Nanoprecipitation is one of the most popular methods for producing polymer nanoparticles. However, the reported results show a large variability. In order to provide a first-hand comparative study, we prepared cellulose-based nanoparticles via different nanoprecipitation methods. Here, the influence of the coagulating solvents acetone, N,N-dimethylacetamide and tetrahydrofuran on the size and shape of the particles via precipitation using dialysis was investigated. The influence of temperature and concentration was determined by dropwise addition of the coagulation medium. Then, via rapid solvent shifting, particles were prepared from cellulose acetates with different molecular masses and the cellulose acetate propionate and cellulose acetate butyrate derivatives in the concentration range of 1–20 mg mL− 1. Thereby, it was possible to prepare spherical particles in the range from 43 to 158 nm. Furthermore, the impact of the molecular weight of these derivatives on the obtained particle size distributions was determined. It is possible to obtain pure regenerated cellulose particles in the nanometer range by a deacetylation of the derivatives. In addition, the findings were used to directly convert cellulose from a DMAc/LiCl solvent system into regenerated cellulose nanoparticles with a size of 10 ± 3 nm.
Graphical abstract
Biodegradation rates and mechanical properties of poly(3-hydroxybutyrate) (PHB) composites with green algae and cyanobacteria were investigated for the first time. To the authors knowledge, the addition of microbial biomass led to the biggest observed effect on biodegradation so far. The composites with microbial biomass showed an acceleration of the biodegradation rate and a higher cumulative biodegradation within 132 days compared to PHB or the biomass alone. In order to determine the causes for the faster biodegradation, the molecular weight, the crystallinity, the water uptake, the microbial biomass composition and scanning electron microscope images were assessed. The molecular weight of the PHB in the composites was lower than that of pure PHB while the crystallinity and microbial biomass composition were the same for all samples. A direct correlation of water uptake and crystallinity with biodegradation rate could not be observed. While the degradation of molecular weight of PHB during sample preparation contributed to the improvement of biodegradation, the main reason was attributed to biostimulation by the added biomass. The resulting enhancement of the biodegradation rate appears to be unique in the field of polymer biodegradation. The tensile strength was lowered, elongation at break remained constant and Young’s modulus was increased compared to pure PHB.
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