最新刊期
卷 ， 期 4 ， 2003
- 摘要：Sulfonated phenolphthalein poly(ether sulfone) (SPES-C) with various sulfonation degree were synthesized by reaction of PES-C with sulfonic acid as sulfonating agent and solvent．Their proton conductivity and methanol permeability as a function of the degree of sulfonation were investigated．For 70.21％ degree of sulfonation,proton conductivity was 3.45 x 10-2 S／cm at 100℃,which is closed to or superior to that of NationοR 115 membrane at the same conditions (4.19×10-2 S／cm)．Methanol permeability of SPES-C was considerable smaller than that of Nation国 115 membrane．Because of their high conductivity and low methanol permeabihty,SPES- C membranes appear to be excellent candidate for use in DMFC applications．
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发布时间：2021-03-19
Rapid Communications
- 摘要：Based on molecular design,a novel biphenonl-like monomer 4-(4′-hydroxyphenyl)-2,3-phthalazin-1-one (DHPZ) was originally synthesized through simple reactions from phenol and phthalic anhydride which are common and easily available chemicals．The synthesizing processes,reaction dynamics and mechanism were studied in detail．According to a lot of experiments and computer-aided molecular simulation,it has been confirmed that this new compound has non-coplanar and twisted structure and the hydrogen atoms in N—H and O一H bonds show similar polycondensation reactivity,so it is proved to be a biphenol-like monomer．By solvent nucleophilic substitution polycondensation,a series of polymers such as poly(ether ketone)(PPEK),poly(ether sulfone)(PPES),poly(ether ketone ketone)(PPEKK),poly(ether sulfone ketone)(PPESK),poly(ether sulfone ketone ketone)(PPESKK),poly(ether nitrile ketone)(PPENK),poly(ether nitrile sulfone)(PPENS) and poly(ether nitrile sulfone ketone) (PPENSK),were successfully prepared from DHPZ,and commercial bihalogen monomers such as difluorodiphenylketone (DFK),dichlorodiphenylsulfone (DCS),[4-(chlorobenzoyl) phenyl]-(4-chlorophenyl) methanone (DCKK) and 2,6-dichlorobenzonitrile (DCBN)．The structures of these resultant polymers were characterized by spectroscopy,and the properties of these polymers were measured．Also the relationships between structures and properties were thoroughly studied．Spectroscopic data show that all these polymers are amorphous．The glass transition temperatures of all these polymers are in the range of 250℃ to 370℃,which can be controlled by the substituted groups or the proportion of the ketone and sulfone groups in the backbones of the polymers．Based on these results,a new molecular designing theory was put forward that introducing the non-coplanar twisted aramatic structure into polymers’backbones contributes to improving polymers’solubility and outstanding thermal resistance at the same time．Directed by this theory,a series of novel diamine,diacid and dianhydride monomers containing phthalazinone moities were successfully synthesized from DHPZ．And the corresponding polymers which have good solubility and outstanding thermal properties such as PPEA,PPEI,PPEAl were prepared．These polymers exhibit excellent comprehensive properties such as good solubility and outstanding thermal properties,forming a polymer system of new structure and high performance．
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发布时间：2021-03-19
Feature Articles
- 摘要：An organic soluble and high molecular weight pulyetherimide(HQDPA-DMMDA) was synthesized based on the HQDPA and DMMDA in NMP by the low temperature solution co-polymerization method．The structure and properties of the PI were characterized by measurements of FT-IR,WAXD,TGA and DSC etc．The results showed that the obtained polyetherimide had an amorphous structure with a d-spacing of 0.5163 nm．The PI was readily soluble in polar solvents such as NMP,DMF and THF etc．Its glass transition temperature was 251℃ and 10％ thermal decomposition temperature under N2 was 528℃．The tensile strength was 107 MPa and the elongation at break was 24％．The permeability data of polyimide membrane for gases such as H2,N2,O2,CO2 and CH4,were collected at 25℃．The permeability for H2 was 3.809 Barrer and the ideal selectivity coefficients for H2／N2 and H2/CH4 were l66.9 and 214.0,respectively．The permeability for N2,O2,CO2 and CH4 were between 0.018～0.576 Barrer.
