最新刊期
卷 ， 期 3 ， 2006
- 摘要：Polypropylene／clay nanocomposites were prepared with three monomers solid—phase grafted PP as compatibilizer The nanostructures were characterized by X—ray diffraction (XRD) and transmission electron microscopy(TEM)．Dynamic thennogravimetric analysis(TGA)of PP and the nanocomposites was petformed Flynn-Wall-Ozawa and Kissinger equations were used to compute the weight loss data and calculate the activation energias of decomposition．The temperature of weight loss of 10％ for the nanocomposites is 40 K higher than that for the neat PP．The decomposition region for the nanocomposites was also found to be much narrow than that for the neat PP．The apparent activation energy of thermal decomposition of the nanocomposites was 50％ higher than that of the neat PP.
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发布时间：2021-03-19 - 摘要：Suspension—emulsion combined polymerization(SECP)process,in which methyl methacrylate(MMA) emulsion pdymefization constituents(EPC)were drop—wisely added to styrene(St)suspension polymerization system,was applied to prepare polystyrene—poly(methyl methacrylate)(PS—PMMA)cole-shell composite particles with a great size The composition of these composite particles was analyzed by FTIR．extraction．1H-NMR and13C-NMR methods．It was found that the molar ratio of MMA／St units in composite particles increased and the content of PMMA latex particles decreased with the increasing of polymerization time after the addition of EPC．So,it was evidenced that PMMA latex particles would coagulate with PS suspension particles in SECP polymerization and a transfer process existed between the two kinds of particles after the coagulation The polymeric composite particles were composed of PS,PMMA and MMA—St copolymer．
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发布时间：2021-03-19 - 摘要：By reactions of FeCl3,NiCl2,CuCl2 and Pb(Ac)2 with polyvinyl alcohol fiber,the complexes of(A) PVA—Fe(Ⅲ),(B)PVA-Ni(Ⅱ),(C)PVA．Cu(Ⅱ),and(D)PVA—Pb(Ⅱ)have been synthesized．The complexes still keep the shape of fiber．They were characterized by IR and XPS measurements．The IR band vO-H shifts to higher wavenumber by 65～86 cm-1,from 3300 cm-1(PVA)to 3365 cm-1(A),3388 cm-1(B),3386 cm-1(C) and 3383 cm-1(D),respectively．And band vC-O shifts to higher wavenumber by 3～5 cm-1：from 1087 cm-1 (PVA) to 1091 cm-1(A),1090 cm-1(B),1092 cm-1(C)and 1090 cm-1(D),respectively．The binding energy of O1s and Fe2p was changed during the formation of the PVA—Fe(Ⅲ)complex．XPS studies indicated that the single peak of O1s in PVA splitted into double peaks for O18 in PVA-Fe(Ⅲ)；and the Fe2P peak shifted from 711.2 eV to 710．9 eV．All these results inlplied the bonding of OH oxygen with metal ion in the complexes.
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发布时间：2021-03-19 - 摘要：The carbocationic polymerization of styrene(St)initiated by using H2O／TiCl4 was conducted at-60℃ in dichloromethane(CH2Cl2)／hexane(n—Hex)(40／60,V／V)in the presence of pyridine(Py)．The effect of Py,H2O and TiCl4 concentrations on the polymerization rate,molecular weight and molecular weight distribution(MWD or Mw／Mn) of polystyrene(PS)were investigated in detail．The results show that a desirable polymerization process with a relatively slow polymerization rate and PS products with relatively narrow molecular weight distribution (MWD,Mw／Mn≈1．8)were obtained in the presence of a small amount of Py．The polymerization rate and molecular weight of PS obviously decreased while MWD maintained almost unchanged(Mw／Mn≈1．8)with the increase of Py concentration．The kinetic order with respect to Py concentration was calculated to be-0 72 on the basis of flint—order dependence of polymerization rate on monomer concentration．The polymerization rate increased,but the molecular weight of PS products decreased with increasing H2O concentration in the polymerization system．The kinetic order with respect to H2O concentration was calculated to be 0．72 on the basis of first—order dependence of polymerization rate on monomer concentration．Both the polymerization rate and the molecular weight of PS products increased greatly with the increase of TiCl4 concentration and a near second-order(β=1.86)dependence on TiCl4 concentration was observed,which may be attributed to the dimer formation of TiCl4．The experimental resuhs also showed that the monomer conversion as well as the molecular weight of polymer products increased．but MWD almost kept unchanged with the polymerization time．The number—average molecular weight of polymers increased linearly with monomer conversion．
