Peter Kofinas

Molecularly imprinted polymer hydrogels displaying isomerically resolved glucose binding

Non-covalent molecular imprinting of poly(allylamine hydrochloride) (PAA HCl) with glucose phosphate mono-sodium salt produced molecularly imprinted polymer (MIP) hydrogels capable of quantitative, isomerically specific binding of glucose. By ionic association of a template molecule, glucose phosphate mono-sodium salt, to the polymer prior to covalent crosslinking, MIP hydrogels were created with an affinity for binding glucose. In this study we have synthesized MIPs using epichlorohydrin, ethylene glucol diglycidyl ether, and glycerol diglycidyl ether as crosslinkers in order to evaluate their effectiveness with respect to molecular imprinting for glucose. MIP hydrogels were also synthesized with the different crosslinkers and varying amounts of the template molecule in an attempt to elucidate the impact of imprint quantities on the effectiveness of the imprinting technique. Batch equilibration studies, using each of the MIPs and similar non-molecularly imprinted polymers were performed to determine their binding capacities with respect to glucose and fructose. The binding capacity data are discussed and employed in the evaluation of the specificity imparted by the imprinting procedure. MIP hydrogels with binding capacities in excess of 0.5 g of glucose per gram of dried gel were synthesized. Isomeric specificity in hydrogels imprinted for glucose was demonstrated by higher binding capacities of glucose than those of fructose in the same polymers.

Block Copolymer Solid Battery Electrolyte with High Li-Ion Transference Number

The electrochemical properties of a solid polymer electrolyte consisting of a diblock copolymer and lithium bis(oxalato)borate, LiBC 4 O 8 (LiBOB) salt, is reported. The spherical microphase-separated diblock copolymer is composed of a majority poly(ethylene oxide) (PEO) block and a minority random copolymer block of methyl methacrylate (MMA) and lithium salt of methacrylic acid (MAALi), PEO-b-(PMMA-ran-PMAALi). Salt-optimized electrolyte membranes of the diblock copolymer and LiBOB salt exhibited an average lithium-ion transference number (T Li+ ) value of 0.9 at room temperature (21-23°C). The solid-state flexible, translucent polymer electrolyte shows a wide electrochemical stability window and excellent interface properties with the lithium metal electrode. The combination of these properties makes these block copolymer membranes viable electrolyte candidates for flexible lithium-ion batteries.

Magnetic properties of CoFe2O4 nanoparticles synthesized through a block copolymer nanoreactor route

The development of self-assembled magnetic CoFe2O4 nanoparticles within polymer matrices at room temperature is reported. Diblock copolymers consisting of poly (norbornene) and poly (norbornene-dicarboxcylic acid) (NOR/NORCOOH) were synthesized. The self-assembly of the mixed metal oxide within the NORCOOH block was achieved at room temperature by processing the copolymer nanocomposite using wet chemical methods. Morphology and magnetic properties were determined by superconducting quantum interference device magnetometry, transmission electron microscopy, wide angle x-ray diffraction, and 57Fe Mossbauer spectroscopy. The CoFe2O4 nanoparticles are uniformly dispersed within the polymer matrix, and have an average radius of 4.8±1.4 nm. The nanocomposite films are superparamagnetic at room temperature and ferrimagnetic at 5 K.

Reactive nitrogen and phosphorus removal from aquaculture wastewater effluents using polymer hydrogels

Abstract We have developed poly(allyl amine hydrochloride) (PAA · HCl) polymer hydrogels, that efficiently remove nitrate (NO 3 − ), nitrite (NO 2 − ), and orthophosphate (PO 4 3− ) nutrient anions from the aquaculture wastewater. The hydrogels were prepared by chemically crosslinking linear PAA · HCl chains with epichlorohydrin (EPI). The anion binding capacity of the pH sensitive polymer gels was measured in standard solutions and studied as a function of gel synthesis parameters. Equilibrium NO 3 –N, NO 2 –N, and PO 4 –P loading of 15, 1.6, and 17 mg/g of dry gel, respectively, were calculated from the measurement of decrease in anion concentration in aqueous solutions using UV–vis spectrophotometry. Batch experiments showed that nutrient concentrations in aquaculture wastewater effluents decreased with regard to PO 4 –P by 98+%, NO 3 –N by 50+% and NO 2 –N by 85+% within 3 h of reaction. The regeneration of the hydrogels was demonstrated by the release of bound nutrient anions upon washing the gels with a 1 N NaOH solution. These results have demonstrated that the hydrogels are appropriate materials for treating aquaculture wastewater effluents, and reducing the nutrient anion concentrations to levels, less than 10 mg/l NO 3 –N, 0.08 mg/l NO 2 –N, and 0.3 mg/l PO 4 –P, suitable for discharge into natural surface waters.

Controlled synthesis of core?shell iron?silica nanoparticles and their magneto-dielectric properties in polymer composites

Low loss core-shell iron-silica nanocomposites with improved magneto-dielectric properties at radio frequencies (1 MHz-1 GHz) were successfully fabricated. A new simple method was developed to synthesize metallic iron (Fe) nanoparticles with uniform size distribution in an aqueous environment at room temperature. Citric acid and oleic acid served as surface-capping agents to control the particle size of the synthesized Fe nanoparticles. Smaller Fe nanoparticles with narrower particle size distribution were obtained as the concentration ratio of iron ions to carboxylic acid groups decreased. The Fe nanoparticles were subsequently coated with silica (SiO(2)) layers to prevent the iron cores oxidizing. Polymer composites were prepared by incorporating Fe@SiO(2) nanoparticles with polydimethylsiloxane (PDMS) elastomers. Experimental results showed that the dielectric permittivity (ε) and magnetic permeability (μ) of the polymer composite increased with increasing amount of Fe@SiO(2) nanoparticle doping. The dielectric loss (tanδ) was near 0.020 at a frequency of 1 GHz.

