Thermal properties of the polyamide from 2-methylpentamethylenediamine anddodecanedioic acid

The polyamide from 2-methylpentamethylenediamine and dodecanedioic acid (MP MD-12) has been studied by differential scanning calorimetry, dynamic mecha nical analysis, dielectric analysis, X-ray crystallography, and simultaneou s small and wide-angle X-ray scattering using synchrotron radiation. The po lymer exhibits polymorphism which is shown to be associated with the incorp oration of the branched diamine. At relatively low temperatures, the crysta l 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 repe at with a shortening of about 10% along the c-axis.