No abstract

The nucleophilic ring opening addition reaction of phenol groups towards oxazoline units has been used for the preparation of hyperbranched poly(ether amide)s. For this the AB 2 monomer 2-(3,5-bishydroxyphenyl)-1,3-oxazoline was synthesized and converted in a highly branched polymer in bulk or solution at temperatures above 190 • C. The resulting hyperbranched polymers exhibit a degree of branching of 50%, as verified by high-resolution NMR spectroscopy, and are highly soluble in polar organic solvents, for example DMF and DMAc, with low solution viscosity. Their glass transition temperatures are in the region of 170 • C and degradation does not start below 300 • C. Melt rheology measurements revealed a predominantly elastic behaviour with a relatively high viscosity at low frequency. A lower melt viscosity was achieved by end group modification. Hyperbranched poly(ether amide)s with phenolic and acetate end groups are fully miscible with linear polyamide 6. When a small amount of the hyperbranched material is added to the PA6 matrix a significant reduction of the melt viscosity could be achieved without changing the mechanical properties of the matrix polymer.

The hyperbranched (HB) aromatic polyamide synthesised by direct polycondensation of 5‐(4‐aminobenzoylamino)isophthalic acid (ABZAIA) has been solution‐ and melt‐ blended with polyamide 6 (PA6) incorporating different end groups. The concentration of p(ABZAIA) in PA6 has been varied from 5 to 30 wt.‐% in order to evaluate the influence of hyperbranched polymer content on blend properties. Viscosity and glass transition (Tg) data of the solution blends underlined the full miscibility between the components in the explored composition range. The miscibility was not related to any specific type of PA6 end group, thus suggesting a major role for its amide groups in interacting (presumably via hydrogen bonding) with HB functional end groups. Well‐separated powder particles have been obtained by precipitation from diluted solutions both for the neat polymers and for the blends. Also, in the case of blends prepared by melt mixing Tg linearly increased with the HB polymer content, again confirming full miscibility between the blend components. Blend characterisation, solubility tests and melt rheology supported the idea that p(ABZAIA) forms reactive blends with polyamide 6 by melt mixing. As a consequence of these reactions, the hyperbranched aramid strongly modified the rheological behaviour of PA6.

The synthesis of aliphatic-aromatic poly(ether amide) dendrimers via ring-opening addition reaction of phenol groups toward oxazoline up to generation 3 is presented. The first and second generation could be prepared both by convergent and divergent approaches. The ring-opening addition reaction was carried out in bulk at temperatures between 140 and 190 °C, followed by hydrogenation of the protecting benzyl ether units with palladium catalyst. The dendrons and dendrimers were characterized by 1 H and 13 C NMR spectroscopy, MALDI-TOF MS, SEC, and DSC. The synthetic scheme applied allowed to prepare perfect dendrimers having identical structure and end groups as previously described hyperbranched polymers which enabled a direct comparison of the properties. Melt rheology measurements on the dendrimers revealed a predominantly elastic behavior with a relatively high viscosity at low frequency, as was found also for the hyperbranched analogues. The second generation of one of the poly(ether amide) dendrimers was mixed with linear polyamide 6 (PA6) in melt up to an amount of 1 wt % in order to evaluate the influence of dendrimers on the properties of the matrix. The dendrimer was fully miscible with the matrix, but in contrast to the hyperbranched polymers of higher molar mass, it had no influence on the melt rheological behavior of the PA6.