Recyclable polymer functionalization via end-group modification and block/random copolymerization

Recyclable polymers offer a great opportunity to address the environmental issues of plastics.Herein,functionalization of recyclable polymers,poly((R)-3,4-trans six-membered ring-fused GBL)(P((R)-M)),were reported via end-group modifications and block/random copolymerizations.Di-n-butylmagnesium was selected to catalyze ring-opening polymerization(ROP)of(R)-M in the presence of a series of functional alcohols as the initiators.Block/random copolymerizations of(R)-M andε-caprolactone(ε-CL),L-lactide(L-LA)and trimethylene carbonate(TMC)were performed to control the onset decomposition temperature(T_(d)),melting temperature(T_(m))and glass transition temperature(T_(g)).These functionalized recyclable polymers would find broad applications as the sustainable plastics.

One-pot green mass production of hierarchically porous carbon via a recyclable salt-templating strategy

Porous carbon materials have exhibited a series of promising applications in supercapacitors and other research fields,yet still confronting the complicated synthetic procedures and massive usage of toxic reagents.Herein,we propose a green and one-pot method to produce heteroatomdoped hierarchical porous carbon materials in large-scale without any toxic reagents employed.Eventually,the as-prepared nitrogen-doped porous carbon(NPC)displays a high specific surface area of 2018 m^(2)g^(-1)together with abundant heteroatom dopants(14.8 wt%O and 1.03 wt%N).The potassium carbonate template can be recycled via a simple rinsing and re-precipitation process.Furthermore,the as-prepared nitrogen-doped porous carbon delivers a high specific capacitance of 361 F g^(-1)at 0.5 A g^(-1)and excellent rate capability of 240 F g^(-1)at 20 A g^(-1)(66.5%capacitance retention).Finally,considering the low-price raw materials and facile green synthesis procedure,the present approach can be easily scalable to prepare biomass-derived heteroatoms doped porous carbon,which is not only applicable for supercapacitor but also for other research fields.

1,4-Hydroquinone is a Hydrogen Reservoir for Fuel Cells and Recyclable via Photocatalytic Water Splitting

Photocatalytic splitting of water was carried out in a two-phase system. Nanocrystalline titanium dioxide was used as photocatalyst and potassium hexacyanoferrate(III)/(II) as electron transporter. Generated hydrogen was chemically stored by use of a 1,4-benzoquinone/1,4-hydroquinone system, which was used as a recyclable fuel in a commercialised direct methanol fuel cell (DMFC). The electrical output of the cell was about half compared to methanol. The conversion process for water splitting and recombination in a fuel cell was monitored by UV-Vis spectroscopy and compared to a simulated spectrum. Products of side reactions, which lead to a decrease of the overall efficiency, were identified based on UV-Vis investigations. A proof of principle for the use of quinoide systems as a recyclable hydrogen storage system in a photocatalytic water splitting and fuel cell cyclic process was given.

TiO_2/Ag composite nanowires for a recyclable surface enhanced Raman scattering substrate

Multifunctional TiO2/Ag composite nanowires are fabricated with a hydrothermal method by precipitating Ag nanoparticles （NPs） on the surfaces of TiO2 nanowires. This hierarchical one-dimensional （1D） nanostructure can be used as a surface enhanced Raman scattering （SERS） substrate with high sensitivity, for detecting the rhodamine 6G （R6G） in a wide range of low concentrations （from 1 × 10 6 M to 1 × 10-12 M）. In addition, the substrate can be self-cleaned under the irradiation of ultraviolet （UV） light due to the superior photocatalytic capacity of the TiO2/Ag composite nanostructure, making the recycled use of SERS substrates closer to reality. With both the evident SERS performance and high efficiency of photocatalytic capacity, such TiOz/Ag composite nanowires demonstrate considerable potential in the chemical sensing of organic pollutants.

Recyclable Cyclohexanediamine Derivatives as Organocatalysts: Organocatalytic Reduction with Trichlorosilane and Aldol Reaction

Reduction of ketimine with trichlorosilane was carried out using bisformamide catalyst 1a derived from cyclohexanediamine to give the corresponding product in 81% yield with 39% ee. Deprotection of the formyl groups of the catalysts 1 gave the corresponding diamines 2 which were utilized in aldol reaction of acetone with 4-nitrobenzaldehyde. The reaction using 2b in brine afforded the aldol adduct in 81% yield with 29% ee.

