最新刊期
卷 ， 期 4 ， 2013
- 摘要：A chiral monomer N-［(R)--tert-butoxycarbonylbenzyl］methacrylamide ((R)-BCBMAM) was synthesized via amidation reaction between methacryloyl chloride and D-phenylglycine tert-butyl ester.Optically active polymers were prepared via free radical polymerization of ((R)-BCBMAM)initiated by AIBN at 60 ℃.In the presence of catalytic amount of trifluoroacetic acid,the tert-butyl of P(R-BCBMAM) was removed to obtain poly{N-［(R)--hydroxylcarbonylbenzyl］methacrylamide} P(R-CBMAM).1H-NMR,IR,CD and GPC were employmed to characterize the chemical structure of the products.The results indicated that the polymerization condition had slight effects on the chiroptical properties of P(R-BCBMAM).The results from specific optical rotation and circular dichroism spectra indicated that the P(R-CBMAM) and P(R-BCBMAM) had great difference in the chiroptical properties.On the basis of the results from circular dichroism (CD),the optical activity of P(R-BCBMAM) was attributed not only to the chirality of amino acid side groups in monomeric units but also to the steric repulsion of tert-butyl groups.P(R-BCBMAM) and P(R-CBMAM) were coated onto silica gels as the chiral stationary phase (CSP) for high performance liquid chromatography (HPLC).The CSPs exhibit superior chiral recognition ability for some racemates.On the other hand,1H-NMR measurements of mixture of polymers and racemic 1,1'-bi-2-naphthol (BINOL) were conducted in chloroform-d.The characteristic hydroxyl proton signal of BINOL was split into two peaks ascribed respectively to the levo- and dextro-isomers.关键词：Free radical polymerization;Chiral vinyl monomer;Optical activity polymer;Chiral recognition ability
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发布时间：2021-03-19 - 摘要：A series of new hyperbranched poly［(9, 9-di-n-octylfluorenyl-2, 7-diyl)-alt-bithiophene］s,(HF8T2s) were successfully prepared by Suzuki polycondensation reaction.The chiral and fluorescent nanoparticles of HF8T2s,with triphenylamine,triphenylbenzene and spirobifluorene as different branched units,were successfully prepared in chloroform/chiral limonene/methanol mixed solvents systems by solvent chirality transfer technology using (R)-(+)- or (S)-(-)-limonene as the chiral source.The chirality of fluorescent nanoparticles was from chiral limonene.The CD signals showed maximum values when the content of branched unit of triphenylamine in the polymer was 4.56%,however,the CD signals disappeared when the content of branched unit of triphenylamine in the polymer increased to 6.76%.The CD signals were tested when the content of branched unit of triphenylbenzene and spirobifluorene in the polymer was 1.85% and 1.78%,respectively.However,the CD signals disappeared when the content of branched unit of triphenylbenzene and spirobifluorene increased to a relatively high value (triphenylbenzene:4.68% and 6.56%;spirobifluorene:4.54% and 6.54%).In the case of HF8T2-TRA2 (triphenylamine as branched unit (1.90%)),the effects of the concentration of hyperbranched polymer repeat units,poor solvent sorts,the ratio of methanol and chiral solvent and the ratios of (R)-(+)-limonene and (S)-(-)-limonene on the CD intensity were investigated.The results indicated that the CD maximum value was obtained,when the ratio of mixed solvents was chloroform/chiral limonene/methanol=0.3/1.8/0.9 (V/V/V) using 5.0 10-5 mol/L as the repeating unit concentration.Under the above conditions,HF8T2s had the relative strong UV-Vis absorption in the range of 350~550 nm,and strong fluorescence emission in 450~700 nm range excited with 420 nm light.The size of nanoparticles formed in the above mixed solvents was about 500 ~ 2000 nm.关键词：Chirality transfer;Limonene;Hyperbranched polymer;Fluorescent nanoparticles;Chiral nanoparticles;Self-assembly
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发布时间：2021-03-19 - 摘要：The chiroptical properties of N-(2-hydroxy-1-naphthyl)methylidene-(S)--phenylethylamine (s-1) were studied as a model of chiral molecular switches.The Schiff base exhibited a pH-responsive chiroptical inversion behavior as a result of breaking and forming of the intramolecular hydrogen bonding and accompanying CC single bond rotation far away from the chiral center.DFT computation results showed that both two preferred conformers of s- 1 and its deprotonated species are stereochemically quasi-enantiotropic.On the basis of these findings we designed a chiral styrene-type monomer (VNP) containing imine linkage and synthesized corresponding polymers through RAFT technique.It was found that the chiroptical