最新刊期
卷 ， 期 7 ， 2006
- 摘要：Chitosan dissolved in CH3 COOH／NaCl aqueous solution was irradiated at various conditions,and the influence of H2O2,N2O,isopropanol,pH and molecular weight of chitosan on the radiation degradation of chitosan in aqueous solutions was investigated．In acidic solutions(pH=3),the degradation of chitosan in aqueous solutions might be attributed to the interaction with both·H and·OH radicals．The degradation of chitosan was slightly faster in the presence of H2O2 or N2O,because the concentrations of·OH radicals increased slightly．The degradation of chitosan was inhibited obviously after adding isopropanol,due to the decrease of both·H and·OH radicals in the presence of isopropanol．With the pH of the solution approaching neutral,the concentration of ·H decreased and the·OH radicals increased rapidly with the presence of H2O2 or N2O．The chain scission of chitosan was promoted significantly after adding H2O2 or saturated with N2O．In addition,it was found that the rate constant of radiation degradation of chitosan increased with the decrease of molecular weight of ehitosan．UV and FTIR analyses of radiation-degraded chitosan manifested that except for carbonyl groups generated at the ends of molecular chains,no obvious change in the main chain structure of radiation—degraded chitosan,comparing with unirradiated chitosan．Therefore,gamma irradiation can be expected as an effective way to control the molecular weight of chitosan without obvious change in its backbone structure．
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发布时间：2021-03-19 - 摘要：Ethylene and p-allyltoluene were copolymerized in the presence of metallocene catalyst rac-ethylenebis-(indenyl)zirconium dichloride—MAO．The polyethylene(PE)copolymer prepared was brominated using radical inifiator and N—bromosuccinimide．1H-NMR showed that each benzyl site was substituted with one bromine atom．Methyl mathacrylate and t-butyl acrylate were polymerized via ATRP process with brominated PE copolymer as macromolecular initiator and CuCl／N．N,N',N',N''-pentamethyldiethylenetriamine as catalyst and the corresponding graft copolymer was synthesized．Polyethylene—graft-poly(t-butyl acrylate)was subsequently converted by hydrolysis with hydrochloric acid to polyethylene—grafl—poly(crylic acid),which was father converted to polyethylene—graft—poly(sodium acrylate)hy reacting with sodium hydroxide．Mulao test indicated that the polarity of polyethylene graft eopolymers relative to that of polyethylene was improved greatly．
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发布时间：2021-03-19 - 摘要：2,4,6-tri(hydroxylphenylmethylamino)-s-trizine(MFP)was synthesized and its structure was characterized by infrared spectroscopy(IR),1H-NMR and element analysis．The kinetics and mechanism for curing of diglycidyl ether of bisphenol A(DGEBA)with MFP were studied by differential scanning calorimeter(DSC)and in situ IR．The results of dynamic DSC thermograms showed that two peaks presented in the proceeding of reaction because of two kinds of active hydrogen in the structure of the MFP molecule,and the first exothermic peak resuhed from the the reaction of amine with epoxy group(Ea=70．5 kJ·mol-1,calculated by Kissinger method)and the second exothermic peak resulted from the reaction of hydroxyl with epoxy group(Ea=86．5 kJ·mol-1,Kissinger method)by comparing with the curing process of DGEBA with a model compound 2,4,6-tri(o-methylhydroxyphenyl—methylamino)-s-trizine(MFoP)．The results of in situ FTIR confirmed this conclusion．
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发布时间：2021-03-19 - 摘要：A series of ionically crosslinked polyampholyte hydrogels were prepared by free radical aqueous copolymerization of acrylamide and the ionic complex of(N,N-diethylamino)ethyl methacrylate and acryl；cacid (poly(acrylamide-co-N,N-diethylaminoethyl methacrylate-co—acrylic acid),designated as PADA)．The investigation indicated that PADA gels exhibited peculiar erosion phenomenon under non—contact direct current electric fields．The erosin rate of PADA gels was related to the voltage of electric field,the concentration of salt solution,pH value of buffer solution．the molar ratio of anionic／cationic monomers,valence of ion and so on．For instance,the erosion rate increased with an increase of voltage or the concentration of salt solution．The erosion kinetics revealed that the erosion rate of PADA gels was almost invariable in experiments．
