100 years of »big molecules«
AND THE BIG CHANGES AHEAD OF THEM
Clariant’s 25th birthday coincides with the 100th anniversary of a pivotal date in chemical history.
In 1920, German chemist Hermann Staudinger began publishing his groundbreaking work on polymers and macromolecular chemistry, for which he later received the Nobel Prize. In our interview, Johannes Benkhoff, Senior Vice President Group Chemical Research at Clariant, and Michael Mager, Head Research Specialty Polymers, tell us why this new concept of »big molecules« was so important – and what is driving research on polymers and plastics today.
In 1920, the term polymer was already known and even the first plastic had been invented, but the chemistry involved was still unclear. How did Hermann Staudinger change this?
Michael Mager: The term polymer did exist, but not in the modern sense. Staudinger discovered that polymers are composed of large molecules with high molecular weight made of many repeating units. At the time, the idea was scoffed at, but today my seat cover, cotton shirt, phone – they’re all known to be these polymers. It was a little like saying there’s no such thing as glass.
Johannes Benkhoff: Yes, reading about it again, I was also surprised by the fieriness of the debate. If you picture the monomers making up polymers as a row of dominoes, Staudinger said they don’t simply topple onto each other but form tight bonds. The idea that there could be such enormous macromolecules was seen as almost indecent at the time. But it turned out to be a paradigm shift that opened many future avenues.
Macromolecules, polymers, plastics – not everyone may know how these terms relate. Can you give us a quick rundown?
Johannes Benkhoff: »Macro« means big, and a macromolecule is simply a big molecule. This can have any structure and comprises repeating units of smaller molecules. A polymer is a substance composed of many macromolecules.
Michael Mager: The repeating units are often arranged in long chains, but polymers can also have branched or star-shaped structures. Plastic is made of myriads of such polymers. While all plastics are made from polymers, however, not all polymers are used as plastics.
Johannes Benkhoff: A protein for instance is a macromolecule made of thousands of repeating amino acids. Silk from caterpillars is a natural polymer and so is cellulose, which plants make from sugars to build cell walls and produce cotton.
So nature has been using Staudinger’s big molecules to make polymer materials long before chemists did. What are some important man-made polymers?
Johannes Benkhoff: All the polyesters and polyamide fibers in our sportswear are polymers, so are the high performance plastics now used to make cars lighter. The table in front of you, your glasses – polymers are used for very many things today.
Why have they become so popular since Staudinger’s days?
Michael Mager: I think one important reason is how easily they can be processed into all kinds of materials and shapes. There are just so many things that wouldn’t be possible, or much harder to realize, only using materials like wood, metal, ceramics or glass. This ranges from a light and sturdy lawn chair everyone can afford to effective insulation for homes.
What is Clariant’s contribution to making polymers?
Johannes Benkhoff: We make additives that enhance polymeric plastics but rarely make plastics ourselves. What we do make are specialty polymers for all kinds of applications. Our Aristoflex® polymers for instance give shampoos and lotions a silky feel. Our TexCare® soil-release polymers help to save energy by making it easier to wash clothes. All this can be done by tweaking the composition and structure of polymers.
Sustainability is now a big issue associated with the big molecules Staudinger found. How does Clariant contribute in this area?
Johannes Benkhoff: We contribute in many ways, and an interesting point here is that you can close the plastic loop in two ways. One is making plastics last longer and helping them to keep their properties throughout recycling, as for example our Exolit® flame retardants do. The other approach, which we also support, is to make them easier to degrade by nature, and to base them more on natural materials.
One of the first plastics already existing in 1920 was celluloid made from natural cellulose. Are we closing the loop back to Staudinger’s time?
Michael Mager: In a very broad sense perhaps. But celluloid was eventually widely replaced because of its high flammability, and natural polymers are generally limited in their properties. To perform like modern materials, they would probably have to be completely broken down and then rebuilt.
Johannes Benkhoff: In a way that’s what chemists did when they created all kinds of structural variations of the first polymers, which are now used in anything from high-tech applications to simple kitchen equipment. And I think that’s what we have to do now: learn from nature and use its materials to create that same kind of variety. That is the great new challenge we have to solve in this century.