From trash to treasure: Chemical recycling and upcycling of commodity plastic waste to fuels, high-valued chemicals and advanced materials

Of all the existing materials, plastics are no doubt among the most versatile ones. However, the extreme increases in plastic production as well as the difficulty of the material for degradation have led to a huge number of plastic wastes. Their recycling rate after disposal is less than 10%, resulting in a series of serious environmental and ecological problems as well as a significant waste of resources. Current recycling methods generally suffer from large energy consumption, the low utilization rate of recycled products with low added value, and produce other waste during the process. Here, we summarized recentlydeveloped chemical recycling ways on commodity plastics, especially new catalytic paths in production of fuels, high-valued chemicals and advanced materials from a single virgin or a mixture of plastic waste,which have emerged as promising ways to valorize waste plastics more economically and environmentally friendly. The new catalyst design criteria as well as innovative catalytic paths and technologies for plastic upcycling are highlighted. Beyond energy recovery by incineration, these approaches demonstrate how waste plastics can be a viable feedstock for energy use with the generation of clean H_(2), high-quality liquid fuels and materials for energy storage, and help inspiring more catalytic process on plastic upcycling to overcome the economical hurdle and building a circular plastic economy.

Thermotolerant and fireproof gel polymer electrolyte toward high-performance and safe lithium-ion battery

Poly(ethylene oxide)(PEO)and its derivatives based gel polymer electrolytes(GPEs)are severely limited in advanced and safe lithium-ion batteries(LIBs)owing to the intrinsically high flammability of liquid electrolytes and PEO.Directly adding flame retardants to the GPEs can suppress their flammability and thus improve the safety of LIBs,but results in deteriorative electrochemical performance.Herein,a novel GPE with chemically bonded flame retardant(i.e.diethyl vinylphosphonate)in cross-linked polyethylene glycol diacrylate matrix,featuring both high-safety and high-performance,is designed.This as-prepared GPE storing the commercial 1 mol L^(-1) LiPF6 electrolyte resists high temperature of 200℃and cannot be ignited as well as possesses a high ionic conductivity(0.60 m S cm^(-1))and good compatibility with lithium.Notably,the LiFePO_(4)/Li battery with this GPE delivers a satisfactory capacity of 142.2 m A h g^(-1) and a superior cycling performance with a capacity retention of 96.3%and a coulombic efficiency of close to 100%for 350 cycles at 0.2 C under ambient temperature.Furthermore,the battery can achieve steady charge–discharge for 100 cycles with a coulombic efficiency of 99.5%at 1 C under 80℃and run normally even at a high temperature of 150℃or under the exposure to butane flame.Differential scanning calorimetry manifests significantly improved battery safety compared to commercial battery systems.This work provides a new pathway for developing next-generation advanced LIBs with enhanced performance and high safety.

Electrode-compatible fluorine-free multifunctional additive regulating solid electrolyte interphase and solvation structure for high-performance lithium-ion batteries

The rapid development and widespread application of lithium-ion batteries(LIBs) have increased demand for high-safety and high-performance LIBs. Accordingly, various additives have been used in commercial liquid electrolytes to severally adjust the solvation structure of lithium ions, control the components of solid electrolyte interphase, or reduce flammability. While it is highly desirable to develop low-cost multifunctional electrolyte additives integrally that address both safety and performance on LIBs, significant challenges remain. Herein, a novel phosphorus-containing organic small molecule, bis(2-methoxyethyl) methylphosphonate(BMOP), was rationally designed to serve as a fluorine-free and multifunctional additive in commercial electrolytes. This novel electrolyte additive is low-toxicity,high-efficiency, low-cost, and electrode-compatible, which shows the significant improvement to both electrochemical performance and fire safety for LIBs through regulating the electrolyte solvation structure, constructing the stable electrode-electrolyte interphase, and suppressing the electrolyte combustion. This work provides a new avenue for developing safer and high-performance LIBs.

