properties of synthetic polymers depend upon the precise reaction conditions and mix of co-polymers. Dissecting out subtle difference in polymer structures often begins with the estimation of molecular weights based on polymer viscosity. However, traditional viscosity measurements require careful calibration and rely on making several assumptions about the characteristics of the polymer/solvent system that may not prove to be correct.
One instrument that circumvents these problems in the Brookhaven Instruments BI-MwA Molecular Weight Analyzer, which uses static light scattering (SLS) to measure molecular weight distributions in dilute polymer solutions. The instrument has a 660 nm diode laser and uses seven different angles to determine the intensity of scattered light as a function of angle and polymer concentration. It can be used in batch or flow mode, as a chromatography detector, or for measuring the rate of polymerization using time dependent static light scattering (TDSLS).
An example of its capabilities is being demonstrated in the Department of Chemistry, University of Cyprus. Researchers led by Costas Patrickios are using the BI-MwA to study the properties and applications of functional amphiphilic block co-polymers, which are prepared using group transfer polymerization chemistry. By analyzing sets of block co-polymers with different molecular weights and compositions, the laboratory can determine accurate size/performance relationships and select the best polymer for a given application.
Studying the formation of polymers in real time is a desirable application of the BI-MwA and was the main reason Dr. Denis Bertin of the Department of Chemistry, Biology and Free Radicals, University of Aix-Marseilles I & III chose to use the BI-MwA to study the polymerization of organic free radicals. “My laboratory is developing new complex architecture polymers and we are using the instrument to obtain real time information on their size and shape. This allows us to optimize the process as well as monitor free radical polymerization online.” The instrument has helped the researchers understand the complicated kinetic phenomena involved and guided the synthesis of new polymers. These are expected to prove useful in applications such as the manufacture of compact discs, televisions and drug delivery systems.
However, it is not just polymer researchers who have found the instrument of benefit. Swiss scientists are the fragrance and flavor company, Firmenich SA are using the BI-MwA to analyze maltodextrins derived from different plant species. “Maltodextrins are used extensively in the food industry, but their behavior in solutions varies depending upon whether they come from wheat, maize, tapioca, or potato and we want to find out why,” explained Dr. Ennio Cantergianai, physical chemist and project leader in the R&D department.
“Understanding the microstructure of maltodextrins is the key and the BI-MwA allows us to look at their molecular weight distributions, regardless of their source.”