最新刊期
卷 ， 期 2 ， 2003
- 摘要：The emission color of polyfluorenes can be turned over entire visible region by incorporating comonomer into polyfluorene backbone．In this paper,we demonstrate color tuning in polyfluorene derivatives by incorporating thiophene into the polyfluorene main chain．High molecular weight (Mn=6000～53000),readily soluable copolymers of different compositions were prepared from 2,7-dibromo-9,9-dioctylfluorene (DOF),2,7-bis(4,4,5,5-tetramethyl-l,3,2-dioxaborolan-2-yl)-9,9-dioctylfluorene and a narrow band gap comonomer 2,5-dibromothiophene using palladium catalyzed Suzuki coupling methods．The comonomer feed ratios of DOF to thiophene were 95:5,90:10,85:15,70:30 and 50:50 respectively．Theresulting copolymers are soluble in common organic solvents,such as THF and CHCl3．The actual molar ratios of DOF to thiophene in the copolymers were estimated by means of elemental analysis．The results indicate that the actual ratio of DOF to thiophene in the copolymer is very close to the feed ratio．The electrochemical,optical,photoluminescent (PL) and electroluminescent (EL) properties of the copolymers were studied．Cyclic voltammogram (CV) indicates that the LUMO level of the copolymers is close to that of the PF homopolymer,and it keeps almost constant for copolymers with different thiophene content．The HOMO level slightly decreases with increasing the thiophene content in the copolymer．PL and EL peaks ale red-shifting with increasing the thiophene content．The maximal EL emission wavelength of the copolymers is red-shifted from 490 nm to 541 nm,when the thiophene content increases from 5％ to 50％．Both PL and EL efficiencies decrease with increasing the thiophene content．The highest external EL quantum efficiency 0.45％ was obtained from the device at the thiophene ratio of 5％ and 10％,respectively．The results indicate that the use of conjugated polyfluorene as wide band-gap segment with a small amount (1％～5％) of narrow band-gap dopant in the molecular level could provide a new way to combine high quantum efficiency along with color turning ability．
- 38
- |
- 10
- |
- 15
发布时间：2021-03-19 - 摘要：Copolymer EPM-g-GMA were prepared by grafting glycidyl methacrylate (GMA) on to EPM in a co-rotating twin-screw extruder．The grafting yield of EPM-g-GMA copolymers was determined by FTIR measurements．The morphology and mechanical properties of PBT blended with EPM-g-GMA were studied．It was found that the increase of the GMA content in the graft copolymer may reduce the particle size of the dispersed phase in the blends of PBT／EPM-g-GMA and improve the cohesion between the component of the blends．The results show that the particle size of the dispersed phase was about 0.5 mm,when the GMA content in the graft copoymer used for blending was 4.7 phr (grams per 100 grams of EPM)．At the same time the izod notch impact strength of the PBT/EPM-g-GMA blend reached 51.6 kJ/m2,which is 31 times as high as that of pure PBT．
- 4
- |
- 12
- |
- 12
发布时间：2021-03-19 - 摘要：The residue-residue contacts in 61 globular protein molecules were studied by using CSU software．The aim is to find the ability of forming the short-range and long-range residue-residue contacts for several residues．It is found that it is easy to form the long-range residue-residue contacts for Leu,Val,Ile,Met,Phe,Tyr,Cys,Trp residues,and it is difficult to form the long-range residue-residue contacts for Glu,Gln,Asp,Asn,Lys,Ser,Arg,Pro residues．The residuce are called residues hydrophobic (H) and hydrophilic (P) residues,respectively,and the other residues is called neutral residue (N)．The average number of long-range contacts per residue is 6.03,4.43 and 3.64 for H,N and P residues respectively．However,the average number of short-range contacts per residue ranges from 2.34 to 2.85,and it is almost no difference among those residues in forming the short-range contacts. Our research may provide some insights into the stability and folding of protein molecules.
