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Shan Zou (promotion date: 10 February 2005)

Exploring individual supra molecular interactions and stimuli-responsive polymers by AFM-based forced spectroscopy

Promotion Date: 10 February 2005

Shan Zou

Basically and simply put I have been measuring the forces between individual molecules, as well as complexes, i.e. small objects. I have also measured the mechanical properties of single polymer chains, using Atomic Force Microscopy (AFM).
Because it is a big help if you know the properties of a single chain, when you design a new material with certain properties. The interesting part about my work is that we are not only focusing on the conventional polymers, we are also concentrating on the “smart” material, called supramolecular polymers. These have the unique properties of being reversible. In supramolecular polymers you have an weak interaction as in hydrogen bonding, or host guest interaction. Because of this weak molecular interaction you get environmental control by increase of temperature, change of solvent etc.

What was your thesis about?

Basically and simply put I have been measuring the forces between individual molecules, as well as complexes, i.e. small objects. I have also measured the mechanical properties of single polymer chains, using Atomic Force Microscopy (AFM).

Why do you want to measure a single polymer chain?

Because it is a big help if you know the properties of a single chain, when you design a new material with certain properties. The interesting part about my work is that we are not only focusing on the conventional polymers, we are also concentrating on the “smart” material, called supramolecular polymers. These have the unique properties of being reversible. In supramolecular polymers you have an weak interaction as in hydrogen bonding, or host guest interaction. Because of this weak molecular interaction you get environmental control by increase of temperature, change of solvent etc.

The long and short of it is that these polymers are easily controlled, solving the problem in the coating technology. My work, however, was not focusing on the actual development of new material, but the fundamental physics behind it. First you need to know the fundamentals of the interactions before you can develop a product. So I have been measuring how much force you need to get these complexes apart on a single molecule level.

So up until now people have been making polymers without knowing the properties?

They know the properties in a general sense, of the entity but not on a molecular level.

And measuring the hydrogen bonding is an important issue as it is a process that occurs all over the human body for instance, but too less is known about the force that is needed.

Measuring synthetic H-bonds with AFM is completely new.

You are from China: what part of China?

I am from the north east, a city called Changchun. It has clear four seasons, now there is minus 26 at present.

How did you get a position here at Mesa?

I wanted to go abroad for my Ph.D. My formal supervisor in China, Professor Xi Zhang from Jilin University at that time, knows the work here and wrote me a recommendation letter.

I had an interview by telephone and later I was accepted. The only difficulty was getting the papers ready, like a visa etc. I am by the way very pleased that Professor Xi Zhang is on the committee and will be here for my promotion.

What did you enjoy most about your time here?

The freedom. It is very easy to communicate here with people, inside and outside the university. So that makes it easy to establish collaborations with institutes all over Europe, which I was encouraged to do. In China it is easy to establish contacts within China, but it being such a vast country makes it more difficult to go abroad. Europe is so much more condensed, everything seems close by.

Did you experience any major setbacks?

No, not really. The one thing I can remember was that I was refused a visa for a conference in the US. They said I could not prove that I had a job in Europe and would actually go back to the Netherlands. They were afraid I would stay in the US.

But in the research itself, no. Of course you encounter difficulties, but nothing disastrous. I was lucky. I do things parallel; I worked mainly on three subjects. If one of them did not go very well, I turned to the other to work on, giving time to think and sort things out in the problem areas. Also on a personal level I have been lucky, my husband joined me here after z few months. He is doing a Ph.D. in another group in UT. Also my family are very supportive since my mother and father are both chemists I could always discuss with them what I have been doing. Especially my mother, who is a professor of Analytical Chemistry, knows nearly every step I took. But also my father, who is a polymer scientist in a more application oriented way, gave me advice numerous times.

Will they be here for your promotion?

No, unfortunately. The visa application takes at least three months and you never know beforehand how things will go with the promotion date. But my mother was here, or actually in Germany were my aunt lives, in 2002.

What are you going to do next?

I have got a postdoc position in Toronto from the 1st May. That means another separation from my husband for another few months. But after that it is his turn to choose, and he likes Europe very much.

For the summary of the thesis, click here.