Nature has evolved the ability to create large and complex molecules in which the precise control over both the sequence and spatial arrangement of the atoms is critical to their performance. The 3-dimensional control over the arrangement of bonds is as important to the function and behaviour of molecules as any other factor and is critical to the structure-function relationships that occur within biological systems. While the effects of stereochemistry on functionality are probably best known for small molecule drugs such as thalidomide (one enantiomer is effective against morning sickness, the other is teratogenic) or naproxen (one enantiomer is used to treat arthritis pain, the other causes liver poisoning and has no analgesic effect), it is also clearly represented in biopolymers where stereochemistry has pronounced effects on structure and hence function. For example, DNA, which is at the heart of all biological systems, requires the chirality of the deoxyribose sugar in its backbone to ensure that the double helical structure can form by supramolecular interaction between the complementary nucleobase residues that are attached to them. Furthermore, the simple stereochemical difference between natural rubber and gutta-percha (the cis- and trans-isomers of high molecular weight polyisoprene respectively) results in remarkable differences in their mechanical properties, with gutta-percha being a harder, more brittle and less elastic material than its isomer.
The distinct influence of the stereochemistry in biopolymers on their structure and hence performance makes it reasonable to expect such aspects of synthetic materials to be equally important. Yet this area had received little study, partially a consequence of the challenges of creating large macromolecules with well-defined sequence and stereochemistry at each repeat unit. Clearly, creating materials with controlled stereochemistry in particular has the potential to result in novel materials with complex behaviour and function. STEREOPOL was inspired by nature to design polymers with exquisite structural control in which the behaviour and properties of the resultant materials were dependent on their stereochemistry. The aim was to use these features to unlock a new parameter in materials design - one that is increasingly important in designing polymers that come from sustainable resources that are often rich in stereochemistry. Thus, the objectives of stereopol were two fold (1) to identify better methods to make polymers with high levels of stereocontrol through simple caalytic methods and (2) to explore how stereochemistry influenced the polymer properties, both in bulk and when interacting in solution phase self assembled particles.
The project was overall highly successful and has led to the discovery of improved routes for polymer synthesis as well as the understanding of how to use stereochemistry to manipulate bulk properties and self assembles particle rearrangements. Many of these represent 'firsts' and have accordingly been published in high impact journals.
