Commercial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) and poly(3hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) were used to prepare microbeads, with diameter ranging from 50 to 100 µm, by an emulsion-evaporation process. The properties of the beads reveal that the elaboration process enables the formation of spherical particles, that the crystallinity of the former polymer is not altered during the process and that the surface roughness of the particles can be tuned by changing the nature of the lateral chain in the PHA structure, in good correlation with its crystalline behavior. The mechanical properties of the different PHA beads are also found to be intimely linked with the crystalline content of the beads, with modulus varying between 1 to 7 GPa. All these properties are also governing the degradation behavior of these materials, as tested under marine environment. With a rapid degradation, similar to cellulose, and a degradation rate correlated with the crystalline content, these results emphasize the interest in developing PHA materials with tunable functions and degradation properties.

Starch, an abundant and low-cost plant-based glucopolymer, has great potential to replace carbon-based polymers in various materials. In order to optimize its functional properties for bioplastics applications chemical groups need to be introduced on the free hydroxyl groups in a controlled manner, so an understanding of the resulting structure-properties relationships is therefore essential. The purpose of this work was to study the multiscale structure of highly-acetylated (degree of substitution, 0.4 < DS ≤ 3) and etherified starches by using an original combination of experimental strategies and methodologies. The molecular structure and substituents repartition were investigated by developing new sample preparation strategies for specific analysis including Asymmetrical Flow Field Flow Fractionation associated with Multiangle Laser Light Scattering, Nuclear Magnetic Resonance (NMR), Raman and Time of Flight Secondary Ion Mass spectroscopies. Molar mass decrease and specific ways of chain breakage due to modification were pointed out and are correlated to the amylose content. The amorphous structuration was revealed by solid-state NMR. This original broad analytical approach allowed for the first time a large characterization of highly-acetylated starches insoluble in aqueous solvents. This strategy, then applied to characterize etherified starches, opens the way to correlate the structure to the properties of such insoluble starch-based materials.

Commercial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) were used to prepare microbeads, with diameter ranging from 50 to 100 µm, by an emulsion-evaporation process. The properties of the beads reveal that the elaboration process enables the formation of spherical particles, that the crystallinity of the former polymer is not altered during the process and that the surface roughness of the particles can be tuned by changing the nature of the lateral chain in the PHA structure, in good correlation with its crystalline behavior. The mechanical properties of the different PHA beads are also found to be intimely linked with the crystalline content of the beads, with modulus varying between 1 to 7 GPa. All these properties are also governing the degradation behavior of these materials, as tested under marine environment. With a rapid degradation, similar to cellulose, and a degradation rate correlated with the crystalline content, these results emphasize the interest in developing PHA materials with tunable functions and degradation properties.