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发布时间：2021-03-19 - 摘要：Polypropylene(PP)microporous membranes were prepared with the composite diluents of soybean oil and di-n-butyl．phthalate(DBP) via thermally induced phase separation(TIPS)．The effects of nano-CaCO3 nucleating agent and nano—CaCO3／pimelic acid bicomponent nucleating agent on the crystalline morphology and mehing behaviom of the PP／soybean oil／DBP system,and on the microstructure of PP membrane were investigated.The experimental results showed that with addition of 0％～4％ single nano-CaCO3 nucleating agent the peak temperature of melting curve of PP in PP／soybean oil／DBP system varied from 150．7 ℃ to 151．3℃,while the peak melting temperature of pure PP is 165℃．The differential scanning calorimetry(DSC)showed that the addition of bicomponent nucleating agent nano-CaCO3(1％-4％)and pimelic acid(0．5％)induced two peaks on the mehing curve．Wide-angle X-ray diffraction(WAXD)measurements proved that PP formed β—phase and α—phase with addition of bicomponnent nucleating agent nano-CaCO3(1％-4％)and pimelic acid(0．5％),while the addition of single nano-CaCO3 nucleating agent resulted in only PP crystals of α-phase,which was consistent with the results of DSC．The addition of single nano-CaCO3 nucleating agent in PP／soybean oil／DBP system had unremarkable effect on the morphology of PP membrane．While nano-CaCO3／pimelic acid(1％／0．5％)bicomponent nucleating agent was used,the PP microporous membrane showed smaller and regular pores．When the nano-CaCO3／pimelic acid content was 2％／0．5％and 4％／0．5％。PP micmporous membrane showed more tiny irregular sphendites,as well as larger pores,which were related to the formation of β phase．
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发布时间：2021-03-19 -
STUDY ON POLYMERIZATION PROCESS OF STYRENE IN ANIONIC POLYURETHANE IONOMER AQUEOUS DESPERSION SYSTEM
摘要：Anionic polyurethane ionomers including amphipathic nanoparticles were prepared by self-emulsifying method．When they were used as emulsifying agents to make styrene polymerize in them,anionic PS／PU nanocomposites dispersions with different PS／PU ratios(W／W)were prepared in situ．The polymerization process of styrene in polyurethane ionomers was studied．The sizes and distributions of the particles were measured by dynamic light scattering,and the structure and morphology of the nanocomposites were observed by transmission electron microscope．The results indicated that PS／PU nanocomposite emulsion with core-shell structure,based on anionic polyurethane as shell,polystyrene as core,was prepared,and when PS／PU ratios were higher than 50：100,some degree of particle aggregations happened．- 2
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发布时间：2021-03-19 - 摘要：Three types of core／shell latexes which containing epoxy groups in the core layer or on the shell layer and carboxyl groups on the shell layer respectively were synthesized by seeded semiconfinuous emulsion polymerization．Two types of reactive blend latexes were obtained by blending epoxy group functional latex and carboxyl group functional latex．The core／shell morphology of latex particles was clearly observed by TEM．The size and distribution of the emulsion particles were investigated by DLS analysis．The latex particles are narrowly dispersed with polydispersity index of 0．062 and number-average diameter of 76 nm．The diffusion and cross—linking of polymer chains for blend latex particles were investigated by measurement of gel content,swell ratio and FTIR．The influences of different core／shell structure of blend latexes on mechanical properties of the films were described．The results intheate that the polymer chains diffusion and cross—linking reaction are enhanced when the epoxy groups are in the core layer and carboxyl groups in the shell layer of latex particles,as a result,the physical and chemical performance of latexfilms are improved．The tensile strength of blend A film is 20．3 MPa when the glycidyl methacrylate(GMA) content is 10wt％．