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发布时间：2021-03-19 - 摘要：The atom transfer radical polymerization (ATRP) of styrene from poly (dimethylsiloxane) (PDMS) macroinitiators was described．Commercially available difunctional PDMS containing vinylsilyl terminal species was reacted with hydrogen bromide resulting in the PDMS macroinitiators containing alkyl bromide end-groups．The ATRP of styrene was then conducted at 130℃ using the PDMS containing alkyl bromide end-groups as initiators,cuprous chloride (CuCl) as catalyst and 4,4′-di(5-nonyl)-2,2′-bipydine (dNbpy) as ligand to produce block copolymers．Using this technique,copolymers consisting of a PDMS center block and polystyrene terminal blocks were synthesized．Analysis of the copolymers by gel permeation chromatography (GPC) showed that the molecular weight increased linearly with the conversion of monomer,and the polydispersity decreased with the progress of polymerization. The molecular weight increased from 6400 to 17890 and the polydispersity ranged from 1.38～1.26,demonstrating that the reaction was controlled and the polystyrene blocks had low polydispersities typical of radical polymerization by all atom transfer process．IR and 1H-NMR analyses of the PDMS macroinitiators and the copolymers showed that the PDMS macroinitiators containing alkyl bromide end-groups were formed,and the copolymers consisted of polystyrene and PDMS．A DSC analysis confirmed the results．Tg in 100℃ and -120℃ were attributed to polystyrene blocks and PDMS blocks respectively,indicating the copolymer consisted of polystyrene and PDMS,the triblock copolymers polystyrene-b-polysiloxane-b-polystyrene (PSt-b-PDMS-b-PSt) were formed．All these results also demonstrated the effectiveness of ATRP to synthesize a variety of inorganic／organic polymer hybrids．
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发布时间：2021-03-19 - 摘要：The queous solutions of 4 sodium alginate samples with different molecular weights,molecular weight distributions and M／G ratios were characterized with GPC,elemental anlaysis,and 1H-NMR．The sol-gel transition was determined by monitoring the dynamic moduli of these solutions with increasing their concentration within the linear viscoelasticity region at 25℃．This transition was found to obey the Winter and Chambon’s relaxation modulus equation G(t)．From the independency of tanδ on frequency ω,the concentration of the gel point cgel and the critical exponent for the sol-gel transition n were estimated．For all samples cgel is 7.6wt％ ～8.0wt％,almost independent of molecular weight Mw,and n equals 0.32～0.38 for three samples with higher Mw and 0.61 for the sample with lower Mw．This finding indicates that physical gelation in aqueous solutions of sodium alginate is mainly induced by the interaction between repeat units of the macromolecules,and that the longer chains contribute more perfect crosslinking structure at the gel point．
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发布时间：2021-03-19 - 摘要：Fourier transform infrared spectroscopy and chemical analysis were applied to study the chlorination reaction mechanism of latex．The results showed that the chlorination mechanism of latex is similar to that from solution：(1) substituted chlorination and cyclization (The initial substitution was created by that chlorine attacked natural rubber molecules with concomitant cyclization reaction),(2) addition-elimination accompanied by a shiftiog of the C=C group and (3) pure substitution．Furthermore,the production of ClC—C=O and RClC—COOH groups was recorded by Fourier transform infrared spectroscopy．This is the largest difference between CNR prepared from latex and from solution．From the ratio of primary,secondary and tertiary C—Cl bands analyzed by 13C—NMR,combined with IR spectrometry and high resolution pyrolysis gas chromatography-mass spectrometry．the chlorination mechanism of CNR from latex and the sequence of —Cl substitution and addition could be introduced．The structure of CNR from latex is not as regular as CNR from solution．The main reason was that HOCl formed at the initial stage of chlorination,and RClC—COOH produced at the later stage of chlorination．Furthermore,a conclusion could be deduced that the chlorination reaction takes place evenly on all NR molecules in the chlorination process in latex．
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发布时间：2021-03-19 - 摘要：The photo-acid generation and the photosensitive acid generation effect of three kinds of bis-(trichloromethyl) triazine derivatives have been studied in this work．From the measurements of absorption,fluorescence and fluorescence quenching spectra and the photo-acid generation it was found that the photosensitive acid generation had the nature of a photo-electronic transfer process．Results indicated that in the fluorescence emission spectra of triazine compounds there were two emission regions,which were attributed to the localized excitation and intra-molecular charge transfer excitation,respectively．Results also indicated that the localized excitation and emission is most important for the photo-acid generation and the intra-molecular charge transfer effect is important for extension of the absorption region. For a perfect molecular design and synthesis of photo-acid generation compounds,attention should be paid to both effects described above,as well as the complementarity and concordance between them.