properties of PVNPs are highly sensitive to acid/base stimulus.The addition of acid produced an intensive Cotton effect at 382 nm for the THF solution of polymer,which is probably derived from the dissymmetric spatial arrangement of interacting chromophores in adjacent pendent groups due to the protonation of imine moiety.Furthermore,the CD signal can be totally reversed with addition of base.Chiroptical signals remained consistent after five acid-base reaction cycles,proving that a robust polymer-based chiroptical switch was established.This promising new type of chiroptical switches is relatively unique as it does not involve any covalent bond formation/breakage or conformational transition of polymer main chains and thus possess distinct advantages,such as fast switching rate,high reversibility and fatigue resistance as well as the nondestructive readout.Using such a reversible and reproducible chiral switching system,we designed the IHIBIT molecular logic gate that might have potential uses in information processing at molecular level.关键词：Chirality;Chroptical inversion;Molecular switches;Acid-base stimulus;Molecular logic gate
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发布时间：2021-03-19 - 摘要：Synthesis and near-infrared electrochromic properties of a novel chiral polyacetylene containing anthraquinone imide as the pendant group are reported.The monomer precursor,6-bromoanthraquinone-2,3-dicarboxylic anhydride,has been synthesized in a good yield via an improved synthetic route.The monomer N'-(1-hexylheptyl)-6-ethynylanthraquinone-2,3-dicarboxylic imide was converted to the polymer by the catalysis of chloronorbornadiene rhodium (I) dimer.Chiral polymers based on achiral monomers could be achieved by using chiral (R)/(S)-phenylethylamine as the cocatalyst,which have obvious Cotton effects in the ultraviolet-visible region.Properties of polymers,such as chirality and solubility could be modulated easily by changing the imide group.The novel polymers have electrochromic properties similar to those of the small anthraquinone imide molecule.Intense absorption peaked at 820 nm in the visible-near infrared range of 500~1200 nm has been observed in the single electron reduction state.关键词：Anthraquinone imide;Chiroptical polymer;Near-infrared electrochromism;Polyacetylene
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发布时间：2021-03-19 - 摘要：Different generations of polyamidoamine dendrimers were successfully incorporated to chloromethyl polystyrene through solid phase synthesis methodology.The peripheral amino groups on these dendrimers have been modified by 2,4-dihydroxybenzaldehyde and salicylaldehyde,respectively.Then the ligands reacted with SnCl22H2 O to obtained chloromethyl polystyrene supported dendritic Sn complexes.The ligands and complexes were well characterized by IR,ICP and XPS.The complexes as heterogeneous catalysts show promising catalytic activities for the Baeyer-Villiger oxidation of cyclic and acyclic ketones with 30% hydrogen peroxide.2-Adamantanone,cyclopentanone,4-methylcyclohexanone,4-tert-butylcyclohexanone,3-methyl-2-pentanone and 4-methyl-2-pentanone have all been oxidized in a reaction catalyzed by these complexes at 70~90 ℃ in different organic solvents,affording the corresponding lactones or esters with high conversion (87%) and selectivity (99%).Compared to the Baeyer-Villiger oxidation of ketones using complexes with different ligands (4-hydroxybenzaldehyde,2,4-dihydroxybenzaldehyde and salicylaldehyde),it was discovered that ligands played a vital role in metal loadings and the catalytic activity of the complexes.Among them,salicylaldehyde modified complexes were found to be the optimum catalysts as they had the highest tin content.The catalysts could be obtained in a simple and efficient manner using environmentally friendly oxidant under mild reaction condition.Moreover,the catalysts can be recycled for several times without losing significantly the catalytic activity.关键词：Dendrimer;Sn complex;Baeyer-Villiger oxidation;Hydrogen peroxide
