Vinyl and phenyl terminated octasilsesquioxane thin films: Evidence for π-stacking induced self-organization of the spherically symmetrical molecules

• Published in: Applied surface science Vol. 478; pp. 636 - 641
• Main Authors: Handke, Bartosz, Gębicka, Natalia, Komolov, Alexei S.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.2019
• Subjects: Atomic force microscopy; Self-organization; Silsesquioxane thin films; Surface induced phases; X-ray reflectivity; X-ray reflectivity; Atomic force microscopy; Silsesquioxane thin films; Surface induced phases; Self-organization
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2019.01.264

Organosilicon compounds are surprising in the diversity of their applications as a result of the enormous diversity in their structure. Of particular interest are the self-assembling possibilities of silsesquioxane molecules leading to the formation of thin films with thicknesses not exceeding tens of nanometers. To date, only cases of self-organization of molecules with a strongly asymmetrical shape have been known. This study is aimed at obtaining confirmation of self-organization of silsesquioxane molecules in which the π-stacking interaction between arranged spherically symmetrical aromatic rings leads to the formation of a new smectic phase not observed for bulk material. For this purpose, the morphology of growth and the structure of thin octasilsesquioxane layers substituted either with vinyl or phenyl groups was compared. Due to the use of molecular beam technique for thin-film deposition under ultra-high vacuum conditions, any undesirable external influences as well as those associated with the solvent were avoided. The main measurement techniques were the X-Ray Reflectometry and Atomic Force Microscopy, which provided the final proof of the key role of aromatic rings in the self-assembly of these spherically symmetrical molecules. [Display omitted] •Comparison of the structure and growth morphology of Vi-T8 and Ph-T8 thin films deposited by PVD technique.•Surface vicinity and the reduced dimensionality is not sufficient to induce new crystalline phases in the thin films.•The dispersive and electrostatic interaction between phenyl rings play a key role in the new smectic phase formation.•Direct observation of the self-organization induced by π-stacking for the spherically symmetric molecules.