最新刊期
卷 ， 期 4 ， 2012
- 摘要：Bacterial nano-cellulose(BC) membranes of high purity,ultrafine network architecture and excellent biocompatibility were used to reinforce the poly(vinyl alcohol)(PVA) hydrogels,which were prepared by physical method of freezing and thawing.The mechanical properties of the BC/PVA composite hydrogels were investigated,the mass percent of PVA,the number of BC layers and some other conditions like pre-treatment method of BC membranes were considered in the preparation process.The mechanical properties of the BC/PVA composite hydrogels were tested by tensile testing machine,the fracture surface of the composite hydrogels and the bonding situation between the BC nano-cellulose membrane and the PVA hydrogel were characterized by the scanning electron microscopy (SEM).The results show that the BC/PVA composite hydrogels have excellent mechanical properties,the tensile strength of the composite hydrogel reaches to 1.74 MPa,and the modulus reaches to 7.82 MPa,when the BC/PVA composite hydrogels are constituted by 15 wt% PVA and two layers of BC membranes.The SEM images show that the interface of the prepared composite hydrogels exhibits excellent bonding.关键词：Poly vinyl alcohol(PVA);Hydrogel;Bacterial nano-cellulose (BC) membrane;Mechanical properties;Interface
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发布时间：2021-03-19 - 摘要：Bacterial cellulose reinforced PVA/PVP double-network hydrogels with different PVA/PVP content were prepared via repeated freezing and thawing method.The structure and properties of the composite hydrogels were studied through X-ray diffraction(XRD),infrared spectrum(IR),scanning electron microscopy(SEM) and mechanical test.SEM results showed that PVP and PVA adsorbed evenly around the BC fiber filaments in BC/PVA/PVP hydrogels,which resulted in the fully rehydration of the composite xerogels in hot water.XRD results showed that there were significant differences between the crystallization of heat-dried and freeze-dried xerogel samples.The crystallization of both BC and PVA were better in heat-dried samples.In addition,the crystallization of BC was inhibited obviously by PVP and PVA.The effect of PVP on the crystallization of PVA in BC/PVA/PVP was similar to that in PVA/PVP hydrolgels.The mechanical test results demonstrated that the mechanical properties of the PVP/PVA hydrogels were strongly enhanced after being reinforced with the net of BC nanofibers.Furthermore,the content of PVP and PVA had an obvious effect on the mechanical properties of the composites.The dynamic viscoelasticity results also showed the strengthen effect of BC,while the elasticity of BC reinforced hydrogels decreased.关键词：Bacterial cellulose;Poly(vinyl alcohol);Poly(vinyl pyrrolidone);Hydrogel;Reinforce
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发布时间：2021-03-19 - 摘要：Sonagashira coupling reaction between 4-bromobenzyl alcohol and trimethylsilylacetylene was carried out and then the trimethylsilyl group was removed to give 4-ethynylbenzyl alcohol.Living ring-opening polymerization of lactide was performed under normal pressure and temperature by using DBU as a catalyst and 4-ethynylbenzyl alcohol as an initiator.1H-NMR spectra and GPC were employed to characterize the chemical structure of the products and analyze the molecular weight and polydispersity.The results indicated that polylactide macromonmers bearing 4-ethynylbenzyloxy end group(PA-PLLA-3k,PA-PLLA-4k,PA-PDLA-3k,and PA-PDLA-4k) were successfully synthesized,and the molecular weight of the macromonmers was controlled effectively.Homopolymerization of the macromonomers was carried out by using [Rh(nbd)Cl]2/Et3N as the catalyst to give poly(phenylacetylene)s with polylactide side chains (poly(PA-PLLA)-3k,poly-(PA-PLLA)-4k,poly(PA-PDLA)-3k and poly(PA-PDLA)-4k).The poly(phenylacetylene)s were characterized by GPC,GPC-MALLS and 1H-NMR.The results indicated that poly(PA-PLLA) and poly(PA-PDLA) possess linear flexible chain with high molecular weight.CD and UV-Vis spectra of the poly-(phenylacetylene)s showed that poly(PA-PLLA) and poly(PA-PDLA) main chains assuredly possess predominantly one-handed helical conformations,and the direction of Cotton effects was affected by the chirality of macromonomers.The direction of Cotton effects of the poly(phenylacetylene)s was the same when the chirality of macromonomers was the same,Cotton effects of the poly(phenylacetylene)s were reverse when the chirality of macromonomers was reverse.The intensity of Cotton effects was various in different solvents,this meant that the regularity of helical conformation of the poly(phenylacetylene) main chain was variable in different solvents.Moreover,the stability of helical conformation of poly(phenylacetylene) decreased with the increasing temperature.关键词：Lactide;Living ring-opening polymerization;Polylactide macromonomer;Homopolymerization of macromonomer;Poly(phenylacetylene);Helical conformation