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发布时间：2021-03-19 - 摘要：The effect of maleic anhydride (MAH) and maleic anhydride grafted polypropylene (PP-2) on the structure and performance of biodegradable non-woven fabric slices of poly(propylene carbonate) (PPC)/ polypropylene (PP) was investigated by melt blending process.FTIR spectra showed that ring-opening reaction happened between the anhydride functional groups of MAH and PP-2 and PPC.The tensile strength of the slices were increased by 116% and 101% respectively with adding 1% MAH or 2% PP-2.This indicates that the tensile strength of the slices can be significantly increased by adding MAH or PP-2.The adding of MAH or PP-2 decreased the melt flow rate,increased the intrinsic viscosity,glass transition and thermal decomposition temperatures and also expanded the temperature ranges for using and processing the slices.The glass transition temperature (Tg) of the slices was increased 4 K by adding 1% MAH.The 5% weight loss temperatures (T_5%) of the slices were increased 40 ℃and 20 ℃, respectively by adding 1% MAH or 2% PP-2.The SEM results of the slices showed that internal depressions and cavities were decreased by adding MAH or PP-2.The adding of PP-2 can improve the compatibility of the slices more significantly than MAH.The 30 days degradation rates of PPC and PP were 4.30% and 0%,PP was not degraded in phosphate buffer solution.The 30 days degradation rate of the slices with additives was higher than 3.80%,this indicated that the non-woven fabric slices of PPC/PP prepared by melt blending process were biodegradable and environment-friendly.Ring-opening reaction,increasing interface adhesion force and reducing interfacial tension maybe the mechanisms of the additives.关键词：Maleic anhydride;Maleic anhydride grafted polypropylene;Poly(propylene carbonate);Polypropylene;Biodegradable;Nonwoven slice
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发布时间：2021-03-19 - 摘要：The fluoropolymer composed of styrene and 4-fluorine styrene was grafted from the surface of PET films via surface initiated atom transfer radical polymerization (SI-ATRP).The influences of different grafting times and composition of monomers on the surface composition,structures and morphology were studied.The surface composition and structures of the modified PET films were characterized by X-ray photoelectron spectroscopy (XPS),Fourier transform infrared spectroscopy (FTIR/ATR) and gel permeation chromatography (GPC).And the results could confirm the successfully grafting of initiators and polymers from the surface of PET films.The surface properties were measured by contact angle measurements.The data of contact angle showed that the surface properties of PET films were related to the reaction time and monomer percentage.As the reaction time increased,the grafting rate and the contact angle of PET films increased,but the surface energy decreased.The contact angle increased from 68? to a maximum of 98? after modifications,and the maximum of the grafting rate reached 20.33%.The surface morphologies of PET film and modified PET film were studied by SEM.After modification the PET film surface had been changed from smooth surface into rough surface.关键词：PET film;Surface initiated atom transfer radical polymerization (SI-ATRP);Surface properties;Contact angle;Fluoopolymer
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发布时间：2021-03-19 - 摘要：A functionalized chitosan derivative named sulfhydryl chitosan (CHS-NAC) was synthesised from chitosan (CHS) and N-acetyl-L-cysteine (NAC),with 1-Hydroxybenzotriazole (HOBt) and 1-ethyl-3-(3-dimethylamino-propyl) carbodiimide hydrochloride (EDAC) as condensation agents.The structure of CHS-NAC was characterized by Fourier transform infrared spectroscopy (FTIR),nuclear magnetic resonance (NMR) and X-ray diffraction (XRD).The content of thiol-group of CHS-NAC was measured to be 4.31110-4 mol/g through calibration curve taking use of Ellmans reagent.A layer of CHS-NAC film was modified onto the surface of glassy carbon electrodes by dispensing 8 L CHS-NAC solution.With the adhesive function of CHS-NAC modified film,gold nanoparticles and cytochrome c were modified onto the surface of glassy carbon electrode respectively.The electrochemical behaviors of these different modified electrodes were studied by cyclic voltammetry and electrochemical impedance spectra.The surface morphology of modified electrodes was characterized by scanning electron microscope (SEM).The influence of scan rate on the cytochrome c modified electrodes was also studied.Results showed that in low scan rate,electrochemical behavior was controlled by the surface process.The electrochemical catalytic analysis for hydrogen peroxide was carried out by using the cytochrome c modified electrode.Results showed that gold nanoparticles and cytochrome c can be fixed on the surface of glassy carbon electrode very well by CHS-NAC,and gold nanoparticles can effectively promote electron transfer of cytochrome c and the ability to electrochemically catalyze hydrogen peroxide.关键词：Ulfhydryl chitosan;Gold-nanoparticle;Modified electrode;Cyclic voltammetry;Cytochrome c;Hydrogen peroxide