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发布时间：2021-03-19 - 摘要：A titanocene complex of η5-pentamethylcyclopentadienyltri—P—chlorophynoxy—titanium[Cp*Ti(O-C6H4-Cl-p)3] was used in combination with methylaluminoxane (MAO) as cocatalyst to catalyze propylene polymerization．The effects of polymerization conditions such as temperature and Al／Ti molar ratio(nAL／nTi)on catalytic activity and molecular weight of polypropylene obtained were investigated．It was found that under the given polymerization conditions the molecular weight of polypropylene increased as the polymerization proceeded at the early stage,and the molecular weight distribution remained narrow(Mw／Mn=1．5～1．8),which displayed the behavior of quasi—living polymerization；while the bimodal GPC profiles indicated a multi—site system at the early stage．In addition,a kinetics equation was presented to study propylene polymerizations at the depressing stage of polymerization rate,and the depressing coefficients under various conditions were obtained．With the depressing coefficient,the polymerization rate could be estimated at any time of the depressing stage．
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发布时间：2021-03-19 - 摘要：A series of main chain liquid crystalline copolyesters with X-shaped two—dimensional mesogenic units and crown ether cycles of trans-4,4’-bis(4-hydroxyphenylazo)dibenzo-18-crown-6 was synthesized via solution cocondensation polymerizations from 4,4’-(α,ω-hexanedioylxy)dibenzoyl dichloride(M1),2,5-bis(P-octyloxybenzoyloxy)hydroquinone(M2)and trans-4,4'-bis(4-hydroxyphenylazo)dibenzo-18-crown-6(M3)as the monomers．The molecular weights of copolyesters are not high,and the[η]of the copolyesters ranges from 0．37～0．25 dL／g．The monomer structures were identified by using elementary analysis,IR,UV,1H—NMR and MS etc．All the copelyester samples are yellowish powders and insoluble at room temperature in THF and CHCl3 except sample CP9 The properties of eopolyestars were investigated by using GPC,[η],DSC,TG,WAXD and POM．It was found that all the copolyesters went into liquid—crystal phase when they were heated over their melting temperature(Tm)．In their liquid crystalline state,the typical mosaic texture or focal—conics texture or broken fan texture of smectic phase,and ball granul texture or thread texture or schlieren texture of nematic phase can be observed．Their melting temperature and isotropization temperature(Ti)changed regularly with varying the trans-4,4'-bis(4-hydr-oxyphenylazo)dibenzo-18-crown-6 unit content in the copolyesters．The WAXD studies also evidenced the liquid crystallinity of these copolyesters.
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发布时间：2021-03-19 - 摘要：Nanocomposites based on polypropylene(PP)and multi—walled carbon nanotube(MWNTs)were manufactured by melt blending．Thermal gravimetric analysis(TGA)showed that carbon nanotubes significantly enhanced the thermal stability of polypropytene in nitrogen．The temperature of onset decomposition was 44 K higher than that of neat PP for nanocompositcs with 3wt％ of MWNTs loaded The effect of MWNTs on the crystallization and melting behavior of polypropylene was not observed．Rheological behavior of PP／MWNTs nanoeomposites showed that storage modulus(G’)and loss modulus(G”)increased with increasing nanotube content．At low frequency．the steady shear viscosity of nanocomposites with 1 wt％of MWNTs was minimal and that of the sample with 5 wt％ nanotube was maximal．Shear thinning tendency increased with increasing frequency．The volume resistivity and surface resistivity of nanocomposite with 5 wt％MWNTs were 9 and 4 order of magnitude．respectively lower than those of the neat PP．It shows that the electrical conductivity can be improved obviously by incorporating a little MWNTs.
