11 research outputs found
Curable Ionic Liquid Prepolymer-Based Ion Gel Coating System for Toxic Industrial Chemical Hazard Mitigation on Porous Substrates
A peelable gel coating
based on a curable ammonium-alcohol ionic
liquid (IL) prepolymer has been developed for the decontamination
of toxic industrial chemicals (TICs) from porous substrates. The physical
properties of these coatings can be tuned by controlling the prepolymer
molecular weight (prepared by RAFT polymerization) and by altering
the formulation of the initial coating mixture. The initially applied
(uncured) solutions can be applied onto porous wood and ceramic substrates
with minimal soak-in, and these films cure quickly in situ under ambient
conditions. These coatings were tested in a series of assays meant
to demonstrate their effectiveness as TIC vapor barriers and materials
that absorb liquid TICs from the aforementioned substrates. The coatings
were found to suppress ∼80% of the vapor released by a TIC
simulant (<i>o</i>-dichlorobenzene) from these substrates
and to extract up to 85% of the mass of the originally applied simulant
that soaked into these substrates
Ionic Liquid Gel-Based Containment and Decontamination Coating for Blister Agent-Contacted Substrates
Current methods to contain and decontaminate materials
contacted
by toxic chemical warfare agents (CWAs) have disadvantages with respect
to ease of delivery, portability, and effectiveness on porous substrates.
A portable, easy-to-use, spreadable coating that immediately acts
as a barrier to contain CWA vapors on contacted substrates and also
decontaminates soaked-in CWAs is highly desired. A new type of decontaminating
barrier coating for sulfur mustard (i.e., blister agent) CWAs has
been developed that is made of (1) a spreadable nonvolatile, fluid
matrix based on a room-temperature ionic liquid (RTIL), (2) an organic
gelator that acts as a solidifying agent to help the applied coating
adhere to and prevent runoff from angled or vertical surfaces, and
(3) a polyamine that acts as a reagent to chemically degrade and help
draw out adsorbed blister agent. When applied to porous and nonporous
substrates contacted with 2-chloroethyl ethyl sulfide (CEES, a mustard
agent simulant), this spreadable, soft solid coating was found to
act as an effective barrier, blocking 70–90% of the CEES vapor
from entering the overhead space compared to uncoated samples. Furthermore,
this reactive gel RTIL coating was able to remove (i.e., draw out
and degrade) 70–95% of the liquid CEES soaked into porous substrates
after 24 h at ambient temperature when applied as a static, single-application
coating. Preliminary studies with added dyes and indicators to this
coating system have shown that the decontamination process may be
followed visually via color changes
Curable Imidazolium Poly(ionic liquid)/Ionic Liquid Coating for Containment and Decontamination of Toxic Industrial Chemical-Contacted Substrates
A curable,
imidazolium-based room-temperature ionic liquid (RTIL)
coating system has been developed for the containment and decontamination
of toxic industrial chemical-contacted surfaces. The curing times
and mechanical properties of this poly(RTIL)/RTIL platform, which
is based on alcohol–isocyanate step-growth polymerization chemistry,
can be tuned by modifying the structures of the step-growth monomers,
the stoichiometric ratio of linear (diol, <b>A</b><sub><b>2</b></sub>) to cross-linking (triol, <b>A</b><sub><b>3</b></sub>) RTIL monomers used, and the amount of free RTIL in
the formulation. When applied to painted steel and rubber test substrates
contacted with <i>o</i>-dichlorobenzene (<i>o</i>-DCB) (a polychlorinated biphenyl simulant), a 50:50 (<b>A</b><sub><b>2</b></sub>:<b>A</b><sub><b>3</b></sub>) step-growth alcohol-RTIL monomer mixture cross-linked with a stoichiometric
amount of a commercial di-isocyanate monomer (<b>B</b><sub><b>2</b></sub>) and containing 43 wt % free RTIL in the coating,
reduced the <i>o</i>-DCB vapor amount by 96–99% compared
to the uncoated, <i>o</i>-DCB-contacted control samples.
