Description du sujet de thèse

The PhD student will aim to develop highly polar bio-based polymers, specifically poly(hydroxyurethane)s (PHUs), with relaxor properties, and integrate them into sustainable energy-harvesting devices. Their structural features will be finely tuned with the controlled introduction of defects to limit interactions, borrowing proven approaches developed for other polymers, including nylons. These changes will then be related to the induced enhancements in relaxor properties through advanced spectroscopic characterization.
Finally, these PHUs will be integrated into energy-harvesting devices using industry-compatible and scalable printing techniques. Their performance across a broad range of applications will be assessed in collaboration with the IMS (Intégration du Matériau au Système) laboratory, thanks to the multidisciplinary and versatile expertise of this project's consortium, composed of internationally recognized leaders in their respective fields.

Contexte de travail

Tackling the climate crisis requires eliminating greenhouse gas emissions, largely by developing sustainable, renewable energy sources. While we are surrounded by abundant renewable energy, the challenge lies in efficiently converting it for use. Energy harvesting conversion is thus crucial for this transition, and advances in materials science, particularly ferroelectric materials, play a key role.
Ferroelectrics enable various energy conversions, such as mechanical and/or thermal to electrical and back. Ferroelectrics, are insulating materials, with high polarization when exposed to electric fields. This originates from their strong dipole interactions, which can be finely tuned through structural defects.
Relaxor ferroelectrics, in which this polarization is reversible, are essential for applications like actuators and electrocaloric coolers. However, current relaxors rely on energy-intensive ceramics, often lead-based. While organic polymers offer cheaper alternatives, their reliance on fluorinated compounds (PFAS) and petroleum-based monomers presents long-term sustainability challenges.

In collaboration with the IMS (Intégration du Matériau au Système) laboratory, the LCPO aims at developing new electroactive polymers to tackle the aforementioned challenges. The LCPO has a vast experience in electroactive polymers. This work includes the precise engineering of the microstructure of these semi-crystalline polymers, alongside in-depth characterization to elucidate their structure-property relationships and enhance their performance in various energy-related applications. These applications include ferroelectric capacitors, piezoelectric energy harvesters, pyroelectric temperature sensors and significant contributions to the development of electrocaloric coolers. The latter involves a patented approach that introduces unsaturation in the backbone of fluorinated polymers, resulting in some of the best electrocaloric performance recorded to date. Additionally, the LCPO has pioneered green chemistry approaches to polymer syntheses and developed processes to create novel bio-based polymers, with built-in features to control their end-of-life.