Electrochemically Initiated Synthesis of Polyacrylamide Microgels and Core-shell Particles

Abstract

Herein, we developed a simple procedure for synthesizing micrometer-sized microgel particles as a suspension in an aqueous solution and thin films deposited as shells on different inorganic cores. A sufficiently high constant potential was applied to the working electrode to commence the initiator decomposition that resulted in gelation. Under hydrodynamic conditions, this initiation allowed preparing different morphology microgels at room temperature. Importantly, neither heating nor UV-light illumination was needed to initiate the polymerization. Moreover, thin films of the cross-linked gel were anchored on different core substrates, including silica and magnetic nanoparticles. Scanning electron microscopy and transmission electron microscopy imaging confirmed the microgel particles’ and films’ irregular shape and porous structure. Energy-dispersive X-ray spectroscopy indicated that the core coating with the microgel film was successful. Dynamic light scattering measured the micrometer size of gel particles with different combinations of acrylic monomers. Thermogravimetric analysis and the first-derivative thermogravimetric analysis revealed that the microgels’ thermal stability of different compositions was different. Fourier-transform infrared and 13 C NMR spectroscopy showed successful copolymerization of the main, functional, and cross-linking monomers.

Electrochemically Synthesized Polyacrylamide Gel and Core–Shell Nanoparticles for 3D Cell Culture Formation

“…Previously, we proposed an electrochemically initiated synthesis of polyacrylamide microgels. 46 In this unique approach, microgels were prepared with and without core−shell support using amphiphilic and hydrophilic monomers. More importantly, this polymerization was initiated at room temperature.…”

“…For that, potentials different from −0.60 V, i.e., −0.70 and −0.80 V vs Ag quasi-reference electrode, were applied for 3 h, while monomer concentrations were 25 mM NIPAM, 25 mM MA, and 50 mM BIS, as previously reported. 46 When a more negative potential of −0.80 V was applied, the gel appearance in the solution was extended over 24 h. This time shortened when a potential of −0.70 V was selected. The shortest gel formation time was needed when a potential of −0.60 V was applied to break ammonium persulfate to generate free radicals in the solution.…”

“…In the Supporting Information, we discussed the mechanism occurring during the electrochemically initiated microgel synthesis (Scheme S1). 46,48 Core particles were dispersed in a solution of monomers and cross-linking monomers of a composition similar to that described above to synthesize core−shell particles.…”

“…42,47 Therefore, the electrochemical synthesis of gels was performed in an aqueous medium. 46 Moreover, microgels were grafted on inorganic substrates with this unique approach to prepare core−shell particles at room temperature. Overall, this approach allowed the synthesis of microgel particles in solution but lacked control over gel size and morphology.…”

“…First, silica particles were surfacefunctionalized with 3-(trimethoxysilyl)propyl methacrylate using an earlier reported procedure to prepare silica-based core−shell particles. 46 A 0.5 mL sample of this suspension was added to the 20 mL sample of the solution for electrochemically aided polymerization. The core−shell particles were centrifuged at 20,000 rpm for 20 min.…”