Flame-retardant oligomeric electrolyte additive for self-extinguishing and highly-stable lithium-ion batteries:Beyond small molecules

Preparing both safe and high-performance lithium-ion batteries(LIBs) based on commonly used commercial electrolytes is highly desirable,yet challenging.To overcome the poor compatibility of conventional small-molecular flame-retardants as electrolyte additives for safe LIBs with graphite anodes,in this study,we propose and design a novel low-cost flame-retardant oligomer that achieves an accurate and complete reconciliation of fire safety and electrochemical performance in LIBs.Owing to the integration of phosphonate units and polyethylene glycol(PEG) chains,this oligomer,which is a phosphonatecontaining PEG-based oligomer(PPO),not only endows commercial electrolytes with excellent flame retardancy but also helps stabilize the electrodes and Li-ion migration.Specifically,adding 15 wt% of PPO can reduce 70% of the self-extinguishing time and 54% of total heat release for commercial electrolytes.Moreover,LiFePO_(4)/lithium and graphite/lithium cells as well as LiFePO_(4)/graphite pouch full cells exhibit good long-term cycling stability.

Multifunctional interlayer with simultaneously capturing and catalytically converting polysulfides for boosting safety and performance of lithium-sulfur batteries at high-low temperatures

Lithium-sulfur(Li-S) batteries as extremely promising high-density energy storage devices have attracted extensive concern. However, practical applications of Li-S batteries are severely restricted by not only intrinsic polysulfides shuttle resulting from their concentration gradient diffusion and sluggish conversion kinetics but also serious safety issue caused by thermolabile and combustible polymer separators.Herein, it is presented for the first time that a robust and multifunctional separator with urchin-like Co-doped Fe OOH microspheres and multiwalled carbon nanotubes(MWCNTs) as an interlayer simultaneously achieves to suppress polysulfides shuttle as well as improves thermotolerance and nonflammability of commercial PP separator. Accordingly, Li-S batteries with modified separator exhibit remarkable performance in a wide range temperatures of-25–100 ℃. Typically, under 25 ℃, ultrahigh initial capacities of 1441 and 827.29 m A h g-1 at 1 C and 2 C are delivered, and remained capacities of 936 and 663.18 mA h g-1 can be obtained after 500 cycles, respectively. At 0.1 C, the S utilization can reach up to 97%. Significantly, at 1 C, the batteries also deliver an excellent performance with remained capacities of high to862.3, 608.4 and 420.6 m A h g-1 after 100, 300 and 450 cycles under 75, 0 and-25 ℃, respectively. This work provides a new insight for developing stable and safe high-performance Li-S batteries.

An Effective Green Porous Structural Adhesive for Thermal Insulating,Flame-Retardant,and Smoke-Suppressant Expandable Polystyrene Foam

To develop an efficient way to overcome the contradiction among flame retardancy,smoke suppression,and thermal insulation in expanded polystyrene(EPS)foams,which are widely used insulation materials in buildings,a novel"green"porous bio-based flame-retard ant starch(FRS)coating was designed from starch modified with phytic acid(PA)that simultaneously acts as both a flame retardant and an adhesive.This porous FRS coating has open pores,which,in combination with the closed cells formed by EPS beads,create a hierarchically porous structure in FRS-EPS that results in superior thermal insulation with a lower thermal conductivity of 27.0 mW·(m·K)^(-1).The resultant FRS-EPS foam showed extremely low heat-release rates and smoke-production release,indicating excellent fire retardancy and smoke suppression.The specific optical density was as low as 121,which was 80.6%lower than that of neat EPS,at 624.The FRS-EPS also exhibited self-extinguishing behavior in vertical burning tests and had a high limiting oxygen index(LOI)value of 35.5%.More interestingly,after being burnt with an alcohol lamp for 30 min,the top side temperature of the FRS-EPS remained at only 140℃with ignition,thereby exhibiting excellent fire resistance.Mechanism analysis confirmed the intumescent action of FRS,which forms a compact phosphorus-rich hybrid barrier,and the phosphorus-containing compounds that formed in the gas phase contributed to the excellent flame retardancy and smoke suppression of FRS-EPS.This novel porous biomass-based FRS system provides a promising strategy for fabricating polymer foams with excellent flame retardancy,smoke suppression,and thermal insulation.

Boosting thermal stability and crystallization of closed-loop-recyclable biodegradable poly(p-dioxanone) by end-group regulation

