Display omitted •Flexible PVC materials suffer from migration of their additives.•Plasticizers covalently bound to the polymer chain avoid migration.•Oligomeric caprolactone additives are prepared by ring-opening polymerization.•An industrially viable sustainable way for plasticization is described. Oligomeric plasticizers for PVC were synthesized using ring-opening-polymerization of caprolactone (CL) initiated by aromatic and heteroaromatic thiol compounds containing hydroxy groups. The obtained plasticizers were chemically bound to the polymer both, in solution and in the melt, with different PVC/plasticizer weight ratios and their efficiency with respect to the degree of anchorage, resistance to migration and plasticization were studied. Thiolates from heteroaromatic thiol plasticizers were too strongly basic and produced partial hydrolysis and transesterification side reactions during the anchorage reaction to the polymer. On the other hand, oligomers carrying an aromatic thiol end group could be bound selectively and without hydrolysis to the PVC chains. The most suitable system was produced on a 50 kg scale and the plasticized materials obtained were analysed showing good degrees of anchorage and excellent plasticizing properties.