Preparation of cellulose-graft-poly(ɛ-caprolactone) nanomicelles by homogeneous ROP in ionic liquid

Self-associating cellulose-graft-poly(ɛ-caprolactone) (cellulose-g-PCL) copolymers were successfully synthesized via homogeneous ring-opening polymerization (ROP) of ɛ-CL onto softwood dissolved pulp substrate in ionic liquid 1-N-butyl-3-methylimidazolium chloride ([Bmim]Cl). An organic catalyst N,N-dimethylamino-4-pyridine (DMAP) was compared with the traditional metal-based catalyst (Sn(Oct)2) as the catalyst of the reaction, and exhibited higher catalytic activity. By controlling the cellulose:ɛ-CL feed ratio and reaction temperature, the molecular architecture of the copolymers can be altered, as evidenced by FT-IR, 1H NMR, 13C NMR, TGA and XRD. The self-assembly behavior of the copolymers in water was investigated and characterized using fluorescence probe, dynamic light scattering (DLS) and SEM. The results showed that the cellulose-g-PCL copolymers could form nanosized micelles (approximately 20–100 nm) in water, and the micelle size and critical micelle concentration (CMC) can be controlled by varying the grafting ratio of PCL. These cellulose-based nanomicelles are expected to be useful in broad application fields.