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发布时间：2021-03-19 - 摘要：The miscibility behavior of polyimides (PI) of different structures and five gasoline components was studied by using Monte Carlo simulation method.The results indicated that the miscibility of 3,3',4,4'-benzophenonetetracarboxylic dianhydride-2,4,6-trimethyl-p-phenylenediamine (BTDA-3MPDA) and gasoline components was prior,and its selectivity of thiophene was better than that of the other PIs.In the temperature of range 300~500 K,the mixed energy between BTDA-3MPDA and gasoline components decreased with increase of temperature.However,the selectivity of thiophene decreased with the increasing temperature.The temperature of 350 K was selected for the further study of the miscibility of BTDA-3MPDA and gasoline components,while the mole free energy between BTDA-3MPDA and thiophene was much smaller than that for the other gasoline components.Thus,BTDA-3MPDA could be played as a selective material for gasoline desulfurization.关键词：Polyimide;Gasoline desulfurization;Monte Carlo simulation;Solubility
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发布时间：2021-03-19 - 摘要：A novel amphiphilic dendron-coil macromonomer3,4,5-tri( n -hexadecyloxy)benzoyloxy polyoxyethylene methacrylate was synthesized by esterification of polyoxythylene (molecular weight M=1000) with 3,4,5-tri(n-hexadecyloxy)benzoyl chloride and followed by methacrylic chloride.The compound was then characterized by means of NMR and FTIR,elementary analysis.Moreover,a new kind of hydrophobically modified alkali-soluble emulsion copolymer (DHASE) was synthesized by emulsion copolymerization of amphiphilic macromonomer 6 with mathacrylic acid and ethyl acrylate.As a comparison,an alkali-soluble emulsion copolymer (MAAEA) of mathacrylic acid and ethyl acrylate was synthesized also.The rheological properties of DHASE and MAAEA aqueous solutions under different solid contents and pH values were studied using controlled stress rheometer.It was found that DHASE aqueous solutions had outstanding alkali-thickening and thixotropy properties and larger zero shear rate viscosity than MAAEA aqueous solutions when pH 6.8 and the solid content of copolymer 1.0 wt%.At the same time,the storage modulus G' was always larger than the loss modulus G over the entire range of frequencies for DHASE aqueous solutions,suggesting formation of physical network structure due to hydrophobic associations of dendron alkyl trails in DHASE aqueous solutions.On the contrary,the MAAEA aqueous solution exhibited Newtorian fluid behavior and its G was always smaller than G' under the same condition.The results demonstrated the potential of this novel amphiphilic dendron-coil macromonomer in hydrophobically modified alkali-soluble emulsion copolymers and associative thickeners in the future.关键词：Amphiphilic dendron;Emulsion polymerization;Hydrophobic association;Rheological property;Alkali-thickening;Thickener
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发布时间：2021-03-19 - 摘要：The surface of poly(p-phenylene-1,3,4-oxadiazole) (p-POD) fiber was fluorinated directly by fluoride (F2).The results of ATR-infrared spectroscopic analysis and X-ray photoelectron spectroscopy(XPS) show that it can effectively generate chemical reactions between p-POD fiber and F2.A mass of CF bonds are formed on the macromolecules of fiber surface and the content of F in the form of CF/C O,CFH and CF2 is 28.2%,which indicates that there are not only substitution reactions but also addition reactions between p-PODs and F2.The curves of thermal gravimetric analysis (TGA) show that there is not impact on p-PODs resistance to high temperature,while the aggregative structures of the fluorinated p-POD fiber are more orderly than those of the original fiber from the wide angle X-ray diffraction pattern.In addition,it takes no change in strength of p-POD fiber after fluorination.Under the condition of 20% concentration sulfuric acid which belongs to the artificial accelerated aging test,the retention of strength of fluorinated p-POD fiber remains 84% which increases by about 90% compared to that of the original fiber.Thus,the acid resistance of p-POD is obviously improved owing to the hydrogen bond formed between F atoms and acid solution which makes the protonation of oxadizoles more harder.Besides,there are compact crosslinking layers formed on the surface of p-POD fiber which can slowdown the aging process.关键词：Poly(p-phenylene-1,3,4-oxadiazoles) fiber;Fluorination;Acid resistance