Reshapeable,rehealable and recyclable sensor fabricated by direct ink writing of conductive composites based on covalent adaptable network polymers

Covalent adaptable network(CAN)polymers doped with conductive nanoparticles are an ideal candidate to create reshapeable,rehealable,and fully recyclable electronics.On the other hand,3D printing as a deterministic manufacturing method has a significant potential to fabricate electronics with low cost and high design freedom.In this paper,we incorporate a conductive composite consisting of polyimine CAN and multi-wall carbon nanotubes into direct-ink-writing 3D printing to create polymeric sensors with outstanding reshaping,repairing,and recycling capabilities.The developed printable ink exhibits good printability,conductivity,and recyclability.The conductivity of printed polyimine composites is investigated at different temperatures and deformation strain levels.Their shape-reforming and Joule heating-induced interfacial welding effects are demonstrated and characterized.Finally,a temperature sensor is 3D printed with defined patterns of conductive pathways,which can be easily mounted onto 3D surfaces,repaired after damage,and recycled using solvents.The sensing capability of printed sensors is maintained after the repairing and recycling.Overall,the 3D printed reshapeable,rehealable,and recyclable sensors possess complex geometry and extend service life,which assist in the development of polymer-based electronics toward broad and sustainable applications.

Recyclable Fe_(3)O_(4)@Polydopamine(PDA) nanofluids for highly efficient solar evaporation

Volumetric solar evaporations by using light-absorbing nanoparticles suspended in liquids(nanofluids)as solar absorbers have been widely regarded as one of the promising solutions for clean water production because of its high efficiency and low capital cost compared to traditional solar distillation systems.Nevertheless,previous solar evaporation systems usually required highly concentrated solar irradiation and high capital cost,limiting the practical application on a large scale.Herein,for the first time in this work,polydopamine(PDA)-capped nano Fe_(3)O_(4)(Fe_(3)O_(4)@PDA)nanofluids were used as solar absorbers in a volumetric system for solar evaporation.The introduction of organic PDA to nano Fe_(3)O_(4)highly contributed to the high light-absorbing capacity of over 85%in wide ranges of 200–2400 nm because of the existence of numerous carbon bonds and pi(π)bonds in PDA.As a result,high evaporation efficiency of 69.93%under low irradiation of 1.0 kW m^(-2)was achieved.Compared to other nanofluids,Fe_(3)O_(4)@PDA nanofluids also provided an advantage in high unit evaporation rates.Moreover,Fe_(3)O_(4)@PDA nanofluids showed excellent reusability and recyclability owing to the preassembled nano Fe_(3)O_(4),which significantly reduced the material consumptions.These results demonstrated that the Fe_(3)O_(4)@PDA nanofluids held great promising application in highly efficient solar evaporation.

Efficient and recyclable Rh-catalytic system with involvement of phosphine-functionalized phosphonium-based ionic liquids for tandem hydroformylation—acetalization

The phosphine-functionalized phosphonium-based ionic liquids(dppm-Q, dppe-Q, dppp-Q and dppb-Q) as the bi-functional ligands enable the efficient one-pot tandem hydroformylationeacetalization. It was found that, in dppm-Q, dppe-Q, dppp-Q and dppb-Q, the incorporated phosphino-fragments were responsible for Rh-catalyzed hydroformylation and the phosphoniums were in charge of the subsequent acetalization as the Lewis acid catalysts. Moreover, the diphosphonium-based ionic liquid of dppb-DQ could be applied as a co-solvent to immobilize the Rh/dppb-Q catalytic system with the advantages of the improved catalytic performance, the available catalyst recyclability, and the wide generality for the substrates.

Viscoelastic and Thermal Properties of Polyurethane Foams Obtained from Renewable and Recyclable Components

This article deals with the study of the viscoelastic and thermal properties of polyurethane (PU) rigid foamsfrom biobased and recycled components. Rapeseed oil (RO) and recycled poly(ethylene terephthalate)(PET) were used to synthesize PU polyols. Addition of adipic acid (ADA) to polyol resulted in improvedthermal and viscoelastic properties of foam materials. ADA content was varied from 1 to 6 wt%. Results ofthe dynamic mechanical spectra indicate an increase of the storage modulus E′ and the loss modulus E″ inthe whole temperature range for specimens with higher loading of ADA. In addition, damping factor shiftedto higher temperatures, but damping intensity remained almost unaffected by the compositions. Scanningelectron microscopy of the foams’ cross sections testified that the average cells’ size of 110 mm was unaffectedby the ADA content in polyol.

