Combining controlled polymerisation and 'click' chemistry
Convenient and efficient ways to make new macromolecular structures are now possible thanks to an innovative synthesis of a new functional polymer by UK researchers.
Using living radical polymerisation (LRP) to make a linear chain, David Haddleton and colleagues at the University of Warwick, made poly(methyl methacrylate) with an azide group at one end of the polymer chain.
A copper(i) catalyst is used to make the azide end of Haddleton’s polymer react with a molecule containing an alkyne group. This forms a five-membered triazole group. The reaction, known as cycloaddition, is an appealing aspect of the synthesis. It is a ’click’ reaction: a synthetically easy and efficient transformation with characteristics such as high yields and good selectivity in mild conditions. Efficient reactions are essential at this stage of the synthesis to ensure the chain ends are successfully modified.
Haddleton’s synthesis design has other attractive features. The polymerisation step and the successive reaction to modify the chain ends are catalysed by the same reagent and can be done in the same reactor. This ’one-pot’ approach, possible only because the chemistry is compatible, means there is no need to isolate chemical intermediates.
LRP is renowned for its ability to control the molecular architecture of a polymer. For example, when LRP is used a functional group can be located exclusively at one end of the polymer chain.
The catalysed reactions combine effectively because they are robust and can tolerate many functional groups, including water. The researchers show the method’s versatility by attaching dye molecules to one end of the polymer chain.
In future, this one-pot approach could be used ’to conjugate a range of polymers to proteins, enzymes and surfaces,’ said Haddelton.