Periodic Reporting for period 2 - CiMaC (Circular Thermoset Materials: How to exploit Precision Engineered Macromolecules in their Bottom-up Design?)
Berichtszeitraum: 2023-05-01 bis 2024-10-31
Thermoset recycling is one of the holy grails of the plastic industry, which is currently facing increasingly stringent international regulations to stimulate finding technological solutions towards the sustainable use of plastics.
While displaying superior properties compared to thermoplastic polymers, thermosets – which have an annual global production of 60 million tons and are for example used in windmill blades and adhesives – represent a major worldwide challenge. Their crosslinked structure presents many hurdles when it comes to recycling and responding to Europe’s desire for a circular economy.
The overarching objective of the CiMaC-program is to propose ground-breaking solutions to the major shortcomings of Covalent Adaptable Networks (CANs), being their long-term dimensional stability and (re)processing ability when using industrial techniques, thereby enabling the urgent uptake of these revolutionary thermosets from academic research to an industrial level. Covalent dynamic chemistry should ideally enable a combination of the bulk processing possible when using thermoplastics and the high durability of thermosets.
The unique concept to tackle this ultimate goal starts from the recognized expertise of my Polymer Chemistry Research group in precision macromolecular chemistry. The central idea is that the use of precisely engineered macromolecules as CAN-precursors will allow an unprecedented regulation of the resulting CAN properties through control over different molecular parameters. In this project, innovative synthetic protocols/methodologies will be implemented for both the development of robust, on-demand debondable adhesives, as well as for providing the first up-scalable extrudable thermoset materials.
While displaying superior properties compared to thermoplastic polymers, thermosets – which have an annual global production of 60 million tons and are for example used in windmill blades and adhesives – represent a major worldwide challenge. Their crosslinked structure presents many hurdles when it comes to recycling and responding to Europe’s desire for a circular economy.
The overarching objective of the CiMaC-program is to propose ground-breaking solutions to the major shortcomings of Covalent Adaptable Networks (CANs), being their long-term dimensional stability and (re)processing ability when using industrial techniques, thereby enabling the urgent uptake of these revolutionary thermosets from academic research to an industrial level. Covalent dynamic chemistry should ideally enable a combination of the bulk processing possible when using thermoplastics and the high durability of thermosets.
The unique concept to tackle this ultimate goal starts from the recognized expertise of my Polymer Chemistry Research group in precision macromolecular chemistry. The central idea is that the use of precisely engineered macromolecules as CAN-precursors will allow an unprecedented regulation of the resulting CAN properties through control over different molecular parameters. In this project, innovative synthetic protocols/methodologies will be implemented for both the development of robust, on-demand debondable adhesives, as well as for providing the first up-scalable extrudable thermoset materials.
In comparison to what I applied for, two additional new chemical platforms have been developed for the synthesis of sequence-defined oligomers (Soete et al., Polym. Chem 2022 and De Franceschi et al., Polym. Chem. 2022).
The second platform - based on the use of a uniform soluble support - allows for the first time the preparation of around 15 gram batches of sequence-defined macromolecules (vs mg-scale using solid supports previously), with potential for much higher scales applicable in a material context (cf. subproject 1).
The methodology, initially developed based on a thiolactone chemistry-based protocol, has been further extended to the formation of oligoamides with different functional groups, either at the end of the chain or as side-chains. The functional end groups were successfully used as crosslinking point to form polymeric networks via thiol-ene chemistry (De Franceschi et al., Chem. Sci. 2024), which is one of the first reports world-wide in which crosslinked materials based on sequence-defined macromolecules has been reported (related to subproject 3).
In parallel, Initial investigations have been performed in order to better understand fundamental aspects in covalent adaptable networks such as the correlation between the composition of a reactive polymer segment to the rate of network rearrangement (Van Lijsebetten et al. Chem. Sci 2022), how to obtain reprocessable thermoset materials with minimal deformation/creep (Van Lijsebetten et al. Angew. Chem., 2022), the development and screening of other dynamic chemistries such as the beta-amino amide approach (Nguyen et al. Polym. Chem. 2024) or the Aza-Michael chemistry (Nguyen et al. Macromolecules 2024) etc (subproject 3). These studies were completed by the first exploration how to control the thermal debonding of epoxy-based adhesives (Van Lijsebetten et al. Adv. Mater. 2023), which is related to one of the deliverables in subproject 4.
In parallel, we collaborate – as planned – with the research group of Prof. Ivo Vankelecom with strong membrane expertise, for providing an alternative pathway making use of nanofiltration membranes for the upscaling of sequence defined structures (Subproject 2). This is planned to be reported in the upcoming 6 months.
In summary, with regard to the 8 milestones mentioned in the application, 5 have been at least partially tackled and published/disseminated (M1.1 M1.2 M2.2 M3.2 M4.1) while ongoing research about the other milestones is in full progress and/or planned in the near future.
