Poly(methacrylic acid co-poloxamer) hydrogel networks were synthesized by free radical solution polymerization and their equilibrium swelling and solute permeation properties were characterized. These gels exhibited p...Poly(methacrylic acid co-poloxamer) hydrogel networks were synthesized by free radical solution polymerization and their equilibrium swelling and solute permeation properties were characterized. These gels exhibited pH dependant swelling and solute diffusivity due to the formation or disruption of hydrogen bonded complexation between methacrylic acid (MAA) and etheric (EO). In neutral and basic conditions (above the swelling transition pH), the copolymer swelling was greatly higher than acid condition. In complexed hydrogels, the diffusion coefficients of vitamin B12 (VB12) were in the range of 10-10 to 10-7 cm2s-1; While in uncomplexed hydrogels, the values were about 210-6 cm2s-1. The comonomer composition and synthesis conditions have great effect on the structure, and thereby, swelling and solute diffusion characteristics of the resultant hydrogels. For the copolymers with composition of less than or more than 1:1 MAA/EO molar ratio, the plot of lnD vs 1/H-1 followed two different linear equations of 慺ree volume theory? respectively.展开更多
A full-relaxation optimization of molecule and the Dreiding force field are employed to obtain the geometry parameters and the conformational energy surfaces of meso or racemic dyad of poly(acrylic acid) (PAA) and pol...A full-relaxation optimization of molecule and the Dreiding force field are employed to obtain the geometry parameters and the conformational energy surfaces of meso or racemic dyad of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA). Three different carbonyl-bond orientations of side-groups resulted in the differences in depth of potential wells in their energetic contours for a meso or a racemic dyad. These discrepancies are interpreted as a result of various fine structures corresponding to grid search conformations as well as thereby different interactions. The analysis on the most stable conformations of PMAA confirmed that the ester groups are nearly perpendicular to the plane defined by the two adjacent skeletal bonds but may possibly change their relative orientations to meet the requirement of lower energy during the conformational state transition. For each polymer, two global energy maps of a meso and a racemic dyad were finally constructed from the superposition of energy data for the three kinds of side-group orientations by the Boltzmann factors. From an ensemble average, the proposed scheme with three rotational isomeric states (RIS) allowed us to access the experimentally unperturbed dimensions of PAA chain via the configurational statistical mechanics. Although the calculation was based on the short-range, local interactions, it was interested to note that the experimental characteristic ratios just fell within the range calculated for atactic chains.展开更多
A highly efficient copolymer (methacrylic acid - co - styrene - divinylbenzene) in situ making high-performance liquid chromatographic column was prepared and evaluated. The column efficiency calculated in terms of he...A highly efficient copolymer (methacrylic acid - co - styrene - divinylbenzene) in situ making high-performance liquid chromatographic column was prepared and evaluated. The column efficiency calculated in terms of height equivalent to a theoretical plate was 25 mu m and rapid separations of small molecules such as substituted aromatic hydrocarbons and aromatic acids were achieved within five minutes.展开更多
The photo-controlled/living radical polymerization of methacrylic acid (MAA) was performed at room temperature by irradiation with a high-pressure mercury lamp using azo initiators and 4-methoxy-2,2,6,6-tetramethylpip...The photo-controlled/living radical polymerization of methacrylic acid (MAA) was performed at room temperature by irradiation with a high-pressure mercury lamp using azo initiators and 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl as the mediator in the presence of (4-tert-butylphenyl)diphenylsulfonium triflate (tBuS) as the accelerator. Whereas the bulk polymerization yielded polymers with a bimodal molecular weight distribution in both the absence and presence of tBuS, the solution polymerization in methanol produced unimodal polymers with the molecular weight distribution of 2.0 - 2.3 in the presence of tBuS. The molecular weight distribution of the resulting poly (MAA) decreased with an in- crease in tBuS. The dilution of the monomer concentration also reduced the molecular weight distribution. The use of the initiator with a low 10-h half-life temperature also effectively controlled the molecular weight. The livingness of the polymerization was confirmed by obtaining linear increases in the first-order conversion versus time, the molecular weight versus the conversion, and the molecular weight versus the reciprocal of the initiator concentration.展开更多