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发布时间：2021-03-19 - 摘要：A negatively charged monodisperse polystyrene (PSt) seed emulsion was first synthesized via batch emulsifier-free emulsion polymerization,and polyethyleneimine (PEI) aqueous solution was then added into the diluted emulsion to modify the particle surface at 25℃ to prepare the positively charged PSt seed particles.Then,the core-shell PSt/TiO2composite microspheres were obtained by adding the diluted modified PSt seed emulsion into the medium of ethanol containing certain amount of tetrabutyl titanate (TBT).Influences of pH and TBT amount on the morphology of PSt/TiO2 core-shell composite microspheres were investigated by TEM and SEM observation.Results showed that it was difficult to form PSt/TiO2 core-shell microspheres under acidic conditions,and a uniform TiO2 shell with about 29 nm in thickness was obtained when pH increased to 7.2,and then the thickness of the TiO2 shell increased with the increase of pH value.When pH was 11.0,the thickness of the TiO2 shell reached 70 nm,but some of the composite microspheres were partially encapsulated.With the increase of TBT amount from 0.01 g to 0.16 g,the thickness of PSt/TiO2core-shell composite microspheres gradually increased from about 0 nm to 60 nm when the amount of PSt seed emulsion was 0.5 g (solid content was 4% by weight) and pH was controlled at 8.5. While the TBT amount increased to 0.32 g,the thickness of the TiO2 shell reduced to 12 nm,and the surface of the composite microspheres became rough gradually.After that,with the increase of TBT amount,the thickness of the TiO2 shell decreased,and a number of TiO2 nanoparticles appeared.The voided TiO2 microspheres were obtained by calcining the PSt/TiO2 composite microspheres at 500℃ for 4 h when the thickness of TiO2 shell in the composite microspheres reached a certain level.关键词：PSt/TiO2composite microspheres;Voided TiO2 microspheres;Morphology;pH value;Precursor
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发布时间：2021-03-19 - 摘要：The branched poly(methyl acrylate) was prepared by using 2-(2-bromoisobutyryloxy) ethyl acrylate as inimer agent,methyl acrylate as monomer and Cu0/CuBr2/PMDETA as catalyst system via single electron transfer living radical polymerization (SET-LRP)in DMSO polar solvent at room temperature.In the polymerization process,gas chromatography (GC),nuclear magnetic resonance spectroscopy (1H-NMR) and triple detection size exclusion chromatography (TD-SEC) were used to analyse and characterize the polymerization and the resulting polymers.The results showed that the polymerization rate was significantly fast at room temperature,when the polymerization time was 130 min,the conversion of monomer methyl acrylate was over 99%.The degree of branching for the branched polymer increased gradually with monomer conversion,and the viscosity of branched polymer was low compared to that of the linear polymer at the same molecular weight.Therefore,the characteristic constant of Mark-Houwink would be minimized to 0.290.In addition,the primary chains with low molecular weight (component 1) in the branched polymers were decreasing during the whole reaction.In the late stages of the reaction,the high branched poly(methyl acrylate) component was mainly obtained.关键词：Single electron transfer living radical polymerization;Methyl acrylate;Branched polymer
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发布时间：2021-03-19 - 摘要：PNIPAAm with terminal amino groups was synthesized using 2-aminoethanethiol hydrochloride (AESH) as a chain transfer agent.It was then reacted with methacryloyl chloride to result in macromer,vinly PNIPAAm.A graft copolymer,P(AN-g-NIPAAm) was synthesized through the copolymerization of acrylonitrile (AN) and vinyl PNIPAAm.Using this graft copolymer as an additive,thermal responsive PAN-based membranes were prepared by the immersion precipitation phase inversion method (IPPI).Results from FTIR and NMR indicate that the molecular weight of PNIPAAm can be effectively modulated by changing the concentration of AESH.Then,the weight average molecular weight (Mw) was measured by laser scattering.Results of captive bubble contact angle measurements and turbidity analysis show that the graft copolymers are still thermally responsive,which is more remarkable with higher PNIPAAm content.XPS analysis proves that the PNIPAAm graft chains are enriched at the membrane surface and pore surface during the course of IPPI because of the hydrophilicity of PNIPAAm.Pure water flux at 40℃ (above the LCST of PNIPAAm) is almost twice as that at 25℃ (below the LCST of PNIPAAm),which is due to the conformation change of PNIPAAm chains.All these results demonstrate the synthesized graft copolymers are effective additives for the preparation of thermal responsive PAN membranes.