Light-Controlled Lyotropic Liquid Crystallinity of Polyaspartates Exploited as Photo-Switchable Alignment Medium.

Two polyaspartates bearing -fluorinated azobenzenes (FAB) as photo-responsive groups in the side chain were synthesized: PFABLA () and co-polyaspartate PpFABLA--PBLA [, 75%(n/n) PFABLA content]. As a consequence of the /-isomerization of the side chain, PFABLA () undergoes a visible-light-induced reversible coil-helix transition in solution: Green light (525 nm) affords the coil, and violet light (400 nm) affords the helix. FAB significantly increases the thermal stability of the -isomer at 20 °C ( = 66 d for the -isomer) and effectively counters the favored back formation of the helix.

A supramolecular and liquid crystalline water-based alignment medium based on azobenzene-substituted 1,3,5-benzenetricarboxamides.

A supramolecular, lyotropic liquid crystalline alignment medium based on an azobenzene-containing 1,3,5-benzenetricarboxamide (BTA) building block is described and investigated. As we demonstrate, this water-based system is suitable for the investigation of various water-soluble analytes and allows for a scaling of alignment strength through variation of temperature. Additionally, alignment is shown to reversibly collapse above a certain temperature, yielding an isotropic solution.

Investigations of the Alignment Process of PBPMLG: H NMR Analysis Reveals a Thermoresponsive 90° Flip of the Polymer.

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.

Treating anisotropic artefacts in circular dichroism spectroscopy enables investigation of lyotropic liquid crystalline polyaspartate solutions.

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 apparent CD is prone to misinterpretations due to artefacts from contributions of e.g.