Properties of self-assembled ZnO nanostructures

Abstract The formation of self-assembled ZnO nanoclusters using diblock copolymers, is reported. The diblock copolymers, consisting of a majority polymer (norbornene) and a minority polymer (norbornene-dicarboxcylic acid), were synthesized with a block repeat unit ratio of 400/50, to obtain spherical microphase separation and hence a spherical morphology for the metal oxide nanoclusters. The self-assembly of the inorganic nanoparticles was achieved at room temperature in the liquid phase, using ZnCl2 precursor dopant and wet chemical processing compatible with semiconductor manufacturing to convert to ZnO. FTIR and XPS spectroscopy, confirmed the association of the ZnCl2 precursor with the minority block and the formation of ZnO, while TEM showed the spherical morphology of ZnO nanoparticles as targeted, and a relatively narrow size distribution ranging between 7 and 15 nm.

Phosphate binding polymeric hydrogels for aquaculture wastewater remediation

Methods that will remove conventional nutrient pollutants such as reactive phosphorus, even at extremely low concentrations, from wastewater effluents are a major need in the aquaculture industry. In this study, novel phosphate binding crosslinked poly(allylamine), PAA · HCl, polymeric hydrogel materials were developed, which efficiently bind phosphate anions in aquaculture wastewater effluents. The polymeric hydrogels were synthesized by chemically crosslinking linear PAA · HCl chains with epichlorohydrin. The phosphate binding capacity of the synthesized pH sensitive polymer gels was studied as a function of various gel processing parameters. Equilibrium orthophosphate (PO43-) loadings of 47 mg g−1 polymer, were calculated from direct measurement of the decrease in phosphate concentration in aqueous solutions using UV spectroscopy. Experiments showed that pollutant concentrations in aquaculture wastewater effluents decreased with regard to PO43- by more than 99%. The ability of the gels to bind phosphates was not fouled by particulate or dissolved complex organics and inorganics, or counterions which are present in aquaculture wastewater effluents. The hydrogels can be regenerated by release of the bound phosphates upon washing with a 1 N NaOH solution. Results demonstrated that the novel crosslinked polymeric hydrogels are appropriate materials for treating aquaculture wastewater effluents, and reducing the phosphorus concentrations to levels, less than 0.01 ppm, suitable for discharge to natural surface waters.

Nanostructured Block Copolymer Dry Electrolyte

We report on the synthesis and characterization of a solid-state polymer electrolyte with enhanced lithium transport based on a self-assembled diblock copolymer. The diblock copolymer consists of a poly(ethylene oxide) (PEO) block and a random copolymer of methyl methacylate (MMA) and lithium salt of methacrylic acid (MAALi). Lithium bis(oxalato)borate, LiBC 4 O 8 (LiBOB) was used as salt in the dry electrolyte. Impedance and temperature studies were carried out to characterize the conductivity performance of the electrolyte. The diblock copolymer [PEO-b-(PMMA-ran-PMAALi)] with added LiBOB (in the molar ratio ethylene oxide:LiBOB = 3:1) was used to form flexible translucent films, which exhibited an average ionic conductivity value of 1.26 X 10 -5 S cm -1 at room temperature (21 °C). Transmission electron microscopy was performed to characterize the morphology of the polymer, and differential scanning calorimetry was carried out to study the thermal properties of the electrolyte.

Hemostatic strategies for traumatic and surgical bleeding

Wide interest in new hemostatic approaches has stemmed from unmet needs in the hospital and on the battlefield. Many current commercial hemostatic agents fail to fulfill the design requirements of safety, efficacy, cost, and storage. Academic focus has led to the improvement of existing strategies as well as new developments. This review will identify and discuss the three major classes of hemostatic approaches: biologically derived materials, synthetically derived materials, and intravenously administered hemostatic agents. The general class is first discussed, then specific approaches discussed in detail, including the hemostatic mechanisms and the advancement of the method. As hemostatic strategies evolve and synthetic-biologic interactions are more fully understood, current clinical methodologies will be replaced.

Self-assembled block copolymer photonic crystal for selective fructose detection

The use of one-dimensional photonic crystals fabricated from a self-assembled lamellar block copolymer as a sensitive and selective fructose sensor is investigated. The polystyrene-b-poly(2-vinyl pyridine) (PS-b-P2VP) films are functionalized with 2-(bromomethyl)phenylboronic acid. The boronic acid moiety confined within the lamellar morphology can reversibly bind to sugars such as fructose, imparting the photonic properties of the PS-b-P2VP film. The films exhibit a detection limit of 500 μM in water and 1mM in phosphate buffered saline. Exposure to a 50 mM solution of fructose invokes a highly visible color change from blue to orange. The films are also able to selectively recognize and respond to fructose in competitive studies in the presence of glucose, mannose and sucrose.