No abstract

New methods of liquid adsorption chromatography were developed to separate poly­(methyl methacrylate) (PMMA) regarding tacticity and molar mass. Gradient and isocratic chromatographic methods were applied to separate the tactic polymers. In particular, the online coupling of HPLC–NMR was used to identify and quantify the microstructural moieties during the chromatographic separation. It was possible to individually follow the elution of the syndiotactic, heterotactic as well as isotactic patterns. Several representative blends of PMMA samples of different tacticities as well as molar masses were well separated and analyzed. The quantification of all tacticities of the HPLC–NMR measurements was performed and the overall compositions were in good agreement with the data on the bulk samples. In addition, SEC–NMR data of predominantly isotactic PMMA show dependences of the tacticity on the molar mass.

For the first time, stereoregular poly(methyl methacrylates) (PMMAs) were separated according to tacticity on a carbon-based stationary phase using solvent gradient interaction chromatography (SGIC). This stationary phase provides superior separation capabilities, enabling the baseline separation of highly isotactic and syndiotactic PMMAs of different molar masses. Two-dimensional liquid chromatography was performed with the SGIC method separating, according to tacticity in the first dimension coupled to size-exclusion chromatography separating according to molar mass in the second dimension, thus providing comprehensive information on both microstructure and molar mass.

For the first time, polybutadiene is separated according to microstructure using solvent gradient interaction chromatography (SGIC). Superior separation of polybutadienes having different microstructures is obtained on a silica-based reversed stationary phase and a mobile phase of acetone-hexane. This SGIC system enables the baseline separation of 1,2-polybutadienes and 1,4-polybutadienes even in cases where the samples have similar molar masses. 2D liquid chromatography is performed with the SGIC method separating according to microstructure in the first dimension coupled to size exclusion chromatography separating according to molar mass in the second dimension, thus providing comprehensive information on both microstructure and molar mass.