Methacrylic acid first was neutralized with an aqueous solution of NaOH to pH = 6.0 similar to 7.0, vinylene carbonate (VCA) was added to the solution, then monomers were copolymerized in paraffin oil by means of reve...Methacrylic acid first was neutralized with an aqueous solution of NaOH to pH = 6.0 similar to 7.0, vinylene carbonate (VCA) was added to the solution, then monomers were copolymerized in paraffin oil by means of reverse-phase suspension polymerization and hydrophilic copolymeric supports were prepared. The properties of the supports were determined using trypsin and results show that the amount of enzymes coupled to the supports and the specific activity of immobilized trypsin are related to the content of VCA structure units, reaction time and concentration of enzyme solution, etc.展开更多
The solid phase graft copolymerization of polypropylene (PP) andmethacrylic acid (MAA) was investigated. benzoyl peroxide(BPO) wasused as initia- tor. The influence of the reactive time,concentration of initiator and ...The solid phase graft copolymerization of polypropylene (PP) andmethacrylic acid (MAA) was investigated. benzoyl peroxide(BPO) wasused as initia- tor. The influence of the reactive time,concentration of initiator and monomer on degree of graft and meltflow index of graft copolymer(PP-MAA) was discussed. The effect ofgraft copolymer on mechanical properties of The glass fibre (GF)reinforced PP composites was also Studied. It is proved that graftcopolymer could obviously Increase the interfacial adhesive strengthbetween PP and GF.展开更多
Poly (methacrylic acid-co-poloxamer) hydrogel networks were synthesized byfree-radical solution polymerization, and the dynamic swelling and in vitro release properties ofmodel drugs, dextromethorphan hydrobromide (DM...Poly (methacrylic acid-co-poloxamer) hydrogel networks were synthesized byfree-radical solution polymerization, and the dynamic swelling and in vitro release properties ofmodel drugs, dextromethorphan hydrobromide (DMP) and vitamin B_(12) (VB_(12)) were studied. Thesegels exhibited pH-dependant swelling and sustained drug release properties, and the water uptakerate and drug release rate in neutral or basic media were higher than that in acidic media. Theresults showed that the water uptake followed non-Fickian or zero order process in neutral or basicmedia, and the release of model drugs from hydrogels of appropriate composition was of zero orderkinetics over a period of several hours.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 kinetics of free-radical crosslinking co-polymerization(FRCCP)of acrylic acid(AA)with both methacrylic acid(MA)(PAMA hydrogel)and maleic acid(MAL)(PAMAL hydrogel)was investigated under the conditions of isothermal...The kinetics of free-radical crosslinking co-polymerization(FRCCP)of acrylic acid(AA)with both methacrylic acid(MA)(PAMA hydrogel)and maleic acid(MAL)(PAMAL hydrogel)was investigated under the conditions of isothermal conventional heating(CH)and under the conditions of microwave heating(MWH)with controlled cooling.The kinetics curves of FRCCP of PAMA and PAMAL hydrogels under the conditions of CH are described with the kinetics model of second order chemical reaction,whereas the kinetics curves under the conditions of CH are described with the kinetics model of Polany-Winger.It is proved that MWH leads to the changes in the rate of FRCCP and to the changes in the values of the kinetic parameters activation energy(Ea)and pre-exponential factor(lnA).It was found the existence of relationship between the values of the kinetic parameters calculated for MWH and CH for PAMA and PAMAL hydrogel synthesis process,which is well-known as compensation effect.The effect of MWH on the kinetics of FRCCP for PAMA and PAMAL hydrogel formation were explained by applying the model of activation by selective energy transfer(SET).The changes in kinetics model,rate of FRCCP and kinetics parameters,caused with the MWH can found wide application in designing novel technologies for obtaining polymers and for synthesis of polymers with novel physico-chemical properties.The suggested mechanism of activation for polymerisation under the conditions of MWH also enables development of novel reaction systems and technologies for polymers productions.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
