Design of liquid crystals with 'de Vries-like' properties: structural variants of carbosilane-terminated 5-phenylpyrimidine mesogens. Issue 18 (18th April 2017)

• Record Type: Journal Article
• Authors: Schubert, Christopher P. J.; Müller, Carsten; Bogner, Andreas; Giesselmann, Frank; Lemieux, Robert P.
• Is Part Of: Soft matter. Volume 13:Issue 18(2017)
• Page Start: 3307
• Page End: 3313
• Publication Date: 2017-04-18
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/c7sm00355b
• Languages: English
• ISSNs: 1744-683X

Abstract

Abstract : Comparative analysis of linear and branched tricarbosilane terminated 'de Vries-like' mesogens. Abstract : Structural variants of the 'de Vries-like' mesogen 5-[4-(12, 12, 14, 14, 16, 16-hexamethyl-12, 14, 16-trisilaheptadecyloxy)phenyl]-2-hexyloxypyrimidine (QL16-6 ), including two isomers with branched iso-tricarbosilane end-groups, were synthesized and their mesomorphic and 'de Vries-like' properties were characterized by polarized optical microscopy, differential scanning calorimetry, small angle and 2D X-ray scattering techniques. A comparative analysis of isomers with linear and branched tricarbosilane end-groups shows that they exhibit comparable mesomorphic and 'de Vries-like' properties. Furthermore, the difference in effective molecular length L eff between the linear and branched isomers in the SmA and SmC phases ( ca. 4–5 Å), which was derived from 2D X-ray scattering experiments, suggests that the linear tricarbosilane end-group is hemispherical in shape on the time-average, as predicted by a DFT conformational analysis at the B3LYP/6-31G* level.