最新刊期
卷 ， 期 12 ， 2008
- 摘要：Hexadecyl trimethylamine bromide (HTAB) modified montmorillonite (OMMT) was prepared by cationic exchange between Na+ and quaternary amine ion,and the layer distance increased by 0.74 nm from 1.26 nm of Na-MMT to 2.00 nm of OMMT,which was very important for late polymer intercalation.Moreover,the existence of long alkyl tail in OMMT enhanced its hydrophobicity,which was beneficial for melt intercalation.The poly(propylene carbonate)(PPC)/OMMT nanocomposites were prepared by melt intercalation of PPC into OMMT,where the as polymerized PPC with number average molecular weight of 8.5×104 was end-capped by maleic acid anhydride before use,and the layer distance increased from 2.00 nm of OMMT to 3.91 nm of PPC/OMMT nanocomposites when the OMMT content increased from 0 to 7 wt％.X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that the PPC/OMMT nanocomposites displayed an intercalated-and-flocculated structure,which was attributed to the strong interaction among the hydroxyl groups at the edges of the layered OMMT.Thermogravimetric analyses (TGA),differential scanning calorimetry (DSC) and mechanical performance testing (Zwick/Z010,Germany) were used for investigation of the thermal and mechanical properties of the nanocomposites.The Young’s modulus increased with increasing OMMT content when the OMMT content was below 5 wt%. When 1 wt% of OMMT was added in the composite,the Young’s modulus of the composite increased by 46.4％ from 691.4 MPa to 1012 MPa,once the OMMT content in the composite reached 5 wt%,the Young’s modulus increased by 61.8% from 691.4 MPa of pure PPC to 1119 MPa of the nanocomposite.In addition to the layered structure of OMMT in the composite,the existence of hydrogen bonding interaction between the hydroxyl groups at the edge of layered OMMT and carbonyl groups in PPC may be another important factor for the above sharp increase.When the OMMT content was over 5 wt%,the dispersion efficiency of OMMT in PPC decreased and inhomogeneous aggregates of OMMT appeared,leading to drop of Young’s modulus,in another respect,the long alkyl tails in OMMT may act as plasticizer to PPC,also leading to decrease of Young’s modulus.It should be noted that,unlike the significant change of Young’s modulus,the tensile strength of the nanocomposite only showed a slight increase of 8.9％ from 43.6 MPa to 47.5 MPa.The thermal decomposition temperature of nanocomposite increased with increasing OMMT load,compared with pure PPC,the thermal decomposition temperature increased by 32.3℃ from 258.6℃ to 290.9℃,which was attributed to the retarding effect of the layered OMMT structure against thermal decomposition.Accordingly,the Tg of the nanocomposites also showed a slight increase of 2.4℃ from 30.9℃ to 33.3℃.Therefore,incorporation of OMMT in PPC/OMMT composites may be a potential way to raise the thermal and mechanical performance of PPC.
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发布时间：2021-03-19 - 摘要：Half-titanocene catalysts (CpTiCl3，CpTi(OBz)3) supported on MgCl2/AlEtn(OEt)3-n were used for ethylene polymerization with a cocatalyst of common inexpensive AlEt2Cl.The polymerization conditions such as the cocatalyst,Al/Ti ratio and temperature had significant effects on catalytic activity and properties of the resultant polyethylene.Results showed that the two supported catalysts exhibited high activity in the presence of AlEt2Cl with 105g PE/(mol Ti#8226;h) magnitude of order,and the viscometric molecular weight of the obtained polyethylene was higher than 105.In addition,the prepared polyethylene was essentially linear polyethylene according to 13C-NMR and DSC analyses.Compared with the corresponding homogeneous catalyst system,the kinetic curves of polymerization were quite steady during the reaction process.It is recommended that the surface morphology and the internal porous structure of the supported catalyst were beneficial for the dispersion of active species,resulting in the increase of the activity,and the active species anchored on confined space of MgCl2/AlEtn(OEt)3-n pores could inhibit the occurrence of β-H elimination reaction.
