Polymers for a Sustainable Future

Abstract

Over the last century, polymers are everywhere we look, have transformed our daily lives, and gained global acceptance. From the clothes we wear, to the utensils used by scientists around the world in labs, the current rate of activities and standard of living couldn't be maintained without polymers and plastics in all shapes or forms. The majority of the polymers we consume everyday are still obtained from fossil fuels and the rate, but also efficacy, with which these polymers are produced in terms of low waste production and low energy consumption is truly astonishing and highlights the power of continuous refinement and improvement of these extraction and fractionation processes. In addition to other factors, this efficiency, which translates into low costs, is still a high hurdle for bio-based, (bio)degradable, or more sustainable polymer alternatives to conquer the market. Nevertheless, a multitude of start-ups and several pilot and full-sized plants have been built solely dedicated to the production of bio-based and bio-degradable polymers on an industrial scale. These steps toward more sustainable polymers have been underpinned by governments or governing bodies emphasising the need for a sustainable future. Whether these are the sustainable development goals of the UN,[1] the pledge for carbon neutrality within the next 20 years, as stated by China or New Zealand, amongst others, or the action plan toward a circular economy as put forward by the European Union,[2] all have provided guidelines along with tight restrictions as to what future economies and communities will look like. In addition to these top-down regulations, the changing perception of plastics within the public provides a customer-based incentive for companies to provide sustainable solutions to the general public. All of these have heavily impacted the direction of polymer science over the last ten years with a five-fold increase in papers with the concepts of “polymer” and “sustainability”. However, care must be taken as to what really constitutes a sustainable polymer. “Sustainability” is not an absolute or hard description but rather exists on a continuum describing the source of starting materials, the process, and end-of-life issues, etc. Importantly, it is always described as a comparison to other processes, whether established or on a lab scale, and must in general be viewed through the lens of life cycle analysis. Recent publications give insights into how this can be achieved for polymers.[3-5] While the initial focus of the field was on obtaining renewable and sustainable building blocks in an efficient manner using catalyzed synthetic routes, the field has broadened to constructing more complex materials systems from these renewable/sustainable building blocks, controlling their architecture more closely, as well as looking at the whole life cycle of the polymeric material. This special issue in Macromolecular Rapid Communications tries to give a glimpse of what “polymers for a sustainable future” could look like and shows that this systemic change is being addressed by leading experts all over the world. The majority of publications within this special issue look at the production of polymeric materials using natural resources such as lignin, cellulose, and chitin. These poorly soluble, abundant building blocks provided by nature itself, are still difficult to process and the transformation into monomers and polymers is still a real challenge. Based on cellulose, Yang, Heinze, Wang, and co-workers created paper-based wearable electronics with high adhesion, reflectivity, and conductivity which are comparable to fossil-fuel based alternatives (2000499). The communication by Zhu, Shi, and co-workers investigates the use of chitosan and agarose in hydrogels to trigger actuation and shape deformation by water and/or heat which could provide sustainable actuators for soft robotics applications (2000342). Further advanced applications are explored