Syntheses and Interfacial Hydrogen-Bonded Network of Hexaalkyl Tris(Melamine) Amphiphiles

Abstract

At the air−water interface N,N‘-dialkylmelamine amphiphiles bind barbituric acid (BA) in the aqueous phase and produce a linearly extended supramolecular network (sometimes referred as supramolecular strand, ribbon, or tape) linked through complementary hydrogen bonds. An amphiphile with more than two hydrogen-bonding sites may produce cross-linked hydrogen-bonded networks on water with the aid of an appropriate aqueous binding counterpart. Thus, we synthesized new amphiphilic molecules, Δ(m,n), that bear three melamine (2,4,6-triamino-1,3,5-triazine) rings and six alkyl chains. The lengths of the inside three alkyl chains (C m H2 m +1) and the outside three alkyl chains (C n H2 n +1) were varied. The influence of alkyl chain length on the monolayer properties and the binding behavior to aqueous BA was examined for Δ(12,10), Δ(12,12), Δ(12,14), Δ(12,18), and Δ(18,12). From FT-IR and X-ray photoelectron spectroscopic measurements of Δ(m,n) LB films, BA was found to bind to one melamine moiety each of Δ(m,n) in a 1:1 ratio through complementary hydrogen bonds. Plausible network models were proposed on the basis of binding stoichiometry and conformational consideration of the tris(melamine) amphiphile.

Challenges and breakthroughs in recent research on self-assembly

“…The air-water interface has been also used for recognition of various aqueous guest molecules including nucleic acids, their bases, nucleosides, and nucleotides [669][670][671][672][673], barbituric acid and related derivatives [674][675][676][677][678], amino acids, saccharides [679][680][681][682][683][684][685][686][687], and others [688,689]. However, most of these examples do not utilize one critical feature of the air-water interface, its dynamic nature.…”

Perylene bisimide organogels formed by melamine·cyanurate/barbiturate hydrogen-bonded tapes

“…These diffractions were accompanied by small diffractions with half and one-third (only for 1 Á dCA) of their d-spacing values (Table 2). These XRD patterns indicate that these aggregates form multilamellar structures via the formation of linear tapelike hydrogen bonding motif ( Figure 9) 25,[31][32][33][34]47 Although no gelation was observed for other systems (1 Á Bar, 2 and 2 Á dCA), their thin films prepared from chloroform solutions showed XRD patterns assignable to multilamellar structures upon heating (Supplementary Figure S3 and Table 2). …”

“…28 For PBI dyes, we have recently succeeded to organize soluble swallow-tailed derivatives, which inherently form one-dimensional columnar structures, 29,30 into two-dimensional lamellar structures 26 by using linear tapelike hydrogen bonding motifs of melamine-cyanurate (2 Á dCA) or melamine-barbiturate (2 Á Bar, Figures 1 and 2). [31][32][33][34] These aggregates are highly soluble in halogenated solvents such as chloroform, thus enabling the fabrication of smooth thin films without notable grain boundaries via solution processing followed by thermal annealing. The resulting thin films could be used as electron transporting layers in organic field effect transistor (OFET) devices.…”

Thermosetting bismaleimide resins generating covalent and multiple hydrogen bonds

“…1,2 The networks are formed almost exclusively by covalent bonds and are generally irreversible. Recently, considerable progress has been achieved on design of supramolecular polymer networks (SPNs) formed by multiple hydrogen bonding (MHB) between various components such as ureidopyrimidinone (UPy) dimer, [3][4][5][6] Hamilton wedge/cyanuric acid, 7 melamine (ML)/cyanuric acid (CA), [7][8][9] and ML/thymine analogs, 10 which are applicable to self-healing 11,12 and shape memory materials, 13 stimuliresponsive gels, 14,15 drug delivery system, 16,17 and so on. However, there are a few studies on polymer networks having both covalent and MHB cross-linkages.…”