A new technique developed at Imperial College London could lead to the next generation of tailor-made materials.

Researchers have developed a method of controlling the composition of a range of polymers, the large molecules that are commonly used as plastics and fibres. They are the building blocks for a vast number of everyday materials.

Polymers are naturally occurring, for example as complex sugars and DNA. The molecules comprise thousands of repeat units of smaller molecules called monomers. The nature and organisation of these monomers within the polymer chain determines the material’s properties, such as how strong or stretchy it is, or how much heat it can withstand.

The new research, published this week in Angewandte Chemie and funded by the Engineering and Physical Sciences Research Council, demonstrates how the chemical reactions used to produce polymers can be controlled, especially in fixing the composition of a polymer using a mixture of up to three different monomers.

The secret lies in understanding and switching ‘on’ and ‘off’ the catalyst used to make the polymers. The researchers found that by using this catalyst control method, it is possible to select the monomers that will be added to the chain and therefore control the pattern and composition of the final polymers.

In this study, the scientists worked on producing polyesters and polycarbonates, which are attractive materials as they are partially obtained from renewable resources, such as plants and carbon dioxide. They are widely used in commodity applications such as consumer goods and packaging.

It is anticipated that the method could eventually be widely used in the manufacture of many different types of polymer materials.

Charlotte Williams, Professor of Catalysis and Polymer Chemistry at Imperial, who led the research, explains: “Our method uses the chemistry between the catalyst and the polymer chain, which affects the kind of monomer added to the chain and so what type of material is produced.  This is a different way of controlling the polymer composition, and one that gives us more control over the properties of the end product.

"Our research is the first step in this direction, but may lead, one day, to scientists being able to engineer polymers with much more desirable properties, such as elasticity or toughness, as well as improve their performance in fields such as drug delivery or regenerative medicine.”

Professor Williams’ team has demonstrated the method, which uses a zinc-based catalyst, using three different monomers, including carbon dioxide - a notoriously unreactive molecule. This chemistry represents a promising approach to adding value to waste CO2, including from waste gas emissions. The next step in the process will be to extend the method to greater varieties and mixtures of monomers.

An Imperial spin out company, Econic Technologies, founded by Professor Williams, is licensing the discovery and commercialising these materials.