查看更多>>摘要：Supramolecular polymers,as a type of dynamic polymers,are subordinate to the interdisciplinary field of polymer chemistry and supramolecular chemistry,whose development has greatly promoted the prosperity of new materials.Notably,molecular weight is one of the most important parameters of supramolecular polymers,which affects the physical/chemical properties and processing applications of materials.Developing new methods for characterizing the molecular weight of supramolecular polymers is crucial for advancing the development of supramolecular polymers.In this review,we elaborate and summarize three strategies for characterizing the molecular weight of supramolecular polymers that recently reported by our research group according to the characteristics of supramolecular polymers,including(1)the molecular weight distinction corresponding to variable fluorescence colors,(2)matching different molecular weights with different fluorescence lifetime,(3)transforming supramolecular polymers into mechanically interlocked polymers or covalent polymers.Besides,we also discuss the limitations of current methods for characterizing supramolecular polymers.We hope that this review can promote the development of supramolecular poly-mers and significantly inspire to exploit new methods to characterizing molecular weight of supramolecular polymers.
查看更多>>摘要：Poly(butylene succinate)(PBS)exhibits many advantages,such as renewability,biodegradability,and impressive thermal and mechan-ical properties,but is limited by the low melt viscosity and strength resulted from the linear structure.To address this,vitrimeric network was in-troduced to synthesize PBS vitrimers(PBSVs)based on dynamic imine bonds through melt polymerization of hydroxyl-terminated PBS with vanillin derived imine containing compound and hexamethylene diisocyanate using trimethylolpropane as a crosslinking monomer.PBSVs with different crosslinking degrees were synthesized through changing the content of the crosslinking monomer.The effect of crosslinking degree on the thermal,theological,mechanical properties,and stress relaxation behavior of the PBSVs was studied in detail.The results demonstrated that the melt viscosity,melt strength,and heat resistance were enhanced substantially without obvious depression in crystallizability,thermal stabili-ty,and mechanical properties through increasing crosslinking degree.In addition,the PBSVs exhibit thermal reprocessability with mechanical properties recovered by more than 90％even after processing for three times.Furthermore,PBSV with improved melt properties shows signifi-cantly improved foamability compared to commercial PBS.This research contributes to the advancement of polymer technology by successfully developing PBS vitrimers with improved properties,showcasing their potential applications in sustainable and biodegradable materials.
查看更多>>摘要：Elastomers with high mechanical toughness can guarantee their durability during service life.Self-healing ability,as well as recyclabili-ty,can also extend the life of materials and save the consuming cost of the materials.Many efforts have been dedicated to promoting the me-chanical toughness as well as the self-healing capability of elastomers at the same time,while it remains a challenge to balance the trade-off be-tween the above properties in one system.Herein we proposed a molecular design driven by dual interactions of acylsemicarbazide hydrogen bonding and Cu2+-neocuproine coordination simultaneously.By introducing the reversible multiple hydrogen bonds and strong coordination bonds,we successfully fabricated an extremely tough and self-healing elastomer.The elastomer can achieve an impressive top-notch toughness of 491 MJ/m3.Furthermore,it boasted rapid elastic restorability within 10 min and outstanding crack tolerance with high fracture energy(152.6 kJ/m2).Benefiting from the combination of dynamic interactions,the material was able to self-repair under 80 ℃ conveniently and could be re-processed to restore the exceptional mechanical properties.
查看更多>>摘要：The incorporation of dynamic covalent bonds into thermosets facilitates the reprocessing of polymer networks,thereby meeting the sustainable requirements for polymer recycling.However,the mechanical properties of many materials often decline significantly upon repro-cessing due to side reactions caused by harsh processing conditions.In this work,we find that the aromatic dithiocarbamate bond can undergo dissociation under mild conditions without the need for a catalyst,enabling the efficient reprocessing of the corresponding polydithiourethane.As a consequence,the mechanical properties of the polydithiourethane can be largely preserved after reprocessing.The discovery of this dyna-mic chemistry is anticipated to broaden the potential for material design in dynamic covalent polymer networks.
查看更多>>摘要：Realizing multiple locked shapes in pre-oriented liquid crystal elastomers(LCEs)is highly desired for diversifying deformations and en-hancing multi-functionality.However,conventional LCEs only deform between two shapes for each actuation cycle upon liquid crystal-isotropic phase transitions induced by external stimuli.Here,we propose to regulate the actuation modes and the locked shapes of a pre-orientated epoxy LCE by combining dynamic covalent bonds with cooling-rate-mediated control.The actuation modes can be adjusted on demand by exchange reactions of dynamic covalent bonds.Derived from the established actuation modes,such as elongation,bending,and spiraling,the epoxy LCE displays varied locked shapes at room temperature under different cooling rates.Various mediums are utilized to control the cooling rate,includ-ing water,silicone oil,and copper plates.This approach provides a novel way for regulating the actuation modes and locked shapes of cutting-edge intelligent devices.