- 3
- |
- 9
- |
- 5
发布时间：2021-03-19 - 摘要：A novel series of Schiff base type polymer liquid crystalline crown ethers was synthesized for the first time by solution polycondensation from 4,4′-(alkylene dioyloxy) dibenzaldyhyde (M1) and diamino-dibenzo-15-crown-5 (M2) as the monomers．Monomer M1 has been synthesized by esterification reaction of aliphatdiyl chloride and 4-hydroxybenzaldehyde. Monomer M2 has been synthesized by reduction reaction of dinitrodibenzo-15-crown-5 in the presence 10％ Pd／C catalyst and hydrazine hydrate．The geometric isomers of dinitrodibenzo-15-crown-5 and diaminodibenzo-15-crown-5 that were synthesized for the first time can not be differentiated by IR spectrum and 1H-NMR spectrum．The molecular weights of the polymers are not high,and the Mn of the polymers ranges from 10100～13000．The monomer structures were identified by using elementary analysis,IR,1H-NMR and MS etc．The properties of polymers were investigated by using GPC,DSC,TG,WAXD and POM．It was found that all the polymers went into a liquid crystal phase when heated to their melting temperature (Tm)．The threaded texture and schlieren texture can be observed．The glass transition temperature (Tg),melting temperature and isotropization temperature (Ti) change with varing the flexible spacer unit in the polymers,all the polymers have higher clearning points and wide mesophase ranges．The WAXD study illustrated that the polymers of 6Ⅰa,6Ⅰc,6Ⅱb and 6Ⅱd are liquid crystalline with a nematic phase．A dispersive peak at 2θ near 20。appeared on their WAXD curves,which is a typical character for quenched nematic liquid crystal polymers．
- 35
- |
- 10
- |
- 4
发布时间：2021-03-19 - 摘要：Recently,some attention has been paid to hydrophobically modified gels (HM-gels) with a small number of hydrocarbon side groups in their chain backbones．However,few papers can be retrieved for fluorocarbon-modified gels although fluorocarbon groups show the strong ability of hydrophobic association than hydrocarbon ones．In HM-gels,the association of hydrophobic side groups affects directly the state and amount of water．Therefore it is necessary to investigate the states of water in fluorocarbon-modified gels in order to understand the relationship between their hydrophobic microstructure and macroscopic properties．In this paper,a series of hydrophobically modified poly(acrylic acid) (HM-PAA) gels were prepared by radical copolymerization of acrylic acid (AA) and a small amount of hydrophobical comonomers,2-(N-ethylperfluorooctanesulfoamido)ethyl methacrylate (FMA) in tert-butanol．The effects of hydrophobic modification on water states of gels were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)．For HM-PAA gel with FMA content of 1％,no melting peaks were observed with water content(Wc) lower than 0.698 mol％ and two melting peaks appeared with Wc higher than 0.698 mol％ in DSC heating curves,which proved the existence of three states of water molecules,that is,free water,non-freezing water and freezing bound water in FMA-modified gels．A method for calculating the melting enthalpy of different states of water in gels the numbers of non-freezing and freezing bound water molecules associated with a polymer unit,n0 and n1 was brought forward．The numbers of non-freezing and freezing bound water molecules associated with a polymer unit,n0 and n1,increased after hydrophobic modification．For the gel sample PAA-FMA1％,the melting enthalpies of freezing bound water and free water were measured to be 7589.03 and 6864.06 J／mol,respectively.
