Efficient carbohydrate modification plays a crucial role in developing the next generation of functional polymers for advanced and targeted applications. In our research, we proposed an efficient and highly selective strategy to graft hydrophobic oligomers onto aldehydes and ketones substrates via oxime ligation inspired by our recent strategy for functionalizing cellulose nanofibers (CNFs) in aqueous environments[1]. Here, we first create PCL oligomers with an aminoxy end-group to enable subsequent oxime ligation. One advantage with approach is the insensitivity of water commonly encountered in conventional graft polymerization methods. In addition, this ligated strategy also enables an efficient and mild method for hydrophobic modifications in water.Our research shows the simultaneous deprotection of the initiator and initiation of ε-caprolactone ring-opening polymerization. The oligomer features an aminooxy functional group which is able to ligate with model aldehydes and ketones. Up to now, we have successfully synthesized a bifunctional initiator with hydroxyl and aminoxy groups and proven its function during ring-opening polymerization of ε-caprolactone to prepare PCL-based oligomers. We observed that a short PCL chain length exhibited consistently high conversion (above 95%) with acetone and xylose in different solvent systems, demonstrating their superior reactivity and versatility in diverse reaction environments. In contrast, for longer PCL chain lengths, the ligation conversion decreases slightly due to limited accessibility of functional groups, and slower diffusion in solution.