Robert A. Mantz

Regenerated silk fiber wet spinning from an ionic liquid solution

Regenerated silk fibroin from Bombyx mori silkworms was extruded into fibers from a 1-ethyl-3-methylimidazolium chloride ionic liquid solvent system; the drawn fibers rinsed in methanol exhibit alignment of the β-sheet crystallites along the fiber axis.

Dissolution of Biopolymers Using Ionic Liquids

Ionic liquids represent a unique class of solvents that offer unprecedented versatility and tunability. Nature has developed a wide variety of materials based upon both proteins and polysaccharides. Many of these materials have unique properties that are a function not only of the material identity but are also largely dictated by processing conditions. Recent work has shown the potential of ionic liquids as solvents for the dissolution and processing of biopolymers. In this research we have expanded upon the limited data available to date using several biopolymers including: silk, chitin, collagen and elastin.

Anodization and Speciation of Magnesium in Chloride‐Rich Room Temperature Ionic Liquids

Magnesium anodization was examined in room temperature AlCl 3 :EMIC and AlCl 3 :DMPIC ionic liquids, where EMIC = 1-ethyl-3-methylimidazolium chloride and DMPIC = 1,2-dimethyl-3-propylimidazolium chloride. For all melts, the AlCl 3 :organic chloride mole ratio was <1, yielding chloride-rich (i.e., basic) compositions. The rate of magnesium anodization was limited by diffusion of chloride ions to the electrode surface. From the Cottrell slopes for magnesium anodization at a Mg disk electrode and for chloride oxidation at a Pt disk electrode, the chloride stoichiometry of the anodization process in AlCl 3 :EMIC was determined to be 4.1 (± 0.5), corresponding to the formation of soluble MgCl 4 2 . Similar chloride stoichiometry was found in AlCl 3 :DMPIC. MgCl 2 buffers the melt to approximate neutrality from the basic side, dissolving as MgCl 4 2- . Magnesium metal was chemically stable in basic AlCl 3 :DMPIC, but it reacted completely and irreversibly with basic AlCl 3 :EMIC to produce colored organic byproducts. Some comments are made on the acidity of NiCl 2 and CdCl 2 in the basic melts.

High‐resolution NMR characterization of a spider‐silk mimetic composed of 15 tandem repeats and a CRGD motif

Multidimensional solution NMR spectroscopic techniques have been used to obtain atomic level information about a recombinant spider silk construct in hexafluoro‐isopropanol (HFIP). The synthetic 49 kDa silk‐like protein mimics authentic silk from Nephila clavipes, with the inclusion of an extracellular matrix recognition motif. 2D 1H‐15N HSQC NMR spectroscopy reveals 33 cross peaks, which were assigned to amino acid residues in the semicrystalline repeat units. Signals from the amorphous segments in the primary sequence were weak and broad, suggesting that this region is highly dynamic and undergoing conformational exchange. An analysis of the deviations of the 13Cα, 13Cβ, and 13CO chemical shifts relative to the expected random coil values reveals two highly α‐helical regions from amino acid 12–19 and 26–32, which comprise the polyalanine track and a GGLGSQ sequence. This finding is further supported by ϕ‐value analysis and sequential and medium‐range NOE interactions. Pulsed field gradient NMR measurements indicate that the topology of the silk mimetic in HFIP is nonglobular. Moreover, the 3D 15N‐NOESY HSQC spectrum exhibits few long‐range NOEs. Similar spectral features have been observed for repeat modules in other polypeptides and are characteristic of an elongated conformation. The results provide a residue‐specific description of a silk sequence in nonaqueous solution and may be insightful for understanding the fold and topology of highly concentrated, stable silk before spinning. Additionally, the insights obtained may find application in future design and large‐scale production and storage of synthetic silks in organic solvents.

Protection of Aluminium Alloys via Hybrid Sol-Gel Coatings with Encapsulated Organic Corrosion Inhibitors

Several heterocyclic organic corrosion inhibitors that contain ionazible functional group were encapsulated into nano-structural hybrid organo-silicate coating to improve its corrosion protection performance on aluminum alloy 2024-T3 substrate. When the coating is formed on the substrate surface, it serves simultaneously as protective barrier and as a reservoir for leachable corrosion inhibitor that is stored and released through the mechanism of reversible ionic interaction with the matrix material. The efficiency of active corrosion protection for these coating systems was examined by electrochemical methods including potentiodynamic polarization (PDS) and electrochemical impedance spectroscopy (EIS). The effects of chemical structure and the loading concentration of the inhibitor within the coating were determined.

Electron transfer kinetics for weakly bonded, labile metal–ligand complexes

The electron transfer kinetics for the weakly-bonded, labile CuI–L (L = CO and ethene) complexes have been investigated with square-wave voltammetry (SWV) in the ionic liquid solvent AlCl3–EMIC (EMIC = 1-ethyl-3-methyl-1H-imidazolium chloride). The oxidation of CuI–L to CuII and free ligand proceeds through an asymmetric quasi-reversible electron transfer mechanism in which the heterogeneous rate constant (k0a) is decreased relative to the rate constant for uncomplexed CuI, and the anodic transfer coefficient (β) is much less than 0.5. The CuI–L bond energies were determined using potentiomtric methods and found to be 9.4 (± 0.8) and 11.1 (± 0.1) kcal mol–1 for the CO and ethene complexes, respectively.