- 40
- |
- 11
- |
- 4
发布时间：2021-03-19 - 摘要：Two blend systems of polystyrene／poly (methyl methacrylate) (PS／PMMA) and polystyrene／poly(ε-caprolactone) (PS／PCL) were studied by using their thin films prepared on a glass substrate by spin-coating from THF respectively．Phase contrast microscopy and scanning electron microscopy (SEM) combined with elementary analysis were used to obtain information on the morphology in these thin films after heat treatment．It was found that PMMA-rich and PCL-rich phases were always continuous in thin films of either blends,even though the PMMA and PCL were the minor component in their blends．This should result from the better wetting abilities of PMMA and PCL on the glass substrate than PS in the blends．The spreading of PMMA or PCL phase in the blends on glass substrate during annealing induced the above results．The function of viscosity of the blend in the evolution of phase structure was also concerned via changing the molecular weight of PS component in the PS／PCL blend thin films．
- 4
- |
- 9
- |
- 4
发布时间：2021-03-19 - 摘要：By using the viscosity theory of Einstein and the molecular parameters of dendrimers,the relationship between the intrinsic viscosity [η] and the generation number of dendrimers was obtained at lhe first time．The unique intrinsic viscosity behavior of dendrimers was explained. Thus,it becomes possible that the intrinsic viscosity of dendrimers can be forecasted theoretically．
- 4
- |
- 14
- |
- 3
发布时间：2021-03-19 - 摘要：A waterborne polyurethane／A-stage phenolic resin dispersion was prepared．The relationship between pH value and the solubility of the phenolic resin in water indicated that the dissolution of A-stage phenolic resin resulted from the ionization of the phenolical hydroxyl groups in basic solution．There were three kinds of granules in the waterborne polyurethane／A-stage phenolic resin dispersion：core-shell,incomplete core-shell and pure polyurethane,depending on the condensation degree and the amount of phenolic resin．The average diameter of the particles in the dispersion and the distribution width of particle size became greater and wider,respectively,with increasing the proportion of phenolic resin,while the stability of the dispersion with regard to heat,mechanical effect and freezing-melting process and the C.C.C value decreased．It Was proved that the stability of the dispersion was determined mainly by the electrical properties of the dispersion,therefore it should belong to real sol,but,to some extent,the dispersion also had some properties of macromolecular solutions．The properties of the coating film prepared by the polyurethane／phenolic resin dispersion were superior to those made of pure PU film,and could modified further by hybridization with SiO2-sol.
- 3
- |
- 9
- |
- 2
发布时间：2021-03-19 - 摘要：The star-shaped block copolymers were prepared by ring-opening polymerization of ε-caprolactone in the presence of multiarm PEG using stannous octoate as a catalyst．Based on these star-shaped PEG-b-PCL,soluble macromers terminated with acrylate groups were synthesized．The amphiphilic nature of the macromers causes them to assume a micellar conformation in water,which enables them to undergo rapid polymerization using photoinitiator under UV radiation．Macromers and their hydrogels were characterized by 1H-NMR、FTIR、DSC、TGA、ESEM、gel content and swelling ratio etc．It is shown that dried gels absorb water rapidly,and hydrogels have high swelling ratio and water content．With the increase of arm numbers of PEG,the temperature of the melting peak of dried gels and the swelling ratio of hydrogels decrease；The photograph of ESEM indicated clearly the network structure of the hydrogel．
- 12
- |
- 9
- |
- 2
发布时间：2021-03-19 - 摘要：The conformations of DNA chains are studied under the elastic rod model by Metropolis Monte Carlo simulation．The energy of DNA chains includes the bending energy EB and the twisting energy ET,and they can be expressed in the form of EB (r)=A—2∫L0κ2 ds and ET(r)=2π2C—L(ΔLk-Wr)2．The energy decreases with increasing the chain length of DNA．We find that EB is greater than ET by 10～102 times．In the same time,the relationship between 〈Rg2〉 and chain length n is 〈Rg2〉=1169.5-3.5×n+0.025×n2．The equation of Lk=Wr+Tw is verified,and the values of Lk and Wr are found to be very close to each other．It shows that DNA chain is easier to be bent than to be twisted．But for the large value of Lk,the tendency of torsion becomes large．Oursimulation can provide a new method to analyze the conformations of DNA chains．
- 30
- |
- 9
- |
- 1
发布时间：2021-03-19 - 摘要：The adsorption of caffeine was studied by using three phenolic resin adsorbents,JDW-1,JDW-2 and JDW-3,prepared in the laboratory and a commercial product Duolite S-761 under static and dynamic conditions. The experimental results show that JDW’s are superior to Duolite S-761 in adsorption of caffeine．A semi-empirical rate equation adequately fits the sorption rate data of caffeine in the initial period till about 32％～51％ of the equilibrium sorption．The results confirm the particle-diffusion control mechanism of the sorption process．The equilibrium sorption date for phenolic resin adsorbents／caffeine systems can be described by the Langmuir isotherm equation with a correlation coefficient larger than 0.99．It implies the monomolecular sorption in these systems.