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发布时间：2021-03-19 - 摘要：A Fe3O4 nanoparticles-stabilized Pickering emulsion,which is a kind of emulsion stabilized by solid particles instead of traditional surfactants, was used as a cross-linking agent.And a novel composite hydrogel was prepared by initiating monomer acrylamide in the appropriate condition.The structure of nanoparticles and composite hydrogel was characterized through X-ray diffraction (XRD) measurements,and field-emission scanning electron microscope (SEM),respectively.Moreover,the properties of hydrogels were studied by swelling ability measurements and swelling kinetics analysis,mechanical test and magnetic response test.It can be found from SEM images that the TPM droplet acted as a cross-linking agent in the reactive system and distributed in the hydrogel network orderly.Swelling test indicated that the composite hydrogels had excellent swelling capacity in comparison to conventional hydrogels,and even could swell to about 100 times of their dry weight.And swelling kinetics analysis results showed that the swelling process of the composite hydrogels did not follow the Fickian swelling kinetics model.The mechanical test results showed that the composite hydrogel exhibited outstanding mechanical performance.The composite hydrogels showed a strength of 150 kPa and high elongation at break of 300%.Moreover,the composite hydrogels could return to original state after stretching to several times of its original length quickly and even could make into a knot without damage.Magnetic response test results indicated that the composite hydrogels exhibited a clear magnetic response.关键词：Hydrogel;High strength;Magnetic;Pickering emulsion
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发布时间：2021-03-19 - 摘要：Several diesters were developed as internal donors of the Ziegler-Natta catalysts,the molecular structures of the diesters are close to that of diisobutyl phthalate.Furthermore,the effects on the performance of the catalysts were studied.Results showed that the catalysts prepared by different preparation processes have the same MgCl2 lattice style ().The changing of diesters have notable influences on the porosity and the specific surface areas of the catalysts, and the polymerization performance and the PP isotactic index vary with different addition ways of the diesters in the preparation processes of the catalysts. When the internal donor is diisobutyl cis-cyclohexane dicarboxylate,the polymerization activity of the catalyst and the PP index are the highest,reaching the level of the industry catalyst. In the polymerization of CAT-2A,using CMMS as the external electron donor,the ratio of Si to Ti is 10 and the ratio of Al to Ti is 100,the polymerization activity and PP isotactic index reach the highest level.关键词：Internal electron donor;Polypropylene;Ziegler-Natta;Diisobutyl phthalate;Diisobutyl cyclohexane dicarboxylate
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发布时间：2021-03-19 - 摘要：Novel phosphorus-containing polypropylene diblock copolymers were synthesized and their thermal decomposing behaviors and flammability were characterized by thermo-gravimetric analysis (TGA) and micro-scale combustion calorimetry (MCC).First,a reactive polypropylene precursor with a terminal styryl group (PP-t-St) at polymer chain end was synthesized via controlled chain transfer reaction to 1,4-divinylbenzene and hydrogen in metallocene-mediated propylene polymerization.Then PP-t-St was reacted with hydrogen bromide through Markovnikov addition in a quasi-quantitative manner,affording 1-bromoethylbenzene group-terminated polypropylene (PP-t-BzBr).ATRP of phosphorous-containing vinyl monomer such as diethyl-(4-vinylbenzyl)phosphonate (DEVBP) was carried out in toluene at elevated temperatures with PP-t-BzBr suspending in the reactant solution,with CuCl/1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) as catalyst.Diblock copolymers containing different amounts of DEVBP units (up to 64.3 wt%) were obtained by adjusting polymerization durations.Differential scanning calorimetry (DSC) experiments indicated that both the crystallinity and crystallization rate of PP were largely retained in PP-b-PDEVBP diblock copolymers.TGA and MCC results showed that char residues increased while heat release rates reduced upon forming the diblock copolymers as compared to the precursory PP-t-BzBr as well as PP-t-St.Overall,this research may lead to a new solution to inherently flame-retardant polypropylene.关键词：Polypropylene;Polyphosphate;ATRP;Block copolymer;Flame retardancy