关键词：PAN;PNIPAAm;Macromer;Blending modification;Thermal responsive membrane
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发布时间：2021-03-19 - 摘要：Polypyrrole nanoparticles were prepared by unstirred oxidation polymerization with TSA as dopant,the structure and morphologies of PPy/TSA nanoparticles were examined by X-Ray Powder Diffraction (XRD),energy dispersive X-ray spectroscopy (EDS),scanning electron microscopy (SEM) and transmission electron microscopy (TEM).Results showed that the diameter of the sphere-like PPy/TSA nanoparticles was ca. 40 nm.The electrochemical performances of PPy/TSA were examined by the cyclic voltammetry (CV),galvanostatic charge-discharge tests,the results indicated that PPy/TSA nanoparticles were characterized by promising reversible capacitance and had high rate-capability.Their specific capacitance was 270 F g-1 at charging current of 10 mA cm-2.However,the specific capacitance decreased by ca. 25.5% after 1000 charging/discharging cycles.Electrochemical impedance spectroscopy (EIS) showed that the repeated charge/discharge process could increase the charge transfer resistance,and reduce the high-frequency capacity of PPy/TSA nanoparticles due to the decrease of pore diameter and specific area of the nanoparticles.In contrast,the capacity at low-frequency increased after 1000 cycles.Raman and infrared spectra proved that the deterioration of specific capacity of PPy/TSA nanoparticles was ascribed to the chemical degradation of the PPy/TSA owing to the repeated redox processes of PPy/TSA molecules.关键词：Supercapacitor;Polypyrrole;Oxidation polymerization;Specific surface area;Capacity deterioration
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发布时间：2021-03-19 - 摘要：Three kinds of sulfonated chitosans,i.e.3,6-O-sulfonated chitosan (OCS),2-N-sulfonated chitosan(NCS) and 2-N-sulfopropyl chitosan (PCS) were synthesized.Their chemical structures were verified by FTIR and 1H-NMR.The sulfonation degree of the sulfonated chitosan,which was determined by elemental analysis,could be varied by changing the amount of sulfonation reagent or the reaction time.To evaluate the growth factor-protective ability of sulfonated chitosans,basic fibroblast growth factor (bFGF),which is one of the most important growth factors in tissue repair,was used as the target protein.By in vitro cell culture,the morphology of fibroblasts cultured in different conditions was observed by the costaining of cytoskeleton and cell nuclei,according to which the cell shape indexes such as perimeter,area and aspect ratio were analyzed.The results showed that bFGF/Heparin has the highest values in all cell shape indexes.However,compared to the pristine chitosan (CS),the combination of bFGF with all sulfonated chitosan did not show any effect on the fibroblasts morphology.By cell viability test,the influence of sulfonated chitosan on protecting bFGF activity was studied.Similar to the results of cell morphology,heparin also showed the strongest ability to promote bFGF activity.However,the sulfonated chitosans showed different protecting ability.For OCS and PCS,no significantly effect on bFGF activity was observed.However,NCS could promote the bFGF activity effectively,since the cell viability was significantly higher than that of bFGF/CS,and reached about 70% of bFGF/Hep.Meanwhile,the effect of sulfonation degree was also studied,showing that the cell viability was not affected by the sulfonation degree of chitosan.All these results indicate that the sulfonation position is the key point of the growth factor-protective ability of sulfonated chitosans.关键词：Sulfonated chitosan;bFGF;Bioactivity;Heparin
