Patrick Navard, Tatiana Budtova, Edith Peuvrel-Disdier

How are polymers and polymer-containing materials organised and structured?

How to use, manipulate and adapt this organisation in order to obtain better performing, cheaper, less polluting materials with new properties?

Our scientific areas consider physical, physico-chemical, thermodynamic and rheological aspects that are needed to understand and master materials processing and to control their final properties.

The research activities of the Polymer Chemical Physics (PCP) group can be divided into 3 main areas:

1.		Thermodynamics-structure-processing of cellulose and its derivatives Cellulose is one of the most abundant natural polymers on Earth. As well as other polysaccharides, cellulose is an alternative to petrol-base polymers due to its biomass-based carbon, biocompatibility and compostability. The work performed in our group concerns the fundamental understanding of cellulose dissolution in various solvents as well as thermodynamics, rheology and structure of cellulose solutions. The results obtained are used for cellulose processing in fibres, films, sponges and aerogels.	Morphology of Aerocellulose : new ultra-light (0.1 g/cm 3) and highly porous (> 95%) pure cellulose « aerogel ».
2.		Suspensions and mixtures. Rheo-optics. Our group has a long-lasting expertise in the studies of polymer melts and solutions structuring and morphological changes under flow, due to the development of original rheo-optical tools (shear cells coupled with optical microscopy and light scattering, counter-rotating systems). Immiscible blends have been extensively studied in the past. Now rheo-optics is used to study the behaviour of particles dispersed in a liquid matrix: deformation of cross-linked soft particles and starch granules (correlation with flavour perception), and dispersion of agglomerates of solid nano-particles in visco-elastic fluids (for tyre industry). The goal is to understand the mechanisms of deformation, rupture and dispersion in processing and to predict material final properties.	Carbon black agglomerate break-up under shear; the agglomerate is within an elastomer.
3.		Gelation and gels Polymers can form networks and gels in a reversible or irreversible way. As far as physical gelation is concerned, the work is performed on polysaccharide solutions. On of the examples of our applications is a replacement of gelatin in medical capsules by a mixture of polysaccharides. The behaviour of chemical gels (hydrogels based on chemically cross-linked polyelectrolytes), such as swelling/contraction and absorption/release of different compounds, is studied as a function of medium pH, presence of ions, linear polymer, electric current, mechanical stresses. The results are used for controlled release applications.	Release of solvent from a polyacrylate gel under shear : rheo-optical observation.

On-going research:

• Preparation of ultra-light and porous cellulose.
  
• Study of the mechanisms of cellulose native fibres swelling and dissolution.
  
• Dispersion of solid agglomerates in visco-elastic fluids.
  
• Preparation of micro-particles with biocides controlled release.
  
• Polysaccharide mixtures.
  
• Behaviour of startch granules under flow, studied by rheo-optics; correlation with flavour perception.