Processable Hyperbranched Aromatic Polyamides

Hyperbranched polymers (HBPs) have received great attention owing to their unique combination of low viscosity, excellent solubility, and facile synthesis. The preparation of HBPs from AB monomers emerged with the initial report by Flory in 1952 [57]. 

Jikei and co-workers [58] described the synthesis of aromatic h) er-branched polyamides (HBPAs), derived from aromatic diamines (A ) and trimesic acid (Bj). Furthermore, Jikei and co-workers, [59] as well as Voit and co-workers [60] have explored these HBPs in more detail, polyamide dendrimers were first reported by Miller and Neenan in 1990 [61]. The synthetic pathway was based on a convergent approach. 1,3,5-Benzenetricarbonyl trichloride and 5-nitroisophthaloyl chloride were used as the core and building blocks, respectively [62]. 

Baek and Harris reported aromatic HBPAs [63], synthesized by the self-polymerization of AB amide monomers containing hydroxyl and two fluoro groups. The reported polymers were amorphous in nature and were very much soluble in common organic solvents such as THF, CHCI3, DMF, DMAc, DMSO, NMP, and m-cresol. The aryl-fluoride-terminated, amorphous polymers had intrinsic viscosities of 0.34 and 0.24 dL/g (30.0 0.1°C in m-cresol) and T s of 210-269°C. 

Shabbir et al. reported the synthesis of an amide group containing aromatic triol and polycondensation of the aromatic triol monomer with various diacid chlorides that resulted in a series of hydroxy-terminated hyperbranched polyfamide esters) (HBPAEs) (PA-16 ) 

Ishida et al. reported three aromatic HBPAs, synthesized by the direct polycondensation of 3,5-diaminobenzoic acid (AB ), first generation (Gl) dendron (AB ), and second generation (G2) den-dron (ABj). The degrees of branching (DB) of the polymers from monomers were 0.32,0.72, and 0.84, respectively, as determined by H-NMR spectroscopy [66]. All aromatic HBPAs prepared from the three different monomers by direct polymerization were soluble in DMF, DMAc, NMP, and DMSO. The of the resulting polymers measured by GPC based on polystyrene standards were in the range of 10 x 10 - 20 x 10 . The fifth generation (G5) dendron was soluble in aprotic polar solvents and THE, whereas both the end-capped HBPAs from ABj and AB were insoluble in THE The authors assume that the difference in solubility is caused by the difference in architecture of the molecule random for the HBPs and spherical for the G5 dendron. 

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Keywords Aromatic polyamides, diamine, separation applications, melt processing, solution processing, hyperbranched... 

It was,and still is, a purpose of our work to illustrate the synthetic potential of "a-b monomers" in the field of aromatic polyethers, polyesters and polyamides (concentrating on polyesters in the present contribution). The preparation of star-shaped and hyperbranched polycondensates is plagued by side-reactions resulting in crosslinks, and thus, clean step-growth processes are a basic requirement for a successfid synthesis. In this connection the potential of silicon mediated polycondensations should be explored, because polycondensations of silylated monomers may be a cleaner process than that of the corresponding nonsilylated (protonated) monomers, for instance, because proton catalyzed side reactions, such as the Fries-rear-rangement, are avoided. 

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