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发布时间：2021-03-19 - 摘要：A series of molecularly imprinted polymers were synthesized via the electron beam radiation polymerization of functional monomer(methacrylic acid) and crosslinking agent(ethylene glycol dimethacrylate) in the presence of quercetin-Ni(Ⅱ) as template and were used as a highly selective separation material for quercetin which is an important active ingredient of Chinese herbs.The interaction between quercetin and Ni(Ⅱ) was investigated with UV-Visible spectroscopy,which reveals the formation of 1∶2 complex in the system.At the same time,the ternary complexation of quercetin,Ni(Ⅱ) and methacrylic acid was verified by similar methods.The characterization of the molecularly imprinted polymer prepared and pure quercetin was analyzed by Fourier transform infrared spectra.The result indicated that the template molecule could be fixed in molecularly imprinted polymer and also could achieve being eluted.Furthermore,the transmission electron microscopy and adsorption dynamic experiments were used to characterize the effect of radiation dose on the morphology and adsorption capacity of molecularly imprinted polymer.The result showed that the three-dimensional cross-linked network structure of the molecularly imprinted polymer prepared in condition of 20 kGy radiation dose was more uniform,and the presence of these internal pores greatly increased the surface area of molecularly imprinted polymer and reduced the embedding of imprinting sites,which was conducive to adsorb the template molecule.In addition,the selective adsorption experiments showed that the molecularly imprinted polymer prepared exhibited significant adsorption selectivity for quercetin compared with the quercetins structural analogs (baicalein and naringenin) in the presence of Ni(Ⅱ) and the max adsorption amount reached 82.22 mol/g.The separation factors were 3.915 and 5.443, respectively.关键词：Electron beam radiation polymerization;Radiation dose;Metal coordination;Molecularly imprinted polymer;Quercetin-Ni(Ⅱ)
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发布时间：2021-03-19 - 摘要：Poly lactic acid(PLA)/zinc oxide(ZnO) pillared saponite nanocomposites were prepared with ZnO pillared saponite synthesized via microwave hydrolysis method.The structure of ZnO pillared saponite and PLA/ZnO pillared saponite nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM).Moreover,the mechanical properties and thermostability of PLA/ZnO pillared saponite nanocomposites were studied.The microstructure showed that the ZnO pillared saponite appeared as exfoliated or partially intercalated nanometer layers, and the TEM showed that the ZnO pillared saponites were evenly dispersed in the PLA matrix in the form of exfoliated layers.The mechanical properties showed that the elongation at break of PLA nanoncomposites was improved when the loading content of ZnO pillared saponite was 0.3 wt%.SEM analysis demonstrated that a visible transformation took place in the section morphology which manifested the toughness of PLA nanocomposites;DSC results displayed that the ZnO pillared saponite decreased the glass transition temperature and cold crystallization temperature,and obviously promoted the crystallinity,which was in accordance with XRD analysis.TG-DTA analysis showed that the thermostability of PLA/ZnO pillared saponite nanocomposites was improved.In a word,a hererogeneous nucleation effect of ZnO pillared saponite on the PLA matrix was testified and all the results showed that the ZnO pillared saponite played an active role in accelerating the crystallization process of PLA matrix.关键词：PLA;ZnO pillared saponite;Composite;Properties
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发布时间：2021-03-19 - 摘要：Thermoresponsive horseradish peroxidase nanocapsules (nHRP) were prepared via in situ precipitation polymerization using N-isopropyl acrylamide (NIPAM) as the monomer.As an example,nHRP was prepared by a NIPAM/HRP mass ratio of 6,under the reaction temperature of 37 ℃, it showed a monodispersed size distribution centered at 13.7 nm and a negative zeta potential centered at (-3.70.3) mV.The modification degrees of HRP were characterized by MALDI-TOF mass spectrometer (MALDI-TOF MS),while the enzymatic activity of the free native HRP,modified HRP and encapsulated nHRP were determined by conducting a standard enzyme activity assay and followed by monitoring absorbance change through UV-Vis spectrometer.The particle size and morphology