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发布时间：2021-03-19 - 摘要：Poly(acrylamide-co-acrylic acid) [P(AM-AA)] has attracted many researchers for its special properties and potential applications in enhanced oil recovery (EOR)．The network-structure of P (AM-AA) in aqueous solutions and the behavior in 0.1 mol／L NaCl aqueous solutions were investigated by a combination of static and dynamic laser light scattering techniques．In the hydrodynamic radius (Rh) distribution of P(AM-AA) molecules in aqueous solutions,a size range of 100～500 nm,which is coincident with the network-structure,is dominant．With the addition of NaCl,the width of hydrodynamic radius distribution decreases,and the radii concentrate in a range below 100 nm．These results provide strong evidence of the existence of network-structure in aqueous solutions of P(AM-AA)．The network-structure will be destroyed with the addition of a small amount of salts,such as NaCl．and then the stability of the solution decreases due to the destruction of the network-structure．In 0.1 mol／L NaCl aqueous solutions,there exists a critical concentration c* (≈1.34×10-3 g／mL)：when c＜c*,the solution of P(AM-AA) is stable and without precipitation for long time；when c＞c*,white flocculent precipitates appear after a period of time．
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发布时间：2021-03-19 - 摘要：The living free radical polymerization of styrene was studied with benzoyl peroxide as the initiator in the presence of TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxy)．It was found that styrene polymerization was distinctly accelerated by means of using malononitrile (MN) as additive．The purpose of this paper is to explore the effect of MN／bpy On the control of molecular weight．These mixture additives were able to control the polymerization of styrene to high conversion (85％) in 4 hours,and samples of molecular weight from 1×104 to 9×104 and with polydispersities of 1.15 to 1.4 were readily obtained．In comparison with the polymerization without any additives,these systems represented a dramatic improvement in the ability to control the molecular weight．The molecular weight of the polymer gradually increased with time,while the narrow molecular weight distribution remained unchanged．The molecular weight evolved in a nearly linear fashion with increasing conversion．Using a 1:1.2 molar mixture of BPO and TEMPO with [Bpy]／[TEMPO]=2／1,[MN]／[TEMPO]=2.5,the conversion of the polymerization at 135℃ reached 85％ in 4 hours,and the polydispersity was below 1.5,and the difference between the theoretical molecular weight and the experimental molecular weight was controlled below 20％．
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发布时间：2021-03-19 - 摘要：N,O-Benzyl chitosan formed cholesteric liquid crystalline phase in concentrated solutions．The helicoidal behavior (including mainly helix pitch and twist sense) of this polymer was studied by means of circular dichroism (CD)．The higher the concentration was,the larger the pitch was,implying the twisting power decreased with the increase of concentration．Two kinds of absorption can be observed in CD spectra．A broad and strong band appeared at 570 nm,but another sharp and weak band appeared at 330 nm．The former arose from the supermolecular helicoidal structure of cholesteric layers；the latter may arise from the helical conformation of chains．Both levels of helicoidal structures changed their signs,when the concentration or solvent varied．When the solution concentration increased (using dioxane as solvent),the two levels of helicoidal structures inversed from left-handed to right-handed one by one．When chloroform was used as solvent and the concentration was 65wt％,the handedness of the two helicoidal structures was left-handed (positive Cotton effect),hut when dioxane or THF was used with the same concentration,a reversed handedness was observed．The influence of solvent may be related to the formation of hydrogen bonds between the solvent molecules and the polymer chains．
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发布时间：2021-03-19 - 摘要：The crosslinked poly(butyl acrylate-co-2-ethylhexyl acrylate)[P(BA-EHA)] latex was synthesized by emulsion polymerization．In the presence of P(BA-EHA) latex,P(BA-EHA)／PVC composite latex was prepared by copolymerization with vinyl chloride in an autoclave．The effects of the amount of P(BA-EHA) latex on the latex particle diameters and mechanical properties of P(BA-EHA)／PVC materials were investigated．The morphology of the materials or the composite latex particles was characterized with the aid of TEM or SEM and dynamic mechanical analysis (DMA)．DMA measurements illustrated that the compatibility between P(BA-EHA) and PVC was well improved．With increasing the P(BA-EHA) content,the loss peak in low temperature range became higher than that of pure PVC,and the maximum value of the loss peak gradually shifted to higher temperature．TEM studies showed that the composite particles had a clear core-shell structure,P(BA-EHA) uniformly dispersed in PVC matrix,the interface between the two phases was indistinct．The fractured surface of the notched sample exhibited clear toughness characteristics．The notched impact strength of the material with 4.2％ P(BA-EHA) was eleven times as large as that of PVC,and the elongation percentage at break was about three times that of PVC．
