Investigations of the Alignment Process of PBPMLG: 2H NMR Analysis Reveals a Thermoresponsive 90° Flip of the Polymer. Issue 38 (20th August 2021)

• Record Type: Journal Article
• Authors: Schirra, Dominic S.; Hirschmann, Max; Radulov, Iliya A.; Lehmann, Matthias; Thiele, Christina M.
• Is Part Of: Angewandte Chemie international edition. Volume 60:Issue 38(2021)
• Page Start: 21040
• Page End: 21046
• Publication Date: 2021-08-20
• Subjects: alignment medium -- isotopic labelling -- NMR spectroscopy -- thermoresponsive polymers; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202108814
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: The application of anisotropic parameters in NMR‐spectroscopy enables the acquisition of spatial and angular information, complementary to those from conventional isotropic NMR‐measurements. The use of alignment media is a well‐established method for inducing anisotropy. PBPMLG is a recently discovered polyglutamate‐based alignment medium, exhibiting thermoresponsive behavior in the lyotropic liquid crystalline (LLC) phase, thus offering potential for deeper understanding of the alignment process. We present one approach for investigating the thermoresponsive behavior by synthesizing specifically deuterated PBPMLG‐isotopologues and their subsequent analyses using 2 H NMR‐spectroscopy. It was possible to relate the observed thermoresponsive behavior to a flip of the polymer with respect to the external magnetic field—an effect never observed before in glutamate‐based polymeric alignment media. Furthermore, a solvent‐induced temperature dependent gelation was verified in THF, which might provide yet another opportunity to manipulate the properties of this alignment medium in the future. Abstract : Deuterated isotopologues of a thermoresponsive, glutamate‐based alignment medium have been synthesized and investigated by 2 H NMR‐spectroscopy, vibrating sample magnetometry and polarized optical microscopy. The measurements show a flip of the polymeric α‐helix in lyotropic liquid crystalline phase, providing further insights into the alignment process of the polymer inside the magnetic field.