查看更多>>摘要：Thermochromic polymers with tunable thermochromism,high stretchability and mechanical strength are of interests for optical infor-mation storage and encryption.In this work,we demonstrate a new design of thermo-fluorochromic carboxylated nitrile butadiene rubber(XNBR)elastomer cross-linked by Eu3+-COOH dynamic coordination with deprotonated imidazole(DPIm)as the ancillary ligand.The presence of DPIm not only improves the mechanical strength and stretchability,but also dramatically intensifies the fluorescence emission and lifetime of the Eu-containing elastomer.The elastomer behaves reversible thermo-fluorochromism with easily tunable transition temperature and emission in-tensity by the simple change of the deprotonation degree of imidazole.The facile tunable thermo-fluorochromism,exceptional mechanical strength,and high stretchability(up to about 5000％)enable the Eu-containing XNBR elastomer with potential applications in soft electronics where optical information storage and encryption are required.
查看更多>>摘要：A series of novel side-chain liquid crystalline(SCLC)copolymers were synthesized by attaching two distinct mesogenic units,namely a chiral cholesteryl-based monomer(M1)and an achiral biphenyl-based monomer(M2),to a poly(3-mercaptopropylmethylsiloxane)(PMMS)back-bone via thiol-ene click chemistry.The influence of side chain composition on the self-assembly behavior and phase structures of these SCLC copolymers was systematically investigated using different instrument.Results indicate that three distinct liquid crystalline phases and four unique molecular configurations were identified within the polymer series,with the emergence of the liquid crystalline phase being a synergistic outcome of the two distinct side chains.This study underscores the critical influence of side chain dimensions,rigidity,and spatial volume on the self-assembly structures and phase characteristics of liquid crystalline polymers,providing valuable insights for the rational design and develop-ment of advanced functional materials with tailored properties.
查看更多>>摘要：Developing hydroscopic actuators with simultaneous high elasticity,shape programmability and tunable actuating behaviors are highly desired but still challenging.In this study,we propose an orthogonal composite design to develop such a material.The developed com-posite elastomer comprises carboxyl group-grafted polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene(SEBS-g-COOH)as the elas-tic substrate,and a synthesized azobenzene derivative as the functional filler(Azo12).By surface treatment using acidic and base solutions,the carboxyl groups on the surface can reversibly transform into carboxylate groups,which render the composite tunable hygroscopic actuating functionality.On another aspect,the added filler undergoes trans-to-cis isomerization when exposed to UV light irradiation,leading to liquefac-tion of the crystalline aggregates formed by Azo12 molecules.The liquefied Azo12 molecules can autonomously resotre their trans form and re-form the crystalline structure.This reversible change in crystralline structure is utilized to realize the shape memory property,and 5 wt％of Azo12 addition is adequate for the composite to exhibit photo-responsive shape memory behavior without compromising much of the elasricity.The regualtion of external geometry by shape memory effect is effective in altering the actuating behavior.The proposed method can be extend to designing different composites with the demonstrated functionalities.
查看更多>>摘要：Sulfur-containing dynamic polymers had attracted significant attention due to their unique chemical structures with high reversibility.Utilizating sulfur,an inexpensive industrial waste product,to synthesize dynamic polysulfide polymers through reverse vulcanization has been a notable approach.However,this method required high temperatures and resulted in the release of unpleasant oders.In this study,we presented a robust method for the preparation of sulfur-rich polymers with dynamic polysulfide bonds from elemental sulfur and inexpensive epoxide monomers via a one-pot strategy at the mild room temperature.Different types of polysulfide molecules and polymers were synthesized by re-acting various epoxide compounds with sulfur,along with the investigation of their structures and dynamic behaviors.It was noteworthy that the obatined polymers prepared from m-(2,3-epoxypropoxy)-N,N-bis(2,3-epoxypropyl)aniline and elemental sulfur exhibit multiple dynamic behav-iors,including polysulfide metathesis and polysulfide-thiol exchange,enabling their rapid stress relaxation,self-healing,reprocessing and degradable properties of the cross-linked polymer.More importantly,the hydroxyl groups at the side chains from epoxide ring opening exhibit-ed potential transesterification.This work provided a facile strategy for designing dynamic sulfur-rich polymers via a mild synthesis route.
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