Polymelamine

Alkylenedicyanamides with the general formula NCNH(CH2) NHCN (n = 4-10) readily form polymers below 100 °C.234 The structure of these polymers is believed to correspond to polymelamines and polydicyanodiamides. Cyanamide polymers can be used to manufacture ion-exchange resins, coatings and adhesives. 

Shell materials can be solvent-based, water-based, molten, reactive, or molecnlar. Variations of atomization, spray coating, and coextrusion are available to deposit shell or matrix materials from solvent, water, or as a molten material. For example, spray drying is snitable for encapsnlating with solvent-based or water-based matrix materials, while spray congealing nses molten fats or waxes. Fewer shell material selections are available with the emulsion-based processes. For example, complex coacervation is most often associated with the use of gelatin as the shell, and the generation of polyurea or polymelamine formaldehyde shells is associated with in situ polymerization. Further limited examples include the use of cyclodextrins for molecular complexation or phospholipids for the formation of liposomes. 

Superplasticizers were discovered in 1960s. The poly- 3-iiaphthalene sulfonates were the first to be introduced and the most widespread superplasticizers followed by polymelamine sulfonates. Organic polymers having carboxylic group are the most recent... 

In another study,two approaches for synthesis of the polymelamine dendrons on silica gel were experimentally compared the divergent solid-phase synthesis (Scheme 15.26b)... 

Scheme 15.25. Synthesis of polymelamine dendrons on solid support by Marsh et al.

Su and coworkers used silica gel with immobilized polymelamine, poly(amidoamine), or poly(propylenimine) dendrons as the microcolumn packing for the flow injection preconcentration and separation of traces of Pt(IV) ions for flame atomic absorption spectroscopy determination.Polyamine dendron-functionalized polystyrene was... 

Removal of another pollutant, atrazine herbicide, by polymelamine dendrons on silica was demonstrated by Simanek and coworkers. The authors revealed two trends. First, the dendrons of higher generation increased the sequestering ability of the hybrid material relative to that of the support modified with the lower generation dendrons. Second, this ability was higher for the dendrons divergently grown on silica, compared to the materials obtained by the focal-point immobilization of the dendrons presynthesized in solution (see Section 15.2.9). 

Two components are needed to construct a dendrimer a multifunctional core and an ABx monomer unit around which to build up the structure. The most commonly used types are polyamidoamine dendrimers (PAMAM), poly 2,2-bis(methylol)propionic acid (PBisMPA) dendrimers, polybenzyl ether dendrimers (PBzE), polymelamine (triazine) dendrimers, polypropyleneimine dendrimers (PPI), and polylysine dendrimers (PEL). PAMAM, PPI and PBisMPA are commercially available. PAMAM (left), PBisMPA (middle) and PPI (right) in Figure 2.7 are the most commonly employed structures in therapeutic applications these have been well characterised both in vitro and in vivo, and their toxicological properties have been evaluated. 

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