Due to the water-solubility of poly(methacrylic acid) (PMAA)

it is hard to synthesize PMAA nanoparticles in water phase.A novel method for the green synthesis of PMAA-based nano-hydrogels in water phase was developed.In the method

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

the electrostatic interactions between the surfactants 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-based nano-hydrogels with PMMA cores and cross-linked PMAA shells.The size and size distribution

surface charges

composition

morphology

structure and pH-response behavior of the resulting nano-hydrogels were characterized by dynamic light scattering

-potential measurement

Fourier transform infrared spectroscopy (FTIR)

and transmission electron microscopy (TEM).The core-shell structure of the PMAA-based nano-hydrogels was disclosed by TEM observations.The size of the PMAA-based nano-hydrogels increases as the amount of MAA increases from 2 mL to 3 mL.However

as the amount of MAA increases to 5 mL

besides the PMAA-based nano-hydrogels

small pure PMAA nanoparticles also appear.Finally

the PMAA-based nano-hydrogels display excellent pH-responses:as the pH value increases from 2 to 7

the expansion of their hydrodynamic volumes approaches 80 times.