Investigations of Multiple Detection of Polymers

Theoretical and experimental aspects of multiple detection analysis of polymers are critically revised for size exclusion chromatography (SEC). In particular, different combinations of detectors, the importance of the injected mass and the influence of the tacticity of polymers are evaluated in respect to the accuracy of the weight fractions of the polymer components. It is also shown how overlapping detector responses of the chemical components will affect the accuracy of the weight fractions. The calculation of the weight fractions is performed with equations derived for n different chemical components and detectors by using the slopes and intercepts of the linear response equations. Several detector combinations of dual detection in SEC are evaluated with PS-b-PMMA diblock copolymers to determine the comonomer compositions and for the first time different combinations of triple detections are performed for the determination of the weight fractions of a blend of three homopolymers, respectively. The correct determination of the weight fractions of minor and main components of polymers is strongly affected by the chosen combination of detectors, the injected mass and the intercept of the response calibrations. It is shown how these conditions have to be changed to obtain correct quantifications of the weight fractions according to the experimental setups. The experimental results are approved with online SEC-H-1/NMR where no response factors are required.