One-Pot Synthesis of Dendritic Poly(amide-urea)s via Curtius Rearrangement. 2. Synthesis and Characterization of Dendritic Poly(amide-urea)s

Abstract

Dendritic poly(amide-urea)s from the first to fourth generations with a very narrow molecular weight distribution were prepared from 1,1,1-tris(4-carboxymethyloxyphenyl)ethane as a core molecule, using aminodicarboxylic acid and aminodicarbonyl azide as two AB 2 monomers in a one-pot procedure. This procedure involves activation of end carboxyl groups with a condensing agent, diphenyl(2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate, condensation of the active amide with aminodicarbonyl azide, the Curtius rearrangement in the presence of aminodicarboxylic acid, and, finally, capping of the end groups with p-tert-butylaniline. All dendritic polymers were obtained quantitatively and fully characterized by elemental analysis and IR and NMR spectroscopies. Number average molecular weights (M n) of dendritic poly(amide-urea)s were estimated by end group analysis, and each dendritic poly(amide-urea) had Mn close to the calculated value. Degrees of branching for the second and third generation dendritic polymers were found to be 0.93 and 0.90, respectively by 1 H NMR spectroscopy.

Liquid crystalline polyureas with oligo(ethylene glycol) sequences

“…However, potentially more useful polyureas are those containing other functional groups such as urea-formaldehyde resins, poly(urethane-urea)s, poly(ether-urea)s, and poly(amide-urea)s [15][16][17][18][19][20].…”

Solvent‐free and nonisocyanate melt transurethane reaction for aliphatic polyurethanes and mechanistic aspects

“…The diisocyanates are highly hazardous, and its continuous exposure causes uncurable respiratory diseases 5, 6. In the last few decades, various nonisocyanate polymerization routes were attempted for polyurethanes and few of them include the following: (i) reaction of bis(chloroformates) with diamines,7 (ii) adiponitrile carbonate with diols or polyols,8 (iii) reaction of urethane diphenol with phosgene,9 (iv) cyclic carbonates with amines,10 and (v) acyl azide‐mediated Curtius rearrangement for hyperbranched polyurethanes11 and dentritic poly(amide urea)s 12. Though these approaches had been widely explored for making oligomers or polyurethane coating applications, low degree of polymerization10 makes these processes less preferable over the conventional isocyanate chemistry.…”

Syntheses, characterization, optical properties, and charge‐transfer complexation study of fluorescent poly(aryl‐ether‐urea) dendrimers

“…The synthesis of aliphatic branched polyurethane has been reported by Clark et al10 Because of the complexity of divergent synthesis, they have reported only the first generation dendrimer. Okaniwa et al11 synthesized dendritic poly(amide‐urea)s via Curtius rearrangement. Aliphatic dendrimers with alternating urethane‐urea links have been described up to second generation by Peerlings et al12 They used a novel AB‐CD 2 approach, involving bis‐isocyanate AB monomer with differential reactivity.…”