Scott T. Iacono

Photoluminescence and ion sensing properties of a bipyridyl chromophore-modified semifluorinated polymer and its metallopolymer derivatives

A difluorovinylene aromatic ether polymer (P1) incorporating periodic 5,5′-distyryl-2,2′-bipyridyl units as metal chelating chromophores was prepared by a transition metal-free step-growth polymerization. P1 displays strong ionochromic and ionoluminescent effects in response to transition metals. Although significant emission quenching is observed upon exposure to most transition metal ions, bathochromically shifted emission is observed upon addition of divalent d10 ions (Zn2+, Cd2+ and Hg2+). A selective 10-fold increase in integrated emission intensity is observed upon addition of Zn2+ to P1. The Zn2+-P1 metallopolymer acts as a ratiometric fluorescent indicator selective for fluoride anions, and the Cu2+-P1 metallopolymer exhibits a striking turn-on fluorescence response (>100-fold increase in integrated intensity) selective for cyanide and fluoride anions.

Preparation of composite fluoropolymers with enhanced dewetting using fluorinated silsesquioxanes as drop-in modifiers

Composite fluoropolymers were prepared by solvent blending fluorinated POSS (F-POSS) with perfluorocyclobutyl (PFCB) aryl ether polymers. The semifluorinated PFCB aryl ether polymers were shown to be hydrophobic, but demonstrated complete wetting by hydrocarbon-based liquids. Upon the incorporation of F-POSS as a drop-in modifier at low weight percent loadings, the composite fluoropolymer spin cast films exhibited increased water in addition to hydrocarbon repellency as determined by contact angle analysis. Composite film surface characterization included SEM and AFM analyses which showed excellent F-POSS dispersion and increased surface roughness. Thermal properties of the blended films were analysed using DSC and this demonstrated that the incorporation of F-POSS did not affect the bulk matrix properties inherent of PFCB aryl ether polymers. This work demonstrated that optimized F-POSS PFCB aryl ether polymer blend formulations have potential use as hydro- and oleophobic materials for seals, fibers, and coatings.

Metastable nanostructured metallized fluoropolymer composites for energetics

Fluoropolymers have long served as potent oxidizers for metal-based pyrolant designs for the preparation of energetic materials. Commercial perfluoropolyethers (PFPEs), specifically known as Fomblins®, are well-known to undergo accelerated thermal degradation in the presence of native metals and Lewis acids producing energetically favorable metal fluoride species. This study employs the use of PFPEs to coat nano-aluminum (n-Al) and under optimized stoichiometric formulations, harness optimized energy output. The PFPEs serve as ideal oxidizers of n-Al because they are non-volatile, viscous liquids that coat the particles thereby maximizing surface interactions. The n-Al/PFPE blended combination is required to interface with an epoxy-based matrix in order to engineer a moldable/machinable, structurally viable epoxy composite without compromising bulk thermal/mechanical properties. Computational modeling/simulation supported by thermal experimental studies showed that the n-Al/PFPE blended epoxy composites produced an energetic material that undergoes latent thermal metal-mediated oxidation. Details of the work include the operationally simple, scalable synthetic preparation, thermal properties from DSC/TGA, and SEM/TEM of these energetic metallized nanocomposite systems. Post-burn analysis using powder XRD of this pyrolant system confirms the presence of the predominating exothermic metal-mediated oxidized AlF3 species in addition to the production of Al2O3 and Al4C3 during the deflagration reaction. Details of this first epoxy-based energetic nanocomposite entrained with a thermally reactive formulation of PFPE coated n-Al particles are presented herein.

Synthesis of 1,3-Diphenyl-6-alkyl/aryl-Substituted Fulvene Chromophores: Observation of π–π Interactions in a 6-Pyrene-Substituted 1,3-Diphenylfulvene

The synthesis, structural, and electronic properties of nine 1,3-diphenyl-6-alkyl/aryl substituted pentafulvenes were studied. Pyrene ring π-π interactions were revealed from analysis of the experimental crystal packing of 1,3-diphenyl-6-(1-pyrene)fulvene and supporting DFT calculations. Photophysical properties derived from UV-vis and fluorescence emission measurements demonstrated tunable and low HOMO-LUMO band gaps for the series. The presented results point to a model synthetic approach for incorporation of extended π systems and donor-π-acceptor groups for fulvene-based electronic materials.

