Molecular structure melamine

PMF-resins usually contain little or no urea. The analysis of the molecular structure of these resins has shown that there is no co-condensation between the phenol and the melamine, but that there are two distinct networks [52-55]. The... 

Figure 5.22 Cu UPD on a Au/mica substrate modified by a hybrid nanostructure consisting of a hydrogen-bonded network and a thiol SAM. (a) Cartoon ofthe hybrid structure and molecular structures of the components. The hydrogen-bonded network is composed of 1,3,5-triazine-2,4,6-triamine (melamine, triangles) and perylene-3,4,9,10-tetracarboxylic di-imide (PTCDI, rectangles) that interact via a triple hydrogen bond (dotted lines). Pores ofthe...

FIGURE 4.3. Molecular structures and schematic representations of tetra- hexa- and octamelamines 2, 3 and 4, respectively, and di(melamine-cyanurate) 5. The molecular structure of DEB and different isocyanuric acid derivatives (CYA) are also shown. 

PMF/PMUF resins, in which the amount of phenol is much higher than in MUPF resins, usually contain only little or no urea at all. The analysis of the molecular structure of these resins has shown that either there is no cocondensation between the phenol and the melamine, but that there exist two distinct networks [90-93], or that cocondensation can indeed occur [88]. The reason for this is the different reactivities of the phenol methy-lols and the melamine methylols, depending under which pH conditions the reaction is carried out. 

Fig. 6 Molecular structures of hydrogen-bonded cyanuric acid-melamine aggregates and corresponding schematics based on ball. rods, and string (BRS) models. (Reprinted with permission from Ref. [36].)...

The catalyst or add source can consist of ammonium phosphate or polyphosphate salts, phosphoric add-derived amides or alkyl or halo-alkyl phosphates. Charring agents are based on molecular structures that can form cross-linked networks such as pentaerythritol, sorbitol, melamine, and phenol-formaldehyde resins. Other polymeric systems capable of intumescence are some polyamides and polyurethanes. Blowing agents help form a porous structure in the char and can fadlitate its formation. Common blowing agents are based on urea and urea-formaldehyde resins, melamines, and polyamides that can liberate moisture. 

Figure 14.3 Molecular structures of melamine and iV2,iV4-dihexadecyl-l,3 5-triazine-2,4,6-triamine.

Figure 11. Molecular structures for melamine derivative 10 and bis-isocyanurate derivative 19 and MALDl-TOF mass spectrum of the 1 2 mixture of 19 and 10 after labeling with Ag (matrix 2,5-dihydroxybenzoic acid)...

Beton and co-workers extended the hydrogen bonding approach to two-component systems, generating a number of structures that utilise different molecular motifs.24 26 In the case of perylene tetracarboxylic diimide (PTCDI) co-adsorbed with melamine (1,3,5-triazine-2,4,6-triamine) on a silver-terminated silicon surface, a network is formed in which the straight edges correspond to PTCDI with melamine at the vertices (Figure 11.6). The network shows large-area pores that the authors used to trap heptamers of C6o molecules. 

Wolf and coworkers [30] have shown that a combination of hydrogen bonding capability with symmetry requirements can enforce similar crystalline arrangements yielding the pattern analogous to that formed by unsubstituted melamine 1 and cyanuric acid 2 (Chapter 1) independent of the steric requirements of the substituents. The pattern can be called molecular fabric. Mascal and coworkers [31] have used this term for their more loose structure 147 exhibiting voids. 

Zerkowski, J. A., MacDonald, J. C., Seto, C. T., Wierda, D. A. and Whitesides, G. M. (1994). Design of organic structures in the solid state molecular tapes based on the network of hydrogen bonds present in the cyanuric acid melamine complex. J. Am. Chem. Soc. 116, 2382. 

This approach mimics familiar biological self-assembly phenomena such as protein folding [ 192], protein aggregation [ 192] and nucleotide pairing [ 188]. It incorporates features described in each of the above strategies (i.e., I—III), to give specialized nanoscopic structures, that can be precisely designed, usually with excellent control over CMDPs. Recent examples include so called structure directed synthesis by Stoddart [3a] (see Chapter 1 of this book) to produce toroidal bis-bipyridinium cyclophanes that are reminiscent of a molecular abacus , melamine-cyanuric acid lattices by Whitesides [193] and unique helical structures based on coordination of bipyridyl units to copper (II) ions by Lehn [194],... 

Figure 2 The structure of the hydrogen-bonded CA M lattice. Three classes of aggregates that we have observed in solution and the solid state are highlighted the rosette, crinkled tape, and linear tape motifs. The molecular strucmres of melamine and cyanuric acid and their abbreviated representation as dark and light disks are shown...

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