A chemically closed-loop-recyclable biodegradable polymer,poly(p-dioxanone)(PPDO),is one of the ideal candidates for single-use plastic products due to its suitability for different application scenarios.Fascinatingly,when PPDO wastes can be collected,its monomer p-dioxanone(PDO) will be obtained through chemical recycling of these wastes;when cannot be collected,the wastes are able to be biodegraded into harmless substances.However,unsatisfied thermal stability and low crystallization rate of PPDO restrict its wider applications.Herein,based on end-group regulation,we simultaneously realized the significant enhancement of thermal stability and crystallization of PPDO through the simple melt processing with tributyl phosphite(TBP) or triphenyl phosphite(TPP).The model reactions were conducted to investigate the reaction mechanism and theoretical products during the preparation of PPDO/phosphite compounds.Two kinds of phosphites were proved to act as the end-capped reagent and chain extender in the melt processing,while TBP presented better reactivity.As a result,the activation energy of thermal decomposition was largely elevated,and the unprecedented T_(5%)(the temperature at a weight loss of 5%) and Tmax(the temperature at a maximum rate of weight loss) of PPDO were obtained,i.e.,T_(5%)of ~330 ℃ and Tmaxof ~385 ℃ in N_(2) atmosphere,T_(5%)of ~240 ℃ and Tmaxof ~317 ℃ in air atmosphere,respectively.Furthermore,the increased crystallization rate,crystallinity,crystalline orderliness,and realizable monomer recovery(yield >90%,purity >99.9%) of PPDO/phosphite compounds were confirmed.

Reversibly Cross-Linking Polyimide and Cyclophosphazene Toward Closed-Loop Recyclable Plastics with High Mechanical Strength,Excellent Flame Retardancy,and Chemical Resistance

Traditional flame-retardant plastics are technically difficult to chemically recycle.The development of newtypes of flame-retardant plastics that are intrinsically capable of being closed-loop recycled and are sufficiently robust and stable to satisfy their practical application is urgently needed.In this study,closed-loop recyclable flame-retardant plastics with high mechanical strength and excellent chemical resistance are fabricated by cross-linking amino-terminated polyimide(PI-NH_(2))and aldehyde-terminated cyclophosphazene(CP-CHO)with imine bonds.The resultant flame-retardant plastic,which is denoted as PI-CP,exhibits a tensile strength of∼115.6 MPa,Young’s modulus of∼2.5 GPa,and glass transition temperature of 316°C.In the PI-CP plastic,the imine bonds are isolated within hydrophobic microenvironments generated by the rigid and hydrophobic polyimide chains and the benzene ring of cyclophosphazenes.As a result,the PI-CP plastics are highly stable in highly acidic and basic aqueous solutions and other commonly used organic solvents.The PI-CP plastic shows outstanding flame retardancy with a limiting oxygen index value of 48.8%.More importantly,the PI-CP plastic can be depolymerized to generate the original PI-NH_(2)and CPCHO monomers in high yields(∼97%)and purity.The recovered monomers can be used to refabricate the original plastics,establishing highly efficient polymer-monomer-polymer circulation and a sustainable plastics economy.

Controlled synthesis and closed-loop chemical recycling of biodegradable copolymers with composition-dependent properties

The closed-loop recycling concept of the polymer wastes into building-block chemicals is attractive,but the closed-loop recycling of copolymers enabled by energy-efficient chemical recycling and cost-effective separations is still facing great challenges.Herein,for the first time,a one-pot sequential copolymerization of γ-butyrolactone(γ-BL) and p-dioxanone(PDO)using an economical ureas/alkoxides catalytic system is conducted to synthesize biodegradable and chemically recyclable poly-(γ-butyrolactone)-block-poly(p-dioxanone)(PγBL-b-PPDO) diblock copolymers with well-defined and controlled structures.The composition-dependent properties of PγBL-b-PPDO copolymers,including thermal properties and crystallization behavior,are investigated.The results show that the thermal stability and crystalline ability of PγBL are enhanced observably by introducing the PPDO block.Significantly,the PγBL-b-PPDO copolymers can be depolymerized efficiently into the corresponding co-monomers with a yield of over 95% by simply low-temperature pyrolysis under vacuum.Moreover,γ-BL and PDO monomers are selectively separated with an isolated purity of about 99% based on the difference in their physicochemical properties.Subsequently,their repolymerization is realized to obtain the copolymers with nearly identical structures and thermostability,demonstrating the closed-loop recycling of copolymers,i.e.,polymerization-depolymerization-repolymerization.This research provides important guidance for the design of novel sustainable polymers towards more efficient chemical recycling,separation and regeneration.