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发布时间：2021-03-19 - 摘要：The effect of self-seeding nucleation on the crystallization behavior of paly(trimethylene terephthalate) (PTT) was studied．The result of differential scanning calorimetry(DSC)indicated that the crystallization temperature of PTT increased obviously under the influence of self-seeding nucleation．Avrami equation was applied to analyze the isothermal crystallization process of PTI.The average value of Avrami exponent is n=3．34,suggesting that the primary crystallization may correspond to a three—dimensional spherulitic growth．Self-seeding nucleation leads to the decrease of crystallization active energy and chain folding work,promotes the overall crystallization process of PTT．
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发布时间：2021-03-19 - 摘要：A series of porous poly(N—isopropylaerylamide-co—acrylic acid)[P(NIPA—co一AA)]hydrogels were prepared by radical polymerization using PEG400,1000,6000 as pore-forming agents during the reaction process．SEM macrographs revealed that the pore size of the hydmgels could be modulated by adjusting the molecular weight or the amount of PEG．The swelling ratio of the porous gels at room temperature was higher than that of the conventional P(NIPA—co-AA)hydregels due to the porous micrestructure．When the hydrogels were transferred to an aqueous medium of 60℃．they shrank rapidly to an equilibrium state and exhibited faster response properties．What’s more,the swelling ratio and responsive rate increased with elevating the molecular weight or the amount of PEG．The prepared mocreporeus hydmgels have potential applications in controlled release of macromolecular active agents．
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发布时间：2021-03-19 - 摘要：Natural rubber(NR)／modified montmorillonite(USM)nanocomposites were prepared by the grafting and intercalating method in latex with monomer butyl acrylate(BA)．X—ray diffraction(XRD)and transmission electron migcrograph(TEM)indicated that the gallenes of USM were obviously enlarged by the effect of BA polymerization in situ between the layers,and USM particles were dispersed in rubber matrix on a nanometers scale,which illuminated the formation of intercalated nanocomposites．The dynamic mechanical analysis(DMA)showed that Tgof NR／USM／PBA nanoeomposites shifted to higher temperature．and tanδ values of vulcanizates at 60℃ were decreased,meaning a good rolling resistance．NR／USM／PBA nanocomposites also showed improved tensile strength,tear strength and other mechanical properties．
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发布时间：2021-03-19 - 摘要：It was found that yttrium tris(2,6-di-tert-butyl-4一methyl phenolate)could be an effective initiator for polymerization of aerylonitrile．The study of influence of solvent showed that DMF with high dielectric constant gave higher conversions(>94％)at 50℃,3 h．The kinetics of acrylonitrile polymerization using Y(OAr)3,in DMF was investigated by the weight method．The results indicated that the rate of polymerization showed a first order relationship with respect to both the monomer(AN)concentration and the initiator[Y(OAr)3]concentration,respectively,and the overall activation energy of polymerization reaction was 22．1 kJ·mol-1according to the Arrhenius equation．13C-NMR studies showed that the PAN prepared had a syndiotactic triad(rr)content of 52％．
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发布时间：2021-03-19 - 摘要：An o—cresolphthalein immobilized cellulose membrane as pH sensitive material was described．The o-cresolphthalein was first reacted with formaldehyde to produeea polymer．The polymer was abbreviated to CPF(o-cresolphthalein—formaldehyde)．Then the CPF was physically entrapped in cellulose diacetate membranes．Finally the membranes were hydrolyzed in 0．1 mol／L NaOH solutions for 24 h to reduce the response time．Advantageous features of the pH—sensitive membrane(CPF—HCDA)include(a)easy of fabrication,(b)a large working range from pH 8．0～13．0,(c)rapid response(2～30 s)and(d)long-term stability for at least six months．So it is a promising material for optical pH sensors and pH test paper of repeated use．
