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Summary
This summary is machine-generated.

Chirality in polymethyl (4-vinylbenzoyl) histidinate (PBHis) polymers can be switched between M- and P-helicity using pH changes. This pH-dependent helical inversion is reversible and driven by imidazole group protonation/deprotonation.

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Area of Science:

  • Polymer Chemistry
  • Supramolecular Chemistry
  • Chiroptical Spectroscopy

Background:

  • Chirality in synthetic polymers is crucial for advanced material applications.
  • Controlling polymer conformation and chirality through external stimuli remains a significant challenge.
  • Histidine-containing polymers offer unique pH-responsive properties due to their imidazole groups.

Purpose of the Study:

  • To investigate the pH-dependent switchable inversion of chirality in a histidine pendant polymer.
  • To elucidate the mechanism behind the observed helical structure changes.
  • To demonstrate single-molecule level characterization of these conformational transitions.

Main Methods:

  • Circular dichroism (CD) spectroscopy to monitor chirality.
  • Fluorescence correlation spectroscopy (FCS) to measure hydrodynamic radius changes at the single-molecule level.
  • Synthesis of polymethyl (4-vinylbenzoyl) histidinate (PBHis) polymer.

Main Results:

  • PBHis exhibits pH-dependent helical inversion, transitioning from M-helicity (below pH 8.0) to P-helicity (above pH 8.0).
  • Further inversion to M-chirality occurs above pH 10.6.
  • These helical structures demonstrate reversible switching of handedness with varying pH.
  • Single-molecule measurements confirmed changes in hydrodynamic radius corresponding to conformational shifts.

Conclusions:

  • The study demonstrates switchable and reversible chirality inversion in PBHis polymers driven by pH.
  • Protonation/deprotonation of imidazole groups and hydroxide-ion-mediated hydrogen bonding are key to the mechanism.
  • This work provides a foundation for designing advanced chiral materials with tunable properties.