This peelable, flexible, solid coating also removed by sorption up
to >99% of the <i>o</i>-DCB liquid applied to the substrates
after 24 h of contact
Effect of Monomer Structure on Curing Behavior, CO<sub>2</sub> Solubility, and Gas Permeability of Ionic Liquid-Based Epoxy–Amine Resins and Ion-Gels
New imidazolium- and pyrrolidinium-based
bis(epoxide)-functionalized
ionic liquid (IL) monomers were synthesized and reacted with multifunctional
amine monomers to produce cross-linked, epoxy–amine poly(ionic
liquid) (PIL) resins and PIL/IL ion-gel membranes. The length and
chemical nature (i.e., alkyl versus ether) between the imidazolium
group and epoxide groups were studied to determine their effects on
CO<sub>2</sub> affinity. The CO<sub>2</sub> uptake (millimoles per
gram) of the epoxy–amine resins (between 0.1 and 1 mmol/g)
was found to depend predominately on the epoxide-to-amine ratio and
the bis(epoxide) IL molecular weight. The effect of using a primary
versus a secondary amine-containing multifunctional monomer was also
assessed for the resin synthesis. Secondary amines can increase CO<sub>2</sub> permeability but also increase the time required for bis(epoxide)
conversion. When either the epoxide or amine monomer structure is
changed, the CO<sub>2</sub> solubility and permeability of the resulting
PIL resins and ion-gel membranes can be tuned
Vinyl-Functionalized Poly(imidazolium)s: A Curable Polymer Platform for Cross-Linked Ionic Liquid Gel Synthesis
Vinyl-Functionalized
Poly(imidazolium)s: A Curable
Polymer Platform for Cross-Linked Ionic Liquid Gel Synthesi
Ideal CO<sub>2</sub>/Light Gas Separation Performance of Poly(vinylimidazolium) Membranes and Poly(vinylimidazolium)-Ionic Liquid Composite Films
Six vinyl-based, imidazolium room-temperature ionic liquid
(RTIL)
monomers were synthesized and photopolymerized to form dense poly(RTIL)
membranes. The effect of polymer backbone (i.e., poly(ethylene), poly(styrene),
and poly(acrylate)) and functional cationic substituent (e.g., alkyl,
fluoroalkyl, oligo(ethylene glycol), and disiloxane) on ideal CO<sub>2</sub>/N<sub>2</sub> and CO<sub>2</sub>/CH<sub>4</sub> membrane
separation performance was investigated. The vinyl-based poly(RTIL)s
were found to be generally less CO<sub>2</sub>-selective compared
to analogous styrene- and acrylate-based poly(RTIL)s. The CO<sub>2</sub> permeability of <i>n</i>-hexyl- (69 barrers) and disiloxane-
(130 barrers) substituted vinyl-based poly(RTIL)s were found to be
exceptionally larger than that of previously studied styrene and acrylate
poly(RTIL)s. The CO<sub>2</sub> selectivity of oligo(ethylene glycol)-functionalized
vinyl poly(RTIL)s was enhanced, and the CO<sub>2</sub> permeability
was reduced when compared to the <i>n</i>-hexyl-substituted
vinyl-based poly(RTIL). Nominal improvement in CO<sub>2</sub>/CH<sub>4</sub> selectivity was observed upon fluorination of the <i>n</i>-hexyl vinyl-based poly(RTIL), with no observed change
in CO<sub>2</sub> permeability. However, rather dramatic improvements
in both CO<sub>2</sub> permeability <i>and</i> selectivity
were observed upon blending 20 mol % RTIL (emim Tf<sub>2</sub>N) into
the <i>n</i>-hexyl- and disiloxane-functionalized vinyl
poly(RTIL)s to form solid–liquid composite films
A Highly Breathable Organic/Inorganic Barrier Material that Blocks the Passage of Mustard Agent Simulants
Garment materials that provide protection against exposure
to toxic
chemical warfare agents (CWAs) not only require the ability to block
the passage of these toxic compounds in vapor form but also the ability
to transport water vapor to allow cooling for the wearer. Only a very
limited number of examples of such “breathable” CWA
barrier materials are known. A new type of reactive organic/inorganic
composite film material is presented that has a very high water vapor
transport rate (>1800 g m<sup>–2</sup> day<sup>–1</sup> for a 220-μm-thick film) and the ability to completely block
penetration of the mustard agent simulant, 2-chloroethyl ethyl sulfide
(CEES), after 22 h of continuous exposure. This new composite material
is based on two components: (1) a cross-linked, diol-functionalized
room-temperature ionic liquid polymer that serves as a dense, flexible
hydrophilic matrix, and (2) a basic zeolite (sodium zeolite-Y (NaY))
that serves as an inexpensive, nucleophilic additive that chemically
degrades the CEES as it enters the film. Preliminary FT-IR studies
