The effect of water/ethanol ratio and monomer concentration on the size and morphology of polyacrylamide nanogels in a surfactant-free synthesis

Abstract

In this contribution, we propose a polyacrylamide surfactant-free nanogel synthesis technique in a water/ethanol system using N,N'-methylenebisacrylamide (MBAm) as a crosslinker agent. The polymerization reactions were carried out using the potassium persulfate (KPS) and N,N,N′,N′-tetramethylethylenediamine (TEMED) redox pair. The main contribution of this paper is a two-dimensional study of the particle size, polydispersity, and morphology as a function of the solvent water/ethanol wt. ratio and wt. % of monomer (acrylamide, AM) during the particle synthesis. The results show that the obtained particles have a similar morphology compared to those prepared using surfactants. The particle size was measured using Quasi-Elastic Light Scattering (QELS) of the redispersed nanogel, obtaining particle sizes from 41 to 1050 nm, with polydispersity values between 0.31 and 1. In all cases, we found three particle sizes with different abundance distributions, each having a prevailing abundancy ranging from 65% to 95%. Finally, the nanogel morphology was analyzed with Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM).

Keywords:

• Surfactant free
• nanogels
• polyacrylamide
• redox pair
• ethanol-water system