Preparation and characterisation of blends based on polyamide 6 and hyperbranched aramids as palladium nanoparticle supports

Solution and melt blends have been prepared by mixing polyamide 6 (PA6) with hyperbranched (HB) aromatic polyamides (aramids) synthesized from A2 (p-phenylenediamine)+B3 (trimesic acid) reactants. The HB aramids (pPDT), were obtained using various polymerization conditions, hence were characterized by different content and ratio of -COOH and -NH2 end group functionalities, as well as different architectures.For comparison, the characteristics of the above blends have been matched to those based on PA6 and the HB aramid synthesised from an AB2 monomer (namely 5-(4-aminobenzoylamino)isophthalic acid, named ABZAIA), which was the topic of a previous paper of ours [O. Monticelli, D. Oliva, S. Russo, C. Clausnitzer, P. Pötschke, B. Voit, Macromol Mater Eng 288 (2003) 318-25. [1]]. Viscosity data and glass transition temperatures of solution and melt blends underlined the good miscibility between the blend components. Blend properties, namely glass transition temperature and rheological behaviour, have been found to depend on concentration and type of the HB aramid. Indeed, the presence of pPDT aramids in the blends caused a weaker variation of the rheological behaviour, with respect to neat PA6, as compared to poly(ABZAIA).Both the above solution and melt blends have been used as supports of palladium nanoparticles. The metal-retaining capability of neat PA6 was greatly enhanced by blending it with pPDT polymers. In these blends, the Pd loading has been found directly proportional to the amino group content of the HB aramid, thus justifying better performances of pPDTs over poly(ABZAIA). The large increase of metal loading in the above blends has not been carried out at expenses of Pd nanoparticle dimensions, as revealed by the unchanged size distribution of metal dispersion by TEM.