Synthesis and characterization of poly(p-dioxanone)-based degradable copolymers with enhanced thermal and hydrolytic stabilities

Herein, we presented a novel biodegradable copolymer via the chain extending reaction of poly(pdioxanone)-co-poly(2-(2-hydroxyethoxy) benzoate)(PPDO-co-PDHB) prepolymer with hexamethylene diisocyanate(HDI) as a chain extender. The structures and molecular weight of PPDO-co-PDHB prepolymer and PPDO-co-PDHB-PU chain-extended copolymer are characterized via hydrogen nuclear magnetic resonance spectroscopy(1 H NMR) and viscosity test. The relationship between the molecular structures and properties of the chain-extended copolymers is established. The PPDO-co-PDHB-PU copolymers possess a better thermal stability comparing with the PPDO homopolymer. The study of mechanical properties shows that the elongation-at-break of PPDO-co-PDHB-PU is much higher than that of PPDO. The investigation of hydrolytic degradation behaviors indicates the degradation rate of PPDO can be controlled by adjusting the PDHB compositions, and proves that chain-extended copolymers exhibit an excellent hydrolytic stability being better than that of PPDO.

Chemically recyclable copolyesters from bio-renewable monomers:controlled synthesis and composition-dependent applicable properties

The development of chemically recyclable polymers is a promising solution to address the dual challenges of the environment and resources caused by petroleum-based plastics.Despite recent advancements,it is highly desirable for developing recyclable polymers to meet the requirements of both practical uses and well-performed recyclability.Bio-renewable monomers have been paid great attention recently as promising potential candidates for establishing a sustainable circular polymer economy.Herein,a sequential copolymerization of various bio-renewable n-alkyl substituted δ-valerolactone((R)VLs)and p-dioxanone(PDO)is conducted to synthesize novel chemically recyclable diblock copolymers poly(p-dioxanone)-block-poly(n-alkyl-valerolactones)(PPDO-b-P(R)VLs)with well-defined and controlled structures.The properties of copolymers including thermal property,crystallization,mechanical property,hydrophilicity and transport property can be tuned effectively to meet the requirements of practical uses by alternating the alkyl substituents(R)and the P(R)VLs content.In addition,the high-efficiency and facile chemical recycling of copolymers to PDO and(R)VL comonomers is realized with a high yield of>96.5%and a high purity of 99%.

Multifunctional robust aerogel separator towards high-temperature,large-rate,long-cycle lithium-ion batteries

Separators is indispensable for the normal operation of lithium-ion batteries(LIBs).However,the widely used commercial polyolefin separators have some inherent deficiencies such as poor thermotolerance,high inflammability and inferior electrolyte wettability,which restrict their further applications of the advanced and safe batteries.Herein,we design a novel thermotolerant(a shrinkage percentage of 0%at 300℃)and flame retarded aerogel separator consisting of aramid nanofibers(ANFs).Because of its high porosity(86.5%±6.1%)and excellent electrolyte uptake(695%),the ANFs aerogel separator has an ionic conductivity of 1.04 mS/cm and a high lithium-ion transference number(0.67),which can endow LIBs with outstanding rate performance and superior cycling performance.Specifically,the ANFs aerogel separator-based batteries possess a discharge specific capacity of 102 m Ah/g with a capacity retention of 90.7%and a Coulombic efficiency of 99.3%after 600 cycles at 5 C.In addition,under an operated temperature of 90℃,the battery with ANFs aerogel separator can still conduct the very steady chargedischarge,presenting a capacity retention of 90.1%and a Coulombic efficiency of 99.6%after 200 cycles at 3 C.Accordingly,the separator can probably serve as a potential candidate for application to advanced and safe LIBs.

Durable flame-retardant,smoke-suppressant,and thermal-insulating biomass polyurethane foam enabled by a green bio-based system

Bio-based polyurethane foam has attracted increasing attentions due to eco-friendliness and fossil feedstock issues.However,the inherent flammability limits its application in different fields.Herein,we demonstrate a green bio-based flame-retardant system to fabricate polyurethane foam composite with durable flame retardancy,smoke suppression,and thermal insulation property.In this system,the green bio-based polyol(VED)with good reactivity and compatibility plays a role of flame retardant and EG acts as a synergistic filler.As a result,the LOI value of foam composite increased to 30.5 vol.%and it achieved a V-0 rating in the UL-94 vertical burning test.Additionally,the peak heat release rate(pHRR)and the total smoke production(TSP)decreased by 66.1%and 63.4%,respectively.Furthermore,the foam composite maintained durable flame retardancy after accelerated thermal aging test,whose thermal-insulating property was maintained even after being treated in high-humidity environment with 85%R.H.for a week.This work provides a facile strategy for durable flame retardancy and long-term thermal insulation performance,and creates opportunities for the practical applications of bio-based foam composites.