Rapid chemical recycling of waste polyester plastics catalyzed by recyclable catalyst

Waste plastics are serious environmental threats due to their low degradability and low recycling rate.Rapid and efficient waste plastics recycling technologies are urgently demanded for a sustainable future.Herein,we report a rapid,closed-loop,and streamlined process to convert polyesters such as poly(ethylene terephthalate)(PET)back to its purified monomers.Using trifluoromethanesulfonic acid or metal triflates as the recyclable catalyst,polyesters such as PET can be completely depolymerized by simple carboxylic acids within 1 h.By coupling this acidolysis with a subsequent hydrogenolysis process,the consumed carboxylic acid was recovered and the closed-loop of PET depolymerization could be established.All catalysts and depolymerization agents are fully recycled while only PET and hydrogen are consumed.

Water-Driven Malleable,Weldable and Eco-Friendly Recyclable Carbon Fiber Reinforced Dynamic Composites

Traditional carbon fiber-reinforced polymers based on thermoset matrix have been extensively used in the fields of wind turbine blades,automotive sector,and aerospace,among many others.However,there is still a major challenge of recycling those polymers due to the high cost and adverse impacts on the environment.In this work,we apply a polyimine network as matrix,which possess considerable tensile and thermal properties,to prepare the carbon fiber reinforced polyimine materials with trifluoromethyl diphenoxybenzene units(CFRFP)using a prepreg-based compression molding method.The CFRFP can be reshaped or reprocessed by heat or with water rapidly,and exhibited multifunction,including welding,chemical recycling,etc.These unique findings gained from our study will facilitate the manufacturing capability and enrich the types of fiber-reinforced composites.

High-Performance Recyclable Furan-based Epoxy Resin and Its Carbon Fiber Composites with Dense Hydrogen Bonding

The emerging biomass-based epoxy vitrimers hold great potential to fulfill the requirements for sustainable development of society.Since the existence of dynamic chemical bonds in vitrimers often reduces both the thermal and mechanical properties of epoxy resins, it is challenging to produce recyclable epoxy vitrimers with both excellent mechanical properties and good thermal stability. Herein, a monomer 4-(((5-(hydroxymethyl)furan-2-yl)methylene)amino)phenol(FCN) containing furan ring with potential to form high density of hydrogen bonding among repeating units is designed and copolymerized with glycerol triglycidyl ether to yield epoxy resin(FCN-GTE), which intrinsically has dual hydrogen bond networks, dynamic imine structure and resultant high performance. Importantly, as compared to the BPA-GTE, the FCN-GTE exhibits significantly improved mechanical properties owing to the increased density of hydrogen bond network and physical crosslinking interaction. Furthermore, density functional theory(DFT) calculation and in situ FTIR analysis is conducted to decipher the formation mechanism of hydrogen bond network. In addition, the FCN-GTE possesses superior UV shielding, chemical degradation, and recyclability because of the existence of abundant imine bonds. Notably, the FCN-GTE-based carbon fiber composites could be completely recycled in an amine solution.This study provides a facile strategy for synthesizing recyclable biomass-based high-performance epoxy vitrimers and carbon fiber composites.

Molecular design of recyclable thermosetting polyimide and its composite with excellent mechanical and tribological properties

Recyclability of thermosetting polymers and their composites is a challenge for alleviating environmental pollution and resource waste.In this study,solvent-recyclable thermosetting polyimide(PI)and its composite were successfully synthesized.The tensile strength,elongation at break,and Young’s modulus of PI are 108.70±7.29 MPa,19.35%±3.89%,and 2336.42±128.00 MPa,respectively.The addition of reduced graphene oxide(RGO)not only enhances the mechanical properties of PI but also endows it with excellent tribological properties.The PI illustrates a high recycling efficiency of 94.15%,but the recycled composite exhibits inferior mechanical properties.The recycling and utilization of PI and its composite are realized through imine bonds(-C=N),which provides new guidance for solving the problem of environmental pollution and resource waste and is potential application in the field of sustainable tribology.