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发布时间：2021-03-19 - 摘要：The aromatic polyesters poly(MDP-IPC)/poly(EDP-IPC) from isophthaloyl chloride (IPC) and methyl/ethyl esters of diphenolic acid (MDP/EDP),which were made from reactions of diphenolic acid (DPA) and methanol/ethanol,were synthesized by interfacial polycondensation with tetrabutylammonium chloride (TBAC) as phase transfer catalyst.The reaction in various solvent/water systems was investigated.It was found that a large mass of capsules were formed at the beginning of the reaction for all solvents examined,and the reaction results depended on the solvents.It is believed that the capsule shells make up of the reaction zone,and a mechanism of the interfacial polycondensation is proposed accordingly.The effect of solvents on the reaction was interpreted based on the interaction between the polymer and the solvent according to the mechanism.The aromatic polyesters with higher yield (77%) and higher intrinsic viscosity (0.66 dL/g) were obtained when dichloromethane was used as solvent.The effect of reaction conditions on the yield and intrinsic viscosity was investigated.It was found that the maximum intrinsic viscosity was reached when the molar radio of MDP to IPC was 1.1,and it was prone to gain polyesters with higher intrinsic viscosity and higher yield at higher concentration of monomers and higher reaction temperature.The thermal performance of the aromatic polyesters was studied by means of DSC and TGA.The glass transition temperature of poly(MDP-IPC) and poly(EDP-IPC) was 149.4℃ and 140.5℃,respectively.The polyesters started to decompose at 300℃ in thermal gravimetric analysis.The results showed that the two polyesters were more heat-resistant and thermostable than the diphenolic acid aromatic polyesters.
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发布时间：2021-03-19 - 摘要：A kind of ε-caprolactone/L-lactide copolymers with varying compositions and molecular weights has been synthesized by using Sn(Ⅱ)octoate as catalyst and 1,4-butanediol as initiator.The copolymerization was carried out under vacuum at 130℃ for 24 h.The copolymer structure was characterized in detail by using GPC,FTIR,1H-NMR,DSC and XRD analyses.It was shown that the chemical compositions and molecular weights of the copolymers were adjustable by changing the monomer molar ratios in feed,and their appearances and physical characteristics were closely related with the variation of composition and molecular weight.The number average molecular weight is changed from 1×104 to 1×105. The melting temperature is in a range from 15℃ to 55℃.A preliminary study was also conducted on the electrospinning process of the resulting copolymers.The copolymer was first dissolved in CH2Cl2 at a concentration of 6 wt%.The solution was then delivered at a constant flow rate (5 mL/h) with an air gap of 20 cm between the metal collector and the needle tip at a driving voltage of 20 kV.Finally ultrafine fibers were obtained,and melting binding between different fibers was evidenced by SEM observation.The solvent cast membrane of LC-96-6k was found to be stronger than that of LC-50-6k.However,their electrospinning nonwoven fabrics showed lower but comparable mechanical properties.
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发布时间：2021-03-19 - 摘要：Quaternized PVA-N,N-dimethyl-3-amido-2-hydroxy-propyl ether(QPVA) and sulphate monoesterified polyvinyl alcohol (SMPVA) self-assembled into polyion complex （SAPIC）,the swelling ability of SAPIC membranes in water was the least when the self-assembled solution’s pH value was 7. The homogeneous SAPIC membranes were dipped in ethanol of different concentrations 60 vol%～90 vol% (with 10% as interval) for 48 h,and the permeation behavior of water in ethanol of different concentrations was observed in these homogeneous SAPIC membranes.The homogeneous SAPIC membranes were dipped in 95 vol% ethanol for 48 h,and the pervaporation behavior of water in 95 vol% ethanol was observed in the temperature range of 20～120℃ with an interval of 20℃ in homogeneous SAPIC membranes.A novel experimental approach using FTIR spectroscopy was applied to follow up the scent of the two types of membranes.The absorption peaks of water and poly-electrolyte groups in SAPIC membranes were identified in 1D- or 2D-FTIR spectra and showed that two states of water,free water and associating water,were formed during permeation by polyion groups in SAPIC.Free water first associated with polyion groups in SAPIC membranes with increase of water in ethanol,thus associated water was formed in SAPIC membranes.The 1D-or 2D-FTIR results also showed that two states of water,free water and associating water,esisted during pervaporation in SAPIC membranes.The free water changed earlier than associated water,and free water was first desorbed with increase of temperature and was separated with ethanol.The pervaportion of SAPIC composite membranes was tested,and the results showed that the permeation flux was 1400 g/(m.h),and the separation factor was 870 for water/ethanol system (containing 95 wt% ethanol).A simple and convenient method was set up for studying the dehydration process of ethanol by using SAPIC membranes.
