TY  - JOUR
AU  - Mukhina, Tetiana
AU  - Richter, Lars
AU  - Vollhardt, Dieter
AU  - Brezesinski, Gerald
AU  - Schneck, Emanuel
TI  - The Complete Phase Diagram of Monolayers of Enantiomeric N-Stearoyl-threonine Mixtures with Preferred Heterochiral Interactions
JO  - Langmuir
VL  - 38
IS  - 41
SN  - 0743-7463
CY  - Washington, DC
PB  - ACS Publ.
M1  - PUBDB-2022-06521
SP  - 12521 - 12529
PY  - 2022
AB  - Langmuir monolayers of chiral amphiphiles are well-controlled model systems for the investigation of phenomena related to stereochemistry. Here, we have investigated mixed monolayers of one pair of enantiomers (L and D) of the amino-acidbased amphiphile N-stearoyl-threonine. The monolayer characteristics were studied by pressure−area isotherm measurements and grazing incidence X-ray diffraction (GIXD) over a wide range of mixing ratios defined by the D-enantiomer mole fraction x<sub>D</sub>. While the isotherms provide insights into thermodynamical aspects, such as transition pressure, compression/decompression hysteresis, and preferential homo- and heterochiral interactions, GIXD reveals the molecular structural arrangements on the Ångström scale. Dominant heterochiral interactions in the racemic mixture lead to compound formation and the appearance of a nonchiral rectangular lattice, although the pure enantiomers form a chiral oblique lattice. Miscibility was found to be limited to mixtures with 0.27 ≲ x<sub>D</sub> ≲ 0.73, as well as to both outer edges (x<sub>D</sub> ≲ 0.08 and x<sub>D</sub> ≳ 0.92). Beyond this range, coexistence of oblique and rectangular lattices occurs, as is clearly seen in the GIXD patterns. Based on the results, a complete phase diagram with two eutectic points at x<sub>D</sub> ≈ 0.25 and x<sub>D</sub> ≈ 0.75 is proposed. Moreover, N-stearoyl-threonine was found to have a strong tendency to form a hydrogen-bonding network between the headgroups, which promotes superlattice formation.
LB  - PUB:(DE-HGF)16
C6  - pmid:36209408
UR  - <Go to ISI:>//WOS:000874211900001
DO  - DOI:10.1021/acs.langmuir.2c01936
UR  - https://bib-pubdb1.desy.de/record/484841
ER  -