- 8
- |
- 11
- |
- 6
发布时间：2021-03-19 - 摘要：The vinylidene chloride(VDC)-vinyl chloride(VC) copolymer is an excellent oxygen and moisture barrier resin available today for food packaging．The copolymer is usually obtained by suspension copolymerization．VDC-VC copolymers may have troubles in fil-forming．The problem is related with the scarcity of the crystalline and melting properties for VDC-VC copolymers．In the present paper,the effects of copolymerization temperature,composition of VDC-VC copolymers and the amount of epoxidized soybean oil (ESO) on the crystallinity and melting point were investigated．It was found that there were two melting peaks of VDC-VC copolymers,and the high melting peak disappeared with increasing copolymerization temperature and VC monomer concentration．A suitable VDC-VC copolymer resin with good processing and melting properties can be obtained by temperature-raising copolymerization technology．The melting point and crystallinity of VDC-VC copolymers and high temperature peak area decreased with increasing the VC composition．The melting point of VDC-VC copolymers decreased with increasing the ESO concentration,but the area ratio of the high to low temperature peaks was not changed．With the Flory’s melting point theory,the effects of copolymer composition and ESO concentration on the decreasing of crystalline temperature were predicted．and the theoretical calculated results were in agreement with the experimental data．
- 38
- |
- 10
- |
- 2
发布时间：2021-03-19 - 摘要：In recent years,materials with negative poisson’S ratio properties have attracted great interest from both scientific and industry fields,since they exhibit special properties：such as dramatic increases in the criss section when a force is applied in the vertical direction and contraction when compacted．In this paper,polyolefin blends with negative poisson’s ratios were prepared successfully．The value of the negative poisson’s ratio of the polyolefin blends was investigated by using a YJY stress flake deformation transducer．A maximum value of -9 was observed for the poisson’s ratio of the blends,and the stable value for samples may reach -1.4. The morphology of the blends was also studied．The results showed that the convacation phenomenon occurred between the two components when the samples were stretched．It also showed that it is possible to get materials with negative poisson’s ratio by decreasing the compatibility of the two components in the blends．
- 11
- |
- 9
- |
- 5
发布时间：2021-03-19 - 摘要：An acrylate-based azo monomer 4-[N-(2-acryloyloxyethyl)-N-ethylamino]-4′-nitro-azobenzene(ANB) was synthesized and grafted to surfaces of PET films by solid-phase graft polymerization using benzophenone as UV photoinitiator．Thus grafted films with photoresponsive surfaces were obtained．Morphology of the surfaces and the cross-section of the grafted films were investigated by Scanning Electronic Microscopy(SEM),which showed that the PET film surfaces were uniformly covered with a layer of azo moieties and its thickness was about 0.4 μm．The photo-induced orientation of the azo chromophores in the grafted films was examined．It was found that the azobenzene groups through rapid trans-cis isomerization oriented perpendicularly to the polarization direction of the light gradually resulting in anisotropic films,when the grafted films were irradiated with a 488 nm linear polarized light A max orientation order parameter about 0.06 was observed after 2 min irradiation．
- 2
- |
- 9
- |
- 3
发布时间：2021-03-19 - 摘要：The PP／graphite compounding powders were prepared by pan-milling at ambient temperature. Under the strong shear in pan-milling process,PP may react solid-mechanochemically with graphite．The crystalline structure changes of PP in the PP／graphite system during pan-milling were characterized by using FTIR,DSC and WAXD techniques．It was found that after pan-milling the crystallinity of PP decreased from 57.2％ to 26.4％,the crystallite size decrease and the distance between crystal faces slightly increased．These changes can be partially recovered during further molding or thermal treatment．The results showed the existence of some content of γ-form crystals of PP in the PP／graphite composites after pan-milling．
- 2
- |
- 10
- |
- 0
发布时间：2021-03-19 - 摘要：The influence of different surface functional groups of nano-SiO2 on nylon 6 in situ polymerization was investigated．FTIR and TGA measurements of silicas isolated from the composites showed that surface grafting was formed during polymerization of silica particles with or without silane pretreatment on the surface,and the percentage of grafting increased with increasing amount of surface functional groups．Compared with pure nylon 6,the presence of silicas with various functional groups resulted in a decreasing tendency of the average molecular weight of nylon 6 in the composites．According to the possibly occurred reactions in the composite systems several bonding styles of surface grafting were proposed．Mechanical tests revealed that the addition of silane treated silica improved the strength and toughness of the composite materials simultaneously,whereas the addition of untreated silica improved the strength at the sacrifice of toughness,indicating the importance of the flexible interlayers introduced by silane treatment.
