Thermal properties of the polyamide from 2-methylpentamethylenediamine and dodecanedioic acid

The polyamide from 2-methylpentamethylenediamine and dodecanedioic acid (MPMD-12) has been studied by differential scanning calorimetry, dynamic mechanical analysis, dielectric analysis, X-ray crystallography, and simultaneous small and wide-angle X-ray scattering using synchrotron radiation. The polymer exhibits polymorphism which is shown to be associated with the incorporation of the branched diamine. At relatively low temperatures, the crystal structure is similar to the gamma form which has been found in many other polyamides. At higher temperatures, a new delta form appears in which the diamine moiety adopts a bent conformation. In this form, the chains follow a zig-zag pattern with two chemical repeats units per crystallographic repeat with a shortening of about 10% along the c-axis.