Macrocycles. 17. The Role of Cyclization in Kinetically Controlled Polycondensations. 2. Polyamides

Two series of kinetically controlled polycondensations were conducted yielding polyamides of aliphatic dicarboxylic acids. First, the bis(trimethylsilyl) derivatives of 1,3-diaminobenzene, 4,4‘-diaminodiphenylmethane, 1,12-diamino-4,9-dioxadodecane, and 1,12-diaminododecane were polycondensed with dicarboxylic acid dichlorides in N -methylpyrrodidone below 0 °C. After optimization of the reaction conditions mainly cyclic polyamides were detectable in the MALDI−TOF mass spectra (up to 13 000 Da) of the semiaromatic polyamides in contrast to the Carothers−Flory theory. In the case of silylated aliphatic diamines, side reactions of the acid chlorides prevented a complete conversion of the amino groups, so that the reaction products mainly consisted of cycles and linear chains having two amino end groups. Second, normal interfacial polycondensations were performed either with 1,6-diaminohexane and adipoyl chloride or with 1,12-diaminododecane and decane-1,10-dicarbonyl chloride. When the loss of acid chloride groups by hydrolysis was compensated by an excess of dicarboxylic acid dichlorides cyclic polyamides were again the main reaction products up to masses of 4000−5000 Da. A new version of the “Carothers equation” taking into account the role of cyclization in kinetically controlled step-growth polymerizations is discussed.