- 3
- |
- 11
- |
- 22
发布时间：2021-03-19 - 摘要：The effects of kinetic factors of phase separation,such as coarsening time and quenching temperature,on the hydrophilic microporous membranes were studied via thermally induced phase separation(TIPS) process using three hydrophilic ethylene-acrylic acid co-polymers(EAA) with different co-unit contents and diphenyl ether(DPE)．The coarsening time and quenching temperature were used to influence the phase separation of the three different EAA/DPE systems,their diluent droplets growth,membrane cell size and crystalline structure．The mechanism of phase separation,liquid-liquid or solid-liquid made,was determined by the quenching temperature．For EAA／DPE systems liquid-liquid phase separation occurred when the quenching temperature was above the crystalline temperature of EAA,and solid-liquid phase separation occurred when the quenching temperature was below the crystalline temperature of EAA．The experimental results showed that the membrane pore size of the EAA/DPE systems was increased with increasing the quenching or cooling temperature．The average size of the cells was 1～3μm,3～5μm and 6～8 μm for samples with a same coarsening of time of 10 min,but differernt quenching temperatares 30℃,60℃ and 90℃,respectively．At the quenching temperature of 30℃,the droplet phase in EAA／DPE systems hardly grew because the temperature was below the crystalline temperature of EAA．The diluent droplet growth was restricted by the high viscosity of the system and the crystalline structure of EAA co-polymer．While at 90℃,it is above the crystalline temperature of EAA co-polymer,a dramatic increase of droplet size occurred with the coarsening time in the begining,and after 8 min the size kept almost unchanged．
- 44
- |
- 10
- |
- 6
发布时间：2021-03-19 - 摘要：Polycarbonate(PC)is an excellent optical material with high transparency,but it also has high birefringence (Δn0=0.106)which has limited its application in computer-use disk．It has been known that the birefringence of polymer blends may be improved by blending two polymers with opposite birefringence．If polycarbonate is mixed with a kind of polymer that has negative birefringence,for example polystyrene(Δn0=-0.10),it is possible to get a low birefringence polymer blend．Unfortunately,PC and PS is immiscible so that the blend is opaque due to high light scattering at the interface between them．To get a homogenous blend,a styrence copolymer was introduced．The miscibility of the binary polymer blend polycarbonate／styrene-acrylonitrile coploymer was studied based on Flory-Huggins theory in this paper．The effect of molecular weight and copolymer composition on the phase behavior and the dependence of transparency and birefringence of the blend on the blend composition were studied．A homogenous PC／SAN blend was prepared．It has been proved that the phase behavior of binary blend is determined by the combination of molecular weight and copolymer composititon．The condition of making a homogenous PC／SAN blend with low birefringence and transparency of 70％ at 630 nm was found,if the polymeri-zation degree of PC and SAN(S volume fraction is 60％) is 90 and 30,respectively．All polymers with required copolymer composition and different molecular weight in this work were prepared in our laboratory．A series of polymer blends with different blend ratio were made and their miscibility was judged by Tg measurements using DSC technique,and the birefringence was measured by a polarizing microscope fitted with a Cenamen compensator．
- 2
- |
- 9
- |
- 3
发布时间：2021-03-19 - 摘要：Photofabrication of surface relief gratings (SRGs) by using two series of epoxy-based azobenzene functionalized polymers was investigated．Polymers with different degree of functionalization were designed and synthesized to understand the chemical intricacies involved at the molecular level in the photofabrication of SRG．The influences of degree of ago functionalization and type of azo groups on inscription rate of the surface relief gratings were studied carefully．It was found that the inscription rate increased with the degree of functionalization．Different type azo chromophores with the same backbone showed very different inscription rates of SRG．The hydrogen bond formed between carboxyl was helpful to the polymer chain mass migration．The azo polymer containing 4-carboxyazobenzene chromophores showed a significantly faster rate of surface deformation than the azo polymer bearing 4-nitroazobenzene chromophores．
- 2
- |
- 11
- |
- 7
发布时间：2021-03-19 - 摘要：A simple casting film of Poly(6-[4-(4-cyanophenylazo)phenoxy] hexyl methacrylate) (PM6ABCN) was made on an untreated surface of a glass substrate and adopted as a typical sample to study photoinduced orientation of azobenzene liquid crystalline side chain homopolymers．Photoinduced orientation process of the sample was examined．A novel domain model was proposed to give a qualitative analysis of the photoinduced orientation below Tg．It was found that the experimental temperature had no effect on the rate of orientaion,and within the domain the temperature higher than Tg was resulted from radiationless decay of absorbed light energy,and the orientation behavior of microscopic domains was identical with that of the macroscopic sample above Tg. An apparent activation energy of the orientation above Tg was found to be 32.76 kJ／mol．It means that this orientation process has a lower temperature dependence than that of the thermal I-N phase transition (340.2 kJ／mol).
