Polycarbonates are all around us: in your plastic drinks bottle; the lenses of your glasses; and the scratch-resistant coating on your phones CDs and DVDs. But they are made from crude oil, a finite resource, making them unsustainable.
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The plastics of the future could be sustainable, made from sugar and carbon dioxide, and be biodegradable say Academics from the University of Bath.
A new process to synthesize alternative polycarbonates using carbon dioxide and sugar, at low pressure and room temperature has been developed by researchers from the Centre for Sustainable Chemical Technologies (CSCT) at the University. Their method of producing plastics is cheaper and safer than current approaches, which use BPA or bisphenol A - a synthetic chemical that is banned from use in baby bottles, and has been shown to seep from containers into food and beverages – and phosgene, a colourless gas used as a chemical weapon in World War I.
Writing in Polymer Chemistry, the Researchers say,“Readily available sugars are a promising inexpensive renewable alternative to fossil-based feedstocks, owing to their natural origin as well as wide structural and stereochemical diversity. As such synthetic carbohydrate-based materials can give properties comparable to industrial polymers as well as enhanced biodegradability and biocompatibility characteristics, and have the potential to mimic biological materials and functions.”
The resulting polycarbonate plastic is comparable to its petrochemical counterpart in that it is strong, transparent and scratch-resistant. It is also biodegradable and can be converted back into carbon dioxide and sugar using enzymes found in soil bacteria.
The new type of BPA-free plastic could replace traditional polycarbonates in baby bottles and food containers, and since it is biocompatible, it could find uses in medical implants or scaffolds for growing replacement organs for transplants.
With an ever-growing population, there is an increasing demand for plastics. This new plastic is a renewable alternative to fossil-fuel based polymers, potentially inexpensive, and, because it is biodegradable, will not contribute to growing ocean and landfill waste. Our process uses carbon dioxide instead of the highly toxic chemical phosgene, and produces a plastic that is free from BPA, so not only is the plastic safer, but the manufacture process is cleaner too.
Dr Antoine Buchard, Whorrod Research Fellow in the Department of Chemistry
Nature provided some inspiration as Buchard and his team at the Centre for Sustainable Chemical Technologies used thymidine – a sugar found in DNA – as a building block upon which to create their novel polycarbonate plastic.
“Thymidine is one of the units that makes up DNA. Because it is already present in the body, it means this plastic will be bio-compatible and can be used safely for tissue engineering applications,” explained PhD student, Georgina Gregory. “The properties of this new plastic can be fine-tuned by tweaking the chemical structure – for example we can make the plastic positively charged so that cells can stick to it, making it useful as a scaffold for tissue engineering.”
Work has already started on a tissue engineering project in collaboration with Dr Ram Sharma from Chemical Engineering, part of the CSCT. Their current work has been published in a series of articles in Polymer Chemistry and Macromolecules.
The Researchers have also begun to look at using other sugars in the process, such as ribose – a simple sugar – and mannose, a sugar monomer.
Dr Buchard added: “Chemists have 100 years’ experience with using petrochemicals as a raw material so we need to start again using renewable feedstocks like sugars as a base for synthetic but sustainable materials. Its early days, but the future looks promising.”
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