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发布时间：2021-03-19 - 摘要：Morphology of poly(styrene—block—dimethylsiloxane)(PS—b-PDMS)copelymer thin films was analyzed by atomic force microscopy(AFM)observation and transition electron microscopy(TEM)measurements．The asymmetric copelymer thin films spin—cast from toluene on mica presented a mesh-like structure,which was different from the spheriealop structure in the bulk．The annealing temperature affected the surface morphology of PS-b-PDMS eopelymer thin films,PDMS microdomains at the surface were increased when the annealing temperature was higher than the PDMS glass transition temperature．The morphology of PS—b-PDMS copelymer thin films was different from solvent to solvent,for thin films spin-cast from toluene,the PS phase was pits in PDMS matrix．While the thin film spin-cast from cyclohexane solution exhibited an island—like structure．small separated PS phase appeared as protrusions over the macroscopically flat surface．The microphase structures of the PS—b-PDMS copolymer thin films were also strongly influenced by the different substrates,for an asymmetric block copolymer thin film,the PDMS and PS phases on silicon substrate presented lamellae structure parallel to the film surface．
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发布时间：2021-03-19 - 摘要：Poly[2-methoxy-5-(2'-ethylbexyloxy)-p-phenylenevinylene](MEH-PPV)is a typical example of solution proeassable conjugated polymers for polymeric light emitting diodes application,which shows good solubility in conlnlon organic solvents．However,gelation or micro-gelation always occurs during the polymerization process．Herein,we report the synthesis of fully soluble MEH—PPV by ultrasonic irradiation method．The raw material was 4-methoxyphenol,and ultrasonic irradiation method was used in the etherification,bromomethylation and polymerization．The polymer is prepared from the bis—bromomethyl monomer through the Gilch route．Compared with the conventional mechanical stirring,ultrasonic irradiation method has shown great advantages with respect to the shorter reaction time,lower reaction temperature,higher yields and higher molecular eight(Mn)of MEH-PPV．The optimized reaction conditions including reaction solvent,temperature,and time,were determined for the related etherification,bromomethylation and polymerization with ultrasonic method．Especially,using ultrasonic method,the gelatification in the polymerization had been overcome．MEH—PPV obtained was fully soluble in THF and chloroform and no gel or micro—gel existed．The structures of the intermediate products and MEH-PPV were determined by IR and 1H—NMR．It was found the MEH—PPV synthesized by ultrasonic irradiation processes had higher luminescence quantum efficiency than that by mechanical stirring．
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发布时间：2021-03-19 - 摘要：Isopropyl methacrylate(iPMA)was selected to copolymerize with N-isopropylacrylamide(NIPAM)for preparing hydrophobically modified temperature—sensitive microgels with tunable phase-transition temperature．Transmission electron microscopy(TEM),turbidimetric method,dynamic light scattering(DIS)technique and differential scanning calorimetry(DSC)were employed to investigate the microgels．TEM and DIS results show that the microgels prepared have regular spherical morphology．DIS,turbidimetrie analysis and DSC show that the volume-phase transition temperatures(VPTTs)of the P(NIPAM—co-iPMA)microgels can be successfully tuned through changing the content of the hydrophobic comonomers．the VPTTs of the microgels decrease almost linearly with the increase of the feed ratio of iPMA．
