Plastics are essential materials in our daily lives. Designing circular polymer materials with sustainable end-of-life processes is an important and rapidly growing research field. Athanassiou and colleagues developed dynamic boronic-ester vitrimers with excellent mechanical properties and biodegradability, representing a significant achievement in the field of dynamic polymers toward this goal.

Starting from bio-based aldehyde-containing aromatic monomers, diamine and a series of diols, linear polyesters with pendant aldehyde groups (PEa-PEe) and crosslinked polyimine-amides (PIA) were synthesized. Compared with previously reported PIA, high biobased content is achieved by utilizing a biobased diamine, Priamine™ 1071 (PA). In addition, the linear polyesters were blended by compression molding with PIA in different proportions to initiate imine exchange between the free aldehyde-groups in the polyesters and imine-groups in PIA. The structures and thermal properties of the obtained linear polyesters and crosslinked polymers were confirmed by NMR, FTIR, SEC, TGA, DSC, DMA and rheological analyses. Compared to most previous polyimine polymers, PIA exhibited higher thermal stability, higher elongation at break (280%) and moderate tensile stress at break of 4.7 MPa. Subsequent blending with linear polyesters provided tunable properties depending on the length of the diol used for polyester synthesis. In brief, somewhat decreased elongation at break between 129 and 189% was observed, while tensile strength at break varied from 3.2 MPa to 12.1 MPa. All the crosslinked materials demonstrated good solvent resistance in common organic solvents with 94-99% gel content. The crosslinked materials showed promising mechanical recyclability with good retention of mechanical properties after repeated compression molding. Furthermore, chemical recycling of PIA was demonstrated under acidic conditions at room temperature leading to repolymerizable aldehydes and amine hydrochlorides. This promising molecular design can be further tuned by the choice of aldehydes, amines and diols to achieve required performance in combination with closed-loop recyclability.

Enzymatic depolymerization of postconsumer polyurethanes (PURs) offers a promising route for sustainable plastic waste management. However, the complex chemistry of PURs containing carbamate, ether, and ester bonds poses a challenge for such a biotechnological process. Here, we explored the deconstruction of a commercial polyether-polyester-PUR through a cascade depolymerization approach, in which a low-temperature thermal pretreatment (180°C, 4 h) was combined with tandem enzymatic hydrolysis. Heat treatment modified the polymer's physicochemical properties, enabling the cutinase HiC from Humicola insolens to cause more than 8% weight loss of the treated PUR films, versus less than 2% of the untreated control after 48 h incubation. Furthermore, the addition of the metagenomic urethanase SP2 completed the one-pot enzymatic cascade, achieving not only depolymerization to the constituent monomer, 4,4′-methylenedianiline (MDA), but also a nearly 3-fold increase in MDA yield compared to using SP2 alone. Docking studies highlighted HiC's specificity toward ester bonds in the PUR polymeric units, and two HiC variants further enhanced degradation within 24 h. Altogether, this work lays the foundation for future investigation and process design for the depolymerization of polyether-polyester-PURs and related materials by cascade enzymatic reactions.

Bioplastics are increasingly being used for packaging applications, leading to the generation of a complex fraction of waste at their end of life. Pyrolysis treatment is one potential technique that can be used to convert bioplastic waste into fuel and energy. Here, pyrolysis of alkaline-treated K85 rice husk-derived bioplastic films was investigated using thermogravimetric analysis (TGA) at different heating rates (10, 20 and 30 K min⁻¹). The influence of different ratios of succinylation and trimethylolpropane triglycidyl ether-induced crosslinking on the combustion as well as the kinetic and thermodynamic characteristics were evaluated. Model-free methods (Kissinger–Akahira–Sunose (KAS), Ozawa–Flynn–Wall (OFW), Starink and Tang) were used to develop the kinetic model of pyrolysis of the bioplastic films. Differential scanning calorimetry showed glass transitions at around 25 °C, where the films passed from a rigid glassy state to a rubbery solid state. TGA results showed that the main decomposition of the bioplastic films happened in the range of 340.0–416.5 °C, while the kinetic models indicated that the average activation energies for the samples were estimated at 142.3–228.3 kJ mol⁻¹ (KAS), 145.0–232.3 kJ mol⁻¹ (OFW), 142.6–288.5 kJ mol⁻¹ (Starink) and 135.8–217.5 kJ mol⁻¹ (Tang). Due to the low energy barrier between activation energy and enthalpy (≤5.7 kJ mol−1), the reaction initiation of the films occurs easily. In conclusion, the results support the suitability of pyrolysis as an effective end-of-life management option for rice husk-derived bioplastic films, directly supporting circular economy goals for biobased materials. The kinetic parameters, validated across four independent models, provide a quantitative foundation for the design and optimization of industrial-scale pyrolysis reactors targeting bioplastic packaging waste streams.