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发布时间：2021-03-19 - 摘要：Binary blends of two grades of nylon 6 and three kinds of commercialized thermotropic liquid crystal polymers (LCPs) (Vectra A950,Vectra B950 and Rodrun LC5000) were prepared by melting blending process,respectively.The ester-amide exchange reaction between nylon 6 and LCPs was analyzed by using diffuse reflectance FTIR spectroscopy (DRIFT) and differential scanning calorimetry (DSC).The blending time,composition and the type of LCPs exerted dramatic influence on the exchange reaction,resulting in the decrease of melting point and crystallinity of nylon 6 in the blends.The increase of blending time promoted the contact and the entanglement of macromolecular chains of the two phases,and therefore,promoted the exchange reaction.The increase of LCP content was another favorable parameter for the exchange reaction.When the content of Rodrun LC5000 was 80 wt%,the melting temperature of nylon 6 in the blend decreased from 219.1℃ to 185.5℃,and the crystallinity was decreased from 37.9% to 20.0%.Compared with Vectra A950 and Vectra B950,Rodrun LC5000 tends to react with nylon 6 more extensively,due to its more flexible molecular chain.The morphology of blends was characterized by using scanning electron microscopy (SEM).It is shown that,unlike other completely incompatible blending systems,the morphology of nylon 6/LCP blends was controlled by blending time as well as the exchange reaction.With the increase of blending time,the morphology of dispersed LCP was developed from droplets to deformed short bars,and finally,fine fibrils with diameter of about 1 μm.
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发布时间：2021-03-19 - 摘要：The cationic polymerization of isobutylene (IB) by utilizing six functional initiator hexaepoxy squalane (HES) in conjunction with TiCl4 was carried out in CH2Cl2/n-Hex (40/60,V/V) solvent mixtures in the absence or in the presence of 2,6-dimethylpyridine (DMP) respectively.The effects of concentrations of HES,DMP on monomer conversion,molecular weight and molecular weight distribution (MWD) of the product polyisobutylene (PIB) were investigated.A small amount of water in the polymerization system in conjunction with TiCl4 could induce a conventional uncontrolled rapid polymerization of IB and led to polyisobutylene with broad molecular weight distribution.It is found that the GPC trace of resultant polymer obtained by HES/H2O/TiCl4 system exhibit a bimodal distribution,which is attributed to the competition of initiation from two different active centers,i.e.,H+TiCl4OH- (A) and HES+TiCl4OH- (B).The initiation from active center (B) increased with an increase in HES concentration.A large dosage of HES (［HES］＝2.24×10-3 mol/L) was needed to decrease the initiation from active center (A) to some extend but it was still difficult to suppress the initiation from (A) and the chain transfer reaction.According to the GPC and NMR characterization results of polymers，the controlled initiation from (B) could almost be achieved and the GPC traces exhibited relatively narrow unimodal MWD by addition of small amount of DMP.The mechanistic role of DMP is suggested to decrease the initiation from (A) and chain transfer to monomer.A desirable cationic polymerization of IB would be achieved with HES/TiCl4 initiation system in the presence of adequate amount of DMP,and the star-branched telechelic polyisobutylenes with relatively narrow MWD and tert-chloride end-groups could be prepared.