Objectives:Monitoring of Cancer Antigen 125(CA125)during ovarian cancer(OC)maintenance treatment with poly(ADP-ribose)polymerase inhibitors(PARPis)may be insufficient when using Gynecologic Cancer Intergroup(GCIG)bioc...Objectives:Monitoring of Cancer Antigen 125(CA125)during ovarian cancer(OC)maintenance treatment with poly(ADP-ribose)polymerase inhibitors(PARPis)may be insufficient when using Gynecologic Cancer Intergroup(GCIG)biochemical progression criteria.This study aimed to evaluate the usefulness of CA125 monitoring in detecting OC recurrence during PARPis maintenance treatment.Methods:This multicenter retrospective cohort study included patients with primary OC who achieved complete or partial response after first-line platinum-based chemotherapy followed by PARPis maintenance treatment.Progressionwas defined using Response EvaluationCriteria in Solid Tumors(RECIST)and GCIG biochemical criteria.New biochemical progression definitions,based on CA125 nadir determined using receiver operating characteristic(ROC)curve analysis,were proposed.Concordance between radiological and biochemical progression was assessed.Results:Of 142 patients,progression was detected in 54(38.03%)and 29(20.42%)using RECIST and GCIG criteria,respectively.The sensitivity,specificity,positive predictive value(PPV),and negative predictive value(NPV)of the GCIG criteria were 53.70%[95%confidence interval(CI):39.61%–67.38%],100.00%[95%CI:95.91%–100.00%],100.00%[95%CI:88.10%–100.00%]and 77.88%[95%CI:72.54%–82.43%],respectively.A cut-off of 1.59×nadir achieved 88.90%sensitivity and 87.20%specificity[Area Under Curve(AUC):91.10%,95%CI:84.70%–97.40%]with a false positive rate(FPR)of 12.67%.Defining biochemical progression as an increase in CA125 of≥3×nadir achieved sensitivity,specificity,PPV,NPV,and FPR of 79.63%[95%CI:66.47%–89.37%],98.86%[95%CI:93.83%–99.97%],97.73%[95%CI:85.91%–99.67%],88.78%[95%CI:82.35%–93.06%],and 1.14%,respectively.Diagnostic accuracy was higher using the≥3×nadir criterion compared with GCIG definition(91.55%vs.82.39%).Conclusion:GCIG biochemical progression criteria during PARPis maintenance treatment after first-line chemotherapymissed 46.3%of progressing patients.Anewcriterion—CA125≥3×nadir—improves sensitivity and NPV,while maintaining high specificity,offering a simple and practical approach for clinical implementation.展开更多
A new polymeric ionic liquid gel was prepared with 1-[(2-methacryloyloxy)ethyl]-3-methylimidazolium bromide(MEMImBr) via radiation-induced polymerization and cross-linking at room temperature.The resultant PMEMImBr ge...A new polymeric ionic liquid gel was prepared with 1-[(2-methacryloyloxy)ethyl]-3-methylimidazolium bromide(MEMImBr) via radiation-induced polymerization and cross-linking at room temperature.The resultant PMEMImBr gel exhibits high strength and flexibility as well as special swelling behavior in oil-in-water(O/W)emulsions.The swelling behavior of PMEMImBr gel in emulsions is similar to that in water except that the swelling rate in emulsions is slightly smaller than that in water.The organic solvents with higher polarity in the emulsions contribute to the swelling of PMEMImBr gels,and the O/W proportion of emulsion in the swollen gel equals approximately that of original emulsion when the concentration of organic solvent is lower than 0.2 g/g.展开更多
Compatibilization is crucial for the blending of immiscible polymers to develop high-performance composites;however,traditional compatibilization by copolymers(pre-made or in-situ generation)suffers from weak interfac...Compatibilization is crucial for the blending of immiscible polymers to develop high-performance composites;however,traditional compatibilization by copolymers(pre-made or in-situ generation)suffers from weak interface anchoring,and inorganic particles have gained extensive attention recently owing to their large interfacial desorption energy,while their low affinity to bulk components is a drawback.In this study,an interfacial atom transfer radical polymerization(ATRP)technique was employed to grow polystyrene(PS)and poly(2-hydroxyethyl methacrylate)(PHEMA)simultaneously on different hemispheres of Br-functionalized SiO_(2) nanoparticles to stabilize a Pickering emulsion,whereby a brush-type Janus nanoparticle(SiO_(2)@JNP)was developed.The polymer brushes were well-characterized,and the Janus feature was validated by transmission electron microscope(TEM)observation of the sole hemisphere grafting of SiO_(2)-PS as a control sample.SiO_(2)@JNP was demonstrated to be an efficient compatibilizer for a PS/poly(methyl methacrylate)(PMMA)immiscible blend,and the droplet-matrix morphology was significantly refined.The mechanical strength and toughness of the blend were synchronously enhanced at a low content SiO_(2)@JNP optimized~0.9 wt%,with the tensile strength,elongation at break and impact strength increased by 17.7%,26.6%and 19.6%,respectively.This enhancement may be attributed to the entanglements between the grafted polymer brushes and individual components that improve the particle-bulk phase affinity and enforce interfacial adhesion.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
