Research Materials

Pitt Scientists Enhance Green Solvent

Liquid and supercritical carbon dioxide have attracted much interest as environmentally benign solvents, but their practical use has been limited by the need for high CO₂ pressures to dissolve even small amounts of polar, amphiphillic, organometallic, or high-molecular-mass compounds.

So-called "CO₂-philes" efficiently transport insoluble or poorly soluble materials into CO₂ solvent, resulting in the development of a broad range of CO₂-based processes. But as the most effective CO₂-philes are expensive fluorocarbons, such as poly(perfluoroether), the commercialization of otherwise promising CO₂-based processes has met with only limited success.

Professor Beckman and his colleagues have shown that copolymers can act as efficient, non-fluorous CO₂-philes if their constituent monomers are chosen to optimize the balance between the enthalpy and entropy of solute-copolymer and copolymer0copolymer interactions. Guided by heuristic rules regarding these interactions, we have used inexpensive propylene and CO₂ to synthesize a series of poly(ether-carbonate) copolymers that readily dissolve in CO₂ at low pressures. Professor Beckman notes that "we expect that our design principles can be used to create a wide range of non-fluorous CO₂-philes from low-cost raw materials, thus rendering a variety of CO₂-based processes economically favorable, particularly in cases where recycling of CO₂-philes is difficult."

One Molecule Thick Coin Coating

One Molecule Thick
Coin Coating

Dr. Enick and his colleagues have perfected the use of an invisible fluorinated coin conservation solution that molecularly bonds to the coin metal and locks in the condition of the coins at the time the solution is applied.

The application of the solution prevents the coins from toning. The application technique involves placing a one-molecule thick coating, referred to as a self-assembled monolayer (SAM) on the coin. The coating can be sprayed on or applied through immersion in the solution.

There are several distinctions between the SAM and conventional polymer or lacquer coin coatings. Lacquer is a transparent coating one-tenth millimeter thick that is visible to the naked eye and is susceptible to cracking, flaking and discoloration when it ages. Because the SAM is actually thinner than a wavelength of light, it is invisible. The SAM will also not peel, crack or discolor, and is more resilient than lacquer because the SAM chemically bonds to the coin surface.

Conventional thiols have a pungent and dangerous odor. For the coin conservation treatment, fluoroalkyl amide thiols (FAT), which emit no detectable or dangerous odor, are employed. The fluorocarbon in the compound is similar in composition to Teflon; the amide groups are capable of attracting the amide group of the adjacent thiol molecule through hydrogen-bonding and the sulfur bonds to the metal.

Amino Acid-Based Polyurethanes for Tissue Engineering

Amino Acid-Based
Polyurethanes for Tissue Engineering

Polyurethanes offer extraordinary versatility and are used in many applications including: thermoplastics for automotive applications, organic and water-borne coatings, foams for seat cushions and insulation, fibers, thermoplastic elastomers (Lycra, etc.), and thermosets. Professor Beckman, in collaboration with Professor Agarwal (School of Dentistry) has generated novel, non-toxic, biodegradable peptide-based urethane polymers that have been successfully evaluated using rabbit bone marrow cells. These polyurethane foams, made from lysine, glycerol, sugar, and tyrosine, support the growth of osteoblasts and biodegrade over a period of time to non-toxic materials. These materials are showing promise as bone-tissue engineering scaffolds. These findings are an exciting precursor to the use of these innovative materials in human reconstructive surgical procedures.

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