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 2H 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.

Circular dichroism (CD) spectroscopy is commonly used for investigation of the secondary structure of biomolecular compounds as well as polymers in isotropic solution. In anisotropic solution, the usage of the...

A series of poly-β-benzyl-l-aspartate-co-poly-β-phenethyl-l-aspartates varying in their copolymer composition as well as with selectively introduced deuterium labels in the backbone or the side-chain were synthesized and their temperature-dependent conformation and orientation with respect to an external magnetic field were characterized by measuring 2H quadrupolar splittings [nuclear magnetic resonance (NMR) spectroscopy] and circular dichroism. All copolymers demonstrate a temperature-dependent change of their helical conformation from right-handed to left-handed (helix reversal) and a change of their alignment from perpendicular to parallel with respect to the magnetic field in an anisotropic solution (helix realignment) at different temperatures. Both effects react differently to a change of copolymer composition, but are concentration, dispersity, and molecular weight independent as well as unaffected by the initiator used for polymerization. The helix realignment by 90° in a magnetic field has not been observed previously for these copolyaspartates. Its existence is proven directly by measurement of the quadrupolar splitting of the specifically labeled polymers and comparison to calculated quadrupolar splittings. Furthermore, the temperature of both transitions was found to be dependent on deuteration at the N-position. The uncovering of the thermo and magnetoresponsiveness will lead to an improved understanding and application scope of the copolyaspartates (e.g., in their use as alignment media in NMR spectroscopy).

Herein, we report the preparation of lyotropic liquid crystalline (LLC) phases of poly-β-benzyl-L-aspartate (PBLA), a polymer that has not been known to form LLC phases before. Compared to other L-configured polypeptides usually forming right-handed helices, PBLA forms left-handed helices. The LLC phase behavior was observed for PBLA in a specific range of molecular weights, exclusively. Living polymerization allowed for this excellent control over the molecular weight. Furthermore, the LLC phase was used as a host matrix for two chiral analytesisopinocampheol and β-pineneused as probes. The interaction between these probes and the polypeptide was measured indirectly using NMR spectroscopy by investigation of the resulting orientation of probes in general and the enantiodifferentiation of the chiral analytes in particular. By comparison of the orientation induced on the probes by PBLA and the well-known poly-β-benzyl-Lglutamate, the effect of side-chain flexibility and conformation of the polypeptides on the alignment process are discussed.

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