Poly(L-lactic acid)(PLLA)has been widely concerned because of its excellent biodegradability and biocompatibility.However,the poor crystallization ability of PLLA during the molding process not only leads to weak mech...Poly(L-lactic acid)(PLLA)has been widely concerned because of its excellent biodegradability and biocompatibility.However,the poor crystallization ability of PLLA during the molding process not only leads to weak mechanical properties but also reduces the processing efficiency,which limits the application of PLLA greatly.Enhancing crystallization ability of PLLA via introducing inorganic nanoparticles usually sacrifices biodegradability or transparency.Here,the microfine fibers with stereocomplex(SC)crystallites were incorporated into PLLA film to tailor the crystallization ability of PLLA as well as the mechanical properties.The results confirmed that the crystallization ability of PLLA matrix under different circumstances could be greatly enhanced by a few amounts of SC crystalline fibers,and synchronously enhanced tensile strength and ductility were also achieved,especially at relatively high temperature.Due to the relatively homogeneous dispersion of SC crystalline fibers and the similar refractive index between components,the PLLA-based film also exhibited high transparency,up to 85%-90%depending on the content of SC crystalline fibers.This work provides guidance for manufacturing transparent PLLA-based packaging materials with good crystallization capability and mechanical properties.展开更多
The increasing deployment of electronics in everyday life has generated great concerns regarding the effective disposal of waste from these components.Here,we focused on a facile sustainable and economical strategy to...The increasing deployment of electronics in everyday life has generated great concerns regarding the effective disposal of waste from these components.Here,we focused on a facile sustainable and economical strategy to provide ideas for this issue.This strategy relied on using appropriate mechanical treatment and sodium lignosulfonate coating to improve the dispersion and interfacial compatibility of bamboo fibers in poly(lactic acid).By optimising the particle size and concentration of sodium lignosulphonate,high value-added and green composites were prepared using sectional pressurization with a venting procedure.The treated composite displayed an ultra-smooth surface(roughness of 0.592 nm),impressive transient properties(disintegration and degradation behaviour after 30 d),and outstanding ultraviolet(UV)shielding properties(100%).These properties hold the promise of being an excellent substrate for electronic devices,especially for high-precision processing,transient electronics,and UV damage prevention.The satisfactory interfacial compatibility of the composites was confirmed by detailed characterisation regarding the related physicochemical properties.This investigation offers a sustainable approach for producing high value-added green composites from biomass and biomass-derived materials.展开更多
Consisting of natural histidine residues,polyhistidine(PHis)simulates functional proteins.Traditional approaches towards PHis require the protection of imidazole groups before monomer synthesis and polymerization to p...Consisting of natural histidine residues,polyhistidine(PHis)simulates functional proteins.Traditional approaches towards PHis require the protection of imidazole groups before monomer synthesis and polymerization to prevent degradation and side reactions.In the contribution,histidine N-thiocarboxyanhydride(His-NTA)is directly synthesized in aqueous solution without protection.With the self-catalysis of the imidazole side group,the ring-closing reaction to form His-NTA does not require any activating reagent(e.g.,phosphorus tribromide),which is elucidated by density functional theory(DFT)calculations.His-NTA directly polymerizes into PHis bearing unprotected imidazole groups with designable molecular weights(4.2-7.7 kg/mol)and low dispersities(1.10-1.19).Kinetic experiments and Monte Carlo simulations reveal the elementary reactions and the relationship between the conversion of His-NTA and time during polymerization.Block copolymerization of His-NTA with sarcosine N-thiocarboxyanhydride(Sar-NTA)demonstrate versatile construction of functional polypept(o)ides.The triblock copoly(amino acid)PHis-b-PSar-b-PHis is capable to reversibly coordinate with transition metal ions(Fe^(2+),Co^(2+),Ni^(2+),Cu^(2+)and Zn^(2+))to form pH-sensitive hydrogels.展开更多
The rising prevalence of drug-resistant Gram-positive pathogens,particularly methicillin-resistant Staphy-lococcus aureus(MRSA)and vancomycin-resistant Enterococci(VRE),poses a substantial clinical challenge.Biofilm-a...The rising prevalence of drug-resistant Gram-positive pathogens,particularly methicillin-resistant Staphy-lococcus aureus(MRSA)and vancomycin-resistant Enterococci(VRE),poses a substantial clinical challenge.Biofilm-associated infections exacerbate this problem due to their inherent antibiotic resistance and complex structure.Current antibiotic treatments struggle to penetrate biofilms and eradicate persister cells,leading to prolonged antibiotic use and increased resistance.Host defense peptides(HDPs)have shown promise,but their clinical application is limited by factors such as enzymatic degradation and difficulty in largescale preparation.Synthetic HDP mimics,such as poly(2-oxazoline),have emerged as effective alter-natives.Herein,we found that the poly(2-oxazoline),Gly-POX_(20),demonstrated rapid and potent activity against clinically isolated multidrug-resistant Gram-positive strains.Gly-POX_(20) showed greater stability under physiological conditions compared to natural peptides,including resistance to protease degradation.Importantly,Gly-POX_(20) inhibited biofilm formation and eradicated mature biofilm and demonstrated superior in vivo therapeutic efficacy to vancomycin in a MRSA biofilm-associated mouse keratitis model,suggesting its potential as a novel antimicrobial agent against drug-resistant Gram-positive bacteria,especially biofilm-associated infections.展开更多
Polyfluoroarenes represent an essential group of compounds in the fields of medical and material chemistry.It is still a challenge to synthesize alkylated polyfluoroarenes.Herein,a Ni-catalyzed reductive alkylation of...Polyfluoroarenes represent an essential group of compounds in the fields of medical and material chemistry.It is still a challenge to synthesize alkylated polyfluoroarenes.Herein,a Ni-catalyzed reductive alkylation of polyfluoroarenes with alkyl halides under mild conditions is reported.Polyfluoroarenes(3~6 F)can reacted smoothly with a diverse range of alkyl halides,such as primary,secondary,and tertiary alkyl iodides.The efficient formation of C(sp2)—C(sp3)can be achieved through the combination of Ni catalysis and(Bpin)2/K2CO3 as terminal reductant.展开更多
