Molecular Design for Dual Circularity: Polyester with Complementary Mechanical and Chemical Recyclability under Mild Conditions.

The plastic waste accumulation requires facile yet effective solutions. Currently mechanical recycling typically leads to downcycling, while the environmental footprint of chemical recycling is often unacceptable. Here, we introduce a dual circularity concept, where rational molecular design paves the way for complementary closed-loop mechanical and chemical recyclability under mild conditions.

Organomediated polymerization.

is pleased to introduce a Collection of articles focused on organomediated polymerization. Here, the Guest Editors highlight the themes within and look towards the future of this research field.

Covalent Adaptable Networks with Tailorable Material Properties Based on Divanillin Polyimines.

Covalent adaptable networks (CANs) are being developed as future replacements for thermosets as they can retain the high mechanical and chemical robustness inherent to thermosets but also integrate the possibility of reprocessing after material use. Here, covalent adaptable polyimine-based networks were designed with methoxy and allyloxy-substituted divanillin as a core component together with long flexible aliphatic fatty acid-based amines and a short rigid chain triamine, yielding CANs with a high renewable content. The designed series of CANs with reversible imine functionality allowed for fast stress relaxation and tailorability of the thermomechanical properties, as a result of the ratio between long flexible and short rigid amines, with tensile strength (σ) ranging 1.

"Like Recycles Like": Selective Ring-Closing Depolymerization of Poly(L-Lactic Acid) to L-Lactide.

Chemical recycling of poly(L-lactic acid) to the cyclic monomer L-lactide is hampered by low selectivity and by epimerization and elimination reactions, impeding its use on a large scale. The high number of side reactions originates from the high ceiling temperature (T ) of L-lactide, which necessitates high temperatures or multistep reactions to achieve recycling to L-lactide. To circumvent this issue, we utilized the impact of solvent interactions on the monomer-polymer equilibrium to decrease the T of L-lactide.

Tailoring Oligomeric Plasticizers for Polylactide through Structural Control.

Structural variations (oligolactide segments, functionalized end groups, and different plasticizer cores) were utilized to tailor the performances of biobased plasticizers for polylactide (PLA). Six plasticizers were developed starting from 1,4-butanediol and isosorbide as cores: two monomeric (1,4-butanediol levulinate and isosorbide levulinate) and four oligomeric plasticizers with hydroxyl or levulinate ester end groups (1,4-butanediol-based oligolactide, isosorbide-based oligolactide, 1,4-butanediol-based oligomeric levulinate, and isosorbide-based oligomeric levulinate). Structural variations in plasticizer design were reflected in the thermal stability, plasticizing efficiency, and migration resistance.

Microwave Assisted Selective Hydrolysis of Polyamides from Multicomponent Carpet Waste.

Selective hydrolysis of polyamide-6 (PA-6) and polyamide-66 (PA-66) from commercial multicomponent PA-6/PA-66/polypropylene (PP) carpet is demonstrated by a microwave-assisted acid catalyzed hydrothermal process, yielding monomeric products and solid polypropylene residue. First, an effective method is established to chemically recycle neat PA-6 and PA-66 granules using microwave irradiation. The optimized, hydrochloric acid (HCl) catalyzed process leads to selective production of monomers, 6-aminocaproic acid or adipic acid and hexamethylenediamine, after only 30 min.

Dual-Functioning Antibacterial Eugenol-Derived Plasticizers for Polylactide.

Dual-functioning additives with plasticizing and antibacterial functions were designed by exploiting the natural aromatic compound eugenol and green platform chemical levulinic acid or valeric acid that can be produced from biobased resources. One-pot synthesis methodology was utilized to create three ester-rich plasticizers. The plasticizers were thoroughly characterized by several nuclear magnetic resonance techniques (H NMR, C NMR, P NMR, HSQC, COSY, HMBC) and by electrospray ionization-mass spectrometry (ESI-MS) and their performances, as plasticizers for polylactide (PLA), were evaluated.

Recyclable Fully Biobased Chitosan Adsorbents Spray-Dried in One Pot to Microscopic Size and Enhanced Adsorption Capacity.

A facile one-pot spray-drying process was developed for fabrication and in situ crosslinking of chitosan microspheres to improve the adsorption capacity by microscopic design. A fully biobased nature was achieved by utilizing genipin (GP) as a crosslinking agent and chitosan-derived nanographene oxide (nGO) as a property tuner. The produced chitosan microspheres were further proven as powerful adsorbents for common wastewater contaminants such as anionic dyes and pharmaceutical contaminants, here modeled by methyl orange (MO) and diclofenac sodium (DCF).

