Merging versatile polymer chemistry with multifunctional nanoparticles: an overview of crosslinkable aromatic polyester matrix nanocomposites.

The current trend in the global advanced material market is expeditiously shifting towards more lightweight, multifunctional configurations, considering very recent developments in electrical aircraft, biomedical devices, and autonomous automobiles. Hence, the development of novel polymer nanocomposite materials is critical to advancing the current state-of-the-art of structural material technologies to address the pressing performance demands. Aiming at expanding the existing material design space, we have investigated crosslinkable aromatic polyester matrix nanocomposites. Aromatic polyesters, in the thermosetting form, are a prospective high-performance/high-temperature polymer technology, which is on a par with conventional epoxy-derivative resins and high-performance engineering thermoplastics in the range of their potential applications. The aromatic matrix-based thermosetting nanocomposites manifest greatly enhanced physical properties enabled by a chemistry-favored robust interfacial covalent coupling mechanism developed during the in situ polymerization reaction with various nanofiller particle configurations. Here, we provide a summary review of our recent efforts in developing this novel polymer nanocomposite material system. We highlight the chemical strategy, fabrication approach, and processing techniques developed to obtain various nanocomposite representations for structural, electrical, optical, biomedical, and tribological applications. The unique characteristic features emerging in the nanocomposite morphologies, along with their physicochemical effects on the multifunctional macroscale properties, are demonstrated. This unique matrix configuration introduces superior performance elements to polymer nanocomposite applications towards designing advanced composite materials.

Aromatic thermosetting copolyester bionanocomposites as reconfigurable bone substitute materials: Interfacial interactions between reinforcement particles and polymer network.

Development of porous materials consisting of polymer host matrix enriched with bioactive ceramic particles that can initiate the reproduction of cellular organisms while maintaining in vivo mechanical reliability is a long-standing challenge for synthetic bone substitutes. We present hydroxyapatite (HA) reinforced aromatic thermosetting copolyester (ATSP) matrix bionanocomposite as a potential reconfigurable bone replacement material. The nanocomposite is fabricated by solid-state mixing a matching set of precursor oligomers with biocompatible pristine HA particles. During endothermic condensation polymerization reaction, the constituent oligomers form a mechanochemically robust crosslinked aromatic backbone while incorporating the HAs into a self-generated cellular structure. The morphological analysis demonstrates near-homogenous distributions of the pristine HAs within the matrix. The HAs behave as a crack-arrester which promotes a more deformation-tolerant formation with relatively enhanced material toughness. Chain relaxation dynamics of the nanocomposite matrix during glass transition is modified via HA-induced segmental immobilization. Chemical characterization of the polymer backbone composition reveals the presence of a hydrogen-advanced covalent interfacial coupling mechanism between the HAs and ATSP matrix. This report lays the groundwork for further studies on aromatic thermosetting copolyester matrix bionanocomposites which may find applications in various artificial bone needs.

Nanofiller-conjugated percolating conductive network modified polymerization reaction characteristics of aromatic thermosetting copolyester resin.

Deliberately controlled interfacial interactions between incorporated nanofiller particles and host polymer backbone chains constitute a critical element in the realm of polymer nanocomposites with tailorable multifunctional properties. We demonstrate the physicochemical effects induced by graphene nanoplatelets (GNP) of different sizes on the condensation polymerization reaction of aromatic thermosetting copolyester (ATSP) through the formation of electrically conductive percolating networks as enabled by interfacial interactions. Carboxylic acid and acetoxy-capped precursor oligomers of ATSP are solid-state mixed with chemically pristine GNP particles at various loading levels. Upon in situ endothermic condensation polymerization reaction, crosslinked backbone of the ATSP foam matrix is formed while the carbonaceous nanofillers are incorporated into the polymer network via covalent conjugation with functional end-groups of the oligomers. The controlled GNP size promotes different electrical percolation thresholds and ultimate electrical conductivities. Microstructural analysis demonstrates GNP distributions in the matrix as well as morphological modifications induced by the formation of conductive percolating GNP networks. Cure characteristics reveal the thermochemical changes prompted in the polymerization processes for GNP content above the requirement for percolation formation. Chemical spectroscopy of the ATSP nanocomposite morphology exhibits the formation of a robust interfacial coupling mechanism between the GNPs and ATSP backbone. The findings here may guide the developmental efforts of nanocomposites through better identifying roles of the morphology and content of nanofillers in polymerization processes.

Synthesis of porous carbon fibers with strong anion exchange functional groups.

Hybrid porous carbon fibers with strong anion-exchangeable functional groups (HACAX) were synthesized by alkylation of pyrolyzed polyacrylonitrile. HACAX exhibits generic stable positively charged functional groups. This expands the applications of porous carbon media for interacting with anions without adjusting pH, such as Cr(vi) adsorption at natural pH.

Mechanical Stress in Immobilized Polycation Thin Films Induced by Ion-Exchange.

