The surface hydrophobization of cellulose nanocrystals (CNCs) by carboxylic acids, biodiesel, or plant oils was conducted via there herein disclosed green process using an one-pot synthetic method. In the process, an aqueous lactic acid syrup served as a solvent to provide a stable and well-dispersed water suspension of CNCs and participated in esterification reactions to produce an intermediate product of polylactic acid (PLA) oligomer grafted CNCs (CNC-g-PLA). This solvent and intermediate product system allows for an in situ solvent exchange from water to lactic acid without prior drying of the CNCs and a subsequent efficient esterification reaction of CNCs with carboxylic acids or esters having a long hydrocarbon chain (FAs). Another advantage of the disclosed process is the ability to reuse the reagents in the subsequent reaction in order to reduce the production cost. Grafting of renewable materials on the surface of CNCs was developed by polyesterification that is capable of being environmentally friendly and mass-produced without any organic solvents or toxic reagents.