最新刊期
卷 ， 期 6 ， 2003
- 摘要：Novel polyelectrolytes (PBANT-AC and PBACT-AC) functionalized with branched side-chains containing electron donor-acceptor type azo chromophores have been synthesized through a post-polymerization azo-coupling reaction route and characterized by 1H-NMR,FTIR and UV-Vis spectroscopy．The degree of functionalization (DF) of PBANT-AC and PBACT-AC were 17％ measured by elemental analysis. The degree of polymerization and its distribution were determined by GPC to be Xn=588 with a polydispersion index 1.3. Glass transition temperatures of PBANT-AC and PBACT-AC were estimated from DSC thermogram to be 139℃ and 159℃,respectively Dichroism. It was optically induced in the spin-coated films of the two polymers under the irradiation of a polarized Ar+ laser beam at 488 nm. The resulting dichroism was detected from UV-Vis spectra,which exhibited a long-term stability at room temperature. The orientational order parameters obtained were 0.12 and 0.09 for the PBANT-AC and the PBACT-AC films. Surface relief gratings were optically inscribed upon exposure to an interference pattern of Ar+ laser beams at modest intensities．The surface modulations were about 45 nm and 80 nm for PBANT-AC and PBACT-AC films estimated from their AFM data.
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发布时间：2021-03-19 - 摘要：The poly(butylene terephthalate)-co-poly (butylene succinate)-b-poly (ethylene glycol) block copolymers (PTSG),employing PEG homopolymers with different number-averaged molecular weight from 400 to 2000 as precursors,with PBS molar fraction (MPBS) varying from 10％ to 30％ were synthesized by melt polycondensation technique and characterized by means of GPC,NMR,DSC and mechanical testing etc. The result of GPC measurements shows single-modal curves with a polydispersity below 2.0 for the copolymers．Analysis on the sequence distribution of the two hard segments in the copolymer chains reveals that the average sequence length of PBT hard segments decreases while that of PBS increases with the increase of MPBS,and the random distribution of the two hard segments is also validated by the degree of randomness around 1.1. Microphase-separation structure is demonstrated by the appearance of two glass transition temperatures (Tg,s,Tg,h) and two melting points(Tm,s,Tm,h) in DSC curves of most samples．Especially,the decrease of the average block length of PBT and the co-crystallization between the two hard segments may cause the depression of the melting point and crystallinity of the hard segments,when MPBS changes from l0％ to 30％ under constant soft segment length．The increase of elongation at break and equilibrium water up-take with the increase of PEG molecular weight and its weight ratio in the copolymer,as well as the decease of crystallinity of hard segments provide a promising method of modulating the flexibility and hydrophilicity of copolymer chains．
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发布时间：2021-03-19 - 摘要：The advantages of acrylamide (AM) polymerization in polyethylene glycol (PEG) aqueous solutions are the lower viscosity and higher monomer concentration of the polymerization system．It may be used to prepare water soluble polymers with high molecular weight which can be directly diluted for use. It overcomes the problems of mixing and heat transfer of polymerization systems,low polymerization rate,and qualities of products in the aqueous homogenous polymerization．On the other hand,AM polymerization in PEG aqueous solutions is performed in water without using any organic solvents. It also overcomes the pollution and recycle problems of organic solvents for inverse phase suspension polymerization,water-in-oil inverse phase emulsion polymerization and precipitation polymerization. It is a new polymerization method for preparing water soluble (co) polymers．In this paper kinetics of AM polymerization in PEG aqueous solutions were studied by the improved bromating method．The effects of initiator,monomer and PEG concentrations,emulsifiers with various HLB values,and polymerization temperature on kinetics of AM polymerization in PEG aqueous solutions initiated by single and redox initiators were investigated. It is found that the monomolecular termination is more than the bimolecular one for AM polymerization in PEG aqueous solutions．The apparent activation energy of polymerization initiated by ammonium persulfate-triethanal amine (APS-TEA) redox initiator (Ea=42.3 kJ／mol) is smaller than that by single initiator APS Ea=96.1 kJ／mol).
