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The team is positioned on nanotechnologies and plant biopolymers, with a main focus on nanocelluloses, for the implementation of bio-based materials. The team develops innovative and sustainable materials, with similar or even superior functionalities compared to their petroleum-based analogues. The aim is to control the structure of a wide range of nanoparticles showing different morphologies and surface chemistry. The team focuses on surface modification of biopolymer by different approaches, including the adsorption of other polymers, targeted chemical and enzymatic modifications, and processes with low environmental impact, low energy processes, and without solvents.
Particular attention is paid to the impact of dense media, to explore the long distance organization behaviors induced by the high concentration, or the influence on the diffusion of molecules such as enzymes in a constrained environment with the objective of controlling and adjusting the functionality of materials. All these modifications and structural models should allow the elaboration of assemblies at nanometric scales to scale up for the elaboration of functional materials with the creation of original structures such as programmable materials while continuing the study of materials already mastered by the team (emulsions, thin films, hydrogels).
Our research is also concerned by all the stages related to the generation and the end of life of materials, with the aim of integrating our work in the bio-economy through a systemic approach on the whole life cycle of a material.
The activity of the NANO team is declined around three scientific priorities:
1. Designing tailored elementary bricks
Controlling the structural variability of biopolymers, nanocrystals, nanofibers
We study the modification of hemicelluloses (xyloglucans, xylans, glucomannans,...) by physical (ultrasound) or enzymatic processes to modulate parameters such as molar mass or molecular structure (e.g. rate of substitution and distribution of substituents of hemicelluloses). Beyond native cellulose nanocrystals (cellulose I), other crystalline structures (cellulose II) are envisaged, we are also interested in nanoparticles varying in morphology (cellulose nanofibers) or in surface chemistry (chitin nanocrystals / nanofibers).
Nanocelluloses surface modification pathways
We focus on three nanocelluloses modification strategies: (i) physical adsorption of biopolymers (hemicelluloses of controlled structural variability) ; (ii) enzymatic modification (including LPMO enzymes, laccases, lipases, etc.) ; (iii) regio-specific targeted chemical functionalization (surface or reducing end) by less energy consuming and less toxic processes (simultaneous multi-functionalization) in order to direct the modification for high value-added objects such as programmable materials.
We combine nanoparticles of biological origin (cellulose or chitin) with a small fraction of other particles, generally inorganic, carrying specific properties accessible on the surface. The nanocrystals thus serve as a substrate for the controlled nucleation and growth of nanoparticles such as Ag, TiO2, CuO, etc. This type of modification uses the principles of the Safer-by-design approach aiming at minimizing the risks for human health and the environment.
2. Assemblies in dense environments
We are exploring phase separation, long-range organizations (alignment), small molecule diffusion and hydration by assessing the impact on rheological/mechanical properties and enzymatic reactivity:
In 2 Dimensions
The understanding of the adsorption processes of biopolymers (cellulose, hemicelluloses, gum arabic, dextran) on surfaces and the elaboration of multilayer thin films by focusing on i) the effect of the charge distribution and the biopolymer structure on hydration to probe mechanical properties ii) the construction of multilayer films with a modular structure or iii) the asymmetric structuration of elementary building blocks (gradient or multi-component films) for the fabrication of responsive materials or actuators.
In 3 Dimensions
The directed self-assembly of biopolymers allows anisotropic constructions such as the alignment of nanocrystals (liquid crystals) or cellulose nanofibrils (cryogels oriented by freeze-casting). These constructions will allow i) to understand the long distance organization as a function of different factors (charge density, hydration...), ii) to study the impact of a constrained environment on the diffusion of small molecules such as enzymes or on the mechanical and sorption properties of materials (cryogels). The micro and millifluidic tool allows the study of concentrated phases in single or multiphase drops on reasonable volumes. These micro-reactors will be used for two purposes: to probe the dynamics of phase separation in relation to the enzymatic activity and to follow the possible variations of the enzymatic activity in a dense organized medium of liquid crystal type.
3. Functional sustainable materials
The expertise developed in the team on the functional building blocks and modes of directed assemblies is declined for the development of innovative materials. In addition to the implementation of bio-based materials with outstanding functionalities (interfacial stability, alignment, gelling ...), the ambition is to develop the multi-functionality or even tend to materials that change their behavior depending on their history. The other ambition is to globally assess the environmental and economic impact of the materials we produce on certain stages of the life cycle.
Functional / multifunctional materials
(i) Emulsions (including Pickering emulsions), foams: stabilizing the interface with functional, chemically modified or hybrid nanoparticles, for biphasic dispersions with photo-catalytic, biocidal or pesticidal properties; modifying the nature of the dispersed or continuous phases; playing on the complexity of the interface (multilayer systems) and multi-encapsulation for programmed releases).
(ii) Hydrogels made of biopolymers or biopolymer/nanoparticle mixtures: understanding the gelling mechanisms especially in the case of binary or ternary mixtures including polymers and nanoparticles; aiming for adjustable mechanical properties and responsive (thermosensitive) properties; encapsulation of stem cells in injectable hydrogels for osteo-articular treatments.
(iii) Ultra-light porous materials (cryogels, aerogels, foams)based on nanocellulose and biopolymers with efficient mechanical properties while preserving reversible water sorption capacities (sponge effect); understanding the interactions between biopolymers during the fabrication process (freezing of aqueous dispersions, mobility of polymers and water).
Actuators fabricated by controlled assembly are modelled to establish a relationship between structure and response to stimuli. The objective is to develop models that describe responsiveness as a function of structural parameters (dimensions, composition, distribution of functional groups) in order to predict the material behavior and to define the combinations of components to obtain controlled multi-responses (programming of activation/deactivation cycles).
Systemic approach to the development of bio-based materials
The design of bio-based materials, beyond the necessary functional performance, must also integrate various aspects that guarantee socio-economic services such as the safety of materials towards humans and the environment (a sensitive criterion in the case of nanomaterials), the sustainability of the resources used, and the consideration or even programming of the end of life. We are also working on the construction of sustainability indicators to evaluate the use of different biomasses, processes, economic valorisation and life cycle of materials.
In each case, the activity of the team is focused on the elaboration of materials, the development of structuring strategies and the characterization of architectures. The evaluation of the properties is carried out in internal collaboration with, in particular, the BIBS platform (NMR, Microscopy techniques, infrared) or external to BIA.
Methods and Equipments
The team is equipped with equipements for sample preparation: centrifuges, high-pressure homogenizer, diafiltration, freeze-dryer, ultrasonic apparatus, stator rotor, etc., and microfluidic and millifluidic devices with all the equipment necessary for the realization of PDMS circuits. We will soon be equipped with a clean room for all activities related to soft lithography.
As far as the "Assemblies" theme is concerned, equipment has been custom-designed to elaborate surfaces (spin-coating, casting) and materials (establishment of phase diagrams for hydrogels, controlled freezing system for cryogels). We are also equipped with a paper press and dryer.
We have equipment for the analysis of surface interactions, namely quartz crystal microbalances (QCM-D E4 and E1, QSense) coupled to a spectroscopic ellipsometer (M2000 U Woolman) and an SPR apparatus (BIAcore X100). Concerning the characterization of biopolymers and materials, we have a UV spectroscope (Serlabo UVS600), an HPSEC (Omnisec Malvern), 3 Olympus microscopes (2 inverted), with cross-polarization and fluorescence modes. We have recently developed an acoustic levitation equipment.