Recyclable polythioesters and polydisulfides with near-equilibrium thermodynamics and dynamic covalent bonds

The accumulation of discarded petroleum-based plastics causes serious environmental crises.Currently,recyclable polymers with neutrality in thermodynamics,such as polyesters,polycarbonates,and polyolefins,have been developed as promising alternatives to traditional petroleum-based polymers.However,the chemical recycle of these polymers usually requires high energy input and expensive catalysts.Dynamic covalent bonds,such as thioester and disulfide bonds,have emerged as building blocks for constructing recyclable polymers that can be rapidly degraded/recycled under mild conditions.In this review,we introduce representative studies on recyclable polythioesters and polydisulfides with respect to their synthetic strategies,thermodynamic manipulation,physicochemical properties,and preliminary applications.We also highlight the important role of kinetic factors played in the design of recyclable polymers.Finally,major challenges,perspectives,and future opportunities in the synthesis and applications of polythioesters/polydisulfides are discussed.

Efficacy of hierarchical pore structure in enhancing the tribological and recyclable smart lubrication performance of porous polyimide

Herein,a porous oil-containing material with hierarchical pore structure was successfully prepared through microtexturing large pores on the surface of porous polyimide(PPI)with single-level small pores.Compared to the conventional oil-containing material,the hierarchically porous oil-containing material exhibited high oil-content,and retained excellent mechanical properties and high oil-retention because of the synergistic effects of large pores and small pores.Furthermore,the lubricant stored in the hierarchically porous polyimide could release to the interface under thermal-and-mechano-stimuli,and the released lubricant could be reabsorbed into the hierarchically porous polyimide via the capillary-force offered by the porous channel.Based on the high oil-content and recyclable oil release/reabsorption,the hierarchically porous oil-containing polyimide exhibited excellent lubrication performance(coefficient of friction was 0.057).Furthermore,the composite could perform 1,069 cycles of smart lubrication(1 h per cycle),which significantly extended the service life of the hierarchically porous oil-containing smart lubrication material.

A novel CRISPR/Cas9 system with high genomic editing efficiency and recyclable auxotrophic selective marker for multiple-step metabolic rewriting in Pichia pastoris

The methylotrophic budding yeast Pichia pastoris has been utilized to the production of a variety of heterologous recombinant proteins owing to the strong inducible alcohol oxidase promoter(pAOX1).However,it is difficult to use P.pastoris as the chassis cell factory for high-valuable metabolite biosynthesis due to the low homologous recombination(HR)efficiency and the limitation of handy selective markers,especially in the condition of multistep biosynthetic pathways.Hence,we developed a novel CRISPR/Cas9 system with highly editing efficiencies and recyclable auxotrophic selective marker(HiEE-ReSM)to facilitate cell factory in P.pastoris.Firstly,we improved the HR rates of P.pastoris through knocking out the non-homologous-end-joining gene(Δku70)and overexpressing HR-related proteins(RAD52 and RAD59),resulting in higher positive rate compared to the basal strain,achieved 97%.Then,we used the uracil biosynthetic genes PpURA3 as the reverse screening marker,which can improve the recycling efficiency of marker.Meanwhile,the HR rate is still 100%in uracil auxotrophic yeast.Specially,we improved the growth rate of uracil auxotrophic yeast strains by overexpressing the uracil transporter(scFUR4)to increase the uptake of exogenous uracil from medium.Meanwhile,we explored the optimal concentration of uracil(90 mg/L)for strain growth.In the end,the HiEE-ReSM system has been applied for the inositol production(250 mg/L)derived from methanol in P.pastoris.The systems will contribute to P.pastoris as an attractive cell factory for the complex compound biosynthesis through multistep metabolic pathway engineering and will be a useful tool to improve one carbon(C1)bio-utilization.

Self-healable, recyclable, ultrastretchable, and high-performanceNO_(2) sensors based on an organohydrogel for room and sub-zero temperature and wireless operation

