Synthesis of polymer/graphene hybrid materials
Professor Per Zetterlund is the Co-Director of the Centre for Advanced Macromolecular Design, a world-renowned centre for polymer synthesis and characterisation. His research focuses on the synthesis of polymeric nanoparticles for a range of applications, and most recently he has developed a new technique using graphene, one of science’s most up-and-coming new materials.
What’s your big discovery?
We have developed a method of taking one of today’s most exciting new materials – graphene – and combined it with emulsion polymerisation, a widely used technology that’s been around since WWII.
We have discovered that when you combine the two, you can achieve interesting results in terms of material synthesis and particle synthesis, with applications ranging from advanced materials all the way to regenerative medicine.
Why have polymer and graphene nanocomposites been attracting such significant attention recently?
Polymers are amazing materials, but do have some drawbacks, as in sometimes the mechanical properties are not what we would wish them to be. Also, most polymers do not conduct electricity.
Graphene is a fascinating material in the sense that it has impressive mechanical properties, and it also has electrical conductivity, so it basically ticks both of those boxes. By incorporating a small amount of graphene into a polymeric material you can substantially improve its properties, that’s what’s really exciting about it.
We’re trying to create hybrid materials that comprise approximately 95% by weight polymer and 5% (or less) per weight graphene. If we can do this in the right way, we will be able to impart much superior mechanical properties to the materials, as well as electrical conductivity.
What might these materials be used for?
There are many implications for developing advanced materials, but one high-tech application we are exploring with the University of Western Australia is looking at preparing electrically conductive polymer particles and films. It is believed that our materials exhibit improved biocompatibility, i.e. the human body would not reject these materials, so we are trying to see how we can use them to stimulate cell growth, which has applications in regenerative medicine.
We have developed a method of taking one of today’s most exciting new materials – – graphene – and combined it with emulsion polymerisation, a widely used technology that’s been around since WWII
Professor Per Zetterlund, Co-Director for the Centre for Advanced Macromolecular Design, UNSW Chemical Engineering
You faced some challenges using pristine graphene. How did you get around them?
The main challenge in preparing composite materials of polymer and graphene is that there tends to be an issue with poor compatibility. When you mix them, they tend to stack as they separate so you don’t have an even dispersion of the graphene throughout the material.
To counter this, we developed a technique using graphene oxide nanosheets as surfactants in miniemulsion polymerisation. The nanosheets stabilise the interface of the monomer droplets, and subsequent radical polymerisation within these droplets result in the formation of nanoscale particles that are coated with graphene oxide sheets. This prevents large scale agglomeration, or restacking of the sheets, thereby giving a homogeneous distribution across the material.
There is a twofold reason for using graphene oxide as the surfactant. Surfactants play a crucial role in traditional emulsion polymerisation, but conventional surfactants have a negative impact on the final properties of the material. Incorporating graphene oxide not only prevents that negative impact but improves the final properties and adds electrical conductivity.
It’s important to note, however, that graphene oxide does not conduct electricity, so an additional step is required to reduce the graphene oxide to its electrically conductive counterpart “reduced graphene oxide.”
So, what’s next?
There is the regenerative medicine aspect, as I’ve already mentioned, but the other key direction is more fundamental. We want to understand what goes on at the molecular level, so we can use that understanding to develop useful materials. Ultimately, I want to explore scalable and energy-friendly, easy-to-implement methods to synthesise electrically conductive polymer films from simple and relatively cheap monomers.
Written by: Penny Jones