Abstract Poly(acrylonitrile- co - N -isopropylacrylamide) (p(AN- co -NIPAM)) core–shell hydrogel nanoparticles were synthesized by microemulsion polymerization and their feasibility as a drug carrier was investigated. Highly monodispersed nanoparticles with desired size range – i.e., 50–150 nm – were prepared by adjusting the reaction conditions. The hydrophobic core of the composite which consists primarily of poly(acrylonitrile), can be easily made highly hydrophilic by converting the nitrile groups to the corresponding amidoxime groups. This provides a level of tunability in the hydrophobicity/hydrophilicity balance of the composite nanoparticle. The thermo-responsive feature of the shell was utilized for the release of a model drug, propranolol (PPL). It is shown that the loading/release capacity of nanoparticles was increased almost two-fold by the amidoximation of the core material.