Poly(butylene succinate-co-furandicarboxylate)(PBSF)and poly(butylene adipateco-furandicarboxylate)(PBAF)are novel furandicarboxylic acid-based biodegradable copolyesters with great potential to replace fossil-derived...Poly(butylene succinate-co-furandicarboxylate)(PBSF)and poly(butylene adipateco-furandicarboxylate)(PBAF)are novel furandicarboxylic acid-based biodegradable copolyesters with great potential to replace fossil-derived terephthalic acid-based copolyesters such as poly(butylene succinate-co-terephthalate)(PBST)and poly(butylene adipate-co-terephthalate)(PBAT).In this study,quantum chemistry techniques after molecular dynamics simulations are employed to investigate the degradationmechanism of PBSF and PBAF catalyzed by Candida antarctica lipase B(CALB).Computational analysis indicates that the catalytic reaction follows a four-step mechanism resembling the ping-pong bibi mechanism,with the initial two steps being acylation reactions and the subsequent two being hydrolysis reactions.Notably,the first step of the hydrolysis is identified as the rate-determining step.Moreover,by introducing single-point mutations to expand the substrate entrance tunnel,the catalytic distance of the first acylation step decreases.Additionally,energy barrier of the rate-determining step is decreased in the PBSF system by site-directed mutations on key residues increasing hydrophobicity of the enzyme’s active site.This study unprecedently show the substrate binding pocket and hydrophobicity of the enzyme’s active site have the potential to be engineered to enhance the degradation of copolyesters catalyzed by CALB.展开更多
Although the efficiency of poly(ethylene terephthalate)(PET)degradation has been successfully improved by depolymerase engineering,mostly by using Goodfellow-PET(gf-PET)as a substrate,efforts to degrade unpretreated P...Although the efficiency of poly(ethylene terephthalate)(PET)degradation has been successfully improved by depolymerase engineering,mostly by using Goodfellow-PET(gf-PET)as a substrate,efforts to degrade unpretreated PET materials with high crystallinity remain insufficient.Here,we endeavored to improve the degradation capability of a WCCG mutant of leaf-branch compost cutinase(LCC)on a unpretreated PET substrate(crystallinity>40%)by employing iterative saturation mutagenesis.Using this method,we developed a high-throughput screening strategy appropriate for unpretreated substrates.Through extensive screening of residues around the substrate-binding groove,two variants,WCCG-sup1 and WCCG-sup2,showed good depolymerization capabilities with both high-(42%)and low-crystallinity(9%)substrates.The WCCG-sup1 variant completely depolymerized a commercial unpretreated PET product in 36 h at 72℃.In addition to enzyme thermostability and catalytic efficiency,the adsorption of enzymes onto substrates plays an important role in PET degradation.This study provides valuable insights into the structure-function relationship of LCC.展开更多
The development of degradable and chemically recyclable polymers is a promising strategy to address pressing environmental and resource-related challenges.Despite significant progress,there is a need for continuous de...The development of degradable and chemically recyclable polymers is a promising strategy to address pressing environmental and resource-related challenges.Despite significant progress,there is a need for continuous development of such recyclable polymers.Herein,PPDOPLLA-PU copolymers were synthesized from poly(p-dioxanone)-diol(PPDO-diol)and poly(L-lactide)-diol(PLLA-diol)by chain extension reaction.The chemical structures and microphase structures of PPDO-PLLA-PU were characterized,and their crystalline properties,mechanical properties,and degradation behaviors were further investigated.Significantly,the distribution of PLLA phase in the copolymer matrix showed a rod-like microstructure with a slight orientation,despite the thermodynamic incompatibility of PPDO and PLLA segments.Moreover,on the basis of this microphase separation,PPDO spherulites can crystallize using the interface of the two phases as nucleation sites.Accordingly,the combined effect of above two contributes to the enhanced mechanical properties.In addition,PPDO-PLLA-PU copolymers have good processability and recyclability,making them valuable for a wide range of applications.展开更多
Poly(octamethylene citrate)(POC)is a promising bioelastomer material in the biomedical field.However,its thermosetting nature poses a significant challenge to processing and molding,especially manufacturing the POC-ba...Poly(octamethylene citrate)(POC)is a promising bioelastomer material in the biomedical field.However,its thermosetting nature poses a significant challenge to processing and molding,especially manufacturing the POC-based elastomer particles as potential,degradable and toughened fillers.Firstly,a Pickering emulsion with a pre-polymer(pre-POC)solution in dimethyl carbonate as a dispersed oil phase,a Pullulan(PUL)aqueous solution as a continuous water phase,and chitin nanocrystal(ChiNC)as a particle-type emulsifier was constructed.Secondly,the POC-based core/shell structured microspheres were prepared by spray-drying of the emulsions,and characterized by a scanning electron microscope and a transmission electron microscope.Finally,the POC-based core/shell structured microspheres were used as elastomer fillers to strengthen and toughen a chitosan film,resulting in 26%increase in the tensile strength and 45%increase in the strain at break;the POC-based core/shell structured microsphere as a double-layer drug release system was built in which the hydrophilic drug of tetracycline hydrochloride(TCH)was released from the outer layer and the hydrophobic drug of curcumin was released from the inner layer,roughly following the Ritger-Peppas model.展开更多
Herein,a simple method for preparing poly(vinylidene fluoride)(PVDF)films with controlledβ/γratios by spin-coating assisted by potassium bromide(KBr)is proposed.The results show that the relative fraction of theβph...Herein,a simple method for preparing poly(vinylidene fluoride)(PVDF)films with controlledβ/γratios by spin-coating assisted by potassium bromide(KBr)is proposed.The results show that the relative fraction of theβphase(denoted as Fβ)for the films prepared on the KBr surface first decreased until a critical temperature(denoted as Tc)was reached,and then increased with increasing spin-coating temperature.This was related to the dissolved K and Br ions in the films.Further experiments showed that below Tc,high humidity can enhance Fβbut exhibit an adverse effect at and above Tc.The high content of K and Br ions in the PVDF/KBr blend film and larger shear stress can facilitate the formation of theβphase,leading exclusively to the formation ofβ-andγ-phases.The mechanism responsible for the change in Fβwith temperature was proposed:below Tc,the decrease in water intake with increasing temperature results in the decline of Fβ,whereas above Tc,the increase in Fβwith temperature is attributed to the synergistic effect of ions and shear stress.Ultimately,this paves the way for fabricating PVDF films with tailoredβ/γratios for electroactive and energy-harvesting applications.展开更多
