PhD thesis: Nanoparticle sIze and surface Chemistry Effects on the dynamic behavior of nano-reinforced polymers: a mechanochemical tuning for more durable materials NICE-LEEGO

  • Compiègne, Oise
  • CDD
  • Temps-plein
  • Il y a 1 mois
Offer DescriptionThe difficulty and the uncertainty in using polymeric materials in crucial components are partly because the nature of microdamage under dynamic loading is not fully understood1. The difficulty is mostly related to the complex hierarchical structure, which distinguishes polymers and nano-reinforced polymers from other materials.
Unlike composite materials, nano-composite behavior depends on the size of the reinforced nanoparticles (NPs). By reducing NP size, we drastically increase the interfacial interaction between the NPs and the polymeric matrix2. Interfacial interaction through hydrogen bonding in the case of PEG-Silica systems turns out to be the driving parameter of the material damage during impact. The loss of the hydrogen bonds induces rotation and counter-rotation of the NP which in turn induces a material shear flow between NP leading to the early initiation of cavitation1. In this case, we did not have any control over the density of the hydrogen bonding energy. In this proposal, we target to work on binary systems where the hydrogen bonding density can be controlled. Therefore, we can tune the system to cover a wider range of configurations from weak to strong interfacial interaction. All this is to answer one fundamental question: Does weaker or stronger interfacial interaction delay or accelerate material damage under high strain rate loading?
The main questions we would like to answer are:
1- How does the hydrogen bonding between the NP and the matrix modulate the material's performance under high strain rate loading, and how can this be monitored?
2- Could we use the grafted chain length and nanoparticle size as leverage to go beyond the limit and enhance the already optimized properties?
The interfacial interaction between the NPs and the surrounding matrix is a key parameter that governs the nano-composite properties. As polymer matrix and surface modifier, poly(2-hydroxyethyl methacrylate) pHEMA will be used due to its peculiar structure carrying a hydroxyl as well as an ester group both capable of H-bond interaction. Compared to pMMA, which is only capable of accepting H-bonds via its ester group, pHEMA will then offer the opportunity of raising the interaction with silica, for a possibly more efficient energy dissipation via the complex interplay of H-bond formation-breaking-exchange.
The project will thus deal with comparing the effect of size (ex 11 nm silica versus 70 nm silica) and surface functionalization (i.e. base silica versus pHEMA-grafted silica) of silica NPs used as fillers in pHEMA/SiO2 nanocomposites. This silica will also be used for surface functionalization, following a conventional protocol consisting in (1) surface functionalization with APDMES, (2) coupling of an NHS-activated RAFT agent (3) RAFT polymerization of HEMA as reported for instance by Benicewicz and co-workers34. Using RAFT polymerization will also allow controlling the degree of polymerization (DP) of pHEMA, thus tuning the molecular weight (MW) of the grafted chains. Bare silica as well as pHEMA-grafted silica will then be dispersed in a pHEMA matrix by either electrospinning or solvent casting. A full set of characterization techniques will be available to explore the materials behavior at the different length scales: XRD, FTIR, DLS for materials microstructure, and Hopkinson Split Pressure Bar will be used to investigate the dynamic response of the obtained material. Fracture profile analysis after damage will be investigated in order to correlate the NP-Matrix interfacial interaction with the dynamic response of the material.RequirementsResearch Field Engineering » Materials engineering Education Level Master Degree or equivalentResearch Field Chemistry » Computational chemistry Education Level Master Degree or equivalentSkills/QualificationsMaster of science in materials science, polymer chemistry, computational chemistryLanguages ENGLISH Level GoodResearch Field Chemistry » Computational chemistryEngineering » Materials engineeringInternal Application form(s) neededThesis proposal - Fahmi Bedoui - Karsten Haupt .pdfEnglish(278.6 KB - PDF)Additional InformationSelection processTo apply, please send CV, motivation letter and two recommendation letters to Professor Fahmi Bedoui atWebsite for additional job detailsWork Location(s)Number of offers available 1 Company/Institute Université de technologie de Compiègne - UTC Country France State/Province Centre de recherche de Royallieu, CS 60319 City Compiègne Postal Code 60203 Street Rue du docteur SchweitzerWhere to apply E-mailfahmi.bedoui@utc.frContact CityCOMPIEGNE WebsiteStreetCentre de Recherches Postal Code60203 E-Mailsalima.aaras-andaloussi@utc.frSTATUS: EXPIRED

EURAXESS