Secondary transitions of aryl-aliphatic polyamides I. Broadband dielectricinvestigation

Dielectric relaxation measurements were performed on two series of aryl-ali phatic copolyamides. The repeat unit of the first series was made of 1 or 1 .8 lactam-12 sequences, a tere- or iso-phthalic moiety, and a 3,3'-dimethyl dicyclohexylmethane unit in regular order. The second series was obtained f rom condensation of terephthalic acid onto 1,5-diamino-2-methylpentane. The dielectric relaxation measurements demonstrated the existence of several s econdary relaxations. The comparison of the results obtained from the two s eries of samples permitted the assignment of gamma, beta and omega relaxati ons, observed in the first series of compounds, to motions of non-conjugate d C=O groups, C=O groups located between a phenyl ring and a flexible lacta m-12 or methylpentane sequence, and C=O groups situated between a phenyl ri ng and a rigid cycloaliphatic moiety, respectively. (C) 1999 Elsevier Scien ce Ltd. All rights reserved.