The second platform - based on the use of a uniform soluble support - allows for the first time the preparation of around 15 gram batches of sequence-defined macromolecules (vs mg-scale using solid supports previously), with potential for much higher scales applicable in a material context (cf. subproject 1).
The methodology, initially developed based on a thiolactone chemistry-based protocol, has been further extended to the formation of oligoamides with different functional groups, either at the end of the chain or as side-chains. The functional end groups were successfully used as crosslinking point to form polymeric networks via thiol-ene chemistry (De Franceschi et al., Chem. Sci. 2024), which is one of the first reports world-wide in which crosslinked materials based on sequence-defined macromolecules has been reported (related to subproject 3).
In parallel, Initial investigations have been performed in order to better understand fundamental aspects in covalent adaptable networks such as the correlation between the composition of a reactive polymer segment to the rate of network rearrangement (Van Lijsebetten et al. Chem. Sci 2022), how to obtain reprocessable thermoset materials with minimal deformation/creep (Van Lijsebetten et al. Angew. Chem., 2022), the development and screening of other dynamic chemistries such as the beta-amino amide approach (Nguyen et al. Polym. Chem. 2024) or the Aza-Michael chemistry (Nguyen et al. Macromolecules 2024) etc (subproject 3). These studies were completed by the first exploration how to control the thermal debonding of epoxy-based adhesives (Van Lijsebetten et al. Adv. Mater. 2023), which is related to one of the deliverables in subproject 4.
In parallel, we collaborate – as planned – with the research group of Prof. Ivo Vankelecom with strong membrane expertise, for providing an alternative pathway making use of nanofiltration membranes for the upscaling of sequence defined structures (Subproject 2). This is planned to be reported in the upcoming 6 months.
In summary, with regard to the 8 milestones mentioned in the application, 5 have been at least partially tackled and published/disseminated (M1.1 M1.2 M2.2 M3.2 M4.1) while ongoing research about the other milestones is in full progress and/or planned in the near future.
As highlighted above, much progress beyond the state of the art has been realized so far.
These include the high-scale synthesis of sequence-defined polymers. Besides the first published up-scalable protocol (vide supra), another one dealing with oligourethanes will be published soon, for which a scale above 50 grams has been reached. To our knowledge, this would be the highest scale ever reported for sequence defined macromolecules, i.e. everything is ready for the implementation in covalent adaptable networks and large scale material characterization.
Also, the development of a protocol towards precise, thermally resilient oligoamides is reached and is currently further explored for the creation of unique molecular tags to be applied in commodity plastics (PET, PA, PP,…). We are preparing a patent application and an ERC-PoC proposal about the industrial implementation of this protocol (by September 2024).
The same straightforward chemistry scheme allowed for the preparation of telechelic sequence-defined oligoamide crosslinkers that are being investigated in a material context with the aim to obtain an unprecedented fine-tuning of material properties and recycling for crosslinked polymeric materials.
In parallel, the research group also pioneered a new dynamic chemistry platform, referred to as the beta-amino amide approach (Polymer Chemistry, 2023). This protocol has recently been selected for the synthesis of a new generation of CANs based on precision oligoamides, which should become the first reported study in which sequence-defined structures have contributed to the development of reprocessable thermosets (one of main project goals).
Finally, research towards on-demand debondable adhesives has been performed and a number of promising results with debondable structural epoxy adhesives have been obtained in that direction (Adv. Mater. 2023).
These include the high-scale synthesis of sequence-defined polymers. Besides the first published up-scalable protocol (vide supra), another one dealing with oligourethanes will be published soon, for which a scale above 50 grams has been reached. To our knowledge, this would be the highest scale ever reported for sequence defined macromolecules, i.e. everything is ready for the implementation in covalent adaptable networks and large scale material characterization.
Also, the development of a protocol towards precise, thermally resilient oligoamides is reached and is currently further explored for the creation of unique molecular tags to be applied in commodity plastics (PET, PA, PP,…). We are preparing a patent application and an ERC-PoC proposal about the industrial implementation of this protocol (by September 2024).
The same straightforward chemistry scheme allowed for the preparation of telechelic sequence-defined oligoamide crosslinkers that are being investigated in a material context with the aim to obtain an unprecedented fine-tuning of material properties and recycling for crosslinked polymeric materials.
In parallel, the research group also pioneered a new dynamic chemistry platform, referred to as the beta-amino amide approach (Polymer Chemistry, 2023). This protocol has recently been selected for the synthesis of a new generation of CANs based on precision oligoamides, which should become the first reported study in which sequence-defined structures have contributed to the development of reprocessable thermosets (one of main project goals).
Finally, research towards on-demand debondable adhesives has been performed and a number of promising results with debondable structural epoxy adhesives have been obtained in that direction (Adv. Mater. 2023).