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发布时间：2021-03-19 - 摘要：A new copolymer of 2-methyl-8-hydroxyquinoline gallium acrylate and methyl methacrylate was prepared．The composition and properties of the copolymers were characterized by FT-IR,UV-vis,DSC,TG and fluorescence spectroscopy．A strong blue-green photoluminescence with maximum at 496 nm was observed for the copolymer/CHCl3 solution．Effects of monomer ratio and concentration on photoluminescence properties of the copolymer were investigated．The results showed that the maximum fluorescence intensity was attained when Ga(Mq)2A:MMA was 1:20．While the wavelength of maximum excitation was approximately 263 nm when the concentration of the copolymer was under 2 g/L,but the wavelength of maximum excitation moved to 365 nm after the concentration was above 4 g/L．The copolymer is soluble in chloroform,acetone and DMF at 25℃,so it can be used to prepare electroluminescent device by spin-coat technology．DSC analysis showed that Tg of the copolymer was 35 K higher than that of PMMA,and the results of TG indicated that the decomposition temperature of PMMA was 140℃,but that of the copolymer exceeded 250℃,so the copolymer exhibited better thermal stability than PMMA．
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发布时间：2021-03-19 - 摘要：A novel hydrophobically associating copolymer composed of acrylamide(AM) and a low amount of 2-phenoxylethyl acrylate (POEA) (＜1.0 mol％) was prepared by a micellar copolymerization technique．These polymers exhibited a strong hydrophobic effect,and showed a large viscosity enhancement at concentrations above c*,owning to occurrence of the interchain hydrophobic association．The different synthesis conditions for copolymers,such as the total monomer concentration,feed composition and ratio of the surfactant to the hydrophobic monomer (SMR) significantly influenced the composition and properties of the polymer．The experimental results showed that the viscosity property and association behavior were pronouncedly dependent on the molecular weight and the hydrophobe content of the polymer,as well as the block length and the distribution of hydrophobes in the polymer chain．
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发布时间：2021-03-19 - 摘要：The critical concentration of surfactant in clusterization of sodium tetradecyl sulfate (SMS),sodium dodecyl sulfate (SDS) and sodium decyl sulfate (SDeS) on polyvinylpyrrolidone (PVP) homolog or polyetheleneglycol (PEG) homolog was studied by means of surface tension．There occur bis-transition points or pseudo double-plateau regions in the γ-lgc curves of the above clusterization systems,which means that soft matter clusters are vielded between the two critical concentrations．The two critical concentration values c1 and c2 could be found along with these γ-lgc curves,and they fulfil the relationship of c1＜cmc＜c2. The c1 value of a given surfactant is basically an invariant,which is independent on the molecular weight and concentration of a certain homolog of macromolecule．Moreover the value of c1 is decreased with the increase of hydrophobicity of the surfactant homolog．The relation between lgc1 and n,the number of alkyl chain carbons of a surfactant,is simply decreasing,which can be expressed by linear equations：lgc1=1.58-0.341 n (R2=0.9981)for PVP-ROSO3Na soft clusters and lgcc1=1.38—0.313n (R2=0.9993) for PEG-ROSO3Na soft clusters．Meanwhile the value of c2 is independent on the molecular weight of the polymer under the same polymer concentrations．
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发布时间：2021-03-19 - 摘要：Dispersion copolymerization of styrene (St) and divinylhenzene (DVB) was carried out in mixture solvents composed of ethanol (EOH) and ethylene glycol monomethyl ether (EGME) using hydroxypropylcellulose (HPC) as a steric stabilizer．Monodispersed crosslinked polystyrene microspheres were prepared in an average diameter range of 6～10 μm．The effects of the amount of styrene,divinylbenzene,initiator AIBN and ratio of EOH／EGME on the average size and size distribution of microspheres,and on the variation of particle number and polymerization rate were studied．With increasing styrene and initiator AIBN,the polymerization rate and the particle size increase,but the size distribution broadens,at the same time the particle number first increases,and then decreases．The particle size increases,and the size distribution becomes narrow with increasing the ratio of EOH/EGME．The concentration of stabilizer has no obvious effect on the polymerization rate and size distribution of particles,but the average size of particles decreases and the particle number increases with increasing the stabilizer concentration．The effects of the post-addition method on the average size of particles and size distribution were also discussed.
