Preparation and Characterization of P(MAA-co-AM) Nanogels

Hydrophilic polymeric nanogels are normally fabricated in organic medium. Here, taking advantage of the specific hydrogen bonding interactions between the monomer pair, hydrophilic poly(methacrylic acid-co-acrylamide) (P(MAA-co-AM)) copolymer nanogel with pH-response was fabricated via a simple copolymerization of MAA, AM and crosslinker ethylene glycol dimethacrylate (EGDMA) in pure water. The size, morphology, composition and structure of the P(MAA-co-AM) nanogels were characterized by dynamic light scattering, FT-IR, TEM and SEM. The formation mechanism of P(MAA-co-AM) nanogels, the effects of various reaction parameters on their preparation, as well as the pH-responsive behavior of the nanogels were studied. Results showed that the in-situ formation of hydrophobic hydrogen bonding complexes led to the formation of stable dispersion of P(MAA-co-AM) nanogels. The nanogels prepared at a molar ratio of MAA to AM of 1.0 had the narrowest size distribution, with 〈D_h〉 of 129 nm and PDI of 0.095, respectively. The size of the nanogels increased with the increasing amount of two monomers, and decreased with the prolonging monomer feeding time or the increasing amount of EGDMA. Also, the P(MAA-co-AM) nanogels exhibited excellent pH-response:as the pH value increased from 4 to 8, their swelling ratio reached 7, and their hydrodynamic volume expanded 343 times.