Recycling aromatic polyester waste into UV-curable covalent adaptable networks (CANs) offers a promising pathway toward bringing more materials into the circular economy. Here, we present a straightforward strategy to convert post-consumer polyethylene terephthalate (PET) bottles and polybutylene terephthalate (PBT) fabrics into photocurable, mechanically reprocessable, and chemically degradable CANs. PET and PBT were first depolymerized via glycolysis or alcoholysis to yield BHET and BHBT, which were subsequently methacrylated to form the resins PR and FR. A third resin, SBJR, containing dynamic imine (Schiff-base) linkages, was synthesized from methacrylated vanillin and Jeffamine to introduce reversible bonding into the network. These components enabled fabrication of two permanently crosslinked polymers (PR100 and FR100) and two covalent adaptable networks (CAN1 and CAN2). Structural analysis verified the expected chemical transformations, and all materials exhibited good thermal stability, with CANs showing slightly reduced T5% due to flexible aliphatic segments and reversible imine bonds. Rheological creep and stress-relaxation studies supported associative imine exchange as the governing mechanism without network dissociation. CAN2 also demonstrated robust solvent resistance and could be mechanically recycled and chemically degraded through imine-exchange-driven depolymerization. Overall, this work establishes an efficient molecular design framework for transforming plastic and textile waste into photocurable materials, advancing the value of plastic waste as a resource for new materials and reduced environmental pollution.

Most contemporary chemical processes rely on non-renewable resources and reagents associated with negative impact on environment and human health. As a result, the safe-and-sustainable-by-design (SSbD) framework is launched to guide the innovation towards safe and sustainable materials and chemical products. Bisphenol A (BPA) is a widely used chemical in the production of plastics but known to activate oestrogen receptors and linked by numerous studies to adverse effects on both human health and the environment. Here we demonstrate how SSbD can lead a multidisciplinary study for the identification of non-oestrogenic BPA analogues suitable for incorporation into high-performance polymeric materials. Toxicological evaluation of a library of 172 bisphenols using an in silico model identified 20 promising candidates that are synthesized from renewable lignin-sourced feedstocks via benign dehydrative catalytic routes. Subsequent in vitro assessment of their oestrogen receptor activity identifies bisguaiacol F as optimal BPA analogue, which is incorporated into a polyester with attractive thermal stability and flexibility. This work demonstrates an effective workflow for the discovery of renewable and non-oestrogenic bisphenols by taking advantage of the synergy of synthetic chemistry, toxicology and computational modelling.

An important aspect before large-scale production and application of bioplastics such as polylactic acid (PLA), is the need to close the life cycle of the material to reduce the need for first-generation biomass and to prevent waste accumulation in the environment. In this work, starting from a high-mass linear commercial PLA, a depolymerization route based on a bulk alcoholysis reaction in the molten state was developed. For this purpose two polyalcohols, pentaerythritol and dipentaerythritol, and an environmentally friendly catalyst, i.e., zinc stearate, were utilized. The formation and specific polyalcohol dependent structure of star-shaped oligomers characterized by a low glass transition temperature was confirmed by spectroscopical and thermal analysis. Indeed, 1H NMR characterization evidenced that the most effective polyalcohol was pentaerythritol, which at the highest concentration in the reaction mixture, namely 10 wt.-%, allowed most of the hydroxyl groups to react, resulting in a system with a Tg of about 20 °C, which was much lower than that of the starting linear polymer, characterized by a Tg of about 60 °C. Moreover, GPC as well as DSC analysis in particular demonstrated the active role of zinc stearate in the transesterification reaction, as the samples prepared without adding the catalyst to the reaction mixture showed a modest reduction in Tg and molecular weight, which decreased from 92,000 g⋅mol−1 to 1700 g⋅mol−1 for the starting linear polymer and the resulting oligomer, respectively, in the case of the sample prepared with the highest amount of PE and with the addition of zinc stearate.The films produced from the star-shaped PLA oligomers were characterized by poor mechanical properties, but the high concentration of alcohol-functionalities could make them applicable in various polymer formulations. The star-shaped polymers were thereby blended with a multifunctional epoxide from renewable sources. The reactivity and compatibility of the two components was proved along with the specific role of zinc stearate remaining from the alcoholysis, in promoting the reaction between the two compounds. Indeed, the produced materials proved to be homogeneous, manageable and also completely enzymatically degradable.