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发布时间：2021-03-19 - 摘要：Being different from other dispersion polymerizations which use nonpolar fatty hydrocarbons or methanol-water as media,this article present the preparation of poly(methyl methacrylate) particles in alcohol-watermixture．In experiments,a certain heating way is applied：at first,the reaction occurs at a relatively high temperature for a given time；then the temperature is lowed and the reaction continues at that temperature to the end．This procedure results in a largely narrowed size distribution. The effects of initiator on the particle size and size distribution are also studied．It is found that even a small amount of KPS can decrease the size of particles and broaden the size distribution apparently.
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发布时间：2021-03-19 - 摘要：A novel soluble azo polyimide has been prepared from a post azo-coupling reaction scheme．The polyimide-based precursor polymer was obtained from the polycondensation of N,N-bis [(3,4-dicarboxypbeny anhydride)-l-carboxyethyl]aniline and 4,4′-diamino-4″-bexadecyloxtriphenylmethane．It is soluble in polar organic solvents such as tetrahydrofuran(THF) and N,N-dimethylacetamide (DMAc)．The azo polymer was synthesized by the reaction of the polyimide-based precursor polymer and diazonium salt．Both the precursor polymer and the azo polymer were characterized by 1H-NMR,DSC,FTIR and UV-Vis spectrometry．The effect of long alkyl side-chain on the enhancement of solubility was confirmed．When the spin-coated azo polymer film was exposed to an interference pattern of Ar+ laser,regularly spaced sinusoidal surface relief grating (SRG) was formed with depths up to 200 nm.The diffraction efficiency of the detecting laser was recorded to monitor the forming process of SRG and the surface structure on the film was also observed directly by using an atomic force microscope. The result shows that the soluble azo polyimide with surface-relief-grating-forming ability has been successfully synthesized．
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发布时间：2021-03-19 - 摘要：A series of polymers containing azo chromophores with different number of methyl substituents have been designed and synthesized．Three epoxy-based precursor polymers were prepared by reactions of diglycidyl ether of bisphenol-A with aniline,3-methylanifine,and 3,5-dimethylaniline respectively．The precursor polymers were reacted with diszonium salt at the final stage of the synthetic routes to introduce donor-acceptor type azo chromophores．The polymers synthesized were characterized by using various spectroscopic methods and thermal analysis．Photoprocessibility of photoinduced surface-relief-gratings on the polymer films was studied carefully．With the same irradiating light intensity and approximately equal film thickness,the rates of SRG formation significantly depend on the number of methyl substituents on the azo chromophores．For polymers with the same type of electron withdrawing group,the inscription rates decrease with the increase of the number of methyl substituents on the azo chromophores．
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发布时间：2021-03-19 - 摘要：Poly (p-dioxanone) and copolymers of p-dioxanone and glycolide were prepared．In order to increasing the plasticity and elasticity of these polymers,nonpoisonous plasticizers(phthalate) were added when they were spun into monofilament absorbable sutures．The polymers were physically admixed with plasticizers under stirring．The structure and properties of poly(p-dioxanone) sutures (PDS) and poly(p-dioxanone-co-glycolide) sutures (PDG) were determined by using DSC,X-ray diffraction and analyzed through examining the changes of strength,flexibility,macromolecular orientation and the level of crystallinity of the sutures．The introduction of plasticizers may lower the strength of intermolecular forces and increase the flexibility of the polymeric structure．When the plasticizer content was about 1％～4％,the PDS and PDG sutures exhibited improvement both in tensile strength and more flexibility．
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发布时间：2021-03-19 - 摘要：Organic montmorillonites (O-MMT) were prepared by treating Na-montmorillonites with alkylammonium ions．The polypropylene／montmorillonite nanocomposites (PMNC) were prepared in two steps．The mother materials were synthesized by an in-situ graft-intercalation method with maleic anhydride and styrene firstly,then PMNC were prepared by blending PP and the mother materials by using a twin screw extruder．XRD results suggested that the layer spacing (d001) of the organic montmorillonites increased from about 1.49 nm up to about 2.96 nm,and the layer spacing (d001) of montmorillonitenm in PMNC from about 2.96 nm up to about 4.0 nm．Mechanical performance tests showed that the noched impact strength (11～12 kJ／m2) and the tensile strength (38～39 MPa) of DMNC with lower montmorillonite contents(1wt％～3wt％) were higher than the noched impact strength (4.12 kJ／m2) and tensile strength (33 MPa) of PP．The mechanical performance of PMNC is superior to PP’s．The morphology of impact fracture surfaces were investigated by SEM and the mechanism of impact fracture was discussed．With the increasing of montmorillonite content,the mechanism of impact fracture was converted into toughness fractures from frangibility fractures．