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发布时间：2021-03-19 - 摘要：Dodecafluoroheptyl methacrylate (DFMA),n-butyl acrylate (BA) and methyl methacrylate (MMA) were copolymerized for preparation of fluorinated latexes through miniemulsion copolymerization without any costabilizer.In this reaction system,extremely hydrophobic DFMA was used as a chemical reagent which made the monomer droplets unimodal distribution.But after a while,the monomer droplets coalescenced together and made the monomer droplet size changing from about 130 nm to 400 nm.The oligomers of poly(dodecafluoroheptyl methacrylate),containing a lot of —CF2— and —CF3 segments with low surface energy,were generated quickly and it was proved from 1H-NMR spectrum which showed DFMA has a high composition in the earlier copolymer.The oligomers not only with extremely hydrophobic but also oleophobic natural capacity would take the same effect of conventional costabilizer on the miniemulsion polymerization to increase the surface of monomer droplets and decrease the monomer droplets size.The monomer droplet or particle size distribution of the semifinished and the final products was determined using LS-230 Coulter particle size analyzer.As the process of polymerization was going on,the smaller monomer droplets or particles would detach from the larger ones.Simultaneously,the particles did not maintain unimodal distribution after the beginning of polymerization.However,as the process of polymerization was going on,the particle size distribution would return to the unimodal distribution again.Between the processes of polymerization,the particle sizes changed from about 400 nm to 80 nm.On the base of fundamental theory of miniemulsion polymerization,the particle sizes of the latexes with the convensional costabilizer would not change too much.So,the reason is the oligomers,first generated at the process of polymerization,contain a lot of —CF2— and —CF3 segments with low surface energy to make the smaller particles existence stably.There is no differences about the particle size distributions between the final products initiated by potassium persulfate (KPS,water-soluble initiator) and 2,2′-azobisisobutyronitrile (AIBN,oil-soluble initiator).There were too much differences between the two kinds of initiator,the final products of this polymerization would exhibit bimodal distributions,if some crosslinking agents were added into the systems to reduce the activities of oligomer chains.One of the peaks was at about 80 nm,equaling to that one without any crosslinking agent,the other one was at about 400 nm,equaling to that one before polymerization.With the same contents of crosslinking agents,the effect on particle size distribution of the final products was much more initiated by AIBN.Because the polymerization was taken place in the center of the particles initiated by AIBN to generate the oligomers,the crosslinking agents would reduce the movement activity of the oligomer and make the oligomers shift to the surfaces of the particle more difficult.However,the effect on particle size distribution of the final products was less initiated by KPS.Because the polymerization initiated by KPS was taken place at the inside surface of the particle,as well as the generated oligomers,the movement of the oligomer was not necessary.On the base of the experimental results,the mechanism of miniemulsion polymerization with in situ formed costabilizer was presented.
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发布时间：2021-03-19 - 摘要：Self-assembled hollow microspheres of conductive poly(m-toluidine) (PMT) were simply synthesized by a template-free method in the presence of ammonium peroxydisulfate (APS) without adding an acidic dopant.The average diameter and the average shell thickness of the PMT hollow microspheres were measured to be 2 μm and 140 nm,respectively.Although without adding acids as the dopants,it has been demonstrated that the PMT hollow microspheres are identical to the conducting state of PMT due to proton (H2SO4) produced during the polymerization,which are conformed by FTIR,UV-Visible spectroscopy and room-temperature conductivity measured by the four-probe method,especially the pH value in reaction solution decreases with increasing the polymerization time.It was proposed that a spherical micelles composed of m-toluidine in aqueous solutions is served as a soft-template in forming the PMT hollow spheres via a self-assembly process.
