Characterization of synthetic copolymers by interaction polymer chromatography: Separation by microstructure

Area of Science:

• Polymer Chemistry
• Chromatography
• Physical Chemistry

Background:

• High-performance liquid chromatography (HPLC) is crucial for polymer analysis.
• Understanding polymer behavior in gradient elution is key for separation science.
• Theoretical models are needed to explain complex polymer interactions in chromatography.

Purpose of the Study:

• To develop and verify a theoretical model for gradient elution of synthetic polymers.
• To investigate the critical point of adsorption (CPA) for polymer homologous series and copolymers.
• To elucidate the influence of polymer microstructure, specifically blockiness, on chromatographic retention.

Main Methods:

• Theoretical derivation using a continuous random-flight model for flexible polymer chains.
• Experimental verification using normal and reversed-phase HPLC with polystyrene standards.
• Synthesis and chromatographic analysis of block and statistical styrene-methylmethacrylate copolymers.

Main Results:

• Accurate equation derived for gradient elution, predicting molar mass-independent CPA for polymer-homologous series.
• CPA predicted and observed for statistical copolymers, dependent on chemical composition and blockiness.
• Blockiness was experimentally confirmed to increase retention, causing blockier polymers to elute later.
• Block copolymers lack CPA and elute between homopolymer critical points, with retention dependent on block length.

Conclusions:

• The derived theory accurately describes polymer gradient elution and CPA.
• Blockiness significantly impacts polymer retention, offering a method for microstructure-based separation.
• Findings provide a foundation for separating statistical and block copolymers based on composition and microstructure using HPLC.