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发布时间：2021-03-19 - 摘要：New fluorinated polyimides with high heat resistance and low dielectric constants have been synthesized by a two-step procedure. The thermal,mechanical and electrical properties were measured,which indicated that the polyimides with pyridine moieties in the main chain showed both good heat resistance and mechanical properties with initial thermal decomposition temperatures of 545～601℃ in nitrogen and elongation at break of 9％～16％ and tensile strength of 94.2～147.3 MPa．The polyimide films showed also good dielectric properties with dielectric constants of 2.86～2.91 at 1 MHz frequency and breakdown voltage of 150.4～197.3 kV／mm,which was mainly because of the high fluoro-content and large free volume in the molecular structures. All the properties made them great potential candidates for advanced packaging in microelectronic applications．
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发布时间：2021-03-19 - 摘要：The crystalline morphology of PCL (poly(ε-caprolactone)) thin film was investigated by AFM (atomic force microscopy)．1％ PCL/chloroform solution was spun-cast on different substrates to get thin films．The thickness of the films is about 100 nm．The thin films were annealed at 120℃ for 48 h,then crystallized at 55℃ for 72 h AFM observation showed that two kinds of crystal morphology formed in PCL thin films on polished quartz substrate,i．e．typical spherulite and unusual pinetree branch-like crystal morphologies．It is considered that the diffusion-control crystallizing process results in the formation of the unusual pinetree branch-like crystal morphology while the PCL film is thin enough. It might be the main reason that the interaction between the substrate and the PCL molecules confines the chain diffusion．When the PCL solution was cast on a quartz substrate with designed aluminum grooves of 10 μm wide,it was observed that the crystallites in the PCL thin film exhibited a regular oriented alinement．The orientation along the groove is preponderant．It implies that the crystal first formed from the edges of the aluminum groove and then grew along the groove．When strong electrostatic field is applied to the groove,the PCL crystallization in the thin film exhibited a different morphology,i．e．the crystal arrangement tends to be parallel to the electrostatic field．
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发布时间：2021-03-19 - 摘要：There are many changes for protein molecules in conformations in the process of folding．The mean-square radius of gyration and its distribution function P(S) were calculated by using the exact enumeration calculation method．It was found that the dimension was large at the beginning of folding,and the range of its distribution was also wide．However,the dimension became small and compact at the end of folding,and the range of its distribution also became small．The mean-square radius of gyration 〈S2〉t with the number of contacts t is shown as〈S2〉t／Nl2=a+bN where a depends on the number of contacts (t) and b is independent of the number of contacts (t),and N is the chain length of two-dimensional protein molecules．There are different distributions for various residue sequences. The value of P(S) nearby the mean-square radius of gyration is more large for the folding sequence．A ratio of SN／DN was also calculated．SN is the number of designing sequences,and DN is the number of designable conformations．It was found that the ratio may be expressed as -1.684+0.3255N ≤ SN／DN ≤ -0.8664+0.3125 N (N ≥ 13) These results may provide some insights into the folding of proteins molecules．
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发布时间：2021-03-19 - 摘要：The Gibbs distribution is introduced into the theory of polymer solutions．The statistical mechanics method is used to deduce the thermodynamic theory of polymer solutions．The analytical expressions of thermodynamic quantities,including the free energy of mixing and the entropy of mixing,are presented in the present theory．The free energy of mixing has three fundamentally different types of contributions,i．e．,the translational free energy,the configurational free energy and the thermal correction free energy. The first two terms of the free energy of mixing are equal to the corresponding terms in the FH theory．The influence of interactions among chain units and solvent molecules on the configuration is included in the third term．In the case of small interactions among solvent molecules and chain units the expression of free energy of mixing in the present theory approximates that of the FH theory．An apparent Flory interaction parameter χAP is introduced in this paper. It not only depends on temperature and the interaction energy as the Flory interaction parameter χ,but also depends on the concentration of polymer solutions．The difference between χAP and χ increases,as the interaction energy increases or the concentration of the solution increases.