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发布时间：2021-03-19 - 摘要：A novel biodegradable ABC type triblock copolymer was synthesized by N-carboxyl anhydride ring-opening polymerization.Triblock copolymer mPEG-poly(asparthyl hydrazide)-PLAla (mPEG-PAHy-PLAla) was synthesized by hydrazine aminolysis.DOX was conjugated to the polymer through a pH-sensitive hydrazone bond.High drug-loaded polymeric micelles were obtained via the - interaction between conjugated and free DOX molecules.FTIR,dynamic light scattering,UV and TEM were used in the characterization and measurements.It was found that this polymer/drug complex could form nano-scaled core-shell-corona trilayer particles in aqueous solution.PLAla,PAHy(DOX) and PEG blocks served as the hydrophobic core,pH-sensitive shell and hydrophilic corona,respectively.The drug release experiments displayed a pH-dependent behavior that DOX release rate increased significantly as the environmental pH value dropped from physiologically 7.4 to acidic values resulted from the cleavage of hydrazone bonds and the increasing of hydrophilicity of PAHy segements at lower pH values.This new platform represents a promising candidate in the formulation of targeted drug delivery systems to the low pH tumor tissues.关键词：Poly(aspartic acid);Hydrazone bond;DOX;pH-responsive
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发布时间：2021-03-19 - 摘要：The styrene-isoprene-butadiene terpolymer rubbers (SIBRs) with different molecular weights and monomer ratios were first synthesized by living anionic polymerization method.A series of ABS resins were prepared via bulk polymerization method under the initiation of difunctional initiator modified by the foresaid SIBR tougheners.The molecular structure,morphology and performances of ABS were characterized by typical phase-separating method,SEC,TEM and mechanical testing,respectively.And SEM technique was used for observing the fractured surfaces of specimens after impact in order to study the fracture mechanism.The results show that with increasing the molecular weight of SIBR,the rubber phase size increases and the grafting degree decreases besides gradually obvious phase interface and improved impact properties.Moreover,increasing the styrene content in SIBR could lead to relatively uniform particles,but goes against the impact resistance due to its rigidity.The SIBR with higher molecular weight and lower styrene content restrains the generation and development of cracks to a certain extent,and correspondingly,the ABS displays ductile fracture mode and the fracture mechanisms are mainly abundant crazing,obvious shear yielding and a great many ruptured ligaments.While the SIBR with lower molecular weight and higher styrene content could not efficiently resist the formation and expansion of cracks,ABS is fractured in quasi-ductile modes and matrix plasticization,stripping and stress whitening are the main fracture mechanism.关键词：ABS resin;SIBR rubber;Structure;Mechanical performance;Fracture mechanism
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发布时间：2021-03-19 - 摘要：In order to investigate the influence of polymer aggregate state and chemical environment on the fluorescent performance of nanocrystal,monodisperse CdS nanocrystal is prepared via liquid-solid-solution synthesis (LSS) strategy,and monodisperse CdS nanocrystals/poly(N-isopropylacrylamide) (PNIPAM) complex hydrogel are prepared by radical polymerization.The microstructure and performance of the monodisperse CdS nanocrystal and the complexes hydrogel are characterized by high resolution transmission electron microscopy (HRTEM),X-ray diffraction (XRD),Fourier transformed infrared spectroscopy (FTIR),differential scanning calorimetry (DSC) and photoluminescence (PL).As evidenced from the HRTEM photos and XRD patterns,CdS nanocrystals show well monodispersity,and their size is about 2.8 nm.PL spectrum shows that CdS nanocrystal has a strong emitting peak around 533 nm and a weak emitting peak around 469 nm.DSC curves suggest that the complex hydrogel is thermosensitive,and LCST of which is higher than that of PNIPAM hydrogel.The results of PL spectra and DSC curves indicate that the complex hydrogel shows well thermosensitive-fluorescent performance,the variation of the fluorescent intensity of the complex hydrogel is in good agreement with its phase transformation.With variation of environmental temperature from 20℃ to 45℃,the complex hydrogel changes from swollen state to collapse state,and the chemical environment around CdS nanocrystal changes from hydrophilic to hydrophobic,quantum yield of CdS nanocrystal changes respectively.The lower the environmental temperature is kept,the lower fluorescent intensity of the complex hydrogel is observed,and the fluorescent intensity changes sharply around its LCST.Testing on PL intensity change of CdS/PNIPAM hydrogel as a function of cooling-heating cycles between 20℃ and 40℃ demonstrates that the thermosensitive-fluorescent performance of the CdS/PNIPAM hydrogel is reversible.关键词：CdS;Monodispersed nanocrystals;Complex hydrogel;Thermosensitive;Photoluminescence