- 5
- |
- 11
- |
- 9
发布时间：2021-03-19 - 摘要：The aggregating state of a polymerizable gelator,4,4′-bis (α-methylacryloyloxy-1,3-ethyleneoxycarbonylpropionamido)diphenyl methoane (BMDM),in gelation of diphenyl ether was investigated by using fluorescein as the fluorescence probe．It was shown that the fluorescence spectra of fluorescein in the gels had a red shift in contrast to those in the solution of diphenyl ether and that the gelation thime decreased with increasing the concentration of BMDM. The orientation of organogel was studied by means of polarized fluorescence．It was found during the gelation of diphenyl ether that the isotropic solution (P0=0) of BMDM was transited to an anisotropic sol(P＞0),and finally the anisotropic sol became isotropic gels (Pgel≈0)．
- 2
- |
- 10
- |
- 3
发布时间：2021-03-19 - 摘要：Three N-catalyst systems were prepared,which contain free donor or different internal donors such as diisobutyl phthalate (DIBP) and 9,9-bis(methoxymethyl) fluorine (BMMF)．The performances of propylene polymerization without external donors in catalyst systems were studied．Poly(propylene)s have been characterized by using gel permeation chromatography (GPC),crystallization fractionation analysis (CRASTAF) and 13C-NMR analysis．It was found that the catalyst with BMMF as the internal donor resulted in polypropylene of best tacticity．It suggests that the internal donors have important influence on polymer tacticity．The polymerization was performed in the presence of different cocatalysts—Et3Al and i-Bu3Al．It was found that the microstructure of polymers obtained with catalyst BMMF (i-Bu3 Al/Ti=300) was as same as that obtained with catalyst DIBP (Et3 Al/Ti=50)．It indicated that the stereoselectivity of the active site depended on the strength of donor coordination．
- 2
- |
- 10
- |
- 6
发布时间：2021-03-19 - 摘要：PET nucleopore membranes with pH value effect were prepared by surface photografting polyacrylic acid with BP as initiator．The grafting degree Dg increased with the rise of monomer concentration and prolongation of irradiation time．With the increase of initiator concentration,the grafting degree has a maximum,which results from the counterbalance between initiating species and self-screening of BP in the reaction solution．Membranes were characterized with XPS,SEM and AFM analysis．The grafted PAA brushes are mainly located on the top surface of the membrane exposed to UV irradiation．No grafting was observed on the back surface and inside the membrane pores．The graft chains around the membrane pores have pore-covering effect．The filtration properties of the membranes are regulated by volume change of the graft brushes that comes from the response to external stimulation of pH value．At low Dg,the permeability of the membranes becomes high as compared to that of the original ungrafted ones because of the improvement in membrane bydrophilicity,but it is not dependent on the pH value of feed solutions．With the increase of Dg,the grafted membrane may act as a pH value．When the pH value varies from 4 to 2,the flux has a leap．The ratio of flux in acidic solution to that in neutral solution rises with the increase of Dg and can be adjusted by controlling Dg values．
- 3
- |
- 12
- |
- 9
发布时间：2021-03-19 - 摘要：The reinforced and toughened PP／PA66 in-situ composites were prepared via an extrusion-drawing-injection molding method．The influence of PA66 weight content (cd) on the phase morphology and mechanical properties of composites together with their functional mechanisms were investigated by contrast to the normal blended materials without drawing．The results show that as cd increases from 0 to 20％,the number of PA66 fibers in-situ formed rises whereas their diameter and its dispersity decrease till cd=15％ and then enhance．Simultaneously,the number of unfibrilized PA66 particles also enlarges．The continuous increment of impact strength of composites,which is superior by 65％ to that of pure PP at cd=20％,can be attributed to the increased number of fibrils and the formation of fibrillar network．The ridigized effects of fibrils and particles on the matrix contribute to the increased Young’s modulus of composites up to a plateau level,which is higher by 36％ than that of pure PP at cd=15％．The tensile strength of composites increases till cd=15％,where its value is greater by 10％ than that of pure PP,and then drops off．This is the counterbalanced effect of the reinforced effect of the dispersed phase on the matrix and the flaw effect at the weak interfaces between two phases．