The exchange of one counterion with another, perchlorate with chloride, induces mechanical stress in polycation matrices. The magnitude of the stress decreases with increasing hydrophobicity of the matrix. Thin films of cross-linked poly(vinylbenzyl chloride) are reacted with trialkylamines to give immobilized poly(vinylbenzyltrialkylammonium chloride) matrices. Mechanical stress in films is measured using a scanning laser apparatus. Each material exhibits tension upon exchange from chloride to perchlorate form, consistent with matrix dehydration. Data are fit to a chemical equilibrium model assuming proportionality between stress and conversion to perchlorate form. Maximum changes in biaxial stress range from 3.1 MPa for a tributylamine-modified film to 16.6 MPa for a trimethylamine-modified film. Selectivity coefficients range from 43 for the trimethylamine-modified film to 370 and 450 for the tributylamine- and tripropylamine-modified films, respectively, indicating greater selectivity for perchlorate in more hydrophobic matrices. These results help clarify the physical origins of perchlorate selectivity in anion-exchange resins.

Synthesis and characterization of silver-nanoparticle-impregnated fiberglass and utility in water disinfection.

A number of researchers have deployed silver (Ag) nanoparticles through a number of techniques on various substrates including carbon, zeolites and polymers for water disinfection applications. However, Ag impregnated on an inorganic fiberglass surface through a simple electroless process was only recently reported for the first time. Fiberglass impregnated with Ag nanoparticles displays superior performance over carbon-based silver support systems but little is known about the factors that affect the architecture of the system, its interfacial properties and its consequent bactericidal activity. In this study, Ag content and particle size on a fiberglass substrate were manipulated by adjusting the AgNO(3) concentration, immersion time, temperature, solution pH and reduction temperature. The reduction chemistry of the Ag-nanoparticle-impregnated fiberglass is described and supported with thermal gravimetric analysis (TGA) and photoelectron spectroscopy (XPS) measurements. The Ag content along with the particle size and particle size distribution were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS) and x-ray diffraction (XRD). The Ag content on the fiberglass mats ranged from 0.04 to 4.7 wt% Ag/g-fiber with a size distribution of 10-900 nm under standard processing conditions. Inductively coupled plasma mass spectrometry (ICP-MS) was used to analyze the Ag desorption from the fiberglass substrate, while the bactericidal properties were evaluated against Escherichia coli (E. coli).

Adsorption of rotavirus and bacteriophage MS2 using glass fiber coated with hematite nanoparticles.

Batch and flow-through experiments were conducted to investigate the removal and inactivation of rotavirus (RV) and bacteriophage MS2 using glass fiber coated with hematite nanoparticles. Batch tests showed a high removal of MS2 (2.49x10(11) plaque forming unit/g) and RV (8.9x10(6) focal forming unit/g) at a low concentration of hematite nanoparticles in solution (0.043g/L and 0.26g/L, respectively). Virus adsorption was, however, decreased in the presence of bicarbonate ions and natural organic matter (NOM) in solution, suggesting a great affinity of iron oxide nanoparticles for these competitors. Adsorption on hematite nanoparticles by MS2 and RV was also tested with aquifer groundwater under saturated flow conditions to mimic environmental conditions with promising results (8x10(8) plaque forming unit/g and 3x10(4) focal forming unit/g, respectively). Desorption of up to 63% of infectious MS2 and only 2% of infectious RV from hematite nanoparticles were achieved when an eluant solution containing beef extract and glycine was used. Transmission electron microscopy (TEM) images showed evidence of electrostatic adsorption of apparently intact MS2 and structurally damaged RV particles to hematite nanoparticles. Results from this research suggest that a cartridge made of glass fiber coated with hematite nanoparticles could be used as a point-of-use device for virus removal for drinking water treatment.

Bactericidal activity of Ag nanoparticle-impregnated fibreglass for water disinfection.

A new bactericidal system composed of fibreglass impregnated with silver (Ag) nanoparticles was developed and tested. Silver content, particle size and distribution were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The antibacterial effectiveness was evaluated against Escherichia coli (E. coli, ATCC 29055). The minimum inhibitory loading was determined to be less than 1.8 wt% of silver nanoparticles per gram of fibreglass. In a 1 h immersion test, using a 0.1 mg fibreglass mat ml(-1), with 2.9 wt% loading of silver nanoparticles completely disinfected 100 ml of 10(6) CFU ml(-1) of E. coli, dramatically outperforming activated carbon fibres impregnated with silver. Inactivation rate studies of 0.05 mg fibreglass mat ml(-1) (Ag 1.8 wt%) with 10(12) CFU E. coli displayed a 7 log reduction in 5 minutes. The activation and reuse of fibreglass (Ag 4.3 wt%) maintained its full effectiveness after two cycles of use and thermal regeneration at 350 degrees C.

Removal of chromium Cr(VI) by low-cost chemically activated carbon materials from water.