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发布时间：2021-03-19 - 摘要：Bv means of the closely intermeshing twin—screw extruder as the reactor and the mixed styrene(S)and butadiene(B)as the monomer,a novel multi—block copolymer(S／B)was synthesized by bulk polymerization with the organic lithium initiator．The PB blocks of eopolymers were cleaved by reaction with hyarogen peroxide in the presence of osmium tetroxide,then the small molecules were removed out of the system by purification It was confirmed by1H—NMR and FTIR,that the double bonds in the molecule chains of the copolymers were fully oxidized,on the other hand,the segments of polystyrene in the molecules of the copolymers were kept intact The segments of polystyrene after oxidization were characterized by GPC cooperating with the multi—angle laser light scartering instrument(MALLS)．It was found that the molecule of the copolymers was made of a segment of polystyrene with Mn of 1×1 04～5×104linking tens of S-B blocks．Cooperated with the survey of TEM photographs,it was confirmed that processing could decide the structure of the polymer molecules．
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发布时间：2021-03-19 - 摘要：A serials of acrylate monomers containing long conjugated azobenzene groups were prepared and polymerized in N,N-dimethylformamide(DMA)using 2,2'-azobis(isobutyronitrile)(AIBN)as initiator at 70℃．The monomers and polymers were characterized by FTIR,1H-NMR and UV．The molecular weights of polyacrylates were determined by gel permeation chromatography(GPC)．The third-order nonlinear optical properties of these polymers were determined by the Z—sean technique with 8 ns pulses at 532 nm,and the relationship between nonlinear optical properties and the molecular structures of substituted chromophores was investigated．The results revealed that all these polymers possessed well nonlinear absorption,and enlarging π-electron conjugated length and strengthening D-π-A push—pull capacity of side—chain chromophores of polymers will effectively enhance the third-order nonlinear optical properties of polymers．
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发布时间：2021-03-19 - 摘要：A tree—type full substituted phenylalanine—poly(lysine)dendrimer(Phe—PL dendrimer) aws synthesized．Poly(lysine)dendrimer(generation 3)(PL dendfimer G3)was prepared using N,N'-di(fluorenylmethoxy—carbonyloxy)-L-Lysine as both the branching agent and the dendritic branch by solid phase peptide couphng method on 1％ cross—linked polystyrene bead functionalized with Fmoc-glycine．Then Phenylalanine was bound to PL dendfimer G3 to form full substituted Phe—PL dendrimer．The product was characterized with MALDI—TOF MS and NMR．The results of MS demonstrated that they both Fmoc—PL and Phe—PL dendrimers G3 have exclusive molecular weights．indicating that they could be developed as a potential ideal nonviral vector．
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发布时间：2021-03-19 - 摘要：Photografting(λ>300 nm)of trimethylol propane triacrylate(TMPTA)onto the surface of low-density polyethylene(LDPE)films was investigated at room temperature in a mixed solvent composed of acetone and water,using benzophenone(BP)as all initiator．It seems that the polyfunctional monomer could be grafted easily onto the surface,forming a cross—linked structure,and as confirmed by IR spectroscopy there were still some double bonds un—reacted．Influences on the photografting of TMPTA were examined and the experimental results indicated that longer irradiation time and higher monomer concentration were useful for the increase of grafted pelymer conversion At a certain concentration of BP,a maximum grafted polymer conversion was obtained,and the decrease of grafted conversion at higher BP concentrations was probably due to the absorption effect of initiator．The increase of grafted polymer conversion Was observed with increasing the water contents．SEM images showed that a lot of small particles appeared on the surface of grafted films,and water contact angle measurements noted that the surface hydrophobicity was improved．
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发布时间：2021-03-19 - 摘要：A well—defined model hard segment was synthesized with 4,4’-diphenylmethane diisocyanate,dimethylolpropionic acid and 1,4-butanediol by means of fractional steps．The sequence distribution of the model hard segment was measured by131C-NMR and its structure and morphology were characterized by FT—IR,DSC and WAXD．A series of polyester based polyurethaneurea(PUU)aqueous dispersions with this well-defined hard segment were prepared．The physical properties of PUU aqueous dispersions and their films were measured．The experimental results showed that the particle size of the aqueous dispersions decreased with increasing the hard segment content from 1 10 nm to 72 nm．and they wele very stable at ambient temperature(more,than one year)．Furthermore,the films prepared with such PUU aqueous dispersions exhibited the excellent water resistance,i-e. low equilibrium water absorbing capacity(at around 5 wt％)and high contact angle of water on the surface(more than 100°)．