Dimethyl sulfoxide(DMSO)possessing strong solvency and high boiling point is a very important aprotic polar solvent in organic and polymer synthesis.Notably,it is also a useful synthon in organic chemistry.However,the...Dimethyl sulfoxide(DMSO)possessing strong solvency and high boiling point is a very important aprotic polar solvent in organic and polymer synthesis.Notably,it is also a useful synthon in organic chemistry.However,the direct incorporation of DMSO in polymer synthesis remains challenging.In this work,DMSO was successfully converted to nitrogen-containing heterocyclic polymers as a monomer via multicomponent polymerizations(MCPs)with dialdehydes and diamines in the presence of K_(2)S_(2)O_(8)/t-BuOK at 120℃in 6 h.A series of poly(phenylquinoline)s with high M_(w)values(up to 5.11×10^(4))were obtained in satisfactory yields(up to 82%),performing good solubility,good thermal and morphological stability as well as excellent film-forming ability.The thin films of poly(phenylquinoline)s exhibit high refractive index value in a wide wavelength range of 400–1700 nm.Thus,this work not only enriches the family of MCPs but also provides an efficient strategy for the conversion of DMSO into functional polymeric materials that are potentially applicable in diverse areas.展开更多
Fluorescent polyurea-carbon dots(PU-CD) were successfully achieved through a co-pyrolysis technique, combining polyurea(PU) with carboxyl-containing carbon dots(PCD) at a temperature of 220 ℃. The PU was fabricated v...Fluorescent polyurea-carbon dots(PU-CD) were successfully achieved through a co-pyrolysis technique, combining polyurea(PU) with carboxyl-containing carbon dots(PCD) at a temperature of 220 ℃. The PU was fabricated via a simple precipitation polymerization process using toluene disocyanate in a water/acetone binary solvent system. PCD was generated by thermal treatment of poly(ethylene glycol)(PEG) at the same elevated temperature. To elucidate the structural characteristics of PU-CD, as well as its precursor components PU and PCD, a comprehensive suite of analytical techniques was employed, including transmission electron microscopy(TEM), Fourier transform infrared spectroscopy(FTIR), nuclear magnetic resonance(NMR), dynamic light scattering(DLS) and X-ray photoelectron spectroscopy(XPS). These analyses confirmed the formation of amide bonds resulting from the reaction between the terminal amines of PU and the carboxyl groups of PCD. An in-depth comparison of the fluorescence properties of PU-CD revealed marked enhancements in fluorescence intensity when contrasted with PU, PEG, and the individual PCD. The research explored the impact of various factors such as concentration, pH in aqueous solutions, and solvent type on the fluorescence emission of these materials, providing valuable insights into their emission mechanisms. It was particularly noteworthy that both PCD and PU-CD exhibited a confined-domain crosslink-enhanced emission effect. Utilizing the aqueous dispersion of PU-CD as a fluorescent probe,the detection of doxycycline(DOX), a long-acting, broad-spectrum, semi-synthetic tetracycline antibiotic, was achieved with a detection limit of 2.9×10^(-7)mol/L. This study introduces a simple, green, and cost-effective fluorescent probe for the detection of DOX, which has significant potential for application in the realms of analytical chemistry and food safety monitoring in the future.展开更多
The sulfonated poly(α-methyl styrene-b-isobutylene-b-α-methyl styrene)copolymers(S-ASIBS)with the average molar percentage of sulfonic acid(-SO_(3)H)groups(SP)ranging from 3.6 mol%to 14.3 mol%could be synthesized by...The sulfonated poly(α-methyl styrene-b-isobutylene-b-α-methyl styrene)copolymers(S-ASIBS)with the average molar percentage of sulfonic acid(-SO_(3)H)groups(SP)ranging from 3.6 mol%to 14.3 mol%could be synthesized by sulfonation of ASIBS with acetyl sulfate.The hydrophilic ionic channels were generated for proton exchange membranes(PEMs)by ion aggregation of-SO_(3)H groups and microphase separation between hydrophobic polyisobutylene and hydrophilic sulfonated poly(α-methyl styrene)segments in S-ASIBS.The proton transport ability was improved while oxidative stability was decreased by increasing SP in S-ASIBS.The appropriate SP of about 12.7 mol%in S-ASIBS provides the available PEMs with high proton transport ability,low methanol permeability and good oxidative stability.The absence of active tertiary hydrogen atoms along S-ASIBS copolymer chains avoids their attack by peroxy radicals.The residual rates of weight(RW)and proton conductivity(Rσ)of S-ASIBS-12.7 membrane after oxidation treatment for 916 h were 84.3%and 88.1%respectively,near to those of commercial Nafion 117(RW=87.9%,Rσ=90.3%).The membrane electrode assembly(MEA)could be prepared by using various S-ASIBS as PEMs for direct methanol fuel cell.The single cell with S-ASIBS-12.7 MEA behaves high performance of open circuit voltage(OCV)of 548 mV and peak power density(Pmax)of 36.1 mW·cm^(-2),which is similar to those of Nafion 117(OCV=506 mV,P_(max)=35.6 mW·cm^(-2)).To the best of our knowledge,this is the first example of advanced S-ASIBS membrane with high proton conductivity,excellent fuel barrier property and remarkable oxidative stability for promising PEMs.展开更多
Semicrystalline polymers usually undergo multilevel microstructural evolutions with annealing and stretching processes,which is es-sential to tailor the physical properties of the polymer.Here,poly(butylene carbonate)...Semicrystalline polymers usually undergo multilevel microstructural evolutions with annealing and stretching processes,which is es-sential to tailor the physical properties of the polymer.Here,poly(butylene carbonate)(PBC)sheets were prepared via isothermal annealing and unidirectional pre-stretching processes,then the changes of PBC in crystallinity,mechanical properties,thermal properties and microscopic changes before and after annealing and stretching were measured,as well as the relationship between microstructure and macroscopic proper-ties before and after stretching.The strengthening mechanism of PBC was also described.It was demonstrated that shish-kabab structure emerged under the pre-stretching process.With the increase of the tensile ratio,the crystallinity,structure and mechanical properties are in-creased differently.Among them,the crystallinity and tensile strength after annealing-stretching treatment increased to 24.45%and 104.5 MPa,respectively,which were about 1.55 times and 3.4 times of those-without any treatment.展开更多
