Recently,
various porous absorbents have been developed and the in situ vacuum/pump-assisted continuous
separation process has proven to be the most efficient technique to
utilize those absorbents for oil spill cleanup. However, to achieve
a high oil removal throughput, a high pumping pressure and/or large
absorbent pore sizes are required, which would compromise the selectivity
of oil/water separation, as water may penetrate the absorbent beyond
a critical external pressure. In this work, this challenge has been
circumvented by employing hierarchically porous polypropylene (PP)
with controlled pore sizes generated from a tricontinuous heterophase
polymer blend system. As compared to unimodal pores, the incorporation
of the secondary smaller pores significantly enhances the oil removal
throughput by up to 4–5 times without the necessity of raising
the pumping pressure or increasing the diameter of the primary pores,
which in turn, prevents compromising the oil/water separation selectivity.
Porous and temperature-sensitive
poly(N-isopropylacrylamide)
(PNIPAam) hydrogels with tunable and enhanced response properties
were prepared by using porous poly(ε-caprolactone) (PCL) molds.
The molds were obtained from melt-processed cocontinuous polymer blends
of ethylene propylene diene monomer (EPDM) and PCL. Quiescent annealing
of the blends resulted in microstructure coarsening, and subsequent
extraction of the EPDM phase yielded the molds. Ultimately, it allowed
control over the average gel pore size from 20 to 300 μm. The
gelling solution was injected within the molds, which were subsequently
extracted, yielding hydrogels with fully interconnected pores. The
porous gels display enhanced thermoresponsive properties in water:
tunable, fully reversible and significantly faster swelling and deswelling
responses following a temperature change across the PNIPAam lower
critical solution temperature, as compared to nonporous gels. The
fabrication process is compatible with a broad choice of gel chemistries,
and allows the fabrication of complex 3D shapes of various sizes.
This work demonstrates that a model system of poly( N-isopropylacrylamide) (PNIPAam) macroporous hydrogels, with tailored microstructures and comprising gold (Au) or silver (Ag) nanoparticles, display enhanced and tunable catalytic activity. These nanocomposites are prepared using polymer templates obtained from melt-processed cocontinuous polymer blends. The reaction rate, controlled by both hydrogel porosity and the PNIPAam lower critical solution temperature, increases by more than an order of magnitude as compared to nonporous gels, and is comparable to micro- or nanocarrier-based systems, with easier catalyst recovery. The fabrication process is scalable, and is compatible with broad choices of polymer blend, gel, and nanoparticle chemistries.
Highly porous poly(N-isopropylacrylamide) PNIPAam hydrogel monoliths with tunable microstructures and comprising gold, silver or palladium nanoparticles, display significant catalytic activity when used in flow-through microreactors.
This study presents a new method for the preparation of organogels embedded with interconnected macropores tunable in size from 180 to 700 μm. The gels are molded in porous polyvinyl alcohol (PVOH) polymer templates obtained from melt‐processed cocontinuous blends of PVOH and poly(ε‐caprolactone) (PCL). The blends are subsequently annealed under quiescent conditions to let their morphology coarsen, and are rendered porous by selectively extracting the PCL. After the injection in the PVOH molds and in situ gelling of a dilute solution of an organic liquid and a low molecular weight gelling agent, 12‐hydroxyoctadecanoic acid, the molds are extracted with water. This yields porous organogels with microstructural features corresponding relatively well to those of the original molds, as revealed by X‐ray microtomography. This method allows control over the gels' average pore size, pore interconnectivity, and volume fraction, and is compatible with a variety of organic liquids and low molecular weight gelators.
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