PhD thesis (M/F) in Chemistry of Materials

Job Description

Thesis Subject

Context: Nacre – an arrangement of Aragonite platelets with an organic matrix in a “brick-and-mortar” structure – is one of many naturally textured composites whose organisation induces extraordinary optical (iridescence) and mechanical (toughening mechanisms) properties. This has raised the interest of scientists in the formation of biomimicking composites, also known as artificial nacres. For example, alumina platelets (Al2O3) and poly(methyl methacrylate) (PMMA) were organised via freeze-casting followed by sintering and polymer infiltration. This multi-step approach can result in incomplete infiltration of the polymer and hence critical defects in the structure. Several examples of thin films are also possible, but the method is not easily scalable for a bulk material. To form a “bulk” nacre-like material, additive manufacturing (AM, also called 3D-printing) seems the most promising, as the shear induced during printing can orient the particles while forming the material. Yet, so far, the research is hindered by the limited amount of bricks available, most research focusing on naturally occurring anisotropic particles (clays, aragonite) or particles whose morphologies can be directly inherited from their inner crystal structure (alumina). Further, works on AM are still required to finely tune the bricks-to-mortar ratio within the material.
Goal: At ICGM, we have developed an approach to design anisotropic silica or zirconia particles, using templating agents to control their morphology.1 Further, by careful surface modification of the particles, we can add a polymer shell around these anisotropic cores via radical polymerisation, to form well-defined core-shell inorganic-organic particles that can be used to form artificial nacres.2 The aim of this PhD is to adjust and optimise the synthesis of the inorganic core and organic shell, and explore the use of these particles to form textured materials, i.e. artificial nacres, via additive manufacturing.
Work Program: The PhD project is focused on the 3 following axes.
1/ Synthesis of the core-shell particles: The anisotropic core, made of silica or zirconia, is prepared using sol-gel chemistry or thermic decomposition in presence of a templating agent. If the synthesis of silica is now well-established (platelets, short/long rods or even donuts), for zirconia we managed to obtain needles or sheet-like particles. The organic shell is obtained by radical polymerisation. For silica, we will polymerise poly(N-isopropylacrylamide) (PNIPAM), a thermo-responsive polymer to design artificial nacres with thermo-modulated optical properties. For zirconia, we will polymerise poly(methyl methacrylate) (PMMA) to form an artificial nacre with relevant mechanical properties.
2/ Inks preparation: After the core-shell particles preparation, the PhD candidate will study their behaviour in aqueous suspension, probing the effect of the shell thickness or the presence of additives in the particles dispersability in water. He/She will notably probe in detail the rheological properties of the particles, such as the viscosity upon shear or small amplitude oscillatory measurements to find suitable conditions for using these suspensions for printing. Among the additives explored, rheology modifiers (surfactants, microgels) will help tune the rheological properties, while monomers, cross-linkers and photoinitiators will be added to allow further photocrosslinking of the shells during printing.
3/ Print an artificial nacre: We will explore during the PhD two printing approaches to obtain the material: Direct Ink Writing (DIW), an extrusion-based technique to form the material filament-by-filament, and Digital Light Processing (DLP), a stereolithography-based technique to form the material layer-by-layer by photopolymerisation. In both techniques, shear will be used to orient the particles during printing. Collaboration with DISAT (Polytechnic Turin) will allow doing DLP under shear.3 The PhD will notably characterise the structural properties of the materials, i.e. the bricks orientation, but also the optical properties using UV-Vis spectroscopy and the mechanical properties via collaboration with MatéIS in Lyon.

PhD profile: The PhD candidate will be in charge of:
- The synthesis of the inorganic core and the polymer shell using sol-gel chemistry and radical polymerisation
- The study of the structural properties of the core-shell particles
- The formulation of inks for printing, with an accent on studying the rheological properties of the inks
- The printing of the materials, first on thin layers before printing bulk 3D materials
- The characterization of the structural, optical and mechanical properties of the materials.
PhD profiles include students with a Master 2 degree in Chemistry of Materials, Material engineering or Soft Matter. Know-how on sol-gel chemistry, or polymerisation strategies or additive manufacturing are welcome. The project is purposefully “large” for a PhD, to allow the candidate to explore the directions that he/she finds interesting (optimisation of core-shell particles synthesis, additive manufacturing of nacres, properties of the materials). Know-how in material characterisation techniques (XRD, TGA, DLS/Laser granulometry, electron microscopy) and/or in rheology of suspensions is required. Previous experience in additive manufacturing is a plus. Motivated and independent candidates are welcome. A very good English level (oral, written) as well as strong communication skills are required.
The PhD candidate will work at the Institut Charles Gerhardt de Montpellier (ICGM), within the D3 department dedicated to Porous and Hybrid materials and will be supervised by Dr. Julien Schmitt. Candidates should be highly motivated and willing to work in an international environment.

Your Work Environment

Balard Chemistry Building, within the Institut Charles Gerhardt de Montpellier. The PhD project will take place within D3 department (Porous and Hybrid Materials). The chemistry laboratories are equipped for the synthesis of inorganic materials, radical polymerisation, material characterisation (in the laboratory or within the UAR PAC Chimie Balard, within the same building. Collaborations with academic partners (Turin, Italy; Lyon, France).
References
(1) Schmitt, J.; Kjellman, T.; Kwaśniewski, P.; Meneau, F.; Pedersen, J. S.; Edler, K. J.; Rennie, A. R.; Alfredsson, V.; Impéror-Clerc, M. Outset of the Morphology of Nanostructured Silica Particles during Nucleation Followed by Ultrasmall-Angle X-Ray Scattering. Langmuir 2016, 32 (20), 5162–5172. https://doi.org/10.1021/acs.langmuir.6b00572.
(2) Schmitt, J.; Hartwig, C.; Crassous, J. J.; Mihut, A. M.; Schurtenberger, P.; Alfredsson, V. Anisotropic Mesoporous Silica/Microgel Core–Shell Responsive Particles. RSC Adv. 2020, 10 (42), 25393–25401. https://doi.org/10.1039/D0RA02278K.
(3) Bertero, A.; Schmitt, J.; Kaper, H.; Coppola, B.; Palmero, P.; Tulliani, J.-M. MOFs Functionalization of 3D Printed Mullite Complex Architectures for CO2 Capture. Applied Materials Today 2024, 40, 102407. https://doi.org/10.1016/j.apmt.2024.102407.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

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