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发布时间：2021-03-19 - 摘要：Copolymerization of propylene oxide and carbon dioxide to form poly(propylene carbonate) was carried out under in-situ -Al2O3 supported rare earth ternary catalyst.Two in situ supporting routes were employed,one was dropping ZnEt2into -Al2O3pre-supported Y(CCl3OO)3-Glycerin system (Y(CCl3OO)3-Glycerin/-Al2O3/ZnEt2),the other was reacting -Al2O3pre-supported ZnEt2with Y(CCl3OO)3-Glycerin system (ZnEt2/-Al2O3/Y(CCl3OO)3-Glycerin).However,the two supported catalysts showed unexpected 24%~36% lower catalytic activity than their unsupported analog.By monitoring the ethane evolution during catalyst preparation,it was observed that the diffusion of three components of rare earth ternary catalyst into pores of -Al2O3 leading to molar ratio disparity of the components and decrease in number of active species,and subsequently loss of the catalytic activity.Moreover,the surface hydroxyl groups react with ZnEt2 forming low active species,also leading to catalytic activity loss.Therefore,two main factors were proposed for improving the catalytic activity of supported catalysts,one was the activity of the active species,the other was the number of active species.By adjusting the molar ratio of three components,the time for grinding-stirring during supporting process,the active species of the in situ supported catalyst,the surface chemistry of the support,the catalytic activity of the supported catalyst may be improved significantly,a state-of-the-art optimal catalytic activity for the in situ supported catalyst showed 3.5% increase over the unsupported analog.关键词：Carbon dioxide;Poly(propylene carbonate);Rare earth ternary catalyst;Supported catalyst
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发布时间：2021-03-19 - 摘要：A conjugated polymer (P-0) containing tetraphenylethene (TPE) groups has been designed and synthesized by Suzuki coupling reaction between 1,2-di[4-(6-bromohexyloxy)phenyl]-1,2-di(4-bromophenyl)ethene (monomer 2) and benzen-1,4-bis(boronic acid)propane-1,3-diol diester (monomer 3).A water-soluble cationic conjugated polyelectrolyte (P-1) was obtained by quaternization of P-0 with trimethylamine at the end of side-chains as a novel method for investigation into the aggregation-induced emission enhancement (AIEE) phenomena and mechanism.The structures of P-0 and P-1 were characterized by 1H-NMR,MALDI-TOF-MS and GPC. P-1 is completely soluble in water and insoluble in common organic solvents such as THF and acetone.When a poor solvent such as THF was added into P-1 aqueous solutions,a slight decrease of the fluorescent intensity of P-1 is observed before the volume rate of THF∶H2O arrived at 60%.However,a dramatic enhancement of luminescence is observed and concomitant with an obvious blue-shift of PL maxima when volume rate of THF∶H2O arrived at 70%.Addition of heparin into P-1 aqueous solution showed a gradual increase in fluorescence intensity at 519 nm without PL maxima shift.Compared with its unit analogue,1,2-di[4-(6-(N,N,N-trimethyl ammonium)hexyloxy) phenyl]-1,2-diphenylethene dibromide (MC-1),the emission enhancement of P-1 showed higher sensitivity and better linearity than that of MC-1. Since heparin has four negative charges per repeat unit,and each polymer repeat unit has two positive charges,the concentrations for the positive and negative charges are the same (2.0 mol/L or 20.0 mol/L) at the saturation point.This indicates that the aggregation-induced emission enhancement stems from the restriction of their intramolecular rotations due to electrostatic attraction as the main driving force between the oppositely charged polymer and heparin,which can eliminate some disturbance factors such as aggregation-caused quenching of light emission.In summary,the present results indicate that cationic conjugated polyelectrolyte with AIEE property is expected to be generalized for studying AIE(E) mechanism and the detection of biological analytes of interest.关键词：TPE;AIEE;Heparin;Conjugated polyelectrolyte
