Room Temperature Synthesis of a Covalent Monolayer Sheet at Air/Water Interface Using a Shape-Persistent Photoreactive Amphiphilic Monomer

Abstract

The shape-persistent monomer 3 with its three 1,8-diazaanthracene (DAA) units is spread and compressed at the air/water interface and the layer then converted into a 1.5 nm thick covalent monolayer sheet by photoirradiation under ambient conditions. The sheet obtained under these extremely mild conditions is mechanically stable to carry its own weight when spanned over TEM grids. While its molecular structure cannot be given yet with certainty, it is likely to be the result of [4 + 4]-cycloaddition dimerizations between the DAA units of neighboring monomers. Evidence is based on the wavelength of the monomer fluorescence emission, the kinetics of this emission’s intensity decay with irradiation time, and the mechanical sheet stability that suggests a surpassing of percolation threshold. Finally, the thermal stability of the sheet is investigated.

Approaching Two‐Dimensional Copolymers: Photoirradiation of Anthracene‐ and Diaza‐Anthracene‐Bearing Monomers in Langmuir Monolayers

“…The mean molecular areas (MMA) of both monomers were known to be ca. 225 Å 2 ( M1 ) and 220 Å 2 ( M2 ) as the present work was started . This similarity finally convinced us that there should be a good chance for co‐spreading.…”

“…These five solutions were then applied to air/water interface and after 30 min—when the chloroform had evaporated—the resulting films were compressed by the barriers of the Langmuir trough to a surface pressure of 20 mN m −1 . This pressure was chosen because it had proven successful in the synthesis of S1 and S2 . The five surface pressure versus MMA isotherms are shown in Figure .…”

“…In order to overcome this limitation, we have not only been focusing on the single crystal but also on the interfacial approach to 2DPs and related mono­layer sheets . Amphiphilic monomers were spread at the air/water interface and bonded to one another either by photoirradiation or by the action of metal ion connectors provided from the subphase . Regarding photoirradiation, which is of particular interest to the present publication, monomers M1 and M2 (Figure a,b) were used to create the corresponding sheets S1 and S2 , respectively.…”

Compounds bearing multiple photoreactive chalcone units: Synthesis and study towards 2D polymerization in Langmuir monolayers

“…They were prepared through a polymerization of self-assembled layers of monomers in either single crystal or at interfaces. The 2D polymerization in a single crystal and at the air/water interface involved monomers in which UV-induced reactions such as [4 þ 4] cycloaddition of anthracene [5e7] and 1,8-diazaanthracene [8], carbonization of hexayine amphiphiles [9], and [4 þ 2] cycloaddition of anthracene and acetylene [10] subunits occurred. An alternative approach to 2D polymers involved the Ullmann reaction in which halogenated monomers were covalently connected on the surface of a metal crystal [11,12].…”

Makroskopische kristalline 2D‐Polymere

“…Teilabbildungen (a)-(e) wurden mit Genehmigung aus Lit [123]. Beispiel einer Polymerisation an der Wasser/Luft-Grenzfläche:a )Glasfaseroptik an einem LBT,m it der durch ein Quarzfenster im Boden des Trogs UV/Vis-Spektren der Monolage an der Grenzfläche aufgenommen werden kçnnen.…”