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发布时间：2021-03-19
Research Article
- 摘要：The Monte Carlo arithmetic invented by Gillespie was used to model the random degradation reaction of linear polymers．The number of molecules having different degree of polymerization was given at anytime in the degradation process．It was found that the number of molecules of high degree of polymerization (DP) decreased rapidly at the very begining of the degradation process．At the same time,the number increase of low DP molecules increased with decreasing the DP of molecules,and a smooth DP distribution was obtained．
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发布时间：2021-03-19 - 摘要：A kind of polyurethane／organically modified montmorillonite (PU／OMMT) nanocomposite based on poly(propylene glycol),1,4-butanediol and 4,4-diphenylmethane diisocyanate was prepared by solution intercalation technology．The results of wide angle X-ray diffraction and TEM showed that the gallery distance of OMMT in the PU matrix was 3～4 nm. As the hard segment content increased,the molecular chains of PU had difficulty in diffusing into the silicate layer galleries for intercalation．Transmission electron microscopy photographs showed that OMMT layers were dispersed well into the PU matrix on the nanometer scale,and an ordered intercalation structure was obtained. Compared with those of pure PU,the tensile strength,the tear strength and the elongation at break increased by about 43％,28％ and 18％ for PU／OMMT(92／8),respectively．The water absorption decreased with increasing the amount of OMMT. Thermogravimetric analysis showed that the PU／OMMT nanocomposites displayed a little higher thermal resistance than that of pure PU in the second pyrolysis stage．
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发布时间：2021-03-19 - 摘要：Polybutadiene (PB)／Montmorillonite (MMT) nanocomposites were prepared by in situ polymerization through anionic polymerization technique．The structure of the nanocomposites was characterized by using XRD and H-NMR. XRD results showed that the crystalline spacing in clay was increased,indicating the intercalation of PB chains in MMT crystallites,and both intercalated and exfoliated nanocomposites were prepared．From the H-NMR spectra of PB and PB／MMT nanocomposites,it could be seen that the microstucture of PB was influenced by MMT．The 1,2 units content of PB molecules increased with the introduction of MMT．The dynamic properties of nanocomposites were measured by DMA．The results showed that Tg and storage modulus were increased,tanδ was decreased with MMT added,indicating that MMT has strong interaction with PB so as to reduce the friction among the chains of PB．The results of TGA revealed that the nanocomposites have better thermal stability than PB.
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发布时间：2021-03-19 - 摘要：Poly-N-vinyl acetamide (PNVA) was synthesized by free radical polymerization．Then a series of complexes of Eu3+ with poly-N-vinyl acetamide were prepared by adding different amount of EuCl3 into the polymer.They were characterized by using UV-visual,IR and fluorescence spectroscopies．The results indicate that Eu3+ ion is incorporated with oxygen atoms of carbonyl in PNVA by electrostatic force．The fluorescence emission intensity was measured on solution samples．The coordination compound can emit red fluorescence at 613 nm after being excited by 277 nm ultraviolet rays,and the fluorescence strength reaches a maximum at an Eu3+ content around 0.226 wt％．
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发布时间：2021-03-19
Research Bulletin
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