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发布时间：2021-03-19 - 摘要：Two types of resins (F401 and PPH) were selected to develop microporous membranes using cast film extrusion followed by stretching.The roles of the molecular weight and molecular weight distribution on the row-nucleated lamellar crystallization and micropore formation were investigated.The relaxation spectra of the resins were examined by dynamic rheology.The content of high molecular weight component (Mw 106) for PPH was 1.5 times larger than that of that for F401. Under the same temperature,the relaxation time of PPH was much longer than of F401.The crystalline orientation was measured by Fourier transform infrared spectroscopy (FTIR).At the same draw ratio (DR),the crystalline orientation of the precursor film for PPH was higher than that of F401.Scanning electron microscopy (SEM) images of the membrane surface showed the high molecular weight component or long chains played a remarkable role in the formation of mircopores and were included in the part of bridging structure as tie chains.Under the same processing condition,the pore structure of microporous membrane for PPH was more regular and uniform.The porosities of the microsporous membranes were tested by the liquid absorption method.For both resins,the porosities of the microporous membranes increased with DR.The content of high molecular weight component of the resins primarily influenced the pore structure of the microporous membranes.关键词：Polypropylene;Relaxation time;Lamellar structure;Orientation;Microporous membranes
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发布时间：2021-03-19 - 摘要：In the present investigation,the effect of the chain structure and aggregation state of bisphenol A polycarbonate (PC) on the crystallization kinetics and morphology of the poly(butylene carbonate) has been studied by DSC and POM.It was found that the addition of bisphenol A polycarbonate A promoted the nucleation of the poly(butylene carbonate),while the chain structure of PC had the opposite influence on the crystal growth rate of the poly(butylene carbonate).The linear bisphenol A polycarbonate polycarbonate accelerates the crystal growth rate of poly(butylene carbonate),while the long chain-branched bisphenol A polycarbonate decelerates it.The phase images of the blends of aliphatic polycarbonates and bisphenol A polycarbonate were obtained under the tapping mode by atomic force microscopy (AFM).The linear bisphenol A polycarbonate shows isolated irregular aggregation with phase size of ca.200 nm in the poly(butylene carbonate),while the formation of condense and continuous network structure by long branched bisphenol A polycarbonate might explain the deceleration effect on the crystal growth rate of the poly(butylene carbonate).关键词：Aliphatic polycarbonates;Bisphenol A polycarbonate;Blends;Crystallization
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发布时间：2021-03-19 - 摘要：Through semi-batch emulsion polymerization,hydrophobically modified associative thickener latexes were prepared using methacrylic acid and ethyl acrylate as the main monomers,behenyl polyethoxylate ether methacrylate as the functional monomer and dially phthalate (DAP) as the crosslinking agent.Ammonium persulfate was used as the initiator.Properties of the thickener latexes prepared with different amount of DAP,including viscosity,particle size and size distribution,were determined.Evolutions of the viscosity and light transmittance with increasing pH in the thickener latexes were followed.With pH starting from 6.0,light transmittance of the thickener latexes sharply increased,reached a maximal value at pH around 8.1,it remained relatively constant with continuing pH increase.As to the viscosity,a significant increase was also observed at the same time with the light transmittance,followed by a slow decline afterwards.It was found that the properties of the thickener latexes were closely related to the DAP amount used in their preparation.Thickening performance and shearing resistance of the associative thickeners were enhanced when thickener polymers were slightly crosslinked with a low amount of DAP;A too large amount of DAP led to deteriorated swelling and dissolution for the latex particles under alkaline condition,reducing therefore the thickening performance of the thickener.The results were fully interpreted and the thickening mechanism was discussed.关键词：Associative latex thickener;BEM functional monomer;Crosslinking agent;Viscosity;Light transmittance
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发布时间：2021-03-19
Research Article
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