Size-Based Characterization of an Ionic Polydiacetylene by Taylor Dispersion Analysis and Capillary Electrophoresis


Subjects: Polymers

This work focuses on the size-based characterization of a water-soluble ionic polydiacetylene with a polycationic structure, poly-[(1,6-bis(N-methylimidazolium)hexa-2,4-diyne)dibromide]. This polymer could not be characterized using classical analytical techniques such as size-exclusion chromatography and MALDI−TOF mass spectrometry due to problems of purification, low quantities available, and difficult laser desorption. The work presented here demonstrates the interest and the complementarity of two independent analytical methods, Taylor dispersion analysis (TDA) and capillary electrophoresis (CE), that require only very small amounts of sample (only a few nanoliters are injected) and that can be easily implemented on commercially available capillary electrophoresis apparatus. TDA is a nonseparative method that allows the absolute determination of the average hydrodynamic radius of the polymer. This method does not require the determination of the polymer concentration in the sample and is not perturbed by the presence of residual monomer. Since the average hydrodynamic radius determined by this method is a weight average value, it also gives information complementary to the average value derived from dynamic light scattering measurements. Simple hydrodynamic modeling allows estimation of a minimal value for the average degree of polymerization. Free solution CE can be used for monitoring the polymerization process and quantifying the degree of conversion. Furthermore, entangled polymer solution CE was used as a size-based separation technique for the characterization of the molar mass distribution using calibration with polyvinylpyridine standards. Number and weight molar mass distributions of the sample were obtained relative to this calibration.