Lignin is a readily available yet heavily underutilised resource due to its severe degree of variability related to the plant source and to the processes employed for its isolation. Being in most cases a by-product of technologies targeting other biopolymers, e.g. cellulose, less attention has been paid to the physicochemical features of the obtained lignin, which can therefore dramatically vary even on a batch to batch basis. To fully valorise the enormous potential of this material, the development of robust and economically sustainable strategies leading to lignin structures with well-defined and homogenous characteristics is of crucial importance. In this respect, fractionation represents a valid option, and thus is attracting increasing interest from the scientific community. Different methodologies have been established and tested on many lignins in the last few years. With the aim of extrapolating general trends in terms of the properties of the obtained lignin cuts and providing useful guidelines for researchers working in this topic, this contribution presents a critical review of the existing approaches for the fractionation of technical lignins. The applications where lignin fractions have found use are also overviewed, with a particular focus on the benefits gained as compared to pristine lignin.

Thermal, structural and physico-chemical properties of different composite edible films based on alginate and pectin with the addition of citral essential oil (citral EO) as an agent to improve barrier properties, were investigated. The obtained films were clear and transparent, with a yellow hue that increased with citral EO addition. All the films displayed good thermal stability up to 160 °C, with a slight improvement observed by increasing the amount of citral EO in the composites. Gas transmission rate (GTR) strongly depended on the polymer structure, gas type and temperature, with improvement in barrier performance for composite samples. Also, citral EO did not exert any weakening action on the tensile behavior. On the contrary, an increase of the elastic modulus and of the tensile strength was observed. Lastly, water contact angle measurements demonstrated the dependence of the film wettability on the content of citral EO.

Copolymers of poly(butylene succinate) (PBS) containing diethylene succinate sequences (PBSPDGS) with different molecular architectures were prepared via reactive blending in the presence of a Ti-based catalyst. In particular, a block copolymer with long sequences and a random one with very short sequences were synthesized, characterized and investigated in terms of enzymatic biodegradability. For comparison, the parent homopolymer PBS has been also prepared by the usual two-stage melt polycondensation. Preliminary biodegradation tests based on the highly sensitive film opacity assay indicated that lipase from Candida cylindracea was the most effective among four different commercially available lipases (e.g., those from Candida rugosa, Candida cylindracea, Aspergillus niveus and hog pancreas) and a serine protease (α-chymotrypsin from bovine pancreas), and that optimal test conditions were 50 enzyme U mL⁻¹, 30 °C and pH 7.0. Under such conditions, copolymers degraded to a much higher extent as compared to PBS. Moreover, the random copolymer degraded 100 times faster than the block one. ATRIR analysis and DSC measurements indicated that the enzyme attacked the amorphous phase first. Further, NMR analysis indicated that enzyme hydrolysis involved preferentially ester groups of DGS sequences, more hydrophilic than the others. These findings confirm previous evidence on the correlation between polymers biodegradation rate and their hydrophilic and amorphous degree. More importantly, they indicate (i) that dramatic increases in polyesters biodegradability can be obtained by introducing ether-oxygen atoms into the polymer chain and (ii) that biodegradability of oxygen etheroatom-containing copolyesters might be tuned within a wide range of rates through the modification of their molecular architecture.