Stereochemistry driven cocrystallization phenomena in partially cycloaliphatic polyamides

Two series of isomeric copolyamides were prepd., viz. colyamides 12.6 for which the adipic acid residues were partially replaced by cis/trans-1,4-cyclohexanedicarboxylic acid (1,4-CHDA), and polyamides 4.14 for which the 1,4-diaminobutane residues were partially replaced by cis/trans-1,4-diaminocyclohexane (1,4-DACH). DSC and WAXS anal. showed that only the trans isomers of both 1,4-DACH and 1,4-CHDA are incorporated into the cryst. phase. During DSC anal., an initial high trans content is preserved in the case of the non-isomerizing 1,4-DACH, whereas the 1,4-CHDA residues gradually isomerize from a high initial trans content to a significantly lower trans content. Since these cis residues are not incorporated into the cryst. domains, the lower second heating m.ps. of the 1,4-CHDA-based copolyamides in comparison with 1,4-DACH-based copolyamides, having similar cycloaliph. monomer contents, can be understood