文摘Poly(methacrylic acid co-poloxamer) hydrogel networks were synthesized by free radical solution polymerization and their equilibrium swelling and solute permeation properties were characterized. These gels exhibited pH dependant swelling and solute diffusivity due to the formation or disruption of hydrogen bonded complexation between methacrylic acid (MAA) and etheric (EO). In neutral and basic conditions (above the swelling transition pH), the copolymer swelling was greatly higher than acid condition. In complexed hydrogels, the diffusion coefficients of vitamin B12 (VB12) were in the range of 10-10 to 10-7 cm2s-1; While in uncomplexed hydrogels, the values were about 210-6 cm2s-1. The comonomer composition and synthesis conditions have great effect on the structure, and thereby, swelling and solute diffusion characteristics of the resultant hydrogels. For the copolymers with composition of less than or more than 1:1 MAA/EO molar ratio, the plot of lnD vs 1/H-1 followed two different linear equations of 慺ree volume theory? respectively.
基金This work was supported by the Youth Science Foundation of Acedemia Sinica the China Postdoctoral Science Foundation, the National Natural Science Foundation of China, and Polymer Physics Laboratory,Academia Sinica
文摘A full-relaxation optimization of molecule and the Dreiding force field are employed to obtain the geometry parameters and the conformational energy surfaces of meso or racemic dyad of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA). Three different carbonyl-bond orientations of side-groups resulted in the differences in depth of potential wells in their energetic contours for a meso or a racemic dyad. These discrepancies are interpreted as a result of various fine structures corresponding to grid search conformations as well as thereby different interactions. The analysis on the most stable conformations of PMAA confirmed that the ester groups are nearly perpendicular to the plane defined by the two adjacent skeletal bonds but may possibly change their relative orientations to meet the requirement of lower energy during the conformational state transition. For each polymer, two global energy maps of a meso and a racemic dyad were finally constructed from the superposition of energy data for the three kinds of side-group orientations by the Boltzmann factors. From an ensemble average, the proposed scheme with three rotational isomeric states (RIS) allowed us to access the experimentally unperturbed dimensions of PAA chain via the configurational statistical mechanics. Although the calculation was based on the short-range, local interactions, it was interested to note that the experimental characteristic ratios just fell within the range calculated for atactic chains.
文摘A highly efficient copolymer (methacrylic acid - co - styrene - divinylbenzene) in situ making high-performance liquid chromatographic column was prepared and evaluated. The column efficiency calculated in terms of height equivalent to a theoretical plate was 25 mu m and rapid separations of small molecules such as substituted aromatic hydrocarbons and aromatic acids were achieved within five minutes.
文摘The photo-controlled/living radical polymerization of methacrylic acid (MAA) was performed at room temperature by irradiation with a high-pressure mercury lamp using azo initiators and 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl as the mediator in the presence of (4-tert-butylphenyl)diphenylsulfonium triflate (tBuS) as the accelerator. Whereas the bulk polymerization yielded polymers with a bimodal molecular weight distribution in both the absence and presence of tBuS, the solution polymerization in methanol produced unimodal polymers with the molecular weight distribution of 2.0 - 2.3 in the presence of tBuS. The molecular weight distribution of the resulting poly (MAA) decreased with an in- crease in tBuS. The dilution of the monomer concentration also reduced the molecular weight distribution. The use of the initiator with a low 10-h half-life temperature also effectively controlled the molecular weight. The livingness of the polymerization was confirmed by obtaining linear increases in the first-order conversion versus time, the molecular weight versus the conversion, and the molecular weight versus the reciprocal of the initiator concentration.