This work aimed to investigate structurally defined biobased polymers as non-leachable and non-toxic UV blockers for sunscreen applications. Two dicarboxylate monomers were synthesized using two lignin-based monomeric aromatic compounds, vanillin and 4-hydroxybenzaldehyde. These two monomers were then polymerized together with linear aliphatic diols of varying lengths to produce UV-active polyesters. The structural, molecular and thermal properties of the resulting polyesters were confirmed by NMR, FTIR, HRMS, GPC, TGA and DSC analyses. These obtained polyesters exhibited high UV-visible absorption in both solutions and creams. Furthermore, the blend creams showed negligible leaching into fresh or salt water after 24 h. Finally, these obtained polyesters were nontoxic to human MG- 63 osteoblasts at concentrations up to 100 mu M. Our findings indicated the potential of this new class of structurally defined biobased polymers as efficient non- leachable UV blockers in sunscreens.

Accelerated production of recyclable and biodegradable polymers is crucial in combating the socioeconomic and environmental issues connected to traditional plastics. While renewable diacids have been in the spotlight for the generation of biobased polyesters with tailored properties by varying the alkyl chain length, capitalizing on diols from biomass for this purpose is underexplored and has mainly focused on linear and branched shorter chain alcohols. Here, we explored the potential of two (-)-alpha-pinene-derived diols (PDOs) as building blocks to generate biobased polyesters harboring bicyclic ring structures in their backbones that can mimic aromatic fossil-based plastics' properties. We demonstrate a concise synthesis of two novel unsymmetrical chiral PDOs on the 20-40 g scale, together with eight structurally differing heat-resistant polyesters, as reflected by high glass transition (T g ) temperatures (90 and 121 degrees C) for two of the polymers. The stereochemistry of PDO-derived polyesters is guided by intramolecular hydrogen bonding made possible by the protruding rings and the polyester backbone. Most of the synthesized polyesters (five) in this study showed potential as adhesives based on the analysis of tensile strength and adhesive properties on paper boards. The steric hindrance of the intact bicyclic alpha-pinene ring structure protruding from the backbone of the polymers can also aid in the degradation process, manifested by facile chemical recycling of these polyesters under mild conditions to recover both monomers. Finally, our results show how the generated rigid polymers are susceptible to enzymatic degradation by PETase and cutinase without any chemical pretreatment. Our results illuminate the potential of expanding the current scope of biobased monomers to bicyclic diols to generate biomaterials with tailor-made properties.

A series of cellulose networks are designed by reversibly crosslinking amino-functionalized 2-hydroxyethyl cellulose (HEC-NH2) with different amounts of vanillin dimer (VA-CHO). The Schiff base reaction between amino-and aldehyde groups creates networks (SBHEC) bridged with crosslinks containing dynamic imine groups. These SBHEC networks can be hot pressed to flexible films with good thermal stability and solvent resistance, including notable stability in water, opposite to water-soluble HEC and HEC-NH2. Compared to HEC-NH2, the cross-linked SBHEC networks exhibit higher glass transition temperatures, elastic modulus, and tensile stress at break, and slightly reduced tensile strain at break. Reprocessing of the SBHEC networks is achieved through hot pressing under facile conditions, leading to good recovery of mechanical properties. Furthermore, the materials can be chemically recycled in a closed-loop by imine-hydrolysis under acidic conditions at room temperature. This releases the original building blocks HEC-NH(2 )and VA-CHO, which can be recured to produce new SBHEC. This work highlights the potential of dynamic covalent cellulose networks as mechanically and chemically recyclable materials, contributing to the development of closed-loop recycling systems.