Preparation of stimuli-responsive nanogels of poly [2-(dimethylamino) ethyl methacrylate] by heterophase and microemulsion polymerization using gamma radiation

Poly [2-(dimethylamino) ethyl methacrylate], PDMAEMA, was synthesized by heterophase polymerization at 70°C using sodium dodecylsulfate (SDS) as stabilizer and potassium persulfate (KPS) as the initiator. Conversions were 60%, polymer content 18%, and intensity average particle diameter, D^sub p^, 32 nm. γ-rays irradiation of PDMAEMA nanolatexes and DMAEMA/H^sub 2^O/SDS microemulsions using ethyleneglycol dimethacrylate produced nanogels responding to temperature and pH. Nanogels shrinked as temperature increased, swelled excessively in acidic solutions (maximum D^sub p^: 498 nm) and deswelled (minimum D^sub p^: 257 nm) in basic solutions for the case of the nanogels obtained from PDMAEMA nanolatexes. pH response to swelling is due to protonation of amine groups in the backbone of PDMAEMA in acidic conditions leading to electrostatic interactions in the nanogel.