A Novel Poly(amido amine) with Methoxy Carbonyl Groups and High Charge Density: Synthesis and Nanoscopic Selfassembly with Polyanion

A novel poly(amido amine) with methoxy carbonyl groups, high charge density and broad nitrogen profile, was synthesized from tetraethylene pentamine (TEPA) and methyl acrylate (MA), and named as PTMA. During synthesis, on one hand, double bond of MA was added with amino group of TEPA by Michael addition reaction and, on the other hand, methoxy carbonyl group of MA was nucleophilicly substituted by amino group of TEPA. There are primary, secondary, tertiary amines and amide groups in PTMA molecule. Acid base titration indicated that the polymer was protonated in the range of both pH 5.0 to pH 7.4 and pH 7.4 to pH 11, which is indicative of not only good self-assembling capability with polyanion but also desirable proton sponge effect as shown by polyethylenimine (PEI). In aqueous solution, PTMA self-assembled with weak anionic polymer, poly(acrylic acid) (PAA), to form nanoparticles. The particle size first increased and then decreased with increasing mass ratio of PTMA to PAA, which is defined as θ. At all examined θ values, self-assembling particles with diameter less than 200 nm were obtained. The UV-Vis absorbance curve of self-assembling complex solution at first day overlapped with that at seventh day, indicating that self-assembling particles were stable.