Catalyzed by a phenoxycyclopentylimine ligated zirconium complex/dried methylaluminoxane (dMAO) system at 40℃ under 1 atm of ethylene pressure
linear vinyl-terminated polyethylene (PE-ene) with nearly 100% of end-functionality was produced
via
ethylene polymerization. With high efficiency
hydroxyl-terminated polyethylene (PE-OH) was subsequently prepared
via
the radical initiated thiol-ene click chemistry between the PE-ene and 2-mercaptoethanol. The PE-OH was then used to react with norbornene-5-carbonyl chloride to synthesize the norbornene-terminated polyethylene macromonomer (PE-NB) through the esterification reaction. The ring-opening metathesis copolymerization (ROMP) of PE-NB and norbornene (NB) with the different feed ratio was conducted in the presence of Grubbs Ⅱ generation catalyst to produce the polyethylene-based graft copolymers. Both random and block polynorbornene-g-polyethylene graft copolymers (PNB-
g
-PE) were then obtained with different feeding mode
i.e
.
the one-batch feeding mode and the sequential feeding mode
respectively. The structures of the graft copolymers were characterized by Fourier transform-infrared and proton nuclear magnetic resonance spectroscopy. The molecular weight and molecular weight distribution of PNB-
g
-PE were determined by high-temperature gel permeation chromatography; the thermal properties of PNB-
g
-PE were also tested by differential scanning calorimetry. The conversion of macromonomer was found to be nearly 100% in the random copolymerization of macromonomer and norbornene. The random graft copolymers were obtained with the molecular weight of 1.79×10
4
-3.14×10
4
with relatively narrow molecular weight distribution (2.09-2.60). The molecular weight of the copolymers decreased gradually with the increase in the feed ratio of PE-NB. The molar fraction of PE in the random copolymers varied from 4.6% to 16.8%
depending on the feed ratio of PE-NB to NB
whereas the molar fraction of PE showed slight influence on the melting point of the PE segments. However
the conversion of macromonomer reached about 80% in the block copolymerization of PE-NB and NB. Due to the steric hindrance
the crystallinity of the graft copolymers slightly decreased in comparison with the corresponding PE precursor.
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