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Comprehensive branching analysis of star-shaped polystyrenes using a liquid chromatography-based approach
Douglas Murima1, Harald Pasch2
1Department of Chemistry and Polymer Science, University of Stellenbosch, Private Bag X1, Matieland, 7602, South Africa.
Analytical and Bioanalytical Chemistry
|June 8, 2019
Summary
Analyzing complex polymer branching is challenging. This study introduces advanced chromatographic techniques to determine branching distribution in star-shaped polystyrenes, offering precise molecular architecture insights.
Area of Science:
- Polymer Chemistry
- Analytical Chemistry
Background:
- Comprehensive branching analysis in complex polymers remains a significant challenge.
- Spectroscopic methods like Nuclear Magnetic Resonance (NMR) provide average branching information but not distribution.
- Size exclusion chromatography (SEC) separates by molecular size, not strictly by branching number.
Purpose of the Study:
- To develop and evaluate advanced chromatographic methods for determining branching distribution in star-shaped polymers.
- To compare the effectiveness of different chromatographic techniques in polymer branching analysis.
- To provide a comprehensive understanding of polymer molecular architecture.
Main Methods:
- Synthesis of model star-shaped polystyrenes with defined architectures (three-arm, four-arm, six-arm).
- Triple detector size exclusion chromatography (TD-SEC) using refractive index, multiangle light scattering, and viscometer detection.
- Proton Nuclear Magnetic Resonance (1H-NMR) spectroscopy for average functionality determination.
- Thermal Gradient Interaction Chromatography (TGIC) and Solvent Gradient Interaction Chromatography (SGIC) for chemical composition separation.
- Comprehensive two-dimensional liquid chromatography (LC×LC) for simultaneous separation by branching and molar mass.
Main Results:
- TD-SEC successfully determined absolute molar masses, radii of gyration, and branching distributions of star-shaped polymers.
- 1H-NMR provided average functionality, showing good agreement with TD-SEC results.
- TGIC and SGIC effectively separated reaction products by the number of branches and resolved by-products.
- LC×LC demonstrated capability to separate polymers based on both branching and molar mass.
Conclusions:
- Advanced chromatographic techniques, particularly LC×LC, offer powerful tools for comprehensive branching analysis of complex polymers.
- Combining TD-SEC and NMR provides reliable average branching information.
- TGIC and SGIC are valuable for resolving complex polymer mixtures based on branching and chemical composition.
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