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发布时间：2021-03-19 - 摘要：Polyvinylacetate(PVAc)and a random copolymer of poly(vinyl acetate-co-isopmpenyl acetate) (PVIPA)with number-average molecular weight(Mn)around 2×104 g／mol and molecular weight distribution (MWD,Mw／Mn4 at-60℃ in the presence of a small amount of additives．The effects of macroinitiator,[TiCl4],the concentration of additives,such as 2,6-di-tert—butylpyridine(DtBP)and 2-methylpyridine(MPY)on monomer conversion and initiation efficiency of PVAc or copolymer PVIPA were investigated．The copolymerization product was extracted by methanol and petroleum ether to remove unreacted macroinitiator and polyisobutylene,respectively,and thus the graft copolymer was obtained．The microstructure and composition of the graft copolymers were characterized by GPC and1H—NMR spectrum．The initiation efficiencv of PVIPA was higher than that of PVAc．The initiation efficiency of PVAc or PVIPA was increased t0 more than 90％ by introduction of a smail amount of DtBP and to around 60％ by addition of an enough amount of MPY．The initiation efficiency increased to near 70％ with increasing the concentration of macroinitiator and TiCl4,respectively．The graft copolymer PVIPA—g—PIB,consisting of PVIPA backbone and PIB side chains of 35．2 mol％．with Mnof 3．7×104 g/mol and MWD of 2．52 could be obtained under proper reaction conditions．The average molecular weight of PIB side chains in PVIPA—g—PIB was further calculated to be around 5．4×103g／mol．
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发布时间：2021-03-19 - 摘要：Poly(N—methylindole)films were synthesized electrochemically by direct anodie oxidation of N—methylindole in pure boron trifluoride diethyl etherate(BFEE)．The oxidation potential of N—methylindole in this medium was measured to be only 0.95 V versus SCE,which was lower than that determined in acetonitrile+0.1 mol／L Bu4NBF4(1．23 V)．Poly(N—methylindole)films obtained from this medium showed good electrochemical behavior and good chemical stability．Poly(N—methylindole)films in dedoped state is soluble in common strong polar organic solvents such as CH2Cl2,dimethyl sulfoxide(DMSO),N,N—dimethylformamide(DMF)．Its structure has been examined by infrared and UV—spectra．Structural analysis confirmed that the polymerization of N-methylindole ring occurred at the 2,3 positions．Fluorescent spectral studies indicated that the emission spectrum had a peak at 380 nm.
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发布时间：2021-03-19 - 摘要：The introduction of functional pendant groups to biodegradable polyesters would be a highly efficient way of improving the properties of polyesters such as hydrophilicity,biodegradation rates,bioadhesion,drug loading,etc．A functional monomer with protected hydroxy group 4-benzyloxymethyl-1,3-dioxolan-2-one,which can also be named 3-benzyloxy-1,2-propanediolcyclic carbonate(BPC),was synthesized by reaction of bis(trichdomethyl)carbonate (BTC)with 3-phenylmethoxymethly-1,2-propanediol,which was easily obtained from the reaction of 3-chloro-1,2- propanediol and sodium phenylmethanolate．Homo—and copolymerlzation of BPC was carried out in bulk using stannous octanoate as a catalyst under different conditions．The properties of the BPC hornopolymers and copolymers with lactide were studied．The copolymerization of BPC and DL—lactide was successfully carried out．The resulting polymer was deprotected by Pd／C catalytic hydrogenation．The hydrophilicity of the deprotected copolymers demonstrated by water contact angle measurements was greatly improved．
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发布时间：2021-03-19 - 摘要：Crystallization of polyamides shows memory of shear even after undergoing a melting process at high temperatures for a long period to erase their thermal history,which was seldom noticed in the past．Considerable change of crystallization behavior of polyamides took place in the samples pre—sheared in various kinds of processing or measuring equipmerits,such as MFR instrument,rheometer,mixer and extruder．The peak crystallization tenaperatures increased bv 5 to 18 ℃ and the half crystallization time decreased to about a half compared to the sample without shear history．What’s more,the most obvious change generally occurred at a very low shear level,beyond which the changes levelled off．Polarized light microscopy revealed the decrease of spherulite size．On the contrary,crystallization of the pre—sheared polyolefins and popsters did not exhibit considerable difference from the unsheared samples．The hydrogen bonding was proposed to account for the memory of shear in polyamides．
