Photodegradable polar-functionalized polyethylenes

Abstract

The degradation of plastics has attracted much attention from the global community. Polyethylenes (PEs) as the most abundant synthetic plastics are mostly studied. PE is non-degradable and non-polar because of the sole presence of the pure hydrocarbon components. Concurrent incorporation of both in-chain cleavable and functional groups into the PE chain is an effective pathway to overcome the non-degradable and non-polar issue; however, the method for achieving this pathway remains elusive. Here, we report the strictly nonalternating (>99%) terpolymerization of ethylene with CO and fundamental polar monomers via a coordination–insertion mechanism using late transition metal catalysts, which effectively prevents the formation of undesired chelates originating from both co-monomers under a low CO concentration. High-molecular-weight linear PEs with both in-chain isolated keto (>99%) and main-chain functional groups are prepared. The incorporation of the key low-content isolated keto groups makes PEs photodegradable while retains their desirable bulk material properties, and the introduction of polar functional groups considerably improves their surface properties.

Polar-Functionalized Polyethylenes Enabled by Palladium-Catalyzed Copolymerization of Ethylene and Butadiene/Bio-Based Alcohol-Derived Monomers

“…ATR-IR analyses were performed for representative ethylene and 2,7-octadienyl ether copolymers, and a polyethylene sample produced by Pd-3 [ 46 ] was also tested as a comparison ( Figure 3 ). As shown in Figure 3 , all the copolymers feature characteristic bands at close 968 cm −1 , assigned to the symmetric C–O–C stretching vibration of the allyl ether unit, which is absent in the PE sample.…”

“…Materials: furfuryl alcohol, tetrahydrofurfuryl alcohol, and solketal were commercially available, which were further dried over Na 2 SO 4 and NaHCO 3 for 2 h and distilled. Palladium catalysts Pd-1 , Pd-2, and Pd-3 were prepared using the literature procedures [ 44 , 45 , 46 ]. All other reagents were commercially available and used as received.…”

Synthesis of Polyethylenes with In-Chain Isolated Carbonyls from CO2 and Ethylene

“…Due to formation of a strong chelate after CO insertions, these copolymerizations inevitably furnish a mixture of isolated and alternating carbonyl units in the presence of excess CO. [21] Compared to that of alternating carbonyl units, in-chain isolated carbonyls may maximize the breakdown of the polymer chains into smaller pieces during photodegradation. [22] In 2021, Nozaki et al reported the synthesis of nonalternating polyketones with excellent isolated carbonyl insertion selectivity from ethylene and metal carbonyls. [23] Inspired by the significant progress made in CO/ethylene copolymerization, we report herein a new copolymerization protocol to prepare polyethylenes with low content isolated carbonyls from CO2 and ethylene.…”

Facile access to diverse polyethylenesvianeutral salicylaldiminato nickel catalysts

“…[1][2][3][4] Since Brookhart et al discovered nickel(II) and palladium(II) catalysts supported by α-diimine ligands, 5,6 late transition metal catalysts have received tremendous attention over the past 30 years and have been proved to be very versatile in accessing diverse polyolefins. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] In contrast to extensive studies on cationic α-diimine nickel (II) catalysts with the activation of co-catalysts, another milestone in catalyst studies, neutral salicylaldiminato nickel(II) catalysts, discovered by Johnson et al 27 and Grubbs et al, 28,29 have better tolerance toward polar media but have attracted much less attention in terms of the production of diverse polyolefins. Unlike the α-diimine nickel(II) catalysts, the active center of this type of catalyst is electrically neutral, and thus it allows ethylene polymerization without the help of Lewisacidic co-catalysts.…”

“…1–4 Since Brookhart et al discovered nickel( ii ) and palladium( ii ) catalysts supported by α-diimine ligands, 5,6 late transition metal catalysts have received tremendous attention over the past 30 years and have been proved to be very versatile in accessing diverse polyolefins. 7–26…”