Self-assembly of metastable langmuir monolayers on planar solid surfaces

Abstract

For several decades, the method of Langmuir monolayers and the Langmuir-Blodgett technique have been unique instruments for the formation and study of ordered ultrathin films, the structure of which can be controlled at the molecular level. In spite of the wide variety of problems relevant to the study of such systems and the diversity of their functional characteristics, the methodological approach to their preparation has remained unchanged for almost a hundred years. When assembling Langmuir-Blodgett films, most of researchers try to achieve a perfect mono or multilayer system on a solid substrate, with exactly reproduced and preserved structural characteristics of a Langmuir monolayer organized on a liquid surface. Nevertheless, in addition to the traditional approach to the preparation of molecularly ordered Langmuir-Blodgett films, a new field of research associated with the self organization of Langmuir monolayers under the action of a moving solid substrate has been developed. The self assembly of this type is based on the use of nonequilib rium structural and phase transitions in metastable Langmuir monolayers brought in contact with a solid sur face. These transitions are accompanied by the spontaneous formation of periodically ordered structures ("patterns") with sizes of elements varying from a few tens of nanometers to several hundreds of microns. This review offers an opportunity for the readers to gain insight into different types of the solid modified self orga nization of Langmuir monolayers using the currently known examples of systems based on lipids, fatty acids, bases, and mixtures thereof. In this review, contemporary ideas are discussed concerning the metastability of Langmuir monolayers, formation mechanisms of periodic patterns in monolayers on solid surfaces, possible practical applications of such systems, and the perspectives of this new and interesting field of the physical chemistry of thin films.

Anion···π Interactions and Metastability: Structural Transformations in a Silver–Pyrazine Network

“…Techniques for synthesising metastable materials are both topical and highly sought after, with refinements to processing techniques having resulted in new and innovative ways of imparting metastability . The drive to create new metastable materials stems from an ever‐growing range of applications including pharmaceutical formulations with improved bioavailability, sensors derived from photoswitchable compounds and switchable molecular magnets .…”