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发布时间：2021-03-19 - 摘要：Polyaniline (PAn) doped with dodecyl benzene sulfonic acid (DBSA) was synthesized by emulsion polymerization of aniline under the presence and absence of a constant magnetic field (0.4T).The effects of temperature on the redox (doping-dedoping) behavior of PAn in PAn/m-cresol solutions were systematically investigated by characterization and analysis of FT-IR spectroscopy,conductivity change of the product/m-cresol solution with temperature under the presence and absence of an external electric field,the changes of pH and colors of the solution.The measurement results of the pH and conductivity in the PAn/m-cresol solution showed that the conductivity of the PAn/m-cresol solution was directly proportional to the concentration of the dissociative doping acid getting away from PAn,and the dedoping degree of PAn was enhanced with the temperature increasing and lowered with the temperature decreasing.Moreover,the PAn/m-cresol solution showed obvious abrupt change in its conductivity from the presence of external electric field to its absence at same temperature.Compared with the abrupt conductivity change in the m-cresol solution of PAn synthesized under the absence of magnetic field,the abrupt conductivity change in the m-cresol solution of PAn synthesized under the presence of magnetic field was more remarkable.However,the conductivities of the m-cresol solutions prepared from dedoped PAn were generally low and inert to the changes of temperature and they never underwent abrupt change in their conductivity from the presence of external electric field to its absence at same temperature.It was thought that because under the presence of an external electric field there was an oriented rearrangement of doped PAn in the m-cresol solution,but not for the dedoped PAn.Moreover,not only the oriented rearrangement under external electric field but also the redox behavior of PAn were related to doping level,the greater the doping level,the more remarkable the special behaviors.
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发布时间：2021-03-19 - 摘要：Triblock copolymers PNPMA-b-PS-b-PNPMA with 146 styrene (St) units and 8,20 and 36 p-nitrophenyl methacrylate (NPMA) units were prepared by ATRP of St using α,α′-dibromo-p-xylene as initiator,and following ATRP of NPMA.Their molecular weights and narrow molecular weight distributions (Mw/Mn=1.03～1.11) were determined by .1H-NMR. and GPC.The anionic copolymer PMAA-b-PS-b-PMAA was synthesized by hydrolysis of PNPMA-b-PS-b-PNPMA,and the cationic copolymer PNPMAAm-b-PS-b-PNPMAAm was prepared by the amino substitution of the same PNPMA-b-PS-b-PNPMA.The complete substitution of NPMA groups was verified by FT-IR spectra.Equal molar PMAA-b-PS-b-PMAA and PNPMAAm-b-PS-b-PNPMAAm both having the same chain lengths were dissolved in common solvent THF with 20% deionized water,and the solution was dialyzed against water to induce the self-assembly of copolymers.The aggregates formed from copolymers with shorter hydrophilic blocks (8 or 20) were deposited in the self-assembly.The aggregates obtained from copolymers with 36 hydrophilic units were studied by TEM and SEM.Polydisperse spheres were observed containing an asymmetrically placed single void space,which has broken through the surface (so-called bowl-shaped aggregates).The size of the bowl-shaped aggregates was measured by DLS to be (565±300) nm.The possible mechanism was discussed.Highly swollen large spheres composed of reverse micelles of hydrophilic cores and PS shells first formed.The diffusion of the solvent inside the large sphere cause bubbles,and they coalesced to a large bubble which broke through the surface of the large sphere that induced the formation of bowl-shaped aggregates.