Poly(vinyl alcohol)(PVA)is a biodegradable and environmentally friendly material known for its gas barrier characteristics and solvent resistance.However,its flammability and water sensitivity limit its application in...Poly(vinyl alcohol)(PVA)is a biodegradable and environmentally friendly material known for its gas barrier characteristics and solvent resistance.However,its flammability and water sensitivity limit its application in specialized fields.In this study,phytic acid(PA)was introduced as a halogen-free flame retardant and biochar(BC)was introduced as a reinforcement to achieve both flame resistance and mechanical robustness.We thoroughly investigated the effects of BC particle sizes(100-3000 mesh)and addition amounts(0 wt%-10 wt%),as well as PA addition amounts(0 wt%-15 wt%),on the properties of PVA composite films.Notably,the PA10/1000BC5 composite containing 10 wt%PA and 5 wt%1000 mesh BC exhibited optimal properties.The limiting oxygen index increased to 39.2%,and the UL-94 test achieved a V-0 rating.Additionally,the PA10/1000BC5 composite film demonstrated significantly enhanced water resistance,with a swelling ratio reaching 800%without dissolving,unlike that of the control PVA.The water contact angle was 70°,indicating that hydrophilic properties remained essentially unaffected.Most importantly,the tensile modulus and elongation at break were 213 MPa and 281.7%,respectively,nearly double those of the PVA/PA composite film.This study presents an efficient and straightforward method for preparing PVA composite films that are flame-retardant,tough,and waterresistant,expanding their potential applications in various fields.展开更多
Oxidative stress,characterized by the excessive accumulation of reactive oxygen species(ROS),is linked to various pathological conditions,including myocardial infarction,cancer,and neurodegenerative diseases.Addressin...Oxidative stress,characterized by the excessive accumulation of reactive oxygen species(ROS),is linked to various pathological conditions,including myocardial infarction,cancer,and neurodegenerative diseases.Addressing ROS-induced cell damage has become a critical focus of biomedical research.In this study,a thermo-sensitive poly(amino acid)hydrogel,composed of poly(ethylene glycol)-block-poly(l-methionine),was prepared for cytoprotection through ROS scavenging.The sol-to-gel transition mechanism of the hydrogel was elucidated,and its potent antioxidant properties and cell protective effects were validated using hydrogen peroxide(H_(2)O_(2))-induced oxidative stress and oxygen-glucose deprivation(OGD)models.The hydrogel significantly mitigated H_(2)O_(2)-induced damage in L929 cells,doubling their survival rate.Additionally,it scavenged approximately 35.8%of the ROS during OGD,reducing mitochondrial oxidative damage and resulting in a 29.4%decrease in apoptotic cell number.These findings underscore the potential biomedical applications of thermo-sensitive poly(amino acid)hydrogels,particularly in treating oxidative stress-related cell damage.展开更多
This article provided a preparation protocol for poly(lactic acid)(PLA)/modified epoxidized soybean oil(ECP)/nano-magnesium oxide(n-MgO)ternary composites and studied their mechanical and antibacterial properties.By m...This article provided a preparation protocol for poly(lactic acid)(PLA)/modified epoxidized soybean oil(ECP)/nano-magnesium oxide(n-MgO)ternary composites and studied their mechanical and antibacterial properties.By means of an organic synthesis technique,epoxidized soybean oil(ESO)is chemically grafted to PLA to synthesize ESO chemically plastically modified PLA,abbreviated ECP.To fabricate PLA/ECP/n-MgO composite materials,ECP acts as a plasticizer and a compatibilizer simultaneously,and n-MgO acts as an enhancer.Then scanning electron microscopy,X-ray diffraction,differential scanning calorimetry,universal tester,and antibacterial research were exploited to characterize the morphology,thermal resistance,mechanical properties,and antibacterial performance of PLA/ECP/n-MgO composites.The experimental results show that ECP acts as a plasticizer by causing heterogeneous nucleation,which increases PLA's crystallinity.Evenly distributed n-MgO can greatly improve PLA's antibacterial qualities.Furthermore,ECP and n-MgO work together to improve the positive aspects of PLA/ECP/n-MgO composites,with PLA/ECP/n-MgO 100/1/0.5 composites having the best overall properties.While improving the mechanical performance and toughness of PLA,this work offers a prospective approach and foundational database for the creation of multifunctional biodegradable composites.展开更多
基金supported by the Sichuan Science and Technology Program(No.2023ZHCG0050)the China Postdoctoral Science Foundation(No.2023M742883)+2 种基金the Science and Technology Innovation Fund for Basic Scientific Research Operating Expenses of Central Universities(No.2682023CX002)the New Interdisciplinary Cultivation Fund of SWJTU(No.2682022KJ040)SEM characterizations were supported by the Analytical and Testing Center of Southwest Jiaotong University。
文摘Poly(L-lactic acid)(PLLA)has been widely concerned because of its excellent biodegradability and biocompatibility.However,the poor crystallization ability of PLLA during the molding process not only leads to weak mechanical properties but also reduces the processing efficiency,which limits the application of PLLA greatly.Enhancing crystallization ability of PLLA via introducing inorganic nanoparticles usually sacrifices biodegradability or transparency.Here,the microfine fibers with stereocomplex(SC)crystallites were incorporated into PLLA film to tailor the crystallization ability of PLLA as well as the mechanical properties.The results confirmed that the crystallization ability of PLLA matrix under different circumstances could be greatly enhanced by a few amounts of SC crystalline fibers,and synchronously enhanced tensile strength and ductility were also achieved,especially at relatively high temperature.Due to the relatively homogeneous dispersion of SC crystalline fibers and the similar refractive index between components,the PLLA-based film also exhibited high transparency,up to 85%-90%depending on the content of SC crystalline fibers.This work provides guidance for manufacturing transparent PLLA-based packaging materials with good crystallization capability and mechanical properties.