of nHRP were characterized using dynamic light scattering (DLS) and transmission electron microscopy (TEM).The results showed a monodispersed nHRP was prepared successfully.Compared with the native HRP,nHRP exhibits significantly improved thermal stability,according to the HRP activity assay.Thermoresponsive behavior of nHRP was examined from 25 ℃ to 45 ℃ by DLS studies,where nHRP showed a responsive temperature at 33 ℃ and a reversible response property.Accordingly,high-speed centrifugation was applied to separate and recycle nHRP at 50 ℃ with a well-retained activity.This work provides a new delicate way to immobilize enzyme based on thermoresponsive enzyme nanocapsules,which is of great interest for effective enzyme separation and recycling and other applications.关键词：Thermoresponsive;Nanocapsule;N-isopropylacrylamide;Enzyme immobilization;Enzyme recycling
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发布时间：2021-03-19 - 摘要：The self-assembly and photoresponsive properties of an amphiphilic azo random copolymer bearing branched azobenzene side chains (PMAPB6P-AA) are reported.The aggregates of PMAPB6P-AA in THF/H2O dispersion were obtained by slowly adding deionized water into a THF solution of the polymer to the water content of 80 vol%.Instead of quenching the aggregates with excess water to form solid colloidal spheres,the dispersion was diluted with a THF/H2O mixture (THF/H2O=1/4,V/V) and then THF in the medium was slowly removed through evaporation.The procedure could generate a series of hollow-structured aggregates with different sizes simply by adjusting the preparation conditions.The hollow aggregates were characterized by transmission electron microscopy (TEM),scanning electron microscopy (SEM) and dynamic light scattering (DLS).Photoisomerization behavior of the azobenzene units was studied to detect the local environment surrounding the molecular probes in the hollow aggregates.Results showed that hollow aggregates possessed the non-spherical morphology at relatively high increasing rate of water content.The size (hydrodynamic diameter) of the hollow aggregates was determined by the polymer initial concentration in THF.The photoinduced isomerization rate and the photoisomerization degree of the hollow aggregates decreased with the increase of polymer initial concentration in THF.The vesicle-like aggregates with a thin shell were formed by diluting the polymer disperse at 23 vol% water content with THF/ H2O (THF/H2O=10/3,V/V) and slowly removing THF through evaporation.For the vesicle-like aggregates,photoinduced disaggregation was observed when irradiated with the 365 nm UV light.The understanding obtained from this study can be used to develop new functional materials from photoresponsive random copolymers.关键词：Branched side chains;Azo random copolymer;Hollow-structured aggregate;Vesicle-like aggregate;H-aggregation;Photoresponsive behavior
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发布时间：2021-03-19 - 摘要：Partially hydrolyzed poly(methyl methacrylate) (h-PMMA)/Ca(OH)2 composites were synthesized by partially hydrolyzing PMMA in alkaline isopropanol solution followed by precipitating Ca(OH)2 in the solution.Composition and structure of h-PMMA/Ca(OH)2 composites were characterized using X-ray diffraction (XRD),Fourier-transform infrared (FTIR),inductively coupled plasma atomic emission spectrometry (ICP) and differential scanning calorimetry (DSC), and influence of the composites on thermal stability of PVC was studied through Congo red tests,dynamic thermal stability tests and thermogravimetry analysis (TGA).UV-Vis spectra,scanning electron microscopy (SEM) and fusion curves were analyzed to study influence of h-PMMA/Ca(OH)2 composites on transparency and fusion behaviors of rigid PVC compounds.The experimental results showed that h-PMMA chains adsorbed on the surface of growing Ca(OH)2 particles through COO-/Ca2+ bonds decreased the size of the final particles and make a better distribution of Ca(OH)2 in the melt-blended PVC compounds.Compared with traditional stabilizers,the prepared h-PMMA/Ca(OH)2 composites were able to quickly capture catalytic,highly mobile HCl so as to improve thermal stability of PVC compounds during the melt-blending significantly.Furthermore,PVC compounds stabilized with h-PMMA/Ca(OH)2 composites displayed an excellent long-time stability with increasing Ca(Ⅱ) content in h-PMMA/Ca(OH)2 composites.At the same time,the h-PMMA/Ca(OH)2 composites could obviously promote fusion of melt-blended PVC compounds while maintaining their transparency.关键词：PVC;Ca(OH)2;Thermal stabilizer;Fusion
