Hollow
Microgel Based Ultrathin Thermoresponsive Membranes
for Separation, Synthesis, and Catalytic Applications
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Abstract
Thermoresponsive
core–shell microgels with degradable core
are synthesized via surfactant based free radical polymerization using
N,N′-(1,2-dihydroxy-ethylene)bis(acrylamide) (DHEA) as a cross-linker
for core preparation. The 1,2-glycol bond present in DHEA is susceptible
to NaIO<sub>4</sub> solution, and thus, the structure can be cleaved
off resulting in hollow microgel. Ultrathin membranes are prepared
by suction filtration of a dilute suspension of core–shell
microgels over a sacrificial layer of Cd(OH)<sub>2</sub> nanostrand
coated on track etched membrane. After removal of the degraded cores
from microgels, the membranes are cross-linked with glutaraldehyde
and the nanostrands are removed by passing a 10 mM HCl solution. The
prepared membranes are thoroughly characterized using scanning electron
microscopy (SEM), atomic force microscopy (AFM), dynamic light scattering
(DLS), and dynamic contact angle for morphology, thermoresponsive,
and hydrophilic properties, respectively. The prepared membranes showed
thermoresponsive permeation behavior and remarkable separation performance
for low molecular weight dyes and lysozyme protein. These membranes
are also used to synthesize gold nanoparticles and immobilize lactate
dehydrogenase enzyme for catalytic and biocatalytic application. The
results for water permeation, solute rejection, and ability to immobilize
gold nanoparticles and enzymes showed its wide range of applicability.
Furthermore, the synthesis of hollow microgel is simple and environmentally
friendly, and the membrane preparation is easy, scalable, and other
microgel systems can also be used. These responsive membranes constitute
a significant contribution to advanced separation technology