Urea oligomer, structure

Fig. 6 (a) Poly(urea) oligraners structure 2) are conformatiraially more stable than poly(aryla-mides) structure 1) [80]. (b) Structure of poly(phenylene ethynylene) polymers and oligomers [5]. (c) Conformation of poly(phenylene ethynyloie) polymers at the oil-water interface [5]... 

The production of melamine-formaldehyde oligomers uses as raw materials formaldehyde and melamine (2,4,6-triamino-l,3,5-triazine). The latter is a crystalline substance, heavily soluble in water (5% at 100°C), and it shows a stronger alkaline character than urea or formaldehyde. From the very beginning, one should note that melamine-formaldehyde oligomer structure depends strongly on working conditions. 

The effect of structural variations in siloxane oligomers in the synthesis and properties of the resulting siloxane-urea copolymers have also been investigated 161). In these studies aminopropyl-terminated poly(dimethyl-diphenyl)siloxane and poly-... 

Therefore, metal plates have been conventionally used. We have performed the research and development of a photopolymer printing plate for a master plate with a new basic structure by combining an oligomer of urea structure having a polyvinyl base with polyvinyl alcohol, photopolymerization initiator and other ingredients. The result shows that the newly developed plate (6) is so good that it has replaced metal plates and has been stably used at leading newspaper companies in Japan where several millions of newspapers are daily issued. 

The second example of electroinitiated polymerization deals with the formation of open pore urea-formaldehyde (OPUF) structure by electrocondensation on the anode of a prepolymerized mixture of urea-formaldehyde oligomers 109 ... 

The molar ratio between reactants plays an important role in ureo-formal-dehyde oligomer production. An increased molar fraction of urea results in a lower content of dimethylenetric linkages in the resins. This structural characteristic allows the production of better-quality products through increased stability and diminished content of low molecular weight species [25,28]. 

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