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发布时间：2021-03-19 - 摘要：Sodium salt of α-olefin sulfonates(AOS),a mixture of sulfonated unsaturated linear hydrocarbon with carbon numbers from C12 to C14,is used in methyl methacrylate／butyl acrylate(MMA／BA)soap-free emulsion copolymerization．The reactivity ratios of AOS—MMA are determined to be rA=1．98 and rM=0．034 for AOS and MMA respectively．In order to assure distribution of AOS units on the out—shell layer of the particles,a semi-continuous emulsion polymerization is used．Latex of high solids of up to 60％ has been obtained with 5％ AOS．And with 1％ AOS,larex solids can reach to 45％ with good stability,whereas this value is limited to 40％ with sodium dodecyl sulfate (SDS) as surfactant．The particle size is in constant increase with latex solids combined with a sharp decrease in particle number when AOS is used；while the particle size and number of particles are kept relatively constant when SDS is used as surfactant．This is attributed to the fact that SDS can either adsorb on or desorb from the particle surface,and AOS would be fixed on a position on the particle surface once copolymerized with MMA and BA．The AOS prepared latex also shows a narrower particle size distribution,and the latex with 35％ is stable after a shelf standing of up to one year．
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发布时间：2021-03-19 - 摘要：Elastomeric replica surface relief structures were prepared by molding poly(dimethylsiloxane)(PDMS) elastomers on the photo-inscribed surface—relief-gratings of azo polymer film．Then polymide(PI)solution was microcontact printing with the elastomeric PDMS on quartz slides．Good surface-relief-grating structures were formed on the quartz slides．Then the quartz slides covered with surface-relief-grating PI films were assembled to liquid crystal(LC)cell．The transmittance passing through the cell between crossed polarizers changed periodically with a regnlas 90°separation of the rotational angle.The pretilt angle of the cell was found to be 2．8°．The results showed that the PI film with surface—relief-grating structures by micrecontaet printing process has good liquid crystal alignment ability．This alignment method call be considered as potentially useful technology in the future LC display (LCD)industry．
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发布时间：2021-03-19 - 摘要：Elaboration of hybrid organic-inorganic nanoparticles by heterogeneous polymerization technology arouse highly interest all over the world because of both the direct application in paint,water-borne adhesive,coating formulations and the potential application in bio—technology field．A new type of organic—inorganic hybrid materials synthesized by the monomers containing alkoxysilane and vinyl groups is highly evaluated because it improves the chemical bonding between the organic and the inorganic components．However,it is seldom used to synthesis nanoparticles because the hydrolysis and condensation of alkoxysilane groups are hardly controlled in heterogeneous polymerization．In this paper,the mechanism of the emulsion copolymerization of 3-trimethoxysilylpropyl methacrylate (MPS)and styrene is studied．The mechanisms of particle morphology and microstructure formation at different conditions are analyzed by following the resultant of hydrolysis using GC,particle size and its distribution by DIS,and the characterization of the morphology of the latex and the microstructure of the polymer with transmission electron microscopy(TEM),infrared(IR)and solid—state NMR．It is found that the processes are carried out with different mechanism at various operating conditions,and the bydrolysis and condensation rates in the media and the partitioning of MPS are the most important parameters．
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发布时间：2021-03-19 - 摘要：A series of polyampholyte hydrogels were prepared by free radical aqueous copolymerization of ionic complex of acrylic acid and(N,N—diethylamino)ethyl methacrylate and acrylamide(PADA gels)．Owing to the hydrogen bonding interaction among acrylic acid molecules,PADA hydrogels in water had the maximum deswening when the molar ratio of anionc and cationic monomers (A／C)was 1.55,but not 1．0 as ordinary．By comparison with covalently crosslinked polyampholyte hydrogels,PADA gels were mole pH sensitive in swelling behavior．The swelling experiments indicated that PADA gels deswelled in buffer solutions of pH 3—4,but swelled when the pH deviated from this pH range．Furthermore,the swelling degree of PADA gels decreased with an increase of A／C in buffer solutions of pH value below 3 and increased in the buffer solutions of pH value higher than 4．The ion strength greatly influenced the equilibrium swelling ratio of PADA gels in the solutions of salts with varied valences．