Preparation of uniformly sized interpenetrating polymer network polyelectrolyte hydrogel droplets from a solid-state liquid crystal shell

Uniformly sized interpenetrating polymer network (IPN) polyelectrolyte hydrogel droplets were produced with solid-state liquid crystal (LC_solid) shells, which had been produced by a microfluidic method. The weak polyelectrolyte hydrogel and the temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) networks were intertwined in the LCsolid shell to produce an IPN structure; the anionic poly(acrylic acid) (PAA) and cationic poly(N-[3-(dimethylamino)propyl] methacrylamide) (PDMAPMA) were utilized for the weak polyelectrolyte hydrogel networks. The anionic PNIPAM/PAA, cationic PNIPAM/PDMAPMA, and zwitterionic PAA/PDMAPMA IPN droplets were successfully produced by the LC_solid shell templates. The PNIPAM/PAA IPN droplets were applied to a Ca²⁺ sensor. Further, the anionic PNIPAM/PAA and cationic PNIPAM/PDMAPMA IPN droplets could adsorb the cationic methylene blue and anionic Acid Red 37 dyes, respectively, while the zwitterionic PAA/PDMAPMA IPN droplets could adsorb both dyes. This method of producing uniformly sized IPN hydrogel droplets from LC_solid shell templates is simple and does not require any sophisticated machines.