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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - POLY-WITTIG (Tuning mechanical properties of elastomers with stereocontrolled Ï€-bonds using Wittig chemistry)

Teaser

Summary

\"Rubbers (also referred to as elastomers) are hugely important and widely used in many industries (such as automotive or medical) as a result of their ability to be deformed yet return to their original size and shape upon removal of stress. Owing to these properties and their wide-ranging applicability, a significant body of research has been, and continues to be directed towards the discovery of new materials (or polymers) with specific properties for a wide array of application areas. However, many of our commercially useful elastomers are thermosets (meaning the polymer chains are irreversibly cross-linked together and can\'t be reprocessed) which limits their reusability and thus contributes to the growing environmental concerns associated with non-recyclable and non-degradable materials. In contrast, thermoplastic elastomers (TPEs) are a special class of materials that display elastic behaviour but are not cross-linked (meaning we can remould them into different shapes after use) and they have the potential to be recycled. However, TPEs are more challenging and expensive to produce than traditional rubbers, thus making TPEs suitable for only specialty applications. Thus, there exists a need to develop more environmentally friendly (reusable) elastomers that are easy to make and inexpensive to produce.

The main objective of this action was to mimic the properties of the specialty elastomers (TPEs) in a material that had a more simple chemical composition and was thus easier to produce. We sought to borrow concepts learned from \"\"natural\"\" elastomers in order to achieve this. In particular, the strength and stretchability of natural elastomers, e.g. those coming from Rubber or Gutta Percha Trees, are known to change depending upon the orientation of chemical bonds in the polymer. However, this strategy has not been used to change properties of synthetic (produced in the lab) elastomers despite the obvious potential advantages. This is primarily because of the inherent challenges associated with controlling the orientation of the chemcial bonds in polymers i.e. nature is much better at this than we are as chemists. However, in this action, we used a straightforward method to make our polymers that also provided us with control over the orientation of the chemical bonds; this allowed us to change our material properties on demand. More importantly, these materials were elastic but they were not thermosets which meant that we could recycle them into whatever form we would like multiple times over. This would be analogous to taking a car tire and remoulding it into a shoe after its usefulness as a tire was exhausted.

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Work performed

The bulk of the research was directed toward preparing polymers with new chemical compositions. Importantly, the compositions (with changeable chemical bond orientation) we were targeting were only accessible by using the method that we developed in this project. After making many new materials, we tested the thermomechanical properties (i.e. stiffness, hardness, flexibility, elasticity, etc) of each one. In many instances we were able to produce materials that displayed elasticity without cross-linking the chemical bonds which was a key aim for the project. Furthermore, the polymers displayed changeable properties that were dependent on the relative orientation of the chemical bonds. For example, when we made polymers with bonds oriented one way, the materials were very tough, but if we changed the orientation we could make them more stretchable.

Concerning dissemination and impact, there are several scientific manuscripts in various stages of publication that have been produced from this project. The researcher created a twitter account (https://twitter.com/JoshWorchPhD) in order to disseminate and discuss the research with the larger science community and general public. A laboratory outreach video for students featuring the synthesis and testing of elastomeric, degradable materials was also produced by the researcher (https://www.youtube.com/watch?v=aZkgPAAkXkU&t=2s). Finally, numerous outreach events (at schools, museums and community festivals) focusing on degradable plastics and elastomers were delivered throughout the duration of the project. Together, these activities highlight the high impact of the action.

Final results

Most polymers that are either not thermosets or composite in nature (i.e. formed from several combined materials) are not elastic making the property of elasticity a relatively rare phenomenon. A major impact of the action was the creation of a simpler elastomer (in regards to the chemical composition) that could easily be changed to be tougher and/or more elastic on demand. This represents a major advancement in the development of recyclable, inexpensive, and adaptive rubber-like materials. Applications for these materials can be envisioned in many industries and they should be particularly suitable for automotive, electronics and medicine (such as a cartilage or skin mimicking material). Finally, we even designed some of the polymers to be degradable which should alleviate some of the environmental problems associated with our irresponsible use of plastics and rubbers.