基金supported by the National Natural Science Foundation of China(Nos.31971741 and 31760195)the Yunnan Fundamental Research Projects(Nos.2018FB066 and 202001AT070141)the Yunnan Agricultural Basic Research Special Projects(No.202101BD070001-086).
文摘The increasing deployment of electronics in everyday life has generated great concerns regarding the effective disposal of waste from these components.Here,we focused on a facile sustainable and economical strategy to provide ideas for this issue.This strategy relied on using appropriate mechanical treatment and sodium lignosulfonate coating to improve the dispersion and interfacial compatibility of bamboo fibers in poly(lactic acid).By optimising the particle size and concentration of sodium lignosulphonate,high value-added and green composites were prepared using sectional pressurization with a venting procedure.The treated composite displayed an ultra-smooth surface(roughness of 0.592 nm),impressive transient properties(disintegration and degradation behaviour after 30 d),and outstanding ultraviolet(UV)shielding properties(100%).These properties hold the promise of being an excellent substrate for electronic devices,especially for high-precision processing,transient electronics,and UV damage prevention.The satisfactory interfacial compatibility of the composites was confirmed by detailed characterisation regarding the related physicochemical properties.This investigation offers a sustainable approach for producing high value-added green composites from biomass and biomass-derived materials.
基金financially supported by the National Natural Science Foundation of China(Nos.22271252 and 22201105)。
文摘Consisting of natural histidine residues,polyhistidine(PHis)simulates functional proteins.Traditional approaches towards PHis require the protection of imidazole groups before monomer synthesis and polymerization to prevent degradation and side reactions.In the contribution,histidine N-thiocarboxyanhydride(His-NTA)is directly synthesized in aqueous solution without protection.With the self-catalysis of the imidazole side group,the ring-closing reaction to form His-NTA does not require any activating reagent(e.g.,phosphorus tribromide),which is elucidated by density functional theory(DFT)calculations.His-NTA directly polymerizes into PHis bearing unprotected imidazole groups with designable molecular weights(4.2-7.7 kg/mol)and low dispersities(1.10-1.19).Kinetic experiments and Monte Carlo simulations reveal the elementary reactions and the relationship between the conversion of His-NTA and time during polymerization.Block copolymerization of His-NTA with sarcosine N-thiocarboxyanhydride(Sar-NTA)demonstrate versatile construction of functional polypept(o)ides.The triblock copoly(amino acid)PHis-b-PSar-b-PHis is capable to reversibly coordinate with transition metal ions(Fe^(2+),Co^(2+),Ni^(2+),Cu^(2+)and Zn^(2+))to form pH-sensitive hydrogels.
基金financially supported by the National Key Research and Development Program of China(no.2022YFC2303100)National Natural Science Foundation of China(nos.T2325010,22305082,52203162,and 22075078)+1 种基金Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism(Shanghai Municipal Education Commission),the Fundamental Research Funds for the Central Universities(nos.JKVD1241029 and JKD01241701)Open Research Fund of State Key Laboratory of Polymer Physics and Chemistry(Changchun Institute of Applied Chemistry,Chinese Academy of Sciences),the Open Project of Engineering Research Center of Dairy Quality and Safety Control Technology(Ministry of Education,no.R202201).
文摘The rising prevalence of drug-resistant Gram-positive pathogens,particularly methicillin-resistant Staphy-lococcus aureus(MRSA)and vancomycin-resistant Enterococci(VRE),poses a substantial clinical challenge.Biofilm-associated infections exacerbate this problem due to their inherent antibiotic resistance and complex structure.Current antibiotic treatments struggle to penetrate biofilms and eradicate persister cells,leading to prolonged antibiotic use and increased resistance.Host defense peptides(HDPs)have shown promise,but their clinical application is limited by factors such as enzymatic degradation and difficulty in largescale preparation.Synthetic HDP mimics,such as poly(2-oxazoline),have emerged as effective alter-natives.Herein,we found that the poly(2-oxazoline),Gly-POX_(20),demonstrated rapid and potent activity against clinically isolated multidrug-resistant Gram-positive strains.Gly-POX_(20) showed greater stability under physiological conditions compared to natural peptides,including resistance to protease degradation.Importantly,Gly-POX_(20) inhibited biofilm formation and eradicated mature biofilm and demonstrated superior in vivo therapeutic efficacy to vancomycin in a MRSA biofilm-associated mouse keratitis model,suggesting its potential as a novel antimicrobial agent against drug-resistant Gram-positive bacteria,especially biofilm-associated infections.
