Construction of lignosulphonate-containing polymersomes and prospects for their use for elemental sulfur encapsulation

The renewable nature and natural origin of sulfite lignin (lignosulfonate) allow considering it as a potential raw material for the synthesis of valuable environmentally friendly polymer nanomaterials. To create them, a deep understanding of the relationship between the structure of the lignosulfonate macromolecule and the nature of intramolecular and intermolecular interactions is necessary, which would make it possible to control selfassembly processes and obtain nanostructures of specified sizes and morphology. The work discusses the structure formation processes occurring in the lignosulfonate - water - acetone system during the spontaneous formation of polymer nanostructures and submicrostructures. The electrostatic effects of sulfo groups and counterions under conditions of changing the medium polarity and their contribution to self -associations of lignosulfonates have been established. A state diagram was plotted for the ternary lignosulfonate - water - acetone system under conditions of induced phase separation at T = 298 K and under atmospheric pressure. The size and zeta- potential of these nanostructures and submicrostructures of lignosulfonates were estimated depending on the composition of the medium of their formation. The morphology of the resulting nanostructures and submicrostructures of lignosulfonates has been established. The vesicular nature of the aggregates (polymersomes) was confirmed, their shape being close to ideal spheroids with one hole, ranging in size from 40 to 500 nm. A multi-stage mechanism for the formation of lignosulfonate nanoassociates and submicroassociates is proposed. The encapsulating ability of our polymersomes with respect to elemental sulfur from the instant of its inception until the loss of aggregative and sedimentation stability was assessed. Lignosulfonate polymersomes can be recommended as additives to prevent the occluding effect of sulfur melts during hydrometallurgical processing of sulfide ores.