To date,development of high-performance,stretchable gas sensors operating at and below room temperature(RT)remains a challenge in terms of traditional sensing materials.Herein,we report on a high-performance NO_(2) gas sensor based on a self-healable,recyclable,ultrastretchable,and stable polyvinyl alcohol–cellulose nanofibril double-network organohydrogel,which features ultrahigh sensitivity(372%/ppm),low limit of detection(2.23 ppb),relatively fast response and recovery time(41/144 s for 250 ppb NO_(2)),good selectivity against interfering gases(NH3,CO_(2),ethanol,and acetone),excellent reversibility,repeatability,and long-term stability at RT or even at−20°C.In particular,this sensor shows outstanding stability against large deformations and mechanical damages so that it works normally after rapid self-healing or remolding after undergoing mechanical damage without significant performance degradation,which has major advantages compared to state-of-the-art gas sensors.The high NO_(2) sensitivity and selectivity are attributed to the selective redox reactions at the threephase interface of gas,gel,and electrode,which is even boosted by applying tensile strain.With a specific electrical circuit design,a wireless NO_(2) alarm system based on this sensor is created to enable continuous,real-time,and wireless NO_(2) detection to avoid the risk of exposure to NO_(2) higher than threshold concentrations.

Repairable,Recyclable,and Regenerable Macrocycle Organic Polymer

Covalent/metal organic frameworks are highly attractive due to their tunable structure and properties,and broad applications in multiple fields.However,they still suffer from numbers of drawbacks including low solubility,harsh synthesis and fabrication,and low mechanical flexibility.Herein,we report a new organic framework consisting of macrocycles and organic frames in its periodic structure,and denote it as macrocycle organic polymer(MOP).The size-tunable macrocycles containing peripheral furan units are synthesized by anionic ring-opening polymerization,which undergo a reversible Diels-Alde reaction with bismaleimide to generate/degrade MOPs at given temperatures.Relying on above features,MOPs exhibit excellent flexibility,healable ability and recycle ability.Interestingly,owing to the“living”nature of anionic ring-opening polymerization,MOPs can self-grow into bigger sizes in the presence of monomer and catalysis,analogs to the living creatures.Moreover,their high porosity and rich thioether structure enable them as good metal ion absorbers and promising applications in wearable electronics.

Mechanical Strong,Highly Adhesive,Recyclable and Transparent Supramolecular Silicone Coatings with Easy Water/Oil Sliding

Traditional silicone materials have poor mechanical properties,poor interfacial adhesion and lack the ability to be reprocessed or recycled.Herein,we developed a novel strategy of incorporating dynamic noncovalent bonds(2-amino-4-hydroxy-6-methylpyrimidine(UPy))into side chain of silicone backbones to construct supramolecular silicone poly(urea-urethane)(SSPu)coatings with excellent mechanical performance,strong interfacial adhesion and multiple time recycling capability.Impressively,the prepared SSPu is endowed with simultaneously enhanced stiffness(272.0±23.2 MPa)and toughness(8.0±2.0 MJ·m^(-3)).Besides,SSPu shows strong interfacial adhesion(up to 9.0±1.3 MPa)to diverse substrate(stainless steel,aluminum,copper,epoxy and glass)with long term stability.Moreover,SSPu exhibits excellent multirecyclability and reusability without significantly decrease of its performance.In addition to the abovementioned features,the enrichment of siloxane backbones in the surface layer endows SSPu with robust repellency to water/oil.Our strategy provides a powerful route to fabricate a new multifunctional silicone elastomer.It is highly anticipated that our strategy can effectively extend the service life of silicone coating which can be applied in a wide variety of areas including self-cleaning,antifouling.

Green Synthesis of Chemically Recyclable Polyesters via Dehydrogenative Copolymerization of Diols

Preparation of chemically recyclable polyesters by ring-opening polymerization(ROP)has made a considerable progress over the past few years.However,this method involves cumbersome synthesis and minimal functional diversity of cyclic monomers.Therefore,it is of great significance to develop novel polymerization methods for direct polymerization of commercially available monomers to prepare recyclable polyesters with versatile functionalities.In present work,we report dehydrogenative copolymerization of commercialα,ω-diols to afford high molecular weight chemically recyclable aliphatic copolyesters(65.7 kg·mol^(-1))by using commercially available Milstein catalyst precursor.The thermal properties of the obtained copolymers could be finely tuned by simply adjusting the feeding ratio of two monomers.The incorporation of aliphatic or aromatic rings into polyester mainchain via copolymerization of 1,10-decanediol with 1,4-cyclohexanedimethanol and 1,4-benzenedimethanol could significantly improve the thermal properties of the resulting copolymers.More importantly,the obtained copolyesters were able to completely depolymerize back to original diols via hydrogenation by the same catalyst in solvent-free and mild conditions,thus offering a green and cost-effective route toward the preparation of widely used polyesters.