文摘Polyfluoroarenes represent an essential group of compounds in the fields of medical and material chemistry.It is still a challenge to synthesize alkylated polyfluoroarenes.Herein,a Ni-catalyzed reductive alkylation of polyfluoroarenes with alkyl halides under mild conditions is reported.Polyfluoroarenes(3~6 F)can reacted smoothly with a diverse range of alkyl halides,such as primary,secondary,and tertiary alkyl iodides.The efficient formation of C(sp2)—C(sp3)can be achieved through the combination of Ni catalysis and(Bpin)2/K2CO3 as terminal reductant.
基金supported by the Joint Funds of the National Natural Science Foundation of China(No.U21A20320)the National Natural Science Foundation of China(No.22106102)was also sponsored by the special fund of State Environmental Protection Key Laboratory of Environmental Health Impact Assessment of Emerging Contaminants(No.SEPKLEHIAEC-202203).
文摘Poly(butylene succinate-co-furandicarboxylate)(PBSF)and poly(butylene adipateco-furandicarboxylate)(PBAF)are novel furandicarboxylic acid-based biodegradable copolyesters with great potential to replace fossil-derived terephthalic acid-based copolyesters such as poly(butylene succinate-co-terephthalate)(PBST)and poly(butylene adipate-co-terephthalate)(PBAT).In this study,quantum chemistry techniques after molecular dynamics simulations are employed to investigate the degradationmechanism of PBSF and PBAF catalyzed by Candida antarctica lipase B(CALB).Computational analysis indicates that the catalytic reaction follows a four-step mechanism resembling the ping-pong bibi mechanism,with the initial two steps being acylation reactions and the subsequent two being hydrolysis reactions.Notably,the first step of the hydrolysis is identified as the rate-determining step.Moreover,by introducing single-point mutations to expand the substrate entrance tunnel,the catalytic distance of the first acylation step decreases.Additionally,energy barrier of the rate-determining step is decreased in the PBSF system by site-directed mutations on key residues increasing hydrophobicity of the enzyme’s active site.This study unprecedently show the substrate binding pocket and hydrophobicity of the enzyme’s active site have the potential to be engineered to enhance the degradation of copolyesters catalyzed by CALB.
文摘Although the efficiency of poly(ethylene terephthalate)(PET)degradation has been successfully improved by depolymerase engineering,mostly by using Goodfellow-PET(gf-PET)as a substrate,efforts to degrade unpretreated PET materials with high crystallinity remain insufficient.Here,we endeavored to improve the degradation capability of a WCCG mutant of leaf-branch compost cutinase(LCC)on a unpretreated PET substrate(crystallinity>40%)by employing iterative saturation mutagenesis.Using this method,we developed a high-throughput screening strategy appropriate for unpretreated substrates.Through extensive screening of residues around the substrate-binding groove,two variants,WCCG-sup1 and WCCG-sup2,showed good depolymerization capabilities with both high-(42%)and low-crystallinity(9%)substrates.The WCCG-sup1 variant completely depolymerized a commercial unpretreated PET product in 36 h at 72℃.In addition to enzyme thermostability and catalytic efficiency,the adsorption of enzymes onto substrates plays an important role in PET degradation.This study provides valuable insights into the structure-function relationship of LCC.
基金financially supported by the National Key R&D Program of China(No.2021YFB3801901)the National Natural Science Foundation of China(Nos.52403138 and U19A2095)+1 种基金Institutional Research Fund from Sichuan University(No.2020SCUNL205)Fundamental Research Funds for the Central Universities,and 111 Project(No.B20001)。
文摘The development of degradable and chemically recyclable polymers is a promising strategy to address pressing environmental and resource-related challenges.Despite significant progress,there is a need for continuous development of such recyclable polymers.Herein,PPDOPLLA-PU copolymers were synthesized from poly(p-dioxanone)-diol(PPDO-diol)and poly(L-lactide)-diol(PLLA-diol)by chain extension reaction.The chemical structures and microphase structures of PPDO-PLLA-PU were characterized,and their crystalline properties,mechanical properties,and degradation behaviors were further investigated.Significantly,the distribution of PLLA phase in the copolymer matrix showed a rod-like microstructure with a slight orientation,despite the thermodynamic incompatibility of PPDO and PLLA segments.Moreover,on the basis of this microphase separation,PPDO spherulites can crystallize using the interface of the two phases as nucleation sites.Accordingly,the combined effect of above two contributes to the enhanced mechanical properties.In addition,PPDO-PLLA-PU copolymers have good processability and recyclability,making them valuable for a wide range of applications.
文摘Poly(octamethylene citrate)(POC)is a promising bioelastomer material in the biomedical field.However,its thermosetting nature poses a significant challenge to processing and molding,especially manufacturing the POC-based elastomer particles as potential,degradable and toughened fillers.Firstly,a Pickering emulsion with a pre-polymer(pre-POC)solution in dimethyl carbonate as a dispersed oil phase,a Pullulan(PUL)aqueous solution as a continuous water phase,and chitin nanocrystal(ChiNC)as a particle-type emulsifier was constructed.Secondly,the POC-based core/shell structured microspheres were prepared by spray-drying of the emulsions,and characterized by a scanning electron microscope and a transmission electron microscope.Finally,the POC-based core/shell structured microspheres were used as elastomer fillers to strengthen and toughen a chitosan film,resulting in 26%increase in the tensile strength and 45%increase in the strain at break;the POC-based core/shell structured microsphere as a double-layer drug release system was built in which the hydrophilic drug of tetracycline hydrochloride(TCH)was released from the outer layer and the hydrophobic drug of curcumin was released from the inner layer,roughly following the Ritger-Peppas model.