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发布时间：2021-03-19
Research Article
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INFLUENCE OF DOPE VISCOSITY ON THE FABRICATION OF PVDF HOLLOW FIBER MEMBRANES WITH SINGLE SKIN LAYER
摘要：Hollow fiber membranes fabricated via dry/wet phase inversion method usually have two dense skin layers,which will increase its resistance of mass transport as a support membrane.It is necessary that the dense skin layer of support membrane has been eliminated to improve separation performance of composite membrane.The excellent chemical resistance of poly(vinylidene fluoride) (PVDF) to many acids and alkalis has made it as an attractive membrane material,and then it’s often fabricated as porous hollow fiber membrane by phase inversion.In the process,the formation of the skin layer is due to the rapid exchange between solvent and coagulation,so many attempts have been made to slow it,so as to control the formation of the skin layer.In this paper,it has been found that the fabrication progress becomes unstable,and the membrane prepared has noncircular lumen,when the “weak" or “soft" coagulation is used.To increase the fabrication solution stability during membrane formation,dope viscosity was focused in this experiment.Dimethyl acetamide (DMAc) was used as solvent as well as internal coagulant,and the additives including LiCl,water and surfactant Span were chosen to investigate their effect on the viscosity of the fabrication solution.The dope viscosity will greatly increase after adding LiCl,while the variety of dope viscosity is unconcerned in the fabrication solution concentration as adding water.The homogenization and stability of the fabrication solution are improved by adding Span,and the viscosity increases at the same time.Without increasing PVDF concentration,the stability of the nascent membrane was improved by increasing the fabrication viscosity.The PVDF hollow fiber membrane with the structure of single outer skin layer and finger-like pore through the cross_section,has been successfully fabricated.The mean pore radius and water flux of the single skin hollow fiber membrane were greatly improved.- 17
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发布时间：2021-03-19 - 摘要：In traditional modified methods,the functionalized nanoparticles appear and behave like solids in the absence of solvents.In this paper,a new family of modified nanoparticles,which exhibit liquid-like behavior in the absence of solvents at room temperature,is prepared.The amine-functionalized multi-wall carbon nanotubes (MWNTs) derivative is obtained in a two-step process comprising of oxidation of the tubes with strong acid and then neutralization reaction and hydrogen bonding followed by a surface reaction with dipoly(ethylene glycol) octadecyl amine.The sample is investigated by Fourier transform-infrared spectrometer analysis (FTIR),X-ray diffraction (XRD),thermogravimetric analysis (TGA),differential scanning calorimeter (DSC) and rheological analysis.As a result,the carboxyl and hydroxyl groups were found on the surface of MWNTs,when MWNTs were modified by strong acid.Dipoly(ethylene glycol) octadecyl amine is 40 wt% corresponding to the dense surface coverage of one modifying molecule per 50 carbon atoms of MWNTs.The material is a viscous liquid at room temperature with lower versatility and it can be dispersed in various solvents due to amphiphilic properties of the modifier molecule.Their dispersion,high thermal stability,low vapor pressure and ability to flow at low temperatures make them attractive as lubricants,plasticizers,or film-forming precursors.
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发布时间：2021-03-19 - 摘要：Poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (poly(NIPAAm-co-DMAAm)),poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) (poly(NIPAAm-co-HEMA)) and poly(NIPAAm-co-DMAAm-co-HEMA)) were synthesized by free radical solution copolymerization using thioglycol as chain transfer agent.Their compositions,molecular weights and thermal transitions were determined by 1H-NMR,GPC analysis and lower critical solution temperature (LCST) determination.Poly(NIPAAm-co-DMAAm) showed markedly increase in LCST with incorporation of hydrophilic DMAAm,while the LCST of poly(NIPAAm-co-HEMA) moved to lower temperature in comparison with polyNIPAAm,although HEMA is also a hydrophilic comonomer.It was suggested that the formation of hydrogen bonds between the nitrogen atoms in NIPAAm and the hydroxyls in HEMA invoked the phenomenon.Accordingly,a series of poly(NIPAAm-co-DMAAm-co-HEMA) with LCST of ca. 40℃ were prepared in a similar way.These copolymers containing side hydroxyl groups had been used to initial the ring opening polymerization of caprolactone (CL) and poly(NIPAAm-co-DMAAm-co-HEMA) grafted PCL copolymers were obtained.Preliminary studies showed that LCST of the grafted amphiphilic copolymers shifted to lower values with the introduction of hydrophobic PCL chains onto the hydrophilic backbone.Their thermal sensitivity decreased with the amount and length of side PCL chains being increased.Ideally,thermal sensitive micelles prepared from these amphiphilic copolymers would be good candidates for target or “smart" drug controlled delivery to treat diseases,such as solid tumor in combination with local hyperthermia therapy.
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发布时间：2021-03-19
Research Bulletin
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