文摘Methacrylic acid first was neutralized with an aqueous solution of NaOH to pH = 6.0 similar to 7.0, vinylene carbonate (VCA) was added to the solution, then monomers were copolymerized in paraffin oil by means of reverse-phase suspension polymerization and hydrophilic copolymeric supports were prepared. The properties of the supports were determined using trypsin and results show that the amount of enzymes coupled to the supports and the specific activity of immobilized trypsin are related to the content of VCA structure units, reaction time and concentration of enzyme solution, etc.
文摘The solid phase graft copolymerization of polypropylene (PP) andmethacrylic acid (MAA) was investigated. benzoyl peroxide(BPO) wasused as initia- tor. The influence of the reactive time,concentration of initiator and monomer on degree of graft and meltflow index of graft copolymer(PP-MAA) was discussed. The effect ofgraft copolymer on mechanical properties of The glass fibre (GF)reinforced PP composites was also Studied. It is proved that graftcopolymer could obviously Increase the interfacial adhesive strengthbetween PP and GF.
文摘Poly (methacrylic acid-co-poloxamer) hydrogel networks were synthesized byfree-radical solution polymerization, and the dynamic swelling and in vitro release properties ofmodel drugs, dextromethorphan hydrobromide (DMP) and vitamin B_(12) (VB_(12)) were studied. Thesegels exhibited pH-dependant swelling and sustained drug release properties, and the water uptakerate and drug release rate in neutral or basic media were higher than that in acidic media. Theresults showed that the water uptake followed non-Fickian or zero order process in neutral or basicmedia, and the release of model drugs from hydrogels of appropriate composition was of zero orderkinetics over a period of several hours.
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the Ministry of Science and Technical Development of the Republic of Serbia,through Project No.172015 OI.
文摘The kinetics of free-radical crosslinking co-polymerization(FRCCP)of acrylic acid(AA)with both methacrylic acid(MA)(PAMA hydrogel)and maleic acid(MAL)(PAMAL hydrogel)was investigated under the conditions of isothermal conventional heating(CH)and under the conditions of microwave heating(MWH)with controlled cooling.The kinetics curves of FRCCP of PAMA and PAMAL hydrogels under the conditions of CH are described with the kinetics model of second order chemical reaction,whereas the kinetics curves under the conditions of CH are described with the kinetics model of Polany-Winger.It is proved that MWH leads to the changes in the rate of FRCCP and to the changes in the values of the kinetic parameters activation energy(Ea)and pre-exponential factor(lnA).It was found the existence of relationship between the values of the kinetic parameters calculated for MWH and CH for PAMA and PAMAL hydrogel synthesis process,which is well-known as compensation effect.The effect of MWH on the kinetics of FRCCP for PAMA and PAMAL hydrogel formation were explained by applying the model of activation by selective energy transfer(SET).The changes in kinetics model,rate of FRCCP and kinetics parameters,caused with the MWH can found wide application in designing novel technologies for obtaining polymers and for synthesis of polymers with novel physico-chemical properties.The suggested mechanism of activation for polymerisation under the conditions of MWH also enables development of novel reaction systems and technologies for polymers productions.