Adaptable Phosphate Networks towards Robust,Reprocessable,Weldable,and Alertable-Yet-Extinguishable Epoxy Vitrimer

Covalent adaptable networks(CANs)combine the uniqueness of thermoplastics and thermosets to allow for reprocessability while being covalently crosslinked.However,it is highly desirable but rarely achieved for CANs to simultaneously demonstrate reversibility and mechanical robustness.Herein,we report a feasible strategy to develop a novel epoxy vitrimer(EV)composed of adaptable phosphate networks(APNs),by which the EVs exhibit promising mechanical properties(tensile strength of 62.5~87.8 MPa and tensile modulus of 1360.1~2975.3 MPa)under ambient conditions.At elevated temperatures,the topology rearrangement occurs relied on phosphate transesterification,which contributes to the shape memory performance,selfhealing,reprocessing,and welding behaviors.Moreover,the incorporation of APNs allows for improvements in anti-ignition and also the inhibition of both heat release and smoke generation to avoid empyrosis,asphyxiation,and toxication during burning,showing expected intrinsic fire safety.Thermal,mechanical properties,and flame retardancy of the reprocessed EVs after hot pressing are very close to those of the original EVs,which is attributed to the suficient reversibility of APNs.Accordingly,combining the aforementioned features,EVs are manufactured as flame-triggered switches for fire alarms,which symbolizes the innovative development of high-performance covalent adaptable polymeric materials.

一种高强高韧自修复聚氨酯弹性体:通过多重氢键及其堆积作用实现微相结构的精确调控（英文）

自修复材料具有优异的使用安全性、更长的寿命、节能和对环境更低的影响等优势,因此受到研究者高度关注.超分子相互作用以其优异的可逆性和对环境刺激的快速响应性,在自修复材料中得到广泛应用.但如何通过合理的分子结构设计获得兼具优异机械性能和自修复能力的高分子材料仍是研究者面临的巨大挑战.本文通过将脲基嘧啶酮(UPy)基团引入到聚丙二醇(PPG)链段中,并精确调控其微相结构,得到了一种强韧的可自修复聚氨酯弹性体PPG-mUPy.聚合物链段中的UPy基团通过二聚形成四重氢键,不仅可以诱导相分离从而形成软硬段结构,还可通过π-π堆积相互作用,在环境温度下形成稳定的微晶,进一步提高聚氨酯材料的机械强度.此外,柔性PPG链段上氨基甲酸酯基团之间存在的弱氢键,赋予了材料超韧特性.通过温度调控启动微晶熔融,释放UPy的可逆特性,赋予材料优异的自修复性能.通过调控PPG链段长度、各组分含量及微观形态,得到综合性能最优样品PPG1000-mUPy50%,其拉伸强度可达20.62 MPa,强度修复效率可达93%.该方法为开发高强高韧自修复高分子材料提供了新的思路.

新型含苯并咪唑结构磺酸盐构建高火灾安全性热塑性聚酯

热塑性聚酯本身具有极高的易燃性,同时在燃烧过程中还会产生浓烟以及严重的熔滴,这已经成为阻碍其广泛应用的主要因素.为了解决这个问题,在本文中,我们合成了一种全新的含磺酸盐以及苯并咪唑结构的离子单体,并将其引入聚对苯二甲酸乙二醇酯(PET,热塑性聚酯模型)分子链中.由于离子聚集以及炭化能力的协同作用,共聚酯在高温下表现出极高的熔体黏度以及优异的成炭能力.当离子单体引入量为8 mol%时,共聚酯能够通过UL-94 V-0级,在测试过程中没有熔滴产生.同时,极限氧指数(LOI)高达33.0 vol%.与PET相比,共聚酯的总产烟量,峰值热释放速率以及最大CO释放速率分别降低了45.2%,60.5%和75.0%.除此之外,共聚酯具有可纺性,同时阳离子染料的竭染率也由PET的6.5%提高到99.6%,表明共聚酯与阳离子染料之间具有很好的亲和性.这种本征阻燃的共聚酯在阻燃织物、艺术品基材、轨道交通与运输的装饰材料方面都有很好的应用前景.

