Other Polyreactions

Exploitation of Pendant Reactive Groups. Pendant and linkage forming stabilizing moieties can be created in this way. Macromolecular stabilizers thus formed have general structures B, C, and E (Scheme 1) and are formally structurally related to stabilizers prepared by other polyreactions. The distribution mode of stabilizing moieties and the presence of foreign structures and mentioned above represent the main difference between stabilizers prepared via different synthetic approaches. 

There are two different ways for carrying out polyreactions in a solvent. When both the monomer and the resulting polymer are soluble in the solvent, one speaks of a homogeneous solution polymerization on the other hand, if the polymer precipitates during the course of the reaction, it is called precipitation polymerization. By addition of a solvent, different effects are obtained Basically, the viscosity of the reaction mixture is decreased in comparison to a bulk polyreaction this facilitates heat transfer, mass transport, and handling. 

Polyreaction of an reactive chelate monomer with other monomers to get a copolymer (Scheme 4)... 

A third definition considers what happens at the actual site of reaction. A chain is joined to a monomer or another chain in each polyreaction. The monomer or other chain may add on to or insert in to the chain being considered. The initiator may be a chain starter or a catalyst and so, may be associated always with one individual chain (one-chain mechanism) or change from chain to chain (multichain mechanism). One can distinguish between... 

The statistical method considers an event relative to other, competing, events. The relative character leads to generalized equations that may be used for different polyreactions, and so, these equations are more general than those of method 1. Thus, it is convenient to discuss the results of the statistical method collectively, but those of the kinetic method are best discussed for each polyreaction separately. 

SEC is presently the most important method for separation and moleeular characterization of synthetic polymers. The method enjoys enormous popularity and most institutions involved in research, production, testing and apphea-tion of synthetie polymers are equipped at least with a simple SEC instrument. Size exclusion chromatograms are often directly transformed into the molar mass dispersity functions (compare section 11.3.3, Molar Mass Dispersity). Often, the molar mass data presented are not absolute, beeause polystyrene or other polymer standards distinct from polymer under study have been employed for the column calibration (see sections 11.6.3 and 11.7.3.1). Still, the data equivalent to the polymer applied to the column cahbration, more or less precisely represent the tendencies of molar mass evolution in the course of building-up or decomposition polyreactions. 

Polyreactions in bulk are carried out without solvents or diluents. In this way, high molecular weights can be obtained frequently with high rates of reaction. The resulting products are very pure, because only monomers and, if necessary, initiators and catalysts are added. Polyreactions in bulk are also advantageous for economical and ecological reasons because recycling and purification of solvents or dispersants as well as the disposal of liquid waste (as in the case of aqueous suspension or emulsion polymerizations) are not necessary. On the other hand. 

Substituents are generally given before the name of the diradical. Poly(vinyl alcohol) (example 4, Table 1-4) is thus correctly called poly-(hydroxyethylene). Another example is poly(l-oxotrimethylene) (example 11, Table 1-4). Note that the name of the diradical is always given in parentheses or other brackets. All examples given in Table 1-4 have structural names which imply a direction in the polymer chain. This direction is not always the same as the direction of chain propagation in polyreactions (see examples 5,6, and 9 in Table 1-4). 

Fructose or other carbohydrates containing hexoses provide a cheap source for the two substituted furfurals 345,346 (Reaction scheme 237) [711]. Catalytic reduction of the acetate 348 cleaves at the heterobenzylic position to give 5-methylfurfural 347. Electrolytic oxidation affords a polyreactive intermediate 349 for future purposes. Weakly acidic thermal treatment causes rearrangement to a norpyrethrolone 350. 

Since the dimer is the major component among the cydic by-produds, in addition to the aforementioned reactions, other equilibrium reactions have to be considered as well the ting opening of the dimer to (aminocaproyl)ami-nocaproic add (hydrolytic ring opening) and the polyreactions, involving the dimer instead of the lactam. 

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