Monomers Mannich bases

Trimerization to isocyanurates (Scheme 4.14) is commonly used as a method for modifying the physical properties of both raw materials and polymeric products. For example, trimerization of aliphatic isocyanates is used to increase monomer functionality and reduce volatility (Section 4.2.2). This is especially important in raw materials for coatings applications where higher functionality is needed for crosslinking and decreased volatility is essential to reduce VOCs. Another application is rigid isocyanurate foams for insulation and structural support (Section 4.1.1) where trimerization is utilized to increase thermal stability and reduce combustibility and smoke formation. Effective trimer catalysts include potassium salts of carboxylic acids and quaternary ammonium salts for aliphatic isocyanates and Mannich bases for aromatic isocyanates. 

Poly(2,6-dimethyl-l,4-oxyphenylene) (poly(phenylene oxide), PPG) is a material widely used as high-performance engineering plastics, thanks to its excellent chemical and physical properties, e.g., a high 7 (ca. 210°C) and mechanically tough property. PPO was first prepared from 2,6-dimethylphenol monomer using a copper/amine catalyst system. 2,6-Dimethylphenol was also polymerized via HRP catalysis to give a polymer exclusively consisting of 1,4-oxyphenylene unit, while small amounts of Mannich-base and 3,5,3, 5 -tetramethyl-4,4 -diphenoquinone units are always contained in the chemically prepared PPO. 

Vinyl,- acrylic, etc.7 as well as acrylonitrile monomers 413-415 are readily obtained from Mannich bases. Further examples coneeming analogous derivatives are reported in Chap. II, A.2. Deuterated compound.s are also ineluded among aery lie acid derivatives along with several variously functionalized compounds. 

The above monomers are obtained mainly by deamination or deaminodccarboxy-lation of carboxylic Mannich bases. Acrylic monomers have also been obtained by addition of alkenc Mannich bases to acrylonitrile and vinyl monomers by deamination of the Mannich bases of alkylpyridines and alkylquinolines. - ... 

Reactions of type (a) are among the most extensively studied, as they include the. synthesis of polyacrylamide Mannich bases, widely employed in water-purification processes. Many other polymeric substrates are, however, succe.ssfully subjected to Mannich reaction (Table 33). Moreover, some polymeric substances need to be suitably functionalized in order to undergo the aminomethylation reaction, as reported for polymeric ketones obtained by oxidation of polyenes." Further macromolecular carbonyl substrates could be provided by interesting vinyl monomers purposely designed to give polymers suitable for Mannich reaction." ... 

Mannich bases arc involved in the synthesis of macromolecular derivatives cither by directly participating in the chemical structute of the final product as monomers, oligomers, etc., or by contributing as essential auxiliaries, such as crosslinking agents, modifiers, etc. (sec Chap. 111). 

The synthetic path a of Fig. 153 makes it possible to obtain, by polyaddition, variously substituted polyenes (394, Fig. 154) starting from styrenic - or acrylic, mainly acrylamidic, monomers. In particular, the vinyl-P-aiylamino propiophenones are prepared from the corresponding Mannich base by amino group replacement and arc used in the synthesis of polymers 390 via copolymerization with styrene. Analogous derivatives are obtained by copolymerization with acrylamides. - " ... 

Mannich bases may afford polycondensation with concomitant amine elimination by reaction with nucleophilic reagents. In order to obtain polymeric products through a repetitive and cumulative reaction, both the Mannich base monomer (A-A) and the nucleophilic species (B-B) need to be at least bifunctional or both the aminomethyl- and nucleophilic groups must be present in the same molecule (A-B). Polymers 400 and 401 (Hg. 156) arc thus yielded, respectively. 

The alkoxylation of the Mannich base with PO (or PO-EO mixtures), takes place by the stepwise addition of the oxiranic monomers, at 80-95 °C, in an inert nitrogen atmosphere [5, 9]. Figure 15.4 shows that the Mannich polyols obtained by the oxazolidine technology have lower viscosities than the corresponding Mannich polyols obtained by classical Mannich reactions. This effect is explained by the low viscosity of the intermediate Mannich bases used as starters. 

The second kind of polycondcnsalion based on the Mannich reaction includes monomers of type A-B (384, Fig. 152), requiring equimolar amounts of formaldehyde in order to produce the polymeric derivatives 385. 

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