Synthesis of Poly(methacrylic acid) Nano-Hydrogels in Water

Driven by the hydrophobic interactions between two surfactants and the hydrogen bonding interactions between the surfactant and monomers,methacrylic acid (MAA) monomers are selectively polymerized on the surface of poly(methyl methacrylate) (PMMA) nanolatex seed formed in-situ,thus realizing the "green" synthesis of PMAA nano-hydrogels in water.Dynamic light scattering,Fourier transform infrared spectroscopy and transmission electron microscopy were used to characterize the size and size distribution,composition,morphology,and pH-response behavior of the resulting nano-hydrogels.The influences of the amount of Tween 20,N,N'-methylene bisacrylamide (MBA) and MAA,the feeding mode of MAA,and the supplement rate of sodium dodecyl sulfate (SDS) on the size and swelling properties of the nano-hydrogels were studied.Results show that the nano-hydrogels have core-shell structure.As the amount of MBA decreases,the amount of Tween 20 increases,or the amount of MAA increases,the size and swelling ratio of the nano-hydrogels both increase.The size and swelling ratio both decrease when MAA is fed semi-continuously.The size decreases slowly as the supplement of SDS is extended from 60 min to 100 min.The PMAA nano-hydrogels display excellent pH-response.When the pH value increases from 1 to 6,their hydrodynamic volumes expand for 64 times.