Low-cost, chemically activated carbon materials, Pellet-600 and PVA-300, were prepared at relatively low temperatures and show more effective removal efficiency of Cr(VI) from water than commercially available activated carbons tested. The Pellet-600 is a pelletized carbon material with high mesoporous volumes and surface area, and the PVA-300 is composed of a high surface area carbon coating on a fiberglass mat substrate. A much faster adsorption kinetics and a much higher adsorption capacity for Cr(VI) are achieved by the Pellet-600. At very low concentrations of Cr(VI), the PVA-300 displays a strong adsorption ability for Cr(VI). XPS data show an increase in the atomic ratio of Cr/C and oxidation of carbon materials after adsorption of Cr(VI). These results suggest that a high content of mesopores with a high surface area and surface functional groups greatly improve the Cr(VI) removal efficiency from water.

Effects of powdered activated carbon pore size distribution on the competitive adsorption of aqueous atrazine and natural organic matter.

The pore size distribution (PSD) of adsorbents has been found to be an important factor that affects adsorption capacity for organic compounds; consequently, it should influence competitive adsorption in multisolute systems. This research was conducted to show howthe PSD of activated carbon affects the competition between natural organic matter (NOM) and the trace organic contaminant atrazine, with a primary emphasis on quantifying the pore blocking mechanism of NOM competition. Isotherm tests were performed for both atrazine and NOM from a groundwater on five powdered activated carbons (PACs) with widely different PSDs. The capacity for NOM correlated best with the surface area of pores in the diameter range of 15-50 A, although some NOM also adsorbed in the smaller pores as evidenced by a reduction in capacity for atrazine when NOM was present. Kinetic tests for atrazine on PACs with various levels of preadsorbed NOM showed that the magnitude of the pore blockage effect by NOM was lower for PACs with higher surface area of pores with diameter in the range of 15-50 A. Therefore increasing pores in the size range where NOM adsorb can reduce the extent of the pore blockage competitive effect on the target compound atrazine. The effect of PSD was further studied with a flow-through PAC-membrane hybrid watertreatment system, in which experimental results successfully verified model simulations by the COMPSORB model.

Advanced mesoporous organosilica material containing microporous beta-cyclodextrins for the removal of humic acid from water.

A new mesoporous organosilica material (beta-CD-Silica-4%) containing microporous beta-cyclodextrins (beta-CDs) has been prepared by the co-polymerization of a silylated beta-CD monomer with tetraethoxysilane in the presence of a structure-directing template, cetyltrimethylammonium bromide. Solid-state 13C and 29Si NMR studies provided evidence for the presence of covalently attached beta-CDs in the mesoporous material. Nitrogen adsorption experiments showed that beta-CD-Silica-4% material had a BET surface area of 460 m2/g and an average mesopore diameter of 2.52 nm. Small-angle powder X-ray diffraction pattern of beta-CD-Silica-4% material revealed the lack of highly ordered mesoporous structure. Adsorption experiments showed that beta-CD-Silica-4% material removed up to 99% of humic acid from an aqueous solution containing 50 ppm of humic acid at a solution-to-solid ratio of 100 ml/g.

Ordered mesoporous organic-inorganic hybrid materials containing microporous functional calix[8]arene amides.

Ordered mesoporous organic-inorganic hybrid materials containing microporous functional calix[8]arene amides have been synthesized and characterized for the first time, and are shown to be effective in removal of trace humic acid contaminant from water.

Novel polymeric chelating fibers for selective removal of mercury and cesium from water.

We report here the synthesis and characterization of two new classes of chelating fibers, namely, (1) polymercaptopropylsilsesquioxane (PMPS) and (2) copper(II) ferrocyanide complexed with poly[1-(2-aminoethyl)-3-aminopropyl]silsesquioxane (Cu-FC-PAEAPS) fibers. These fibers were evaluated for selective removal of trace amount of mercury and cesium ions respectively in the presence of competing metal ions from water. The PMPS and Cu-FC-PAEAPS fibers were prepared by coating their corresponding soluble prepolymers, which are derived from mercaptopropyltrimethoxysilane and [1-(2-aminoethyl)-3-aminopropyl]trimethoxysilane monomers, respectively, on a glass fiber substrate, followed by a cross-linking step at 120 degrees C. The fibers were characterized through infrared spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). These novel materials are extremely efficient in removing low concentrations of mercury and cesium ions from water in the presence of high concentrations of sodium or potassium ions. They were shown to remove trace mercury and cesium contaminants effectively to well below parts per billion concentrations under a variety of conditions.

Novel nanoporous hybrid organic-inorganic silica containing iminodiethanol chelating groups inside the channel pores.

Novel nanoporous hybrid organic-inorganic silica with covalently bound iminodiethanol chelating groups inside the channel pores has been synthesized by template-directed co-condensation of tetraethoxysilane (TEOS) and organo-trimethoxysilane (CH3O)3SiR [IDES, R = (HOCH2CH2)2NCH2CH(OH)CH2O(CH2)3], and is shown to be very efficient in recovery of germanium and antimony oxides from water.