Anionic polycondensation and equilibrium driven monomer formation of cyclic aliphatic carbonates.

The current work explores the sodium hydride mediated polycondensation of aliphatic diols with diethyl carbonate to produce both aliphatic polycarbonates and cyclic carbonate monomers. The lengths of the diol dictate the outcome of the reaction; for ethylene glycol and seven other 1,3-diols with a wide array of substitution patterns, the corresponding 5-membered and 6-membered cyclic carbonates were synthesized in excellent yield (70-90%) on a 100 gram scale. Diols with longer alkyl chains, under the same conditions, yielded polycarbonates with an ranging from 5000 to 16 000.

Isosorbide as Core Component for Tailoring Biobased Unsaturated Polyester Thermosets for a Wide Structure-Property Window.

Biobased unsaturated polyester thermosets as potential replacements for petroleum-based thermosets were designed. The target of incorporating rigid units, to yield thermosets with high thermal and mechanical performance, both in the biobased unsaturated polyester (UP) and reactive diluent (RD) while retaining miscibility was successfully achieved. The biobased unsaturated polyester thermosets were prepared by varying the content of isosorbide, 1,4-butanediol, maleic anhydride, and succinic anhydride in combination with the reactive diluent isosorbide-methacrylate (IM).

Tunable chitosan hydrogels for adsorption: Property control by biobased modifiers.

A sustainable strategy to fabricate chitosan-based composite hydrogels with tunable properties and controllable adsorption capacity of trace pharmaceuticals was demonstrated. Two biobased modifiers were utilized to tune the properties, nano-graphene oxide (nGO) derived from chitosan via microwave-assisted carbonization and oxidation, and genipin as the crosslinking agent. An increase in genipin content facilitated an increase in the degree of crosslinking as shown by improved storage modulus and decreased swelling ratio.

Exploiting Ring-Opening Aminolysis-Condensation as a Polymerization Pathway to Structurally Diverse Biobased Polyamides.

A pathway to biobased polyamides (PAs) via ring-opening aminolysis-condensation (ROAC) under benign conditions with diverse structure was designed. Ethylene brassylate (EB), a plant oil-derived cyclic dilactone, was used in combination with an array of diamines of diverse chemical structure, and ring-opening of the cyclic dilactone EB was revealed as a driving force for the reaction. The ROAC reactions were adjusted, and reaction conditions of 100 °C under atmospheric pressure using 1,5,7-triazabicyclo[4.

Isocyanate-Free, UV-Crosslinked Poly(Hydroxyurethane) Networks: A Sustainable Approach toward Highly Functional Antibacterial Gels.

An increased sustainabile awarness has inspired the development of new polymeric networks in a remarkable way and this strive should be combined with environmentally concerned end-uses. Therefore, a UV-crosslinked polyhydroxyurethane film with antibacterial properties is developed. First, a hydroxyurethane precursor is synthesized using aminolysis condensation, circumventing the use of isocyanates.

Superiorly Plasticized PVC/PBSA Blends through Crotonic and Acrylic Acid Functionalization of PVC.

Superior plasticization efficiency was achieved by a grafting from functionalization of the PVC backbone. This was deduced to a synergistic effect of internal plasticization and improved intermolecular interactions between PVC and an oligomeric poly(butylene succinate--adipate) (PBSA) plasticizer. A mild grafting process for functionalization of the PVC chain by crotonic acid (CA) or acrylic acid (AA) was used.

One-pot inimer promoted ROCP synthesis of branched copolyesters using α-hydroxy-γ-butyrolactone as the branching reagent.

An array of branched poly(ɛ-caprolactone)s was successfully synthesized using an one-pot inimer promoted ring-opening multibranching copolymerization (ROCP) reaction. The biorenewable, commercially available yet unexploited comonomer and initiator 2-hydroxy-γ-butyrolactone was chosen as the inimer to extend the use of 5-membered lactones to branched structures and simultaneously avoiding the typical tedious work involved in the inimer preparation. Reactions were carried out both in bulk and in solution using stannous octoate (Sn(Oct)) as the catalyst.

