Nature—the perfect chemist

KAUST Distinguished Professor of Chemical Science Nikos Hadjichristidis (left) heads the University's Polymer Synthesis Laboratory. He and his research team work on manipulating macromolecules at the nanoscale. File photo.

​-By Sonia Turosienski, KAUST News

Many people lament the ubiquity of plastic and other polymeric materials, but imagining a world without these is difficult. Planes would be heavier and consume much more fuel; surgeons would have fewer options to offer patients in need of artificial organs; and eye glasses would be heavier and more fragile.

Nikos Hadjichristidis, KAUST distinguished professor of chemical science, heads the University's Polymer Synthesis Laboratory, which boasts a strong collaboration with the lab of Yves Gnanou, KAUST distinguished professor of chemical science and acting vice president for academic affairs.

Hadjichristidis explained that polymeric materials—of which plastics are a small subset—are crucial to everyday life. Macromolecules, the building blocks of polymers, are readily found in nature—in proteins, DNA and polysaccharides.

"Polymeric materials and specifically plastics have an important role to play in our lives, but it is up to scientists to make them more sustainable and consumers to be more responsible about recycling and use," he stated.

KAUST Distinguished Professor Nikos Hadjichristidis (center) works with his research team on campus to develop polymeric materials with unprecedented properties. File photo.

Hadjichristidis describes himself as a macromolecular architect, manipulating macromolecules at the nanoscale.

"Similar to how an architect designs a house or a bridge, we do this for macromolecules with different shapes," he noted. "We design a chemical reaction and then build the reactor that will synthesize the molecule. Macromolecular architecture is very important since the 'heart' of the properties of polymeric materials is situated at the macromolecular level."

One of the approaches Hadjichristidis and his team are known for is anionic polymerization using high vacuum techniques. The technique is highly specialized and used in only a handful of labs around the world, as the barrier to entry is learning glassblowing.

"You have to work in a vacuum because the anions are very sensitive to humidity and oxygen. We use handmade, customized glassware made in the lab to control the reactions. It is a very delicate technique that can take up to six months to learn," Hadjichristidis explained.

KAUST Distinguished Professor Nikos Hadjichristidis (right) works with two of his researchers in his Polymer Synthesis Laboratory on campus. File photo.

Tired of tire waste

One of the ways Hadjichristidis and his group are working towards reducing pollution from the materials side is rethinking tires. Tires are difficult to recycle because they cannot be melted—they are currently either repurposed; used as a component in asphalt; burned; or left in landfills. Burning and landfills, however, pose problems because tires release toxins, and, due to their bulky nature, they take up space in overburdened landfills.

Hadjichristidis has been thinking about how to make tires recyclable since he was a postdoctoral student. At KAUST, one of the projects he is working on is developing a polymerization process that uses physical instead of chemical cross-linking to make a polymeric material for tires that is thermoplastic—a quality that denotes a polymer that is liquid above a certain temperature and solid when cooled, yet elastic enough to be road-worthy.

In polymer chemistry, elasticity and thermoplasticity are often at odds, but Hadjichristidis and his team are able to make triblock copolymers using polystyrene and polydienes with both qualities (thermoplastic elastomers). The next challenge is to use this approach to make a polymer to use in tire manufacturing that is stable to high temperatures on the road.

KAUST Distinguished Professor Nikos Hadjichristidis (left) noted that his research work is inspired by nature—the 'perfect chemist.' File photo.

"If we can recycle tires, then this will have a huge impact on the environment. Our goal is to replace tires by creating a very strong thermoplastic elastomer that can be recycled," he said.

Hadjichristidis and the research team also work on other areas related to recycling, which include biodegradable polyethylene (to solve the plastic bags problem) and biocompatible/biodegradable polymers (polyethers and polyesters) for medical applications.

Inspired by nature

Hadjichristidis has been recognized as a pioneer for his work on conceiving and developing polymeric materials with unusual architectures.

"I'm interested in unusual architecture because it guides us to new materials and unprecedented materials," he said.

Hadjichristidis was awarded the highest prize in his field—the American Chemical Society Award in Polymer Chemistry—in 2015. Today, his lab is known as one of the most prominent and innovative hubs for complex macromolecular architecture.

"I take my inspiration from nature. The aim of all polymer chemists is to design materials with predetermined properties in the way nature—the perfect chemist—does," he concluded.

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