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发布时间：2021-03-19 - 摘要：It was further confirmed through the anionic bulk polymerization of -methylstyrene (mSt) initiated by n-butyl lithium (n-BuLi)/tetrahydrofuran (THF) that the aggregators of n-BuLi could initiate anionic polymerization,which resulted in forming of the supramolecules,then these supramolecules would be dissociated during the further polymerization.The results have further verified the new initiating mechanism of anionic polymerization proposed previously.With the in situ 7Li-NMR during the polymerization of mSt under D-benzene as solvent,THF as regulator and n-BuLi as initiator,it was further confirmed that in the system,there existed a conversion process of the initiator aggregators from pluralistic aggregated structure to the binary one.Meanwhile,in situ 7Li-NMR of isoprene polymerization under D-benzene solution initiated by n-BuLi also verified the conversion process of the initiator aggregators.It was also found that when a small amount of THF was mixed in the mSt polymerization system,the two or three of hexameric aggregators might be connected by THF.However,these connected aggregators would be dissociated preceding that of hexameric aggregators themselves.Furthermore, with the increasing of n-BuLi/THF (mole ratio) from 1∶1 to 1∶5,the huge aggregators of n-BuLi could be changed into hexameric ones.关键词：Anionic polymerization;Mechanism;Supramolecule;7Li-NMR;Hexameric aggregator
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发布时间：2021-03-19 - 摘要：The relationship between line tension and bending rigidity of extended bilayer membrane is studied in this paper.Extensive simulations of bilayer membrane with different projected areas were performed,and three regions have been found,i.e.,freely fluctuating membrane,extended membrane and extended membrane with a pore.Surface tension () calculated from stress tensor is in good agreement with that (fluc) calculated by fitting the membrane fluctuation data in freely fluctuating region and extended region except that at the transition point fluc is a little higher than .By introducing a very simple model,line tension of the pore can be calculated from bending rigidity and membrane thickness which is ignored in the classical Helfrich model,on the other hand,bending rigidity can be determined by line tension and membrane thickness.The results in the pore region show that the bending rigidity got from the simple model is in good agreement with the bending rigidity calculated by fitting the membrane fluctuation data in the freely fluctuating region and extended region.A convenient method for measuring the bending rigidity of bilayer membranes is then proposed.关键词：Bilayer membrane;Surface tension;Line tension;Bending rigidity
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发布时间：2021-03-19
Research Article
- 摘要：Novel chiral and achiral bisphenol A and bisphenol AF based benzoxazine monomers were synthesized from the reaction of bisphenol A (bisphenol AF) with paraformaldehyde and primary amines,including (R)-(+)--methylbenzylamine and/or (S)-(-)--methylbenzylamine,via solventless method.The chemical structures and properties of the benzoxazine monomers were identified by Fourier transform infrared spectroscopy (FTIR),proton nuclear magnetic resonance (1 H-NMR),polarimeter,and high performance liquid chromatography (HPLC).The curing behavior and thermal properties of benzoxazine monomers and cured polymers were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).The results showed that solventless method provided faster reaction rate,higher yields,and was more environmentally friendly than conventional solvent method.Achiral benzoxazine monomers with double chiral center consisted of four isomers,such as two racemic isomers and two mesomeric isomers.The content of mesomeric isomers was higher than that of racemic isomers.Chiral and achiral benzoxazine monomers underwent the same curing behavior.For achiral polybenzoxazines,the methyl and benzyl chains in racemic and mesomeric structures twined for each other in a disorderly manner to be like a wedge due to the different stereo-configuration of achiral benzoxazine molecules,which resulted in lower free volume and tighter packing of the polymer than those of chiral polybenzoxazines.Consequently,achiral polybenzoxazines showed higher glass transition temperature than that of chiral polybenzoxazines and bisphenol A-aniline based polybenzoxazines.Moreover,CF bond with high dissociation energy contributed to improvement of thermal properties of the polymer.As a result,the bisphenol AF-based polybenzoxazines displayed higher thermal properties than bisphenol A-based polybenzoxazines.关键词：Chiral benzoxazine;Achiral benzoxazine;Solventless method;Curing behavior;Thermal properties