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发布时间：2021-03-19 - 摘要：A fluorinated aromatic pyridine—bridged dianhydride 2,6-bis(3’,4'-dicarboxyphenyl)-4-(3”,5”- bistrifluorophenyl)pyridine dianhydride(6FDAPA)has been synthesized by the Chiehibabin’s reaction of 3,4-dimethyl acetophenone and 3,5-bis(trifluorometbyl)benzaldehyde,followed by oxidization and dehydration reactions．Two polyimide films were prepared by the dianhydride 6FDAPA and the unfluorinated dianhydride 2,6-bis (3’,4’-dicarboxyphenyl)-4-phenyl pyridine dianhydride(DAPA)with 1,4-bis(4-amino-2-trifluoromethylphenoxy) benzene(6FAPB),respectively via the two-step polycondensation procedure．The PI-2,derived from 6FDAPA and 6FAPB showed thermal properties similar to those of PI-1,derived from DAPA and 6FAPB．The PI-2 had glass transition temperature of 280℃ and initial thermal decomposition temperature of 580℃．Furthermore,the PI-2 film exhibited higher transparcncy than that of PI-1 and showed cutoff wavelength of 345 nm and more than 80％ of transmittance at 450 nm．
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发布时间：2021-03-19 - 摘要：A kind of soluble polyimide(PI)was synthesized based on 4,4’-oxydiohthalic dianhydride(ODPA)and 4,4’-diamino-3,3’-dimethyldiphenylmethane(DMMDA) via low temperature solution polycondensation and chemical imidization．The structure and properties of the obtained PI were characterized by measurements of FT-IR．1H-NMR,DSC and TGA etc．The results showed that the PI was readily soluble in polar solvents such as DMF．DMAc and NMP etc．Its glass transition temperature was 264℃ and 10％thermal deeomposition temperature under N2 was 521℃．The tensile strength was 137 MPa,and the elongation at break was 18％．The asymmetry membrane was prepared by phase inversion method of ODPA—DMMDA and was observed by SEM．In the sulfur reduction experiments,the membranes display good selectivity and hish pervaporation performance for thiophene in the gasoline．The enrichment factor was 3．68 and the flux was O．92 kg／m2h when tested with a n—heptane／thioohene feed at 350 K.
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发布时间：2021-03-19 - 摘要：The fluorescence quenching techniques,including steady—state fluorescence quenching(SSFQ) and time—resolved fluorescence quenching(TRFQ),were applied to determine the aggregation number(NA)of self-assembled aggregates of the hydrophobically associating water-soluble muhicopolymer of acrylamide(AM)and 2-phenoxylethyl acrylate(POEA)．This polymer easily hydrophobicany associates in water to form micelle—like aggregates,which serve as solubilization sites of pyrene probe molecules and quencher benzophone．Fluorescence results measured were well fit to the Possion quenching model It was found that the NA was influenced significantly by the hydrophobe content and the hydrophobic block size of the copolymer．The NA enhanced with increasing the hydrophobe content and decreasing the block length,as well as increased with increasing the concentration of copolymers and sodium chloride．The relationship among the polymer chain structure,aggregation number and viscosity of polymer solutions were discussed.
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发布时间：2021-03-19 - 摘要：β—cyclodextrin(β—CD)-containing acrylic monomers(β—CD-6一A)with different substitution degree were prepared by using dicyclohexylcarbodiimide(DCC)as condensation agent,and a functional hydrogel was synthesized by copolymerization of β-CD-6-A with acrylic acid(AA)using a redox initiator system in aqueous solutions．The nuclear magnetic resonance(1H—NMR),infrared spectroscopy(IR)and swelling experiments were employed to characterize the β-CD modified monomers and their copolymers．The results show that the resin’s equilibrium swelling ratio(ESR)possesses pH—sensitivities．The mechanisms of controlled drug release were investigated by using an anti—cancer drug,chlorambucil(CHL),as the model medicines at different medium．The release behavior of CHL from the hydrogels β-CD—AA indicated that the release ratio of CHL is affected by the pH value,and the cumulative release at pH=6．8 was higher than that at pH=2．0．In addition,the release efficiency of CHL from the hydrogels with β-CD is higher than that of the hydrogels without β-CD．
