pH-Sensitive Nanogel Possessing Reactive PEG Tethered Chains on the Surface

Poly(ethylene glycol) possessing a polymerizable vinylbenzyl group at one end and a carboxylic acid group at the other end was synthesized via the anionic polymerization of ethylene oxide. 1 H NMR, SEC, and MALDI-TOF-MS studies confirmed that each poly(ethylene glycol) chain quantitatively possessed vinylbenzyl and carboxyl end groups. Emulsion polymerization of 2-(diethylamino)ethyl methacrylate was carried out to obtain a nanometric-sized gel (nanogel) in the presence of a cross-linking agent such as ethylene dimethacrylate, using the obtained α-vinylbenzyl-ω-carboxy-PEG as a stabilizing reagent. The size of the obtained nanogels was controllable in the range between 50 and 680 nm. The nanogel was confirmed to have a PEG shell layer with a carboxylic acid group at the distal end of each PEG strands from the ζ-potential measurement at varying pHs. The pH-sensitive swelling/deswelling behavior of the nanogels was studied by dyanmic light scattering to confirm their volume phase transition at a pH around 7.0. These prepared nanogels are expected to have potential utility in applications such as diagnostics and controlled drug releasing devices.