Multifunctional protective aerogel with superelasticity over−196 to 500℃

Protective materials that possess superelasticity and multifunctionality over a broad temperature range are urgently needed in various advanced applications.However,under harsh work conditions,the performance of current materials may largely deteriorate to lose protective functionality.Herein,we report a bidirectionally oriented multi-walled carbon nanotubes(MWCNTs)-reinforced chitosan carbon aerogel(CS-MWCNT)that possesses superelasticity,high electromagnetic interference shielding,thermal insulation,and infrared stealth at both low temperatures(such as liquid nitrogen)and high temperatures(such as alcohol flames).Highly oriented lamellar arch structures combined with an MWCNTs-reinforced carbon skeleton act as elastic segments to disperse the stress during compression and endow CS-MWCNT with the ability to recover to almost the original size after being compressed at−196-500℃.The lamellar structures make CS-MWCNT thermally insulating and infrared stealth with a low thermal conductivity of~0.03 W/(m·K).Furthermore,a high electromagnetic interference(EMI)shielding effect of 64 dB is realized via an absorption-dominant EMI shielding mechanism derived from the successive inherently conductive carbon lamella,and the EMI shielding performance is largely maintained after treatment under extreme conditions like low temperature,high temperature,as well as cyclic compression.This work provides a new strategy for the development of temperature-invariant multifunctional aerogels for harsh environment applications.

Bio-based removable pressure-sensitive adhesives derived from carboxyl-terminated polyricinoleate and epoxidized soybean oil

A novel kind of fully bio-based PSAs we re obtained through the curing reaction between two components derived from the plant oils:carboxyl-terminated polyricinoleate(PRA) fro m the castor oil and epoxidized soybean oil(ESO).The get content,glass transition temperature(Tg),rheological behavior,tensile strength,creep resistance and 180° peel strength of the PSAs were feasibly tailored by adjusting the component ratio of ESO to PRA.At low cross-linking level,the PSAs behaved like a viscous liquid and did not possess enough cohesiveness to sustain the mechanical stress during peeling,The PSAs cross-linked at or near the optimal stoichiometric conditions displayed an adhesive(interfacial) failure between the substrate and the adhesive layer,which were associated with the lowest adhesion levels.The PSAs with the dosage amount of ESO ranging from 10.20 wt% were tacky and flexible,which exhibited 1800 peel strength ranging from 0.4~2.3 N/cm;and could be easily removed without any residues on the adherend.The process for the preparation of the fully bio-based PSAs was environmentally friendly without using any orga nic solve nt or other toxic chemical,herein showing the great potential as sustainable materials.

Porous carbon/Fe composites from waste fabric for high-efficiency electromagnetic wave absorption

Nowadays,a large amount of waste fabrics has brought huge environmental and resource problems,while the traditional recycling routes are downcycling with low efficiency and complex separation processes.Herein,we demonstrate a green and facile route to up-recycle waste fabrics(cotton-polyester blending or cotton fabrics)into a high-performance microwave absorber.In this design,an assistant coating was deposited onto the fiber surface of the waste fabric through the assembly of tannic acid-Fe^(2+)(TA-Fe^(2+)),which effectively catalyzed the polymer fiber into highly graphitized porous carbon fiber at high temper-atures.Meanwhile,the Fe nanoparticles from the reduction of Fe^(2+)ions were evenly embedded on the surface of porous carbon fibers.Consequently,the resultant porous carbon/Fe composites with hierarchi-cal microstructures displayed excellent microwave absorption performances.Typically,the microwave ab-sorber from waste polyester-cotton blended fabric could reach a minimum reflection loss(RL)of-50.5 dB at a thin coating thickness of 1.7 mm,and the minimum RL from waste cotton fabric absorber reached-47.1 dB at a thickness of 2.5 mm.This work provides a new idea to convert waste fabrics into high value-added microwave absorbing materials in a simple and environmentally friendly way,which will help reuse resources and protect the environment.

优异的无应力双向光热响应形状记忆偶氮液晶聚氨酯网络

本文以羟基修饰偶氮液晶小分子为单体、异氰酸酯为扩链剂、四臂聚乙二醇为交联剂一锅法合成了一系列液晶聚氨酯网络(PULCN(AZO)s),并通过调节反应原料的投料比精确控制网络结构.该交联网络呈现两个独立的热转变温度(Ttrans),以此为驱动温度可实现热致三重形状记忆效应.进一步利用氨酯键在高温下的动态热交换获得单畴化液晶交联网络,该交联网络不仅可呈现热致无应力双向形状记忆效应,同时利用偶氮苯光致异构转变特性,还可以在450和550 nm可见光的照射下分别展示出弯曲与回复的光致形变能力.将光、热响应的无应力可逆形变结合在单一循环中,可实现材料在多个形状之间的可逆变化.该材料有望应用于多功能设备中.