Synthesis and characterization of comb-shaped poly(amido amine)-g-PEO via Michael addition polymerization

Linear pH-sensitive poly(amido amine)s were synthesized via Michael addition polymerization of N-aminoethyl piperazine (AEPZ) or 4-aminomethyl piperidine (AMPD) with 1,12-dodecylene diacrylamide (DDA). Successive Michael addition reaction of acryl-terminated poly(ethylene oxide) (A-PEO) with the secondary amine of linear poly(DDA–AEPZ) that has one secondary amine in every repeating unit afforded PEO-grafted poly(amido amine). Variation of grafting degree could be obtained conveniently via tuning the feed molar ratio of acryl/secondary amine. When this ratio equals to 1.2, all the secondary amines on the backbone of poly(DDA–AEPZ) (or poly(DDA–AMPD)) were consumed and the comb-shaped polymers were formed. The amphiphilic comb-shaped poly(DDA–AEPZ)-g-PEO was molecularly dissolved in water at pH 2.0 (w/v=0.25%), and micelles were formed when pH value of aqueous solution was adjusted to 6.5. 1H NMR data verify the formation of micelles due to the disappearance of signals attributed to poly(DDA–AEPZ). The formation of micelles can be confirmed further by TEM photos, they show that all the particles are approximately spherical and their number-average diameter is around 95 nm.