The monomer and polymer chemistry of 4,5-dicyano-2-vinylimidazoles.

摘要

An efficient, process scale synthesis of 1-Z-1-amino-1,2-dicyano-3-aza-1,3,5-hexatriene (acrodamn), via Schiff base condensation of acrolein and diaminomaleonitrile (DAMN), is described. The new method is superior because oligomeric byproduct is minimized and yields are nearly quantitative. An acid catalyzed oligomerization pathway of acrodamn is proposed. A process scale synthesis of 4,5-dicyano-2-vinylimidazole (vinazene) is also described in detail. The new method improves the previous method in terms of yield and ability to free-radically polymerize the resulting product.;The alkylation of vinazene proceeds with strong electrophiles, to yield a new family of vinylic monomers. The compound, 4,5-dicyano-1-methyl-2-vinylimidazole, (1-methylvinazene) undergoes Michael-addition with pyrrolidine, morpholine and thiophenol, allowing estimation of the α-anion's basicity as 14 < pKMeVz < 22. Vinazene oligomerizes via Michael addition at high temperatures, yielding an “in-chain” imidazole polymer. Vinazene, 1-methylvinazene, and 1-ethylvinazene brominate readily, but subsequent elimination does not afford the analogous acetylenes. Similarly, these compounds undergo Diels-Alder reactions with cyclopentadiene, preferring formation of endo products.;Kinetic studies of the radical polymerization of vinazene reveal a linear relationship between number average molecular weight and monomer concentration, and a linear relationship between number average molecular weight and the inverse square-root of initiator concentration. Direct measurements of kinetic rates for vinazene yielded kapp = kp/2✓k tfkd values of 7.2 ± 0.25 × 10−3 and 6.6 ± 0.27 × 10−3. Direct measurements of kinetic rates for 1-methyl yielded kapp = kp/2✓ktfkd values of 4.3 ± 0.31 × 10−3 and 3.7 ± 0.06 × 10 −3. The kinetics data obeyed a first order rate law typical of free-radical addition polymerization.;The homopolymerization of vinazene yielded acidic materials with molecular weights ranging from 100,000 to 200,000 and having polydispersities between 2.0 and 2.9. The Mark-Houwink constants for poly(vinazene) in 0.05 M LiBr in N-methyl-pyrrolidinone are K = 3.35 × 10−5 and a = 0.889. Brittle, free-standing films of poly(vinazene) can be cast from organic solvents, or aqueous ammonia.;Copolymerizations of vinazene and 1-methylvinazene with styrene were studied; the reactivity was not adequately described by the terminal model. Vinazene and 1-methylvinazene were preferentially incorporated into copolymer composition to a high degree, even at low feed compositions. Copolymerizations of 1-methylvinazene with styrene, mediated by TEMPO,0 improved control of copolymer composition over a variety of monomer feed compositions.