- 7
- |
- 11
- |
- 9
发布时间：2021-03-19 - 摘要：A series of phenolphthalein containing copolymers were synthesized from nucleophilic polycondensation of 4,4′-dichlorobenzophenone (DCDPK),4,4′-dichlorodiphenyl sulphone (DCDPS) and phenolphthalein (PP)．In order to investigate their chain structures,13C-NMR spectra of these copolymers were recorded．The average sequence lengths,the degrees of randomness and compositions of the copolymers were calculated from the intensities of three kinds of signals,which corresponded to the chemical shifts of three kinds of quaternary carbon atoms in phenolphthalein units in the copolymers．The same results obtained from the three sorts of signals indicated that except the block copolymer,the degree of randomness of other copolymers was approximate to 1,in other words,these copolymers were random copolymers．
- 6
- |
- 9
- |
- 3
发布时间：2021-03-19 - 摘要：A series of polyimide／titania(PI／TiO2) nanocomposite membranes with different contents of TiO2 were fabricated by sol-gel process based on an organic soluble PI and the tetrabutyl titanate in the common solvent NMP．TEM was employed to observe the microstructure of the composite membrane．The solvent resistance was measured through extraction experiment in polar solvents such as NMP,DMF and THF et al,at 25℃ for 72 h．The thermal properties were investigated by DT-DTG and DSC．The result showed that the average size of TiO2 particles was about 10 nm in the composite membrane,which contained TiO2 22.3％ by weight．The solvent resistance and the thermal properties of the composites were greatly enhanced as compared with the pure PI．The residues of the extraction of the composites in NMP increased with the contents of TiO2,and so did the thermal decomposition temperatures and the glass transition temperatures．All of these changes showed that the molecular chains of PI were chemically attached to the three-dimension framework of TiO2 nano-particles in the composites．An assumption was promoted to explain the relationship between the properties and the structures of PI／TiO2 nano—composites．
- 39
- |
- 10
- |
- 5
发布时间：2021-03-19
Research Article
- 摘要：Cross-linked polystyrene microspheres with quarternary ammonium have been prepared via surfactant-free emulsion polymerization．It Was confirmed that the sizes of the microspheres decreased at a certain extent when the contents of the initiator,cross-linked reagent or functional monomer were increased．TEM observation indicated that the size of polymer microspheres ranged from tens of nanometer to hundreds of nanometer．The XPS results showed that the hydrophilic quarternary ammonium groups tended to be rich on the surface of the microspheres during the polymerization．In addition,their swelling ratio can be investigated by using the “in-situ”swelling measurement of polymer microspheres．
- 36
- |
- 8
- |
- 2
发布时间：2021-03-19 - 摘要：Two liquid crystal monomers,cholesteryl 10-undecylenate (M1),and cholesteryl 4-(10-undecylenoyloxy)-benzoate (M2),and their respective side-chain liquid crystal homopolymers (P1,P2) were synthesized．Their liquid crystal properties were characterized by POM and DSC method．M1 could form sematic liquid crystal and cholesteric liquid crystal,while M2-only cholesteric liquid crystal. The Polymers,P1 and P2,exhibited sematic liquid crystal behavior. The results also indicated that,because of the structure of 1.4-COO-Ar-COO-in M2 and P2,the isotropization tempretures of the liquid crystalline M2 and P2 were higher than those of M1 and P1,respectively,and the temprature range of LC phases of M2 was also wider than that of M1．Homopolymer P1,was applied in the capillary column gas chromatography as a novel stationary phase and showed ideal separating selectivity．A mixture of anthracene,phenanthrene and acenaphene and a mixture of dichlorobenzene isomers were well separated．
