A strategy is reported herein to covalently graft hyperbranched polyethylenes (HBPEs) onto magnetic nanoparticles(NPs).Core-shell Fe3O4@SiO2 magnetic NPs (FS) were first synthesized via a reverse microemulsion method and then surface modified with a coupling agent

3-acryloxypropyltrichlorosilane

to render acryloyl-functionalized FS (FS-Acryl).The resulting FS-Acryl was further reacted with a Pd-diimine catalyst

［(ArN C(Me)-(Me)C NAr)Pd(Me)(NCMe)］+SbF6- (1)

to give a FS-supported Pd-diimine catalyst (FS-Pd).Surface-initiated/catalytic ethylene polymerization was then carried out with the FS-Pd at 0.1 MPa/15 ℃ for different periods

finally rendering a series of HBPE-grafted FS hybrids (FS-HBPE).The structure and morphology of the as-synthesized FS-HBPE were characterized with Fourier-transformed infrared (FTIR) spectroscopy

thermogravimetry analysis (TGA)

transmission electron microscopy (TEM)

scanning electron microscopy (SEM)

wide-angle X-ray diffraction (WAXRD)

proton nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC)

and their magnetic performance was also evaluated.It is well confirmed that HBPE can be successfully grafted onto FS via the surface-initiated/catalytic chain walking ethylene polymerization

with effectively adjustable polymer grafting ratio simply by changing polymerization time.The resulting FS-HBPE is found to be superparamagnetic and can be stably dispersed in a series of organic solvents at room temperature

with excellent magnetic reponse performance.With these advantages

the resulting FS-HBPE nanocomposites could be potentially used as catalyst supports for various organic reactions.