Polyethylene materials with in-chain ketones from nonalternating catalytic copolymerization

Abstract

Polyethylene with a nickel’s worth of CO The biggest problem with polyethylene, the most abundantly manufactured plastic, is that it doesn’t break down easily once it is discarded. Chemists have long sought to introduce small quantities of carbon monoxide (CO) into polyethylene chains to promote photodegradation, but too much CO tends to jump in and spoil the plastic’s other properties. Baur et al . report that nickel catalysts coordinated by bulky phosphinophenolate ligands can catalyze ethylene polymerization with approximately 1% CO incorporation, preserving tensile strength while promoting degradation under ultraviolet exposure (see the Perspective by Sobkowicz). —JSY

Impact of Carbonyl Group Incorporation in Semicrystalline High-Density Polyethylene

“…Previously, the 13 CO chemical shifts of 13 C-keto-functionalized PE measured in solution could be assigned to different CO-ethylene comonomer sequences along the main chain as arising from the synthesis method, i.e., IC, DC n , and APK, across which the CO groups are distributed with an approximate relative ratio of 1:1:1 on average (see the Materials subsection). A detailed shift assignment in the given bulk (amorphous and crystalline) states is actually a nontrivial issue, as taken up further below.…”

Impact of Carbonyl Group Incorporation in Semicrystalline High-Density Polyethylene

“…Previously, the 13 CO chemical shifts of 13 C-keto-functionalized PE measured in solution could be assigned to different CO-ethylene comonomer sequences along the main chain as arising from the synthesis method, i.e., IC, DC n , and APK, across which the CO groups are distributed with an approximate relative ratio of 1:1:1 on average (see the Materials subsection). A detailed shift assignment in the given bulk (amorphous and crystalline) states is actually a nontrivial issue, as taken up further below.…”

Impact of Carbonyl Group Incorporation in Semicrystalline High-Density Polyethylene

“…However, these changes remain minor, indicating that the addition of up to 1.6 mol-% keto groups has little overall impact on the thermal properties of polyethylene. This observation is consistent with the prior DSC observations [10], where negligible differences were found between a The DSC results suggest that keto incorporation has a minimal effect on the thermal properties of polyethylene, in strong contrast to a recent systematic investigation of the effect of small amounts of non-crystallizable comonomers [25]. Octene comonomers were shown to reside in a diffuse interphase and to lead to a reduction of T m and ∆H m by 15 • C and 50%, respectively, at a comparable content of 1.6 mol-% comonomers.…”

Attractive Ni … O Interactions Enable Non‐Alternating Ethylene‐Carbon Monoxide Copolymerization

“…All three catalysts produce high molecular weight keto-polyethylenes under the conditions studied (Figure 4d). The presence of CO significantly increased polymer molecular weights for all catalysts, consistent with previous observations (Figure 4d) that the presence of CO reduces ß-hyride elimination [11]. S4).…”

Impact of Carbonyl Group Incorporation in Semicrystalline High-Density Polyethylene

“…Previously, the 13 CO chemical shifts of 13 C-keto-functionalized PE measured in solution could be assigned to different CO-ethylene comonomer sequences along the main chain as arising from the synthesis method, i.e., IC, DC n , and APK, across which the CO groups are distributed with an approximate relative ratio of 1:1:1 on average (see the Materials subsection). A detailed shift assignment in the given bulk (amorphous and crystalline) states is actually a nontrivial issue, as taken up further below.…”

Impact of Carbonyl Group Incorporation in Semicrystalline High-Density Polyethylene

“…However, these changes remain minor, indicating that the addition of up to 1.6 mol-% keto groups has little overall impact on the thermal properties of polyethylene. This observation is consistent with the prior DSC observations [10], where negligible differences were found between a The DSC results suggest that keto incorporation has a minimal effect on the thermal properties of polyethylene, in strong contrast to a recent systematic investigation of the effect of small amounts of non-crystallizable comonomers [25]. Octene comonomers were shown to reside in a diffuse interphase and to lead to a reduction of T m and ∆H m by 15 • C and 50%, respectively, at a comparable content of 1.6 mol-% comonomers.…”

Attractive Ni … O Interactions Enable Non‐Alternating Ethylene‐Carbon Monoxide Copolymerization

“…All three catalysts produce high molecular weight keto-polyethylenes under the conditions studied (Figure 4d). The presence of CO significantly increased polymer molecular weights for all catalysts, consistent with previous observations (Figure 4d) that the presence of CO reduces ß-hyride elimination [11]. S4).…”

Impact of Carbonyl Group Incorporation in Semicrystalline High-Density Polyethylene

“…Previously, the 13 CO chemical shifts of 13 C-keto-functionalized PE measured in solution could be assigned to different CO-ethylene comonomer sequences along the main chain as arising from the synthesis method, i.e., IC, DC n , and APK, across which the CO groups are distributed with an approximate relative ratio of 1:1:1 on average (see the Materials subsection). A detailed shift assignment in the given bulk (amorphous and crystalline) states is actually a nontrivial issue, as taken up further below.…”

Impact of Carbonyl Group Incorporation in Semicrystalline High-Density Polyethylene

“…However, these changes remain minor, indicating that the addition of up to 1.6 mol-% keto groups has little overall impact on the thermal properties of polyethylene. This observation is consistent with the prior DSC observations [10], where negligible differences were found between a The DSC results suggest that keto incorporation has a minimal effect on the thermal properties of polyethylene, in strong contrast to a recent systematic investigation of the effect of small amounts of non-crystallizable comonomers [25]. Octene comonomers were shown to reside in a diffuse interphase and to lead to a reduction of T m and ∆H m by 15 • C and 50%, respectively, at a comparable content of 1.6 mol-% comonomers.…”

Attractive Ni … O Interactions Enable Non‐Alternating Ethylene‐Carbon Monoxide Copolymerization

“…All three catalysts produce high molecular weight keto-polyethylenes under the conditions studied (Figure 4d). The presence of CO significantly increased polymer molecular weights for all catalysts, consistent with previous observations (Figure 4d) that the presence of CO reduces ß-hyride elimination [11]. S4).…”