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Objectives:Monitoring of Cancer Antigen 125(CA125)during ovarian cancer(OC)maintenance treatment with poly(ADP-ribose)polymerase inhibitors(PARPis)may be insufficient when using Gynecologic Cancer Intergroup(GCIG)biochemical progression criteria.This study aimed to evaluate the usefulness of CA125 monitoring in detecting OC recurrence during PARPis maintenance treatment.Methods:This multicenter retrospective cohort study included patients with primary OC who achieved complete or partial response after first-line platinum-based chemotherapy followed by PARPis maintenance treatment.Progressionwas defined using Response EvaluationCriteria in Solid Tumors(RECIST)and GCIG biochemical criteria.New biochemical progression definitions,based on CA125 nadir determined using receiver operating characteristic(ROC)curve analysis,were proposed.Concordance between radiological and biochemical progression was assessed.Results:Of 142 patients,progression was detected in 54(38.03%)and 29(20.42%)using RECIST and GCIG criteria,respectively.The sensitivity,specificity,positive predictive value(PPV),and negative predictive value(NPV)of the GCIG criteria were 53.70%[95%confidence interval(CI):39.61%–67.38%],100.00%[95%CI:95.91%–100.00%],100.00%[95%CI:88.10%–100.00%]and 77.88%[95%CI:72.54%–82.43%],respectively.A cut-off of 1.59×nadir achieved 88.90%sensitivity and 87.20%specificity[Area Under Curve(AUC):91.10%,95%CI:84.70%–97.40%]with a false positive rate(FPR)of 12.67%.Defining biochemical progression as an increase in CA125 of≥3×nadir achieved sensitivity,specificity,PPV,NPV,and FPR of 79.63%[95%CI:66.47%–89.37%],98.86%[95%CI:93.83%–99.97%],97.73%[95%CI:85.91%–99.67%],88.78%[95%CI:82.35%–93.06%],and 1.14%,respectively.Diagnostic accuracy was higher using the≥3×nadir criterion compared with GCIG definition(91.55%vs.82.39%).Conclusion:GCIG biochemical progression criteria during PARPis maintenance treatment after first-line chemotherapymissed 46.3%of progressing patients.Anewcriterion—CA125≥3×nadir—improves sensitivity and NPV,while maintaining high specificity,offering a simple and practical approach for clinical implementation.
基金supported by the National Natural Science Foundation of China (No. 11375019)
文摘A new polymeric ionic liquid gel was prepared with 1-[(2-methacryloyloxy)ethyl]-3-methylimidazolium bromide(MEMImBr) via radiation-induced polymerization and cross-linking at room temperature.The resultant PMEMImBr gel exhibits high strength and flexibility as well as special swelling behavior in oil-in-water(O/W)emulsions.The swelling behavior of PMEMImBr gel in emulsions is similar to that in water except that the swelling rate in emulsions is slightly smaller than that in water.The organic solvents with higher polarity in the emulsions contribute to the swelling of PMEMImBr gels,and the O/W proportion of emulsion in the swollen gel equals approximately that of original emulsion when the concentration of organic solvent is lower than 0.2 g/g.
基金financially supported by the National Natural Science Foundation of China(Nos.22172028,21903015,and 22403017)Natural Science Foundation of Fujian Province of China(No.2022J05041)。
文摘Compatibilization is crucial for the blending of immiscible polymers to develop high-performance composites;however,traditional compatibilization by copolymers(pre-made or in-situ generation)suffers from weak interface anchoring,and inorganic particles have gained extensive attention recently owing to their large interfacial desorption energy,while their low affinity to bulk components is a drawback.In this study,an interfacial atom transfer radical polymerization(ATRP)technique was employed to grow polystyrene(PS)and poly(2-hydroxyethyl methacrylate)(PHEMA)simultaneously on different hemispheres of Br-functionalized SiO_(2) nanoparticles to stabilize a Pickering emulsion,whereby a brush-type Janus nanoparticle(SiO_(2)@JNP)was developed.The polymer brushes were well-characterized,and the Janus feature was validated by transmission electron microscope(TEM)observation of the sole hemisphere grafting of SiO_(2)-PS as a control sample.SiO_(2)@JNP was demonstrated to be an efficient compatibilizer for a PS/poly(methyl methacrylate)(PMMA)immiscible blend,and the droplet-matrix morphology was significantly refined.The mechanical strength and toughness of the blend were synchronously enhanced at a low content SiO_(2)@JNP optimized~0.9 wt%,with the tensile strength,elongation at break and impact strength increased by 17.7%,26.6%and 19.6%,respectively.This enhancement may be attributed to the entanglements between the grafted polymer brushes and individual components that improve the particle-bulk phase affinity and enforce interfacial adhesion.
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.