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发布时间：2021-03-19 - 摘要：Based on propylene heterogeneous copolymerization with the aid of RGT-aligned Ziegler-Natta catalyst, a novel in-reactor PP alloy with cross-linking EPR has been prepared through ,-diene such as 1,9-decadiene (DD) addition.The polymerization results show that DD monomer has a good reactivity with ethylene and propylene monomers and a minor effect on the composition of copolymers.DD monomer has been successfully bonded into the backbones of ethylene-propylene random copolymer,resulting in branching and cross-linking of the EPR.The melt flow rate (MFR) of the new hiPP shows an obvious drop after the introduction of DD monomer;while the gel content increases with the increasing of DD monomer.Morphology study by SEM reveals that cross-linking EPR greatly promotes the dispersivity of rubber phase in PP matrix.The size of rubber particles reduces with the branching and cross-linking density.The results of mechanical properties tests indicate that cross-linking EPR can potentially enhance the toughness of hiPP without or with little compromise of the rigidity and processibility,which is very meaningful to achieve the rigidity-toughness balance of PP resins.
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发布时间：2021-03-19
Research Bulletin
- 摘要：Backbone-thermosensitive hyperbranched polyethers were synthesized in one step by the cationic ring-opening copolymerization of tetrahydrofuran and glycidol. The hyperbranched polyethers had soft polytetrahydrofuran segments in the backbones, and their structures were characterized by quantitative 13C-NMR. Then the degree of branching and the ratio of glycidol units incorporated into the structure were also calculated. The molecular weight and molecular weight distribution were characterized by size exclusion chomatography-multi-angle laser light scattering (SEC-MALLS). The thermoresponsive phase transition behavior of the hyperbranched polyether in aqueous solution was intensively investigated by UV-Vis spectrometer equipped with a thermocell. It was found that the UV transmittance of the aqueous solution of the hyperbranched polyethers decreased dramatically when the temperature was increased above LCST, but the balance of phase transition was very slow and the phase transition time was up to 30 min. At the same time, the kinetics of phase transition and final value of UV transmittance were dependent on the temperature, which suggested that the phase transition process could be effectively controlled by adjusting the temperature. TEM inspection showed that the hyperbranched polyethers in aqueous solution could assemble to form micelles at low temperatures. And then, the micelles gradually aggregated as the temperature was increased above LCST, which caused the slow and controlled phase transition process.关键词：Hyperbranched polymer;Thermosensitive polymer;Slow phase transition
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发布时间：2021-03-19
Rapid Communications
- 摘要：The investigations on the structure and relaxation behavior of the amorphous phase are crucial for understanding the structure and property of crystalline polymers.In this review,we introduce the structures of the amorphous phase in crystalline polymers at first.Then,the effect of the morphology,molecular weight and crystallinity of the crystalline polymers on the relaxation behaviors of the amorphous phase in the crystalline polymers is described.The relaxation behaviors of the amorphous phase in crystalline polymers under confinement and in ultra-thin films are reviewed.The influence of extra force such as drawing,on the relaxation behaviors of the amorphous phase in the crystalline polymers is also discussed.As the amorphous phase plays an important role in the crystalline polymers,the effect of the amorphous phase on the mechanical properties and melting process of the crystalline polymers is discussed in detail in this review.At last,the structure evolution of the amorphous phase during the isothermal crystallization process of crystalline polymers is summarized.关键词：Crystalline polymers;Mobile amorphous phase;Rigid amorphous phase;Relaxation
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发布时间：2021-03-19
Reviews
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