Block and random copolyamides of poly(m-xylylene adipamide) and poly(hexamethylene isophthalamide-co-terephthalamide): Methods of preparation and relationships between molecular structure and phase behavior

Copolymerization of poly(m-xylylene adipamide) (MXD6) and poly(hexamethylene isophthalamide-co-terephthalamide) (PA6I-6T) was used as an efficient strategy to prepare amorphous homogeneous systems with improved properties mainly for packaging applications. The preparation of block copolymers was first of all tried by co-extrusion of the two polymers and then by thermal treatments at high temperatures in DSC or mixing in Brabender, also in the presence of a catalyst. The occurrence of transamidation reactions led to macromolecular structures with different randomness degrees. Further, random copolymers, with the full range of compositions, were synthetized from monomers, by a fast and simple two-stage melt polycondensation. For all the copolymers, the sequence distribution was studied by using a H-1 NMR method developed by the Authors. The effects of preparation procedures, of mixing temperature and time, of the presence of a catalyst on the chemical structure, and, then, on final properties were studied. Interesting correlations among block length, monomer distribution and phase behavior were discussed.