Synthesis And Characterization Of Nanogels Via UV-Photopolymerization

Highly crosslinked polymers are readily synthesised by photoinitiated polymerisation of multifunctional monomers and telechelic polymers.The main advantage of using UV radiation to initiate the chain reaction lies in the very high polymerisation rates that can be reached under intense illumination,so that the liquid to solid phase change takes place within a fraction of a second.Another distinct feature of light-induced reactions is that the polymerisation will occur only in the illuminated areas,thus allowing complex relief patterns to be produced after solvent development.In this paper,Core-shell Fe₃O₄ nanogels with controllable sizes were synthesized under UV irradiation by using Fe₃O4 nanoparticles as core,N-(2-Aminoethyl) methacrylamide(AEM) as monomer and N,N'-Methylenebisacrylamide(MBA) as cross-linker.The effects of concentrations of AEM and MBA,irradiation time on the particle sizes of Fe₃O₄ nanogels were detailed.The particle size,size distribution, morphology,structure and magnetism of nanogels were characterized by dynamic light scattering(DLS),transmission electron microscopy(TEM),FTIR, thermogravimmetric analysis(TGA),vibrating sample magnetometer(VSM), respectively.Results showed that superparamagnetic nanogels with different sizes and narrow size distributions could be synthesized by varying the irradiation time and concentrations of monomer and cross-linker.Comparing with Fe₃O₄ nanoparticles,the stability of magnetic nanogels was improved due to their high zeta potential,although their saturation magnetization showed a little tendency to decrease.The effect of the photoinitiated polymerisation in coordinated-induction coordination micelles was also discussed.The synthesis of the cross-linked micelles was carried out using a two-step process.The first step involved self-assembly of PEO-b-PLG copolymers into block ionomer complexes in the presence of divalent metal ions,such as Ca²⁺(or Ba²⁺,Sr²⁺). Electrostatic neutralization of the polyion blocks by metal ions resulted inhydrophobization of these blocks and spontaneous micelle formation.At the second step,cross-linking of the core of the PEO-b-PMA/Ca²⁺ micelles was achieved using UV-Photopolymerization between AEM.