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发布时间：2021-03-19 - 摘要：A series of aliphatic polyureas with different hard segment contents were synthesized by the reaction of isophorone diisocyanate with Jeffamine D2000 and isophorone diamine as chain extender in solution．The effect of hard segment contents on the morphology and mechanical properties for these polyureas was studied by using DSC and FTIR etc．The experimental results showed that the polyureas exhibited a partial phase separated morphology．The polyurea with higher hard segment contents showed a better compatibility between the soft and hard segments,and a higher degree of hydrogen bonding for the urea carbonyl groups existed in the system,but the values of Tg for the soft segment regions almost did not depend on the hard segment content．The tensile strength,hardness and shear strength of polyurea specimens were enhanced greatly with increasing the hard segment content.
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发布时间：2021-03-19 - 摘要：The synthesis of side chain cholesteric liquid crystalline polymers (Pn series) and elastomers (Pe series) containing both 4-allyloxybenzoylcholeseterate (Mch) and 4-allyloxybenzoyloxy-4′-methoxyphenyl (Mn) or 2-tert-butylhydroquinone di(4-(b-acryloyloxy hexyloxy) benzoate) (Mnc) mesogenic side groups was described．The chemical structures of the obtained polymers and elastomers were confirmed by FT-IR spectroscopy．Their mesomorphic properties and phase behavior were investigated with POM,DSC,TGA and X-ray measurements．The liquid crystalline polymers Pn1～Pn8 and elastomers Pe1～Pe7 exhibited cholesteric grandjean texture or oily streak texture．In Pn series,with increasing the concentration of the cholesteric mesogenic Mch,the glass transition temperature(Tg) increased from 8.7℃ to 65.7℃,and the clearing point temperature(Tc) increased from 42.0℃ to 251.8℃．In Pe series,with increasing the concentration of the nematic liquid crystalline crosslinking agent Mnc,Tg decreased from 65.7℃ to 52.7℃,and Tc had no significant change．When the concentration of Mnc was greater than 8 mol％,the DSC curves of Pe6 and Pe7 did not show the clearing point temperatures,but POM observations exhibited the grandjean texture,which did not disappear until their decomposition．The polymers Pn1～Pn11 and elastomers Pe1～Pe7 had wide mesomoephic temperature ranges．TGA measurements showed that the temperature at which a 5％ mass loss occurred was higher than 280℃ for all the liquid crystalline polymers and ealastomers．
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发布时间：2021-03-19 - 摘要：Poly(DL-lactide-co-glycolide) (PDL-LGA) copolymers with different DL-lactide／glycolide (DL-LA/GA) mole ratios were prepared by bulk ring-opening copolymerization of DL-LA with GA using tin octoate(Sn (Oct)2) as catalyst．Analytical results by 1H and 13C-NMR indicated that the mole fraction of glycolidyl units in the copolymers was a little higher than the feed mole fraction of GA,and the second mode of transesterification occurred during copolymerization．Copolymerization at 160℃,the average sequence length of glycolidyl (lGG) of the copolymers increased as the feed mole fraction of GA increased and the average sequence length of lactidyl (lLL) decreased. It was found that the transesterification coefficient of the second mode of lactidyl units (TⅡ[GLG]) decreased as the feed mole fraction of GA increased and reached to the least at a GA feed fraction of 50 mol％,after that,it increased gradually．In the case of copolymerization of L-LA with GA (L-LA／GA=75／25) at the same conditions,both the TⅡ [GLG] and lGG of the copolymer were higher than those of the corresponding PDLDL-LGA．As the copolymerization temperature increased,the TⅡ [GLG] increased,suggesting that the transesterification of the second mode became stronger；however,the value of lGG for the copolymer with higher DL-LA／GA feed mole ratio (75／25) was somewhat decreased and the lLL had no obvious change,whereas the copolymer with relatively lower DL-LA／GA feed mole ratio(50／50) behaved just conversely,i．e．,the value of lGG changed a little and lLL was somewhat decreased,indicating that the copolymerization was also affected by comonomers and other factors．Higher copolymerization temperature was more efficiently to change the microstructure of the copolymer chains than the prolonged copolymerization time at lower temperature．The glass transition temperature (Tg) and the solubility in chloroform of the copolymers synthesized at a given temperature decreased as the feed mole fraction of GA increased；however,the effect of polymerization temperature on the Tg of the copolymers with the same DL-LA／GA feed mole ratio became relatively complicated,indicating that the effect of polymerization temperature on the microstructure of the copolymers