Switching from Controlled Ring-Opening Polymerization (cROP) to Controlled Ring-Closing Depolymerization (cRCDP) by Adjusting the Reaction Parameters That Determine the Ceiling Temperature.

Full control over the ceiling temperature (T) enables a selective transition between the monomeric and polymeric state. This is exemplified by the conversion of the monomer 2-allyloxymethyl-2-ethyl-trimethylene carbonate (AOMEC) to poly(AOMEC) and back to AOMEC within 10 h by controlling the reaction from conditions that favor ring-opening polymerization (T > T) (where T is the reaction temperature) to conditions that favor ring-closing depolymerization (T < T). The ring-closing depolymerization (RCDP) mirrors the polymerization behavior with a clear relation between the monomer concentration and the molecular weight of the polymer, indicating that RCDP occurs at the chain end.

Simultaneous Polymerization and Polypeptide Particle Production via Reactive Spray-Drying.

A method for producing polypeptide particles via in situ polymerization of N-carboxyanhydrides during spray-drying has been developed. This method was enabled by the development of a fast and robust synthetic pathway to polypeptides using 1,8-diazabicyclo[5.4.

Toward "Green" Hybrid Materials: Core-Shell Particles with Enhanced Impact Energy Absorbing Ability.

Restrained properties of "green" degradable products drive the creation of materials with innovative structures and retained eco-attributes. Herein, we introduce the creation of impact modifiers in the form of core-shell (CS) particles toward the creation of "green" composite materials. Particles with CS structure constituted of PLA stereocomplex (PLASC) and a rubbery phase of poly(ε-caprolactone--d,l-lactide) (P[CL--LA]) were successfully achieved by spray droplet atomization.

Highlighting the Importance of Surface Grafting in Combination with a Layer-by-Layer Approach for Fabricating Advanced 3D Poly(l-lactide) Microsphere Scaffolds.

A combined surface treatment (i.e., surface grafting and a layer-by-layer (LbL) approach) is presented to create advanced biomaterials, i.

Poly(lactide)-g-poly(butylene succinate-co-adipate) with High Crystallization Capacity and Migration Resistance.

Plasticized polylactide (PLA) with increased crystallization ability and prolonged life-span in practical applications due to the minimal plasticizer migration was prepared. Branched plasticized PLA was successfully obtained by coupling poly(butylene succinate-co-adipate) (PBSA) to crotonic acid (CA) functionalized PLA. The plasticization behavior of PBSA coupled PLA (PLA-CA-PBSA) and its counterpart PBSA blended PLA (PLA/PBSA) were fully elucidated.

Thermodynamic Presynthetic Considerations for Ring-Opening Polymerization.

The need for polymers for high-end applications, coupled with the desire to mimic nature's macromolecular machinery fuels the development of innovative synthetic strategies every year. The recently acquired macromolecular-synthetic tools increase the precision and enable the synthesis of polymers with high control and low dispersity. However, regardless of the specificity, the polymerization behavior is highly dependent on the monomeric structure.

Homocomposites of Polylactide (PLA) with Induced Interfacial Stereocomplex Crystallites.

The demand for "green" degradable composite materials increases with growing environmental awareness. The key challenge is achieving the preferred physical properties and maintaining their eco-attributes in terms of the degradability of the matrix and the filler. Herein, we have designed a series of "green" homocomposites materials based purely on polylactide (PLA) polymers with different structures.

Macromolecular Design via an Organocatalytic, Monomer-Specific and Temperature-Dependent "On/Off Switch". High Precision Synthesis of Polyester/Polycarbonate Multiblock Copolymers.

The employment of a monomer-specific "on/off switch" was used to synthesize a nine-block copolymer with a predetermined molecular weight and narrow distribution ( = 1.26) in only 2.5 h.

In Situ Synthesis of Magnetic Field-Responsive Hemicellulose Hydrogels for Drug Delivery.

A one-pot synthetic methodology for fabricating stimuli-responsive hemicellulose-based hydrogels was developed that consists of the in situ formation of magnetic iron oxide (Fe3O4) nanoparticles during the covalent cross-linking of O-acetyl-galactoglucomannan (AcGGM). The Fe3O4 nanoparticle content controlled the thermal stability, macrostructure, swelling behavior, and magnetization of the hybrid hydrogels. In addition, the magnetic field-responsive hemicellulose hydrogels (MFRHHs) exhibited excellent adsorption and controlled release profiles with bovine serum albumin (BSA) as the model drug.