Porous membranes built up from hydrophilic poly(ionic liquid)s

Porous polymer membranes via electrostatic complexation triggered by neutralization are fabricated for the first time from a water-soluble poly(ionic liquid) (PIL). The porous structure is formed as a consequence of simultaneous phase separation of the PIL and ionic complexation, which occurred in a basic solution of a non-solvent for the PIL. These membranes have a stimuli-responsive porosity, with open and closed pores in isopropanol and in water, respectively. This property is quantitatively demonstrated in filtration experiments, where water is passing much slower through the membranes than isopropanol.Comment: 13 pages, 3 figure

Layer-by-layer coated imidazolium – styrene copolymers fibers for improved headspace-solid phase microextraction analysis of aromatic compounds

The design of poly(ionic liquids) (PILs) and their application as solid phase microextraction (SPME) fibers has been attracting enormous attention mainly due to the need for new SPME coating materials with improved analytical sensitivity. In this work, the tunability of PILs is explored by preparing different imidazolium monomers bearing benzyl, naphtylmethyl or pentyl pending groups that were subsequently co-polymerized, by reversible addition–fragmentation chain transfer (RAFT) polymerization with styrene. The obtained co-polymers showed excellent thermal stability up to 275 °C, with no melting point up to 250 °C. SPME fibers were prepared by an innovative approach based on layer-by-layer spray coating. The thin (<10 μm) SPME coatings were tested in GC-FID for the detection of volatile aromatic compounds such as benzene (B), toluene (T), ethylbenzene (E) and xylene (X) present in aqueous samples and the extraction parameters optimized. Superior results were obtained when comparing these LbL PILS-based SPME fibers with a commercial fiber composed of poly(dimethylsiloxane), with an increase in the detectable areas of 83%, 69%, 57% and 58% for B, T, E and X, respectively. Low relative standard deviations were obtained for the same fiber (< 5.6%) and also for different fibers (< 9.8%). Furthermore, a spiked soil sample was used to mimic a real contaminated soil sample and excellent recovery results, ranging from 67.0% to 102.2%, were obtained.publishe

Quantitative modeling of \textit{in situ} x-ray reflectivity during organic molecule thin film growth

Synchrotron-based x-ray reflectivity is increasingly employed as an \textit{in situ} probe of surface morphology during thin film growth, but complete interpretation of the results requires modeling the growth process. Many models have been developed and employed for this purpose, yet no detailed, comparative studies of their scope and accuracy exists in the literature. Using experimental data obtained from hyperthermal deposition of pentane and diindenoperylene (DIP) on SiO$_2$, we compare and contrast three such models, both with each other and with detailed characterization of the surface morphology using ex-situ atomic force microscopy (AFM). These two systems each exhibit particular phenomena of broader interest: pentacene/SiO$_2$ exhibits a rapid transition from rough to smooth growth. DIP/SiO$_2$, under the conditions employed here, exhibits growth rate acceleration due to a different sticking probability between the substrate and film. In general, \textit{independent of which model is used}, we find good agreement between the surface morphology obtained from fits to the \insitu x-ray data with the actual morphology at early times. This agreement deteriorates at later time, once the root-mean squared (rms) film roughness exceeds about 1 ML. A second observation is that, because layer coverages are under-determined by the evolution of a single point on the reflectivity curve, we find that the best fits to reflectivity data --- corresponding to the lowest values of $\chi_\nu^2$ --- do not necessarily yield the best agreement between simulated and measured surface morphologies. Instead, it appears critical that the model reproduce all local extrema in the data. In addition to showing that layer morphologies can be extracted from a minimal set of data, the methodology established here provides a basis for improving models of multilayer growth by comparison to real systems.Comment: 34 pages (double-spaced, including figures and references), 10 figures, 3 appendice

Nanoporous ionic organic networks: from synthesis to materials applications

The past decade has witnessed the rapid progress in synthesizing nanoporous organic networks or polymer frameworks for various potential applications. Generally speaking, functionalization of porous networks to add extra properties and enhance materials performance could be achieved either during the pore formation (thus a concurrent approach) or post-synthetic modification (a sequential approach). Nanoporous organic networks which include ion pairs in a covalent manner are of special importance and possess extreme application profiles. Within these nanoporous ionic organic networks (NIONs), here with a pore size in the range from sub-1 nm to 100 nm, we observe a synergistic coupling of the electrostatic interaction of charges, the nanoconfinement within pores and the addressable functional units in soft matter resulting in a wide variety of functions and applications, above all catalysis, energy storage and conversion, as well as environmental operations. This review aims to highlight the recent progress in this area, and seeks to raise original perspectives that will stimulate future advancements at both the fundamental and applied level.Comment: 67 pages, 25 figures, Chemical Society Reviewers, 201

Layered Zeolite Materials And Methods Related Thereto

A novel oxide material (MIN-I) comprising YO2; and X2O3, wherein Y is a tetravalent element and X is a trivalent element, wherein X/Y=O or Y/X=30 to 100 is provided. Surprisingly, MIN-I can be reversibly deswollen. MIN-I can further be combined with a polymer to produce a nanocomposite, depolymerized to produce predominantly fully exfoliated layers (MIN-2), and pillared to produce a pillared oxide material (MIN-3), analogous to MCM-36. The materials are useful in a wide range of applications, such as catalysts, thin films, membranes, and coatings.Regents Of The University Of MinnesotaGeorgia Institute Of Technolog

