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Published on: February 7, 2017
Correlation between structures of chiral polymers and their efficiency for chiral resolution by crystallization
Tali Menahem1, Martin Pravda, Yitzhak Mastai
1Department of Chemistry, Institute of Nanotechnology, Bar-Ilan University, Ramat-Gan, Israel.
Chirality
|May 21, 2009
Summary
Chiral polymers with alpha-helical structures are effective resolving agents in crystallization. Their helical conformation, unlike random coils, enhances chiral resolution efficiency, guiding polymer additive design.
Area of Science:
- Polymer Chemistry
- Crystallization Science
- Chiral Separation
Background:
- Chiral polymers are crucial for enantiomeric separation.
- Controlling polymer conformation is key to optimizing their function.
- Crystallization is a vital process for chiral resolution.
Purpose of the Study:
- To investigate the correlation between chiral polymer conformations (alpha-helical vs. random coil) and their efficiency as chiral resolving agents.
- To synthesize and characterize chiral block copolymers for crystallization applications.
- To provide guidelines for designing effective chiral polymer additives.
Main Methods:
- Synthesis of chiral block copolymers: polyethylene oxide with chiral glutamic acid oligopeptide segments (PEG(113)-b-(+)-(S)-Glu(20)).
- Chiral resolution of rac-threonine using synthesized polymers as additives.
- Circular Dichroism (CD) spectroscopy to determine polymer conformations (pH-dependent switching between helical and random coil).
- Analysis of crystallization kinetics, crystal morphology, and enantiomeric excess.
Main Results:
- Chiral block copolymers could switch between alpha-helical and random coil conformations based on pH.
- Only polymers with alpha-helical conformations of the chiral segment demonstrated effectiveness in chiral resolution during crystallization.
- The conformation of the chiral polymer significantly impacts crystallization kinetics, crystal morphology, and the degree of chiral resolution.
Conclusions:
- The alpha-helical conformation of chiral polymer segments is essential for efficient chiral resolution in crystallization.
- Polymer conformation, controllable by external stimuli like pH, dictates resolving agent efficacy.
- This study offers valuable insights for the rational design of chiral polymer additives for enhanced enantioseparation via crystallization.
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