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发布时间：2021-03-19 - 摘要：Bulk ring-opening copolymerization of γ-valerolactone(γ-VL)and ε-caprolactone(ε—CL)was carried out with boron trifluoride etherate complex(BF3·OEt2)as catalyst．The structures of the resultant copolemers were determined by 1H—NMR and13C-NMR spectroscopies．The molecular weight,composition and melting point of the copolymers were characterized by means of GPC,1H—NMR and DSC,respectively．Although being unable to ring—opening homopelymerize,γ-VL was ring—opening copelymerized with ε-CL to give copelymem P(γ-VL-co-ε-CL) containing certain amount of γ—VL unit．The introduction of γ—VL unit resulted in significant deerease of the molecular weight and melting point of the copolymers．The reactivity ratio of ε-CL and γ-VL was estimated as 17．6and 0．0078,respectively,by the K—T metllod．
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发布时间：2021-03-19 - 摘要：The gelation rheology approach was employed to study the weak gel formation of partial hydrolyzed polyacrylamide(HPAM)／phenol／formaldehyde／resorcinol at various concentrations of HPAM and crosslinker under the conditions of the reservoir temperature and salinity．By analyzing the group conversion versus the conversion of the CROSS—linked macromolecules．it was revealed that near the gel point the gelation process was at the early stage of the reaction kinetics,which simplified the study of crosslinking kinetics．Comprehensive data of kinetic process were obtained as a result of the study of the linear viscoelasticity and nonlinear rheological behaviors It is found that the effect of concentrations of HPAM and crosslinker to the gelation and gel intensity is similar,which reflects the common kinetic characteristics of the cmsslinking reaction．After an induced period the complex viscosity rises as an exponential function of time,which is the characteristics of first—order reactions．The critical HPAM concentration for gel formation is around 250 mg／L．In addition,rheological models of complex viscosity and apparent viscosity in steady shear were introduced to describe the gelation process．
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发布时间：2021-03-19
Research Article
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SYNTHESIS AND CHARACTERIZATION OF POLYPHENYLENE DENDRIMERS CONTAINING TERMINAL TRIMETHYLSILYL GROUPS
摘要：Polyphenylene dendrimers 11,12 and 13 containing terminal trimethylsilyl groups have been synthesized by phosphine-free palladium chloride catalyzed Suzuki couplings of 1,3,5-tris(3’,5'-dibromophenyl)benzene 9 with aryl boronic acids 5 and 6．These macromolecules were characterized by Fourier transform infrared(FTIR),nuclear magnetic resonance(NMR)and matrix assisted laser desorption／ionization time of flisht(MALDI-TOF)moss spectra．Gel permeation chromatograph(GPC)indicated that the hydrodynamic radium of 12, with trimethylsiliyl (-TMS)groups substituted at para—positions on its terminal benzene rings,was larger than that of 13．with trimethylsiliyl groups substituted at meta—positions on its terminal benzene rings．X-ray powder diffraction patterns showed that dendrimer 12 was of a certain amount of crystallinity and dendrimer 13 was amorphous．- 4
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发布时间：2021-03-19 - 摘要：The partially disentangled polymer samples prepared are expected to crystallize easier than bulk polymers,which can be attributed to much fewer interchain entanglements within and between particles．Poly(vinyl chloride)(PVC)samples were prepared by freeze—extracting the solutions in various solvents and with vatting concentrations The results of FTIR analysis showed that when the concentrations of the solutions were lower than the overlap concentration C*,the PVC samples prepared from the good solvent had mole ordered structure due to much fewer interchain entanglements．While the concentrations of the solutions were higher than c*．the PVC samples prepared from the bad solvents had more ordered structure．
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发布时间：2021-03-19 - 摘要：A series of monomers{2,5-bis[(5-alkyl—phenyl)-1,3,4-oxadiazole] styrene}(BOXE)were designed and synthesized．By radical polymerization initiated BPO with a novel series of mesogen—jacketed pdymem containing 1,3,4-oxadiazole were prepared．Molecular weight and molecular weight distribution of polymem were measured by GPC．The glass transition temperature(Tg)and thermal stability of polymem were studied by DSC and TGA．The results indicate that these polymem have good thermal stability These liquid crystal polymers have well defined structure,and possess special photo—electronic properties．
