Truly Biodegradable Plastic That Could End Ocean Waste
Imagine a shopping bag with the strength of Kevlar® but the biodegradability of whatever’s sitting at the bottom of your crisper.
Year 2020 marks 100 years of modern plastic and an undesirable environmental impact, but with the right chemistry, our old love affair with plastics could be reignited by new research into intelligent polymers that break down on command.
Dr Hendrik Frisch from QUT’s Soft Matter Laboratory is developing an innovative technique to make tailored, remotely controllable plastics and other polymers.
“Many current biodegradable shopping bags still have a very limited biodegradability under real world conditions, especially in marine environments,” Frisch said.
“Our research goal is to produce fully biodegradable plastics so even microplastics are recognised by microorganisms as food.”
Frisch’s research will combine the radical polymerisation method used to make plastics with the natural building blocks of peptides to create a new class of high-end hybrid polymers.
The new polymerization technique would be compatible with today’s polymer production methods and thus contribute to a move towards more sustainable plastic materials, according to Frisch.
“Polymer chains in plastics — whether that’s a plastic bag or takeaway cup — are made up of really long linear chains we call the polymer backbone.
“For most polymers it is a carbon backbone that brings them together. We know how to attach natural building blocks to the sides of these carbon backbones but the backbone itself doesn’t break down.
“That is the reason a polystyrene cup thrown into the ocean will stay there for a very long time.
“It has a molecular structure that doesn’t exist in nature, which is why there are no enzymes or natural biological building blocks that can break it down.”
Hybrid molecules recognised by nature
Frisch and his team aim to incorporate selected natural peptides into the carbon backbone of polymer molecules to control the properties of the resulting polymer-peptide hybrid materials.
“The molecule would assemble or disassemble in response to its chemical or biological environment.
“That will allow us, for instance, to translate the degradability of natural building blocks into plastic materials.
“If plastic becomes readily degradable, we will make great steps towards fighting plastic pollution, particularly in marine environments which is one of the greatest threats to the future of our planet.”
Other customisable functions
Seemingly contradictive to degradability, the ability to insert the natural building blocks into synthetic polymer also holds potential for the design of robust materials.
“By embedding peptides that strongly interact or stick to each other, like spider silk, we can control the interactions between different polymer chains,” Frisch said.
“Specific peptides within spider silk make it a highly organised and robust structure, offering strength and extensibility beyond most man-made fibres.
“If combined with the right peptide sequence and synthetic polymer, we could mimic that performance.
“Such interactions between polymer chains are key to the function of high-performance polymers used for armour and aerospace research, such as Kevlar® and Technora®.”
The possibility to tailor polymeric materials towards endurance, triggered mechanical transformation and degradability is extremely promising for industrial and medical applications, according to Frisch.
“We could design materials where we use external stimuli, like pH levels, to turn toughness, endurance, degradability or other features on or off.
“What I hope for is to tailor hybrid materials in such a way we can make things with a biological use — like implants that have natural sequences recognised by the body.
“The body’s responses to foreign material, like inflammation and other immune responses, can lead to implant rejection.
“If we can introduce specific natural peptide sequences into the coating of implants, the body could recognise the hybrid materials and prevent unwanted responses.”
Materials with natural sequences recognised by nature would also provide an opportunity to establish completely new manufacturing processes.
“There are some manufacturers of high-performance polymers in Australia, but the production of intelligent polymers would be a completely new stream of manufacturing,” Frisch said.
Frisch received an ARC DECRA Fellowship in 2020 for his research project — Programming Polymer Function via Ring-opening Polymerisation of Peptides.
Bringing this new class of polymers into action, he will spend the next three years exploring how the embedded peptide sequences can be programmed but expects to have proof of principle results within 1–1.5 years.
Strong backing
Frisch is affiliated with QUT’s Centre for Materials Science and School of Chemistry and Physics. He and his team are embedded in QUT’s Soft Matter Laboratory and are mentored and sponsored by ARC Laureate Fellow Professor Christopher Barner-Kowollik and his group.
Based on QUT’s re-energised research agenda, initiating strong new independent research streams, while being embedded in a world-leading research group, is a powerful blueprint for the development of highly innovative and successful early career researchers that QUT seeks to adapt across its research endeavours.
Frisch will collaborate with other experts from QUT’s chemistry and physics research community, including those within the Central Analytic Research Facility (CARF).
To analyse the microstructures of the materials, he will also draw on expertise from QUT’s Inorganic Nanomaterials Laboratory led by QUT’s ARC Laureate Fellow Professor Dmitri Golberg.
More information
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