Structure and properties of glycomaterials

Research carried out by the team has historically been focused on semi-crystalline polysaccharides (cellulose, but also starch and chitin), their morphology, structure and intrinsic properties, their organization within natural edifices, and their use in the design of new functional materials via their chemical modification and/or self-assembly and/or the development of new processes.

Semi-crystalline polysaccharides are hierarchically organized within natural structures, in fibrillar form when they have a structural role (cellulose, chitin…) or in granular form as an energy storage (starch). Their biosynthesis, their arrangement within these structures, and their intrinsic crystalline organization are some of the team’s historical themes that remain very active and take place in collaboration with biologists, biochemists and biomechanists.

In the particular case of cellulose and chitin, which are essential building blocks of many living organisms (terrestrial plants, algae, fungi, crustaceans, insects, etc.), they appear as elongated semi-crystalline objects with at least one nanometric dimension. In vivo, thanks to their intrinsic properties and structural organization, these crystalline polysaccharides provide physical properties such as resistance and adaptability to mechanical stress or play a role in signaling through the creation of physical colors, to name but a few examples. The cellulose and chitin nanofibrils that can be extracted from these organisms, and the nanocrystals obtained by their fragmentation, can be manipulated in vitro and possess a wide range of properties, making them excellent candidates for the design of partially or fully biobased materials. Mastering how to obtain, characterize and handle them is one of the team’s key themes.

As materials, these nanocelluloses or nanochitins come from abundant, renewable resources and are biocompatible, biodegradable and lightweight while offering remarkable mechanical properties, which make them key elements for the design of innovative materials. Moreover, these bio-based nanoparticles possess unique physical and chemical specificities: chirality, high aspect ratio and anisometric physical properties. These objects are also remarkable colloids: their surface properties can be physically or chemically modulated to vary their colloidal stability and interactions in different media. Additionally, their orientation/organization can be modified by applying external fields (electric and magnetic, shear, ultrasound, etc.). For these reasons, they are the subject of fast-growing interest from academic and industrial researchers, as demonstrated by the almost exponential growth in the number of publications and patents in the field over the last ten years.

In recent years, these historical themes have been broadened by the study of flexible polymers naturally associated in vivo with these crystalline polysaccharides (e.g., hemicelluloses, pectins, lignin), the development or intensification of physical and chemical processes (e.g., gas-phase chemistry, sonication) to modify the physical or chemical properties of natural structures (e.g., wood), the derivatization of oligosaccharides to form new objects by crystallization, and the design of hybrid materials associating these biobased objects with inorganic nanoparticles of interest. Other avenues of investigation are the development of biomimetic materials inspired from natural structures or “improved” natural structures taking profit from their intrinsic properties.

As a general strategy, the investigations carried out by the SPG team aim at determining the detailed structure of the materials to establish structure-property relationships. To achieve this goal, we follow a multi-scale approach to identify the structure, morphology and organization of these objects/materials from the atomic and molecular scales to the macroscopic level via the supramolecular and colloidal dimensions.

Our research is based on tools and concepts from a variety of scientific fields including crystallography, biophysics, soft matter and materials science, colloid and polymer science, combined with numerous advanced imaging, spectroscopic, thermomechanical analysis and modeling techniques: solid-state NMR, infrared spectroscopy, radiation scattering and diffraction (notably on large instruments), electron and scanning probe microscopy.

Through these themes and experimental approaches, the team interacts with different scientific communities (polymer and soft matter, biochemistry and biology, biomechanics and wood science, chemical engineering and processes, etc.) and frequently forges contacts with the industry in the fields of biomass processing, specialty chemicals or the design of composite or functional materials.