posted on 2021-11-02, 18:36authored byNupur Gupta, Yen Nan Liang, Jia Wei Chew, Xiao Hu
Hydrogel
composites with skin layer that allows fast and selective
rejection of molecules possess high potential for numerous applications,
including sample preconcentration for point-of-use detection and analysis.
The stimuli-responsive hydrogels are particularly promising due to
facile regenerability. However, poor adhesion of the skin layer due
to swelling-degree difference during continuous swelling/deswelling
of the hydrogel hinders its further development. In this work, a polyamide
skin layer with strong adhesion was fabricated via gel–liquid
interfacial polymerization (GLIP) of branched polyethyleneimine (PEI)
with trimesoyl chloride (TMC) on a cross-linked N-isopropyl acrylamide hydrogel network containing dispersed poly
sodium acrylate (PSA), while the traditional m-phenylenediamine
(MPD)-TMC polyamide layer readily delaminates. We investigated the
mechanistic design principle, which not only resulted in strong anchoring
of the polyamide layer to the hydrogel surface but also enabled manipulation
of the surface morphology, porosity, and surface charge by tailoring
interfacial reaction conditions. The polyamide/hydrogel composite
was able to withstand 100 cycles of swelling/deswelling without any
delamination or a significant decrease in its rejection performance
of the model dye, i.e., methylene blue. Regeneration can be done by
deswelling the swollen beads at 60 °C, which also releases any
loosely bound molecules together with absorbed water. This work provides
insights into the development of a physically and chemically robust
skin layer on various types of hydrogels for applications such as
preconcentration, antifouling-coating, selective compound extraction,
etc.