ジアミンとジアルデヒドの縮合によるCH=N結合を持ったポリマー (ポリイミン) の合成

抄録

In this paper, syntheses and characterizations of polymers containing CH=N bond in main chain (polyimine) will be described. Polyimines could be synthesized by the condensation of primary diamines and dialdehydes. The polymers were prepared first by Krässig and Greber in 1953. However, numerous polymerization techniques (solution, melt, Schiff-base exchange and others) and conditions tried have not given high molecular weight polyimines because of the insolubility and the high melting point. But, the discovery of m-cresol method by Suematsu and solid state polymerization by Morgan made high molecular weight polyimine formation possible. m-Cresol accelerated CH=N bond formation keeping a homogeneous solution. The reaction rate in m-cresol was as fast as that of acid chloride and primary amine in benzene, though top limit of degree of polymerization was not very high because of the presence of an equilibrium between polymerization and depolymerization. However, exclusion of reaction-water produced higher molecular weight polymers. The reaction rate in m-cresol was found to obey the reversible second order equation, defined as v=k [CHO] [NH₂] -k^* [C=N] [H₂O], where k is the rate constant in polymerization and k^* in depolymerization. The condensation in dilute solution resulted in the formation of macrocyclic imines in high yield. This could be explained not in terms of cyclization theory by Stockmayer et al., but favourable conformational changes and an equilibrium shift accompanied by the separation of products. Chain length of most aromatic polyimines is calculated according to the equation P_n=1/2 [3.6 (Aυ_C=N/Aυ_C=O) +1], where Aυ_C=N and Aυ_C=O are the absorbance of υ_C=N and υ_C=O respectively. An equation [η] =1.9×10^-3M^1.20 by Millaud holds in poly- (p-xylidene-2-methyl-p-phenylenediamine).