- 34
- |
- 9
- |
- 1
发布时间：2021-03-19 - 摘要：Atom transfer radical polymerization of styrene initiated by α,α- dibromotoluene and cataIyzed by copper (I) bromide／2,2′-bipyridine was carried out．The produced polymers had narrow molecular weight distributions and controlled molecular weights that were proportional to monomer conversion．In order to show that α,α-dibromotoluene is a bifunctional initiator for atom transfer radical polymerization of styrene,polymerization of styrene using a mixture of 1-phenyl ethyl bromide and α,α-dibromotoluene initiators was also carried out．The GPC trace of obtained polystyrene exhibited bimodal distribution．The peak appearing at lower elution time corresponds to polymer from α,α-dibromotoluene and the other one corresponds to polymer from 1-phenyl ethyl bromide．The ratio of peak molecular weight of the polymer from α,α-dibromotoluene to that from 1-phenyl ethyl bromide was found to be close to two,confirming that the polymer from α,α-dibromotoluene grows from both ends of the polymer chain．Furthermore,the ratio of the two peak surface area changed with the molar ratio of α,α-dibromotoluene to 1-phenyl ethyl bromide.
- 34
- |
- 8
- |
- 2
发布时间：2021-03-19 - 摘要：Based on the model of random walk on the simple cubic lattice,the distribution function of conformation of a polymer chain in an interfacial layer was deduced．If the model chain was consisted of N segments,it was possible to form both the tail chain,when the terminal segments were adsorbed at the interface,and the adsorbed chain with the non-terminal group．The conformational number Ωtail of a tail chain is equal to Ωfree/(6πN)1/2,where Ωfree is the conformational number of a chain in free state and equals to 6N for this random walk model．It was found from theoretical analysis that,for the set of a chain attached non-terminally to the interface,the total conformational number Ωtot is equal to Ωfree/6．As an result,the average conformational number Ωm for the chain attached non-terminally to the interface is Ωfree／6N．In the case of short chain,for instance N is equal to about 10,the conformational number Ωtail of tail chain is even larger than the total number Ωtot. In the limitation of long chain,however,the conformational number Ωtail for tail chain is nuch large than Ωm,but smaller than Ωtot．The conclusion is that the distribution function of conformation for chains in the interfacial layer is not uniform,but has a special distribution form described in this paper．
- 39
- |
- 9
- |
- 2
发布时间：2021-03-19 - 摘要：The effect of heating modes in drawing process on the structure and properties of PET fibers was investigated．Sample B was prepared by drawing amorphous as-spun PET filaments under laser radiation．A CO2 laser (γ=10.6 μm,30 W) was used for this purpose,and the diameter of its radiation area was about 3 mm．The feeding speed of the filaments was 50 m／min,and the draw ratio was 5.0．Sample A was prepared under the same conditions except the heating mode,the filaments were heated by hot rolls．Some difference in structure and mechanical properties were found for the two samples．Sample B exhibited high tenacity (0.8 GPa),elongation (9.2％) and toughness (O.047 GPa)．The latter was about 1.8 times as high as that of sample A．Both of the samples were obviously oriented．WAXD and density measurements showed the crystallinity and the crystallite size of sample B were larger than those of the sample A．
- 2
- |
- 11
- |
- 2
发布时间：2021-03-19
Research Bulletin
- Postal code：100190
- Tel：010-62588927 Email：gfzxb@iccas.ac.cn
- Technical support is provided by Beijing Founder electronics co., LTD 京ICP备05002797号-8
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0