The accumulation of plastic waste in the environment is a growing problem. Ironically, these materials were first created as environmentally friendly synthetic alternatives to natural materials such as wood or bone. We call these synthetic materials “polymers” because they are composed of long connected chains of “monomers” which you can visualize similar to beads (monomers) making up a necklace (polymer).

It turns out that we can use chemistry to assemble polymers in different configurations. Notably, there are thermoplastics which are composed of long linear chains, and thermosets which contain strong chemical bonds linking linear chains together (like a fishing net). These chemical bonds linking thermoset polymer chains together are called cross-links. Due to these differences in material structure, thermoplastics such as the polyethylene terephthalate, used in plastic water bottles, can be heated to be melted and recycled, whereas thermosets such as tires would burn upon heating instead of melting to be re-formed into a new shape. However, although you might think that thermoplastics are better since they can be recycled, both thermoplastics and thermosets have important uses. In particular, due to the additional chemical bonds, thermosets typically possess better mechanical properties.

In order to address the challenges associated with not being able to recycle thermoset materials, many research groups have begun replacing the permanent cross-link bonds with dynamic covalent bonds. What are dynamic covalent bonds? This idea combines two important concepts from general chemistry which are the covalent bond and the concept of equilibrium (Le Chatelier’s Principle). A change in temperature can shift the equilibrium between reactants and products, or in this case, a chemical bond vs. no chemical bond.

We can incorporate dynamic covalent bonds into thermoset materials, using the effect of temperature to give them similar properties to the cross-linked thermoset materials at low temperatures. Due to the temperature dependence of the dynamic covalent bonds, they can be processed at very high temperatures for recycling, much like thermoplastics. These materials are called “covalent adaptable networks” (CANs), and sometimes they are also called “vitrimers” depending on the dynamic bond exchange mechanism.

In the Hamachi Group, we are interested in studying CANs and developing the chemistry to make new classes of covalent bonds dynamic. This research involves a mixture of organic chemistry techniques (1H NMR, GC/MS, FTIR) and materials engineering techniques (tensile testing, DSC, DMTA). You do not need prior experience with these techniques to be able to participate in a research project, although it is suggested that you have taken the first two quarters of gen chem.

Covalent Organic Frameworks (COFs) are a class of crystalline, porous polymers synthesized from well-defined molecular building blocks called monomers. They are similar to CANs in that they are both polymers with dynamic cross-links, however CANs are generally not porous and not crystalline. COFs are porous and crystalline due to the nature of the monomers used and the synthetic conditions used to make the polymers. By swapping out the monomers for ones of different shapes and sizes, we can change the structure of the crystal as well as the size and shape of the pores. A good way to visualize a COF is to think of a porous sponge, where each pore is very small and exactly the same size. This high surface area allows COFs to adsorb gasses/analytes and to be used in molecular separations.

In the Hamachi Group, we are interested in developing methods to synthesize new COFs with novel linkage chemistries. This research involves a mixture of organic chemistry techniques (1H NMR, GC/MS, FTIR) and materials engineering techniques (PXRD, SEM, surface area analysis). You do not need prior experience with these techniques to be able to participate in a research project, although it is suggested that you have taken the first two quarters of gen chem.

How small is a nanometer? If you were to take the diameter of a human hair and split it in half twenty times, that would be approximately the size of a nanometer. Scientists are interested in nanoparticles because at those small length scales, new properties can emerge. One example is gold nanoparticles at the nanoscale which range in color from red, to purple, to blue, based on their shape and size. Another example is the cadmium selenide nanoparticles that Dr. Hamachi studied during her Ph.D. which glow a rainbow of colors from red to blue based on the particle diameter.

In the Hamachi Group, we are interested in nanoparticle synthesis and characterization. For many applications, it is important to consistently make a narrow size distribution of nanoparticles. We seek to develop new synthetic methods to achieve this. This research involves a mixture of organic chemistry techniques (1H NMR, FTIR) and materials engineering techniques (PXRD, SEM, DLS). You do not need prior experience with these techniques to be able to participate in a research project, although it is suggested that you have taken the first two quarters of gen chem.