BRANCHED POLYMER ELECTROLYTES: RESPONSIVE NANOMATERIALS FOR CONTROLLED ION MOBILITY

Polymers containing ionic groups such as polyelectrolytes and polymerized ionic liquids are promising candidates for the design of organized ionically conductive media due to their controlled morphology, robust chemical and thermal stability, and single-ion conductivity. However, while polymerization of ionic groups affords electrolytes a greater degree of dimensional control, the effect of nonlinear chain architecture remains mostly an unexplored consideration, despite the unique functional group densities, chain conformations, counterion condensation, and dynamics of branched polymers. First, the stimuli-responsive interfacial assembly and tunable morphologies of star-shaped polyelectrolyte block-copolymers and polymerized ionic liquids in monolayers and multicomponent systems are examined. In the former case, a dual-responsive star-graft block-quarterpolymer with variable arm number, arm length, and grafting density are integrated into hydrogen-bonded multilayer films and their morphologies were evaluated in different environments using surface probe microscopy and neutron reflectivity. The results point toward the amphiphilicity endowed by the star-graft architecture as the chief factor controlling the temperature and pH-induced conformational changes which lead to the diverse star-like clustering at the molecular scale. Likewise, the surface organization of linear and star-shaped polymerized ionic liquids in monolayers and multilayers is compared under variable adsorption conditions for polymers with the different branching architectures. Both studies demonstrate how polyelectrolytes and polymerized ionic liquids with branched architecture assemble into multilayer films with variable porosity, thickness, and textured morphologies featuring compartmentalized internal morphologies that are remarkably distinct from traditional multilayer systems. The second part of this work focuses on the ion transport in polyelectrolytes comprised of star and hyperbranched polymerized ionic liquids. Long-chain arms were found to exhibit more sluggish and elastic dynamics at longer timescales while the glass transition temperature, rates of segmental relaxation, ion disassociation, and dc conductivity were similar regardless of the polymer architecture and arm length. But when polymerized ionic liquids are branched on a smaller scale, such as in the ionic liquid tethered macromolecules consisting of both POSS and hyperbranched polyester cores, considerable shifts in the glass transition temperatures and conductivities were observed. This ability to control the ion mobility in polymerized ionic liquids near the Tg is critical for the development of solid-state electrolytes in which it is desirable to have high conductivities in the near glassy state. Overall, this dissertation provides an initial view of branched polymer electrolytes as uniquely versatile nanomaterials in the assembly of multifunctional polymer electrolytes with tunable morphologies and controlled ion transport properties.Ph.D

Dynamic and interaction of cytochrome c with Pf1 virus

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em BioOrgânicaCytochrome c is a positive protein and the Pf1 virus surface is negative forging strong electrostatic complex. When a critical ratio concentration of Cytochrome c and Pf1 virus is achieved a spontaneous complex is formed. The maximum association upon addition of cytochrome c to Pf1 solutions is about 1700 cytochrome c molecules to one Pf1 virion particle. The effect of univalent salt concentration on protein polyelectrolyte complex formation was measured by Dynamic Light Scattering. Complex disaggregation occurred when monovalent salt concentration increased. The assembly process was also observed by NMR at low salt concentration in the system. The aggregate can be gradually dissociated in order to enable NMR spectra acquisition. Depending on virus/cytochorme c ratio or ionic strength concentration we could shift from free protein and virus in solution to transient binding or fully immobilized complex. It was possible to map the most affected regions of the oxidized heme cytochrome c, with chemical shift variation due to the binding to Pf1 virus, during salt titration. Dry and liquid samples of Cytochrome c and Pf1 at different ratios and pH were studied and evaluated by Atomic Force Microscopy. The system was also studied above the critical salt concentration of complex dissociation by PGSEDOSY NMR. A gradual decrease in the translational diffusion coefficient of cytochrome was caused by higher content of Pf1 virus in solution. We conclude that a strong electrostatic correlation between pf1 virus and cytochrome c occurs even after complex dissociation

Synthesis, characterization and applications of ionic supramolecular assemblies

Supramolecular ionic assemblies not only provide alternatives to conventional polymers, but also introduce unique and interesting functions for the design of "smart" polymeric assemblies for use in a number of fields due to their programmable and reversible properties. Research in the area has led to an understanding of the connection between molecular contributions and macroscopic properties, as well as a range of applications from material processing/manufacuturing to energy transfer and storage. To this end, we have developed a library of charged building blocks based on ionic liquids to create functional supramolecular ionic assemblies. The polymeric ionic assemblies prepared from a di-phosphonium and poly (acrylic acid) were first studied and found to have the potential to be utilized as "smart" materials due to their ability to reversibly respond to stimuli such as temperature and pressure. With the interest of elucidating the molecular contributions to the bulk macroscopic material properties, six supramolecular assemblies were sequentially characterized in terms of thermal, rheological and X-ray studies. The effect of side alkyl chain was found to dramatically change the material properties. A second type of supramolecular assembly was investigated based on a poly-phosphonium ionic liquid, which was complexed with a number of carboxylic acids. The material properties were easily manipulated from a sticky fiber to a brittle solid by changing the composition of the carboxylic acid. A crosslinked supramolecular assembly combining ionic interactions and weak covalent bonds, specifically disulfide bonds, was next designed and characterized. The network properties could be switched between "on and off" using mild conditions. The polymeric ionic networks and their building block ionic liquids are also of interest as safe electrolytes in energy storage devices due to their non-flammability, non-volatility, etc. We have identified one ionic liquid with superior thermal stability, high lithium salt solubility, and good conductivity in a lithium metal battery. The prototype battery performed safely at 100 degree celsius for more than 30 days. Thermally stable Li metal batteries are of interest in the oil industry for downhole applications. These studies were extended to an ionic polymer that exhibits a lamellar structure as a new polymer electrolyte