基金support from the National Natural Science Foundation of China(Nos.52203026 and 52027804)。
文摘Herein,a simple method for preparing poly(vinylidene fluoride)(PVDF)films with controlledβ/γratios by spin-coating assisted by potassium bromide(KBr)is proposed.The results show that the relative fraction of theβphase(denoted as Fβ)for the films prepared on the KBr surface first decreased until a critical temperature(denoted as Tc)was reached,and then increased with increasing spin-coating temperature.This was related to the dissolved K and Br ions in the films.Further experiments showed that below Tc,high humidity can enhance Fβbut exhibit an adverse effect at and above Tc.The high content of K and Br ions in the PVDF/KBr blend film and larger shear stress can facilitate the formation of theβphase,leading exclusively to the formation ofβ-andγ-phases.The mechanism responsible for the change in Fβwith temperature was proposed:below Tc,the decrease in water intake with increasing temperature results in the decline of Fβ,whereas above Tc,the increase in Fβwith temperature is attributed to the synergistic effect of ions and shear stress.Ultimately,this paves the way for fabricating PVDF films with tailoredβ/γratios for electroactive and energy-harvesting applications.
基金supported by the Scientific Research Start-up Fund Project of Anhui Polytechnic University for Introducing Talents(No.2022YQQ081)Natural Science Research Project of the Anhui Educational Committee(No.2024AH050133)the National Natural Science Foundation of China(No.22101088)。
文摘Dimethyl sulfoxide(DMSO)possessing strong solvency and high boiling point is a very important aprotic polar solvent in organic and polymer synthesis.Notably,it is also a useful synthon in organic chemistry.However,the direct incorporation of DMSO in polymer synthesis remains challenging.In this work,DMSO was successfully converted to nitrogen-containing heterocyclic polymers as a monomer via multicomponent polymerizations(MCPs)with dialdehydes and diamines in the presence of K_(2)S_(2)O_(8)/t-BuOK at 120℃in 6 h.A series of poly(phenylquinoline)s with high M_(w)values(up to 5.11×10^(4))were obtained in satisfactory yields(up to 82%),performing good solubility,good thermal and morphological stability as well as excellent film-forming ability.The thin films of poly(phenylquinoline)s exhibit high refractive index value in a wide wavelength range of 400–1700 nm.Thus,this work not only enriches the family of MCPs but also provides an efficient strategy for the conversion of DMSO into functional polymeric materials that are potentially applicable in diverse areas.
基金supported by the Nature Science Foundation of Shandong Province,China(Nos.ZR2022MB051 , ZR2021MB112)Science and Technology Bureau of Jinan City(No.2021GXRC105),Postdoctoral Science Foundation of China(No.2022M712343)+1 种基金Jinan City University Integration Development Strategy Project(No.JNSX2024030)a key laboratory of special functional aggregates of the Ministry of Education,Shandong University(No.JT-2023-02).
文摘Fluorescent polyurea-carbon dots(PU-CD) were successfully achieved through a co-pyrolysis technique, combining polyurea(PU) with carboxyl-containing carbon dots(PCD) at a temperature of 220 ℃. The PU was fabricated via a simple precipitation polymerization process using toluene disocyanate in a water/acetone binary solvent system. PCD was generated by thermal treatment of poly(ethylene glycol)(PEG) at the same elevated temperature. To elucidate the structural characteristics of PU-CD, as well as its precursor components PU and PCD, a comprehensive suite of analytical techniques was employed, including transmission electron microscopy(TEM), Fourier transform infrared spectroscopy(FTIR), nuclear magnetic resonance(NMR), dynamic light scattering(DLS) and X-ray photoelectron spectroscopy(XPS). These analyses confirmed the formation of amide bonds resulting from the reaction between the terminal amines of PU and the carboxyl groups of PCD. An in-depth comparison of the fluorescence properties of PU-CD revealed marked enhancements in fluorescence intensity when contrasted with PU, PEG, and the individual PCD. The research explored the impact of various factors such as concentration, pH in aqueous solutions, and solvent type on the fluorescence emission of these materials, providing valuable insights into their emission mechanisms. It was particularly noteworthy that both PCD and PU-CD exhibited a confined-domain crosslink-enhanced emission effect. Utilizing the aqueous dispersion of PU-CD as a fluorescent probe,the detection of doxycycline(DOX), a long-acting, broad-spectrum, semi-synthetic tetracycline antibiotic, was achieved with a detection limit of 2.9×10^(-7)mol/L. This study introduces a simple, green, and cost-effective fluorescent probe for the detection of DOX, which has significant potential for application in the realms of analytical chemistry and food safety monitoring in the future.
基金financially supported by the National Natural Science Foundation of China (No. 21774006)
文摘The sulfonated poly(α-methyl styrene-b-isobutylene-b-α-methyl styrene)copolymers(S-ASIBS)with the average molar percentage of sulfonic acid(-SO_(3)H)groups(SP)ranging from 3.6 mol%to 14.3 mol%could be synthesized by sulfonation of ASIBS with acetyl sulfate.The hydrophilic ionic channels were generated for proton exchange membranes(PEMs)by ion aggregation of-SO_(3)H groups and microphase separation between hydrophobic polyisobutylene and hydrophilic sulfonated poly(α-methyl styrene)segments in S-ASIBS.The proton transport ability was improved while oxidative stability was decreased by increasing SP in S-ASIBS.The appropriate SP of about 12.7 mol%in S-ASIBS provides the available PEMs with high proton transport ability,low methanol permeability and good oxidative stability.The absence of active tertiary hydrogen atoms along S-ASIBS copolymer chains avoids their attack by peroxy radicals.The residual rates of weight(RW)and proton conductivity(Rσ)of S-ASIBS-12.7 membrane after oxidation treatment for 916 h were 84.3%and 88.1%respectively,near to those of commercial Nafion 117(RW=87.9%,Rσ=90.3%).The membrane electrode assembly(MEA)could be prepared by using various S-ASIBS as PEMs for direct methanol fuel cell.The single cell with S-ASIBS-12.7 MEA behaves high performance of open circuit voltage(OCV)of 548 mV and peak power density(Pmax)of 36.1 mW·cm^(-2),which is similar to those of Nafion 117(OCV=506 mV,P_(max)=35.6 mW·cm^(-2)).To the best of our knowledge,this is the first example of advanced S-ASIBS membrane with high proton conductivity,excellent fuel barrier property and remarkable oxidative stability for promising PEMs.
