Post-doctoral position: Solid-state NMR within heterogeneous polymer-based elastomers (Total/Hutchinson & CNRS)

A 24-month post-doctoral position is opened in the framework of a collaborative project between TOTAL/HUTCHINSON and CNRS (ICMPE, East Paris Institute of Chemistry and Materials Science, UMR 7182 CNRS / University Paris-East, Thiais, France). The post-doctoral researcher will develop his / her research activities at the Hutchinson Research Center (Châlette-sur-Loing, France) and at ICMPE (Thiais), in the Department "Complex Polymer Systems". He / she will be co-supervised by Brice Gabrielle (Hutchinson) and Cédric Lorthioir (ICMPE). Hutchinson is a world leader in rubber processing. CNRS is the main governmental research organization in France, involved in all scientific fields.

This project aims at extending the solid-state NMR investigations of the cross-link density, developed at the Hutchinson Research Center for natural rubber in the relaxed state. Two complementary research topics will be addressed in the framework of this post-doctoral stay.

In a first step, we propose to go further in the analysis of the heterogeneity of the cross-link density observed within complex elastomer-based materials. Several kinds of low-field 1H NMR approaches, among which 1H double-quantum NMR measurements, were developed over the last 15 years. These experiments enabled to get a precise description of the network structure for cross-linked elastomers. In particular, a key information that may be derived from these experiments is the distribution of the cross-link density, as reflected by the distribution of the so-called homonuclear dipolar couplings, Dres. Such a distribution is crucial to get a better understanding of the relationships between the network structure and their mechanical behaviour. In the case of a single elastomer with a relatively simple chemical structure, the distribution of Dres may unambiguously be interpreted as resulting from the occurrence of heterogeneities in the cross-link density. The situation is more complex in the case of elastomer-based materials that may be composed of several polymer components, some of them displaying 1H complex macromolecular architectures. Under these conditions, a wide – and sometimes multi-modal – distribution of Dres is detected through low-field 1H NMR measurements and the assignment of such a distribution at a (macro)molecular level may become difficult. In the case of a multi-modal distribution of Dres, information about the nature of the protons involved in the various Dres components of the distribution is particularly relevant since it may avoid erroneous interpretation of the experimental data in terms of heterogeneous cross-linking. However, such an information may be difficult to obtain using low-field and static 1H NMR-based approaches. The aim of the first step of this project is to implement spectroscopic approaches that may allow the origins of the multi-modal feature of the Dres-distribution to be rationalized, in the context of complex polymeric materials. Spectroscopic approaches, based on high-resolution 1H solid-state NMR, will be used.

In the second step of this project, the evolution of the network structure under thermal aging will be investigated. Indeed, the local constraint experienced within multi-component polymer materials is a relevant parameter in order to understand the behaviour of such complex materials under fatigue. To address this point from an experimental point of view, an experimental set-up, aimed at stretching the materials of interest in situ, in the NMR spectrometer, will be designed. Once this instrumental part of the project addressed, we will determine the evolution of the Dres-distribution upon stretching in order to determine the local constraint experienced by each kind of component chains. Though such a stretching device has already been designed in other research groups in Europe, less attention has been paid to the evolution of the chain stretching within strongly heterogeneous (multi-component) materials.

Requirements: Solid educational background and PhD in polymer physics / polymer physical chemistry or, alternatively, a previous experience in solid-state NMR.

Status: Two-year contract

Desired start date: June/September 2017

Laboratories / research centers:

HUTCHINSON S.A., Research Center, Châlette-sur-Loing, France; Website: http://www.hutchinsontires.com

and:

East Paris Institute of Chemistry and Materials Science (UMR 7182 CNRS / University Paris-East Créteil), Department "Complex Polymer Systems", Thiais, France; Website: http://www.icmpe.cnrs.fr

Supervision:    Brice Gabrielle (Hutchinson) / Cédric Lorthioir (ICMPE)

Contact:    Please submit a cover letter, curriculum vitae and contact information for two / three references. The cover letter should include a brief description of your research interests. These applications should be
sent to Brice Gabrielle (Hutchinson; brice.gabrielle@cdr.hutchinson.fr) and/or Cédric Lorthioir (ICMPE; lorthioir@icmpe.cnrs.fr).