Cooking up Polymers: A Q&A with Maxwell Robb

Ever since his parents bought him a chemistry kit in elementary school, Maxwell (Max) Robb has wanted to be a chemist. Now, as a new assistant professor of chemistry at Caltech, Robb possesses the grown-up equivalent of a chemistry kit—a new state-of-the-art laboratory for making materials, in particular plastics that respond to mechanical forces. Robb's research has important applications like sensing stress in plastics, where mechanically sensitive molecules could signal impending damage by changing color. But his passion lies in fundamental chemistry. "I like making new things and exploring the chemical world," he says.

Robb moved to Pasadena after a postdoctoral fellowship at the University of Illinois at Urbana-Champaign. He earned his PhD in chemistry in 2014 from the University of California, Santa Barbara, and his bachelor's degree in chemistry from the Colorado School of Mines in 2009. 

We sat down with Robb to learn more about his research and why making plastics is not that different from cooking. 

Tell us more about your field of synthetic polymer chemistry.

In my lab, we make new materials. We make small molecules as well as large molecules such as polymers, which are long chains of repeating units. You can think of a polymer as being like a spaghetti noodle. If you cook spaghetti, you end up with a tangled ball of noodles. The same is true for the materials we make in our lab—the polymers become tangled together, and this gives rise to many of their properties.  

What kinds of materials are you making?

The research in my group focuses on functional polymers, or functional plastics. We're interested in tuning the structure of these materials, at the molecular level, so that when you apply a stimulus, by pulling on the material or applying a mechanical force, it causes some chemical reaction, some transformation, to take place. Such changes would provide a simple visual cue, for example, that would allow you to identify if a plastic component has been subjected to a potentially damaging stress. We are particularly interested in developing polymers that provide a visual readout of the amount of force a material has experienced.  

And how might these materials be used?

This technology could be applied to personal protective equipment—helmets, for instance—to provide immediate information about the severity of an impact to the head. That feedback could then be used to inform medical treatment. For industrially relevant plastic components, we could identify stresses early on that would eventually cause the material to fail, so that the parts could be repaired or replaced before more significant damage occurs. We are also working on a type of "invisible ink" for polymeric materials—where mechanical force would be used to write a pattern that can be revealed later using a secondary stimulus.

How do you go about making these new materials?

Typically, we start with an idea for a new molecule or material and then we perform computational calculations to try to predict how the molecule will respond to mechanical force. From there, we go into the lab and synthesize the new materials. Sometimes we will modify existing molecules that we know behave in certain ways, and sometimes we'll develop completely new materials. However, the ability to design new mechanically responsive molecules from the ground up is still a big challenge in the field. My group is working on this by developing the fundamental framework for understanding how force is coupled to molecular reactivity.

What do you like about Caltech?

The community aspect of Caltech is really special, coupled with the small size of the Institute. The people here are incredibly friendly, open, and supportive. People are collaborative, everyone is doing amazing science, and there are zero barriers to interacting with anyone on campus. And the students are absolutely amazing. I've been lucky to recruit an outstanding group of researchers.

What do you do in your spare time?

I like hiking and exploring the outdoors. I love living near the mountains. I enjoy trying all the restaurants that Pasadena offers, but I also like to cook. Synthetic chemistry is a lot like cooking. I think there's a correlation between being a good synthetic chemist and being a good cook at home. I wish I had more time to be creative in the kitchen. Watching a good TV show or movie is one of my guilty pleasures.