基金supported by the Sichuan Provincial Regional Innovation Cooperation Project(No.2024YFHZ0159).
文摘Semicrystalline polymers usually undergo multilevel microstructural evolutions with annealing and stretching processes,which is es-sential to tailor the physical properties of the polymer.Here,poly(butylene carbonate)(PBC)sheets were prepared via isothermal annealing and unidirectional pre-stretching processes,then the changes of PBC in crystallinity,mechanical properties,thermal properties and microscopic changes before and after annealing and stretching were measured,as well as the relationship between microstructure and macroscopic proper-ties before and after stretching.The strengthening mechanism of PBC was also described.It was demonstrated that shish-kabab structure emerged under the pre-stretching process.With the increase of the tensile ratio,the crystallinity,structure and mechanical properties are in-creased differently.Among them,the crystallinity and tensile strength after annealing-stretching treatment increased to 24.45%and 104.5 MPa,respectively,which were about 1.55 times and 3.4 times of those-without any treatment.
基金supported by the Zhejiang Provincial"Vanguard"and"Leading Goose"R&D Program(No.2025C02203)the Zhejiang Provincial Natural Science Foundation of China(No.LTGS24C130001)the Fund for Key Scientific Research in the Public Interest of Ningbo(No.2024S009)。
文摘Poly(vinyl alcohol)(PVA)is a biodegradable and environmentally friendly material known for its gas barrier characteristics and solvent resistance.However,its flammability and water sensitivity limit its application in specialized fields.In this study,phytic acid(PA)was introduced as a halogen-free flame retardant and biochar(BC)was introduced as a reinforcement to achieve both flame resistance and mechanical robustness.We thoroughly investigated the effects of BC particle sizes(100-3000 mesh)and addition amounts(0 wt%-10 wt%),as well as PA addition amounts(0 wt%-15 wt%),on the properties of PVA composite films.Notably,the PA10/1000BC5 composite containing 10 wt%PA and 5 wt%1000 mesh BC exhibited optimal properties.The limiting oxygen index increased to 39.2%,and the UL-94 test achieved a V-0 rating.Additionally,the PA10/1000BC5 composite film demonstrated significantly enhanced water resistance,with a swelling ratio reaching 800%without dissolving,unlike that of the control PVA.The water contact angle was 70°,indicating that hydrophilic properties remained essentially unaffected.Most importantly,the tensile modulus and elongation at break were 213 MPa and 281.7%,respectively,nearly double those of the PVA/PA composite film.This study presents an efficient and straightforward method for preparing PVA composite films that are flame-retardant,tough,and waterresistant,expanding their potential applications in various fields.
基金financially supported by the National Key R&D Program of China(No.2022YFB3808000)the National Natural Science Foundation of China(No.U21A2099)+2 种基金the Science and Technology Development Program of Jilin Province(No.20240101002JJ)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.Y2023066)the Plan for Enhancing Health Science and Technology Capacity in Jilin Province(No.2020J041).
文摘Oxidative stress,characterized by the excessive accumulation of reactive oxygen species(ROS),is linked to various pathological conditions,including myocardial infarction,cancer,and neurodegenerative diseases.Addressing ROS-induced cell damage has become a critical focus of biomedical research.In this study,a thermo-sensitive poly(amino acid)hydrogel,composed of poly(ethylene glycol)-block-poly(l-methionine),was prepared for cytoprotection through ROS scavenging.The sol-to-gel transition mechanism of the hydrogel was elucidated,and its potent antioxidant properties and cell protective effects were validated using hydrogen peroxide(H_(2)O_(2))-induced oxidative stress and oxygen-glucose deprivation(OGD)models.The hydrogel significantly mitigated H_(2)O_(2)-induced damage in L929 cells,doubling their survival rate.Additionally,it scavenged approximately 35.8%of the ROS during OGD,reducing mitochondrial oxidative damage and resulting in a 29.4%decrease in apoptotic cell number.These findings underscore the potential biomedical applications of thermo-sensitive poly(amino acid)hydrogels,particularly in treating oxidative stress-related cell damage.
基金Funded by the National Natural Science Foundation of China(No.21104031)the Education Department of Hunan province in 2020(No.20C1589)。
文摘This article provided a preparation protocol for poly(lactic acid)(PLA)/modified epoxidized soybean oil(ECP)/nano-magnesium oxide(n-MgO)ternary composites and studied their mechanical and antibacterial properties.By means of an organic synthesis technique,epoxidized soybean oil(ESO)is chemically grafted to PLA to synthesize ESO chemically plastically modified PLA,abbreviated ECP.To fabricate PLA/ECP/n-MgO composite materials,ECP acts as a plasticizer and a compatibilizer simultaneously,and n-MgO acts as an enhancer.Then scanning electron microscopy,X-ray diffraction,differential scanning calorimetry,universal tester,and antibacterial research were exploited to characterize the morphology,thermal resistance,mechanical properties,and antibacterial performance of PLA/ECP/n-MgO composites.The experimental results show that ECP acts as a plasticizer by causing heterogeneous nucleation,which increases PLA's crystallinity.Evenly distributed n-MgO can greatly improve PLA's antibacterial qualities.Furthermore,ECP and n-MgO work together to improve the positive aspects of PLA/ECP/n-MgO composites,with PLA/ECP/n-MgO 100/1/0.5 composites having the best overall properties.While improving the mechanical performance and toughness of PLA,this work offers a prospective approach and foundational database for the creation of multifunctional biodegradable composites.
