Synthesis of a novel type of octyltetramethyldisiloxane-containing olefinic macromonomer and its copolymerization with ethylene

•Designed and synthesized a novel type of low-oxophilicity siloxane-containing olefinic macromonomer, OO7.•Demonstrated copolymerizability of OO7 macromonomer with ethylene by vanadium catalyst and prepared poly(ethylene-co-OO7).•Demonstrated that OO7 incorporation in PE significantly benefits PE chain flexibility with Tg between −74.3 to −64.0 °C.•Demonstrated that poly(ethylene-co-OO7) is an excellent lubricant for HDPE, adding 10% resulted in 44% increase in MFR.

This paper reported the synthesis of a novel type of octyltetramethyldisiloxane-containing olefinic macromonomer (1-oct(7-en)yl-3-octyl-1,1,3,3-tetramethyldisiloxane or OO7), the copolymerization of OO7 with ethylene by vanadium catalyst, the evaluation of poly(ethylene-co-OO7) as additive on the flow, mechanical and thermal properties of polyethylene. The novel siloxane-containing comonomer OO7 was synthesized by a two-step hydrosilylation route, with only one oxygen atom in the molecule. The comonomer had low oxophilicity and hence could be readily copolymerized with ethylene by VCl3(THF)3 catalyst with a high activity of 14 kg/mmolV·h at the comonomer feed of 160 mmol/L. The OO7 incorporation reached to 4.9 mol%. The reactivity ratios were: rE = 41.6, rOO7 = 0.021 and rE•rOO7 = 0.87, which indicated a tendency of random copolymerization. DSC analysis revealed that the glass transition temperatures (Tg) of poly(ethylene-co-OO7) were in the range between −74.3 °C to −64.0 °C, lower than that of a LLDPE control sample of the similar composition. The melting endotherm of poly(ethylene-co-OO7) was broadened and shifted to a lower temperature range with increase of the OO7 content. Adding 10% poly(ethylene-co-OO7) as lubricant to HDPE increased 44% melt flow rate (MFR) of the blend. However, the mechanical and thermal properties of the blends were not adversely affected, compared to HDPE.

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