New family of bioplastics offers property retention as well as degradability and recyclability
Last year I reported on the development of a type of polyester biomaterial, designed for use in soft tissue repair or flexible bioelectronics, that a team of researchers from the University of Birmingham in the UK UK and Duke University in the US had managed to “tune” it to allow for both the rate at which it degrades in the body and its mechanical properties.
We were recently contacted about another collaborative development between the two universities, this one involving a research team that created a new family of sustainably sourced polymers that would retain all the same properties as typical thermoplastics, but are mechanically degradable and recyclable.
Photo credit: University of Burmingham
The researchers used raw materials made from sugar to make two new polymers, one stretchy like rubber and the other tough but ductile like most commercial plastics. Specifically, they used isoidide and isomannide compounds as building blocks, both of which are made from sugar alcohols and have a rigid ring of atoms.
The team found that the isoidide-based polymer exhibited similar stiffness and malleability to common plastics and similar strength to engineering resins such as nylon 6. Although isoidide and isomannide differ only in 3D spatial orientation of two bonds, it is known as stereochemistry, the isomannide material was found to have similar strength and toughness, but also showed high elasticity, recovering its shape after deformation.
Also notably, the materials have been shown to retain their excellent mechanical properties after spraying and heat treatment – the usual method of mechanical recycling of plastics.
The researchers used state-of-the-art computer modeling to simulate how polymer chains wrap and interact to produce such different polymer properties. The unique 3D shapes of the sugar derivatives facilitate different movements and interactions of the long chains, causing the huge difference in physical properties observed.
By creating copolymers containing both isoidide and isomannide units, the team discovered that they could control mechanical properties and degradation rates independently of each other. As such, this system would open the door to using the unique forms of sugars to independently tune degradability for a specific use. without significantly change the properties of the material.
The chemical similarity of these bioplastics means that, unlike many of today’s commodity plastics, they can be mixed together to produce materials with comparable or improved properties.
“The ability to blend these polymers together to create useful materials offers a distinct advantage in recycling, which often has to deal with mixed feeds,” said Josh Worch, of Birmingham’s School of Chemistry, and co-author of the research.
Connor Stubbs, also from the Birmingham School of Chemistry, said: “Petroleum-based plastics have been the subject of decades of research, so catching up with them is a huge challenge. We can look to the unique structures and shapes that biology has to offer to create much better plastics with the same breadth of properties that current commercial plastics can offer.”
Matthew Becker, a professor at Duke University, said: “Our results truly demonstrate how stereochemistry can be used as a central theme for designing durable materials with truly unprecedented mechanical properties.”
Professor Andrew Dove, who led the Birmingham research team, said the study really demonstrates what is possible with sustainable plastics. “While we need to do more work to reduce costs and study the potential impact of these materials on the environment, in the long term, it is possible that these types of materials can replace petrochemical-based plastics which do not not readily degrade in the environment.”
A joint patent application has been filed by Birmingham Enterprise University and Duke University. The researchers are now seeking industrial partners interested in licensing the technology.
The study, Sugar Polymers with Degradability and Stereochemical Mechanical Properties, is published in the Journal of the American Chemical Society, and is available at: https://doi.org/10.1021/jacs.1c10278