PADA gels exhibited typical antipolyelectrolyte effect in univalent NaCl solutions．In multivalent CaCl2 and trisodium citrate (TSC)solutions,however,PADA gels also exhibited amtipolyelectrolyte effect only in lower concentrations of salt．In salt solutions with higher concentration,the swelling ratios of PADA gels decreased with the increment of concentration．This might be attributed to the ionic crosslinkage formed by multivalent ions．Similar to the influence of pH on the swelling degree of PADA gels,the swelling ratios of PADA gels decreased in CaCl2 solutions with the increment of A／C,whereas,increased in TSC solutions with the increment of A／C．The unique behavior seems to be related to the charge characteristics of multivalent ions．
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发布时间：2021-03-19 - 摘要：The effects of injection temperature on the dispersion phase and mechanical properties of polyoxymethylene／thermoplastic polyurethane elaster(POM／TPU)blends were investigated．The experimental results shewed that the notched impact strength of POM／TPU blends was greatly influenced by injection temperatures,and the highest value,19．1 kJ／m2,appeared at 195℃,two times as high as the value obtained at 175℃．Because the viscosity ratio of POM to TPU changed with temperature,and reached 1 at around 195℃,and TPU formed strips—like structure in POM matrix along with the flow direction of the melt during injection,which could effectively absorb impact energy,prevent growth of crazes and formation of cracks．With increase of injection temperature,the average particle size of TPU decreased,and the particle size distribution became narrower．It is an effective way to toughen POM by adjusting the viscosity ratio of the dispersion phase and the matrix and controlling the morphology of the dispersion phase．
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发布时间：2021-03-19 - 摘要：The chemical states of titanium of TiCl4·donor,and MgCl2-supported Ziegler-Natta catalysts obtained by milling method and precipitation method,and the interactions between TiCl4,donor,and MgCl2 were studied by XPS and IR methods,and the electron binding energies of Ti2p3 in TiCl4·Mgcl2,TiCl4·donor and TiCl4·MgCl2·donor and the characteristic adsorption peaks of C＝O bond or c—O—c bend in MgCL2·donor,TiCL4·donor and TiCL4·MgCL2·donor were compared．The results showed that the oxidation states of titanium species in Ziegler-Nana catalysts using different compounds,such as benzoate,phthalate,1,3-diether as internal electron donors weRE different．The internal donor did not react directly on titanium,but transfered electron to titanium through MgcL2 as medium,and inereased the electron-cloud density of Ti species,and thus decreased the oxidation state and electron binding energy of Ti species．
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发布时间：2021-03-19 - 摘要：Poly(phthalazinone ether nitrile ketone)s(PPENK)modified via hydrolysis of cyano groups with NaOH was studied in order to find a hydrophilic resin applicable to heat—resistant waterborne coatings．The propeties of hydrolyzates．HPPENKa(O．5 h),HPPENKb(1．5 h)and HPPENKc(3．5 h),were measured by differentia lscanning calorimetry(DSC),thermogravimetrie analysis(TGA),contact angle(water)and solubility．The results indicated that the nitrile conversion ratio and Tgof hydrolyzates increased whereas the weight loss ratio of HPPENK decreaased as bydrolysis time was prolonged．As expected,the hydrophilicity of HPPENK was improved greatly,e.g. when CN conversion ratio was 93．82％,the water contact angles was decreased from 75．3°of PPENK to 54．4°of HPPENK．By studying the effect of the reaction co-solvents,reaction temperature and NaOH concentration on hydrolysis,the optimal synthetic technology was found to be reaction at 120℃ with 6 mol／L NaOH solution and DMAc as co-solvent．Aqueous dispersions based on three modified resins were prepared and their storable stability were listed a8 follows：HPPENKc>HPPENKb>HPPENKa．Especially,the deposition of HPPENKc dispersion was nDt found aflter more than 30 days．The structures of hydrolyzares were characterized by FT IR,1H-NMR．
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发布时间：2021-03-19
Research Article
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