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发布时间：2021-03-19 - 摘要：The isothermal shrinkage stress of highly oriented semi—crystalline poly(ethylene terephthalate)(PET) fiber was studied in the temperature range from 102℃ to 221℃．The data of the isothermal shrinkage stress on logarithmic time scales could be simply shifted to obtain a superimposed curve when the temperature was not above 186℃．The relationship between the shih factors and the experiment temperatures could be described satisfactorily by the Williams—Landel-Ferry equation with C1=71．9 and C2=511．7．Therefore,the increasing of shrinkage stress with treated time,resulted from the release of“frozen”stress in the oriented polymer materials,was resulted from the activation of the segments due to the glass transition．The much higher values of C1 and C2 than those of the non—crystalline materials were due to the higher stiffness of the molecules contributed to the stress increasing,which were constrained by the crystallization and the chain entanglement in a highly oriented semi-crystalline polymer．It was also proven by a wide α-relaxation peak up to 170℃ indicated by the tan δ-temperature curve．When the temperature was equal to or higher than 186℃,the decreasing of the isothermal shrinkage stress could be observed after it reached the maximum stress．According to the three-phase model of PET fiber provided by Prevorsek,such high tenperature stress relaxation was due to the viscose flow of the extended non—crystalline molecules located between micro—fibrils．which was also indicated by the α'-relaxation from 180℃ to 250℃．
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发布时间：2021-03-19 - 摘要：SalenMX has drawn much attention recently,because it is nonsensitive to moisture and effoctive for copolymerization of CO2 and epoxides．However,usually expensive organic metal compounds were used．A low cost procedure of SalenMX preparation is described that SalenAl(OPr)can be obtained by using aluminium／iso—propoxide reacted with SalenH2in tetrahydrofuran at room temperature overnight．The catalyst precursor Schiff-base SalenH2(N,N’-Bis(salicylidene)-1,2-phenylenediamine) was synthesized by refiuxing 2 equiv salicylaldehyde and 1 equiv of 1,2-phenylendiamine in methnol for a period of time．SalenH2 and SalenAl(OPr)were characterized by FT-IR,mass Spectroscopy．UV-Vis and 1H-NMR．The copolymerization of carbon dioxide and eyelohexene oxide (CHO)was carried out at 80℃ for a certain period time using 50 mg SalenAl(OPr)as catalyst．SalenAl(OPr)had been shown to be an effective catalyst for the copolymerization of CO2 and CHO along with a small quantity of byproduct cyclic carbonate．The addition of various cocatalysts,including DMAP,N-Melm,DBU and Bu4NCl or Bu4NBr salts can greatly enhance the rate of eopolymerization．The copolymers were produced with>95％carbonate linkages and<5％cyclic carbonates．The highest catalytic efficiency is 190 g eopolymer per g catalyst.
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发布时间：2021-03-19 - 摘要：The soluble photosensitive polyimides were synthesized by the copolymerization of 3,3'-diaminochalcone(mDAC),bis(3-aminophenyl)-3,5-bis(trifluoromethyl)phenyl phosphine oxide(mDA6FPPO)and 4,4’-(hexafluoroisopropylidene)-diphthalic anhydride(6FDA)．The polymers were characterized by FR-IR spectrum,and the properties of polymers were also discussed. The results show that the polyimides have excellent solubility in conventional organic solvents such as NMP,DMF,THF and acetone．The Tgs of polyimides are ranged in 256℃～277℃．The polymers are stable up to over 400℃ and the residual weights at 800℃ are between 46％～50％．The resulting polyimides have good adhesive properties,and they were found to increase with increasing the mDA6FPPO content．The photosensitivity of the polymers was investigated by observations of UV—Vis spectral changes during UV irradiatino.
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发布时间：2021-03-19 - 摘要：“Living”radical polymerization of methyl methacrylate was investigated using a new reaction system,ethyl 2-bromoisabutyrate／CuBr／[mim][HCOO]／MMA,in which[mim][HCOO]ionic liquid was a good solvent to CuBr．Polymerization of methyl methaerylate was carried out in[mim][HCOO] in the absence of any organic ligands. The polymerization mechanism belongs to an ATRP process．The polymerization was closely controUed and was a fast reaction when compared to pdymerizafion in non—polar solvents in[mim] [HCOO]at 50℃．The polymers weIe easily separated from the catalyst．Analysis of the PMMA for residual copper by atomic absorption spectrophotometer．shows a copper contentof 3．80×10-3％(1％is expected,if no copperis removed)．
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发布时间：2021-03-19
Research Bulletin
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