Plastics are a key component of virtually any technology today. Although their production consumes enormous feedstock resources, plastics are largely disposed of after their useful service life. In terms of a circular economy, 1-8 desirable re-utilisation of post-consumer sorted polymers ('mechanical recycling') is hampered by deterioration of materials performance. 9,10 Chemical recycling 1,11 via depolymerisation to monomer offers an alternative to retain high performance properties. The linear hydrocarbon chains of polyethylene 12 enable crystalline packing and provide excellent materials properties. 13 Their inert nature hinders chemical recycling, however, necessitating temperatures > 600 °C and recovering ethylene with < 10 % yield. 3,11,14 Here, we show that renewable polycarbonates and polyesters with a low-density of in-chain functional groups as break points in a polyethylene chain can be recycled chemically by solvolysis with > 96 % recovery. At the same time, the break points do not disturb the crystalline polyethylene structure, and the HDPE (high density polyethylene)-like materials properties are fully retained upon recycling. Processing can be performed by common injection moulding and the materials are well-suited for additive manufacturing. Selective removal from model polymer waste streams is possible. The virgin polymers result from polycondensation of long-chain building

We report a novel polyester material generated from readily available biobased 1,18‐octadecanedicarboxylic acid and ethylene glycol possesses a polyethylene‐like solid‐state structure and also tensile properties similar to high density polyethylene (HDPE). Despite its crystallinity, high melting point (Tm=96 °C) and hydrophobic nature, polyester‐2,18 is subject to rapid and complete hydrolytic degradation in in vitro assays with isolated naturally occurring enzymes. Under industrial composting conditions (ISO standard 14855‐1) the material is biodegraded with mineralization above 95 % within two months. Reference studies with polyester‐18,18 (Tm=99 °C) reveal a strong impact of the nature of the diol repeating unit on degradation rates, possibly related to the density of ester groups in the amorphous phase. Depolymerization by methanolysis indicates suitability for closed‐loop recycling.

We report a novel polyester material generated from readily available biobased 1,18‐octadecanedicarboxylic acid and ethylene glycol possesses a polyethylene‐like solid‐state structure and also tensile properties similar to high density polyethylene (HDPE). Despite its crystallinity, high melting point (Tm=96 °C) and hydrophobic nature, polyester‐2,18 is subject to rapid and complete hydrolytic degradation in in vitro assays with isolated naturally occurring enzymes. Under industrial composting conditions (ISO standard 14855‐1) the material is biodegraded with mineralization above 95 % within two months. Reference studies with polyester‐18,18 (Tm=99 °C) reveal a strong impact of the nature of the diol repeating unit on degradation rates, possibly related to the density of ester groups in the amorphous phase. Depolymerization by methanolysis indicates suitability for closed‐loop recycling.

18) exhibits high density polyethylene-like material properties and, as opposed to high density polyethylene (HDPE), can be recycled in a closed loop via depolymerization to monomers under mild conditions. Despite the in-chain ester groups, its high crystallinity and hydrophobicity render PE-18,18 stable toward hydrolysis even under acidic conditions for one year. Hydrolytic degradability, however, can be a desirable material property as it can serve as a universal backstop to plastic accumulation in the environment. We present an approach to render PE-18,18 hydrolytically degradable by melt blending with long-chain aliphatic poly(H-phosphonate)s (PP). The blends can be processed via common injection molding and 3D printing and exhibit HDPE-like tensile properties, namely, high stiffness (E = 750−940 MPa) and ductility (ε tb = 330−460%) over a wide range of blend ratios (0.5−20 wt % PP content). Likewise, the orthorhombic solid-state structure and crystallinity (χ ≈ 70%) of the blends are similar to HDPE. Under aqueous conditions in phosphate-buffered media at 25 °C, the blends' PP component is hydrolyzed completely to the underlying long-chain diol and phosphorous acid within four months, as evidenced by NMR analyses. Concomitant, the PE-18,18 major blend component is partially hydrolyzed, while neat PE-18,18 is inert under identical conditions. The hydrolysis of the blend components proceeded throughout the bulk of the specimens as confirmed by gel permeation chromatography (GPC) measurements. The significant molar mass reduction upon extended immersion in water (M n (virgin blends) ≈ 50−70 kg mol −1 ; M n (hydrolyzed blends) ≈ 7−11 kg mol −1 ) resulted in embrittlement and fragmentation of the injection molded specimens. This increases the surface area and is anticipated to promote eventual mineralization by abiotic and biotic pathways of these HDPE-like polyesters in the environment.

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