A novel method for the "green" synthesis of PMAA nano-hydrogels in water was developed.In the method

small poly(methyl methacrylate) (PMMA) nanolatex particles formed "in situ" were used as the seeds.Meanwhile

the hydrogen bonding interactions between the surfactant tween 20 on the surfaces of the seeds and MAA monomers were utilized to realize the selective polymerization of MAA on the surfaces of the PMMA seeds

thus resulting in the formation of PMAA nano-hydrogels with PMMA cores and cross-linked PMAA shells.Magnetic PMAA nanoparticles were further fabricated by an "in situ" oxidization precipitation method.The size and size distribution

composition

morphology

structure

pH-response behavior and magnetic property of the resulting PMAA nano-hydrogels and magnetic PMAA nanoparticles were characterized.The hydrogen bonding interactions between tween 20 and MAA (PMAA) prompt the selective growth of a crosslinked PMAA layer on the surfaces of PMMA seed latex

resulting in the formation of PMAA nano-hydrogels with PMMA cores and cross-linked PMAA shells.The core-shell structure of the PMAA nano-hydrogels was disclosed by TEM observations.The PMAA nano-hydrogels display excellent pH-responses:as the pH value increases from 1 to 6

the expansion of their hydrodynamic volumes approaches 50 times.The magnetic PMAA nanoparticles were superparamagnetic and with a saturation magnetization as high as 50 A ·m2/kg.