on this new reactive barrier material suggest that the OH groups on
the ionic polymer not only facilitates water vapor transport but may
also help activate mustard-type vapors for reaction with the imbedded
NaY
Effect of counter-ion on the thermotropic liquid crystal behaviour of bis(alkyl)-tris(imidazolium salt) compounds
<div><p>Recently, new thermotropic ionic liquid crystals (LCs) with a hexyl-linked tris(imidazolium bromide) core and two terminal alkyl chains were synthesised and characterised. To explore the effect of different counter-ions on the LC behaviour of this system, derivatives with BF<sub>4</sub><sup>−</sup> and Tf<sub>2</sub>N<sup>−</sup> counter-ions were prepared and analysed. Five of the BF<sub>4</sub><sup>−</sup> derivatives were found to exhibit thermotropic LC behaviour. The 12-, 14- and 16-carbon tail BF<sub>4</sub><sup>−</sup> compounds form SmA phases. The 18- and 20-carbon tail homologues form what appears to be a smectic phase but are weakly mesogenic and harder to characterise. Only two of the Tf<sub>2</sub>N<sup>−</sup> derivatives exhibited mesogenic behaviour. The 18-carbon tail Tf<sub>2</sub>N<sup>−</sup> compound forms an as-yet unidentified, highly periodic smectic phase with positional order while the 20-carbon tail homologue forms a periodic SmA phase. The Tf<sub>2</sub>N<sup>−</sup> mesogens have much lower clearing points even though their LC phases have more order than the Br<sup>−</sup> and BF<sub>4</sub><sup>−</sup> mesogens. X-ray diffraction showed that these mesogens have different amounts of tail interdigitation between the smectic layers depending on the counter-ion present. Atomistic molecular dynamics simulations indicated that counter-ion size plays an important role in defining the density of the ionic region, which in turn affects the amount of interdigitation in the smectic phases.</p></div
Glycerol-Based Bicontinuous Cubic Lyotropic Liquid Crystal Monomer System for the Fabrication of Thin-Film Membranes with Uniform Nanopores
Glycerol-Based Bicontinuous
Cubic Lyotropic Liquid
Crystal Monomer System for the Fabrication of Thin-Film Membranes
with Uniform Nanopore
Morphological Phase Behavior of Poly(RTIL)-Containing Diblock Copolymer Melts
The development of nanostructured polymeric systems containing
directionally continuous poly(ionic liquid) (poly(IL)) domains has
considerable implications toward a range of transport-dependent, energy-based
technology applications. The controlled, synthetic integration of
poly(IL)s into block copolymer (BCP) architectures provides a promising
means to this end, based on their inherent ability to self-assemble
into a range of defined, periodic morphologies. In this work, we report
the melt-state phase behavior of an imidazolium-containing alkyl–ionic
BCP system, derived from the sequential ring-opening metathesis polymerization
(ROMP) of imidazolium- and alkyl-substituted norbornene monomer derivatives.
A series of 16 BCP samples were synthesized, varying both the relative
volume fraction of the poly(norbornene dodecyl ester) block (<i>f</i><sub>DOD</sub> = 0.42–0.96) and the overall molecular
weights of the block copolymers (<i>M</i><sub>n</sub> values
from 5000–20 100 g mol<sup>–1</sup>). Through
a combination of small-angle X-ray scattering (SAXS) and dynamic rheology,
we were able to delineate clear compositional phase boundaries for
each of the classic BCP phases, including lamellae (Lam), hexagonally
packed cylinders (Hex), and spheres on a body-centered-cubic lattice
(S<sub>BCC</sub>). Additionally, a liquid-like packing (LLP) of spheres
was found for samples located in the extreme asymmetric region of
the phase diagram, and a persistent coexistence of Lam and Hex domains
was found in lieu of the bicontinuous cubic gyroid phase for samples
located at the intersection of Hex and Lam regions. Thermal disordering
was opposed even in very low molecular weight samples, detected only
when the composition was highly asymmetric (<i>f</i><sub>DOD</sub> = 0.96). Annealing experiments on samples exhibiting Lam
and Hex coexistence revealed the presence of extremely slow transition
kinetics, ultimately selective for one or the other but not the more
complex gyroid phase. In fact, no evidence of the bicontinuous network
was detected over a 2 month annealing period. The ramifications of
these results for transport-dependent applications targeting the use
of highly segregated poly(IL)-containing BCP systems are carefully
considered