Facile synthesis of hydrophobic fluoroalkyl functionalized silsesquioxane nanostructures

New fluorinated polyhedral oligomeric silsesquioxane (F-POSS) structures possessing a high degree of hydrophobicity have been prepared via a facile corner-capping methodology.

Activating Aluminum Reactivity with Fluoropolymer Coatings for Improved Energetic Composite Combustion.

Aluminum (Al) particles are passivated by an aluminum oxide (Al2O3) shell. Energetic blends of nanometer-sized Al particles with liquid perfluorocarbon-based oxidizers such as perfluoropolyethers (PFPE) excite surface exothermic reaction between fluorine and the Al2O3 shell. The surface reaction promotes Al particle reactivity. Many Al-fueled composites use solid oxidizers that induce no Al2O3 surface exothermicity, such as molybdenum trioxide (MoO3) or copper oxide (CuO). This study investigates a perfluorinated polymer additive, PFPE, incorporated to activate Al reactivity in Al-CuO and Al-MoO3. Flame speeds, differential scanning calorimetry (DSC), and quadrupole mass spectrometry (QMS) were performed for varying percentages of PFPE blended with Al/MoO3 or Al/CuO to examine reaction kinetics and combustion performance. X-ray photoelectron spectroscopy (XPS) was performed to identify product species. Results show that the performance of the thermite-PFPE blends is highly dependent on the bond dissociation energy of the metal oxide. Fluorine-Al-based surface reaction with MoO3 produces an increase in reactivity, whereas the blends with CuO show a decline when the PFPE concentration is increased. These results provide new evidence that optimizing Al combustion can be achieved through activating exothermic Al surface reactions.

Reversible addition–fragmentation chain transfer (RAFT) copolymerization of fluoroalkyl polyhedral oligomeric silsesquioxane (F-POSS) macromers

Reversible addition–fragmentation chain transfer (RAFT) polymerization techniques were used to copolymerize an F-POSS macromer with methyl methacrylate (MMA) to produce novel copolymers that possess excellent wetting-resistant behaviour and are the first examples of covalently bound F-POSS nanocomposites for improved surface robustness. These F-POSS/MMA copolymers have also been used to coat cotton fabrics, resulting in both superhydrophobic and oleophobic behaviour.

Facile preparation of fluorovinylene aryl ether telechelic polymers with dual functionality for thermal chain extension and tandem crosslinking

New fluorovinylene aromatic ether polymers, possessing dual reactivity, have been successfully prepared via the step-growth polymerization of commercial bis(trifluorovinyl) aromatic ethers and bisphenols.

Fabrication, characterization, and energetic properties of metallized fibers.

Polystyrene fibers loaded with an energetic blend of nanoaluminum (n-Al) and perfluoropolyether (PFPE) were successfully fabricated via electrospinning producing nanothermite fabrics. Fibers were generated with loadings up to 17 wt % n-Al/PFPE incorporated into the fiber. Microscopy analysis by SEM and TEM confirm a uniform dispersion of PFPE treated n-Al on the outside and inside of the fibers. Metallized fibers were thermally active upon immediate ignition from a controlled flame source. Thermal analysis by differential scanning calorimetry (DSC) found no change in glass transition temperature when comparing pure polystyrene fibers with fibers loaded up to 17 wt % n-Al/PFPE. Thermal gravimetric analysis (TGA) revealed a shift in decomposition temperatures to lower onsets upon increased loadings of n-Al/PFPE blends, consistent with previous studies. Flame propagation studies confirmed that the metallized fibers are pryolants. These metallized fibers are a recent development in metastable intermolecular composites (MICs) and details of their synthesis, characterization, and thermal properties are presented.

Utilization of a Meldrum's acid towards functionalized fluoropolymers possessing dual reactivity for thermal crosslinking and post-polymerization modification

New thermally cross-linkable and/or post-functionalizable perfluorocyclobutyl (PFCB) polymers containing Meldrums acid moieties have been successfully prepared via the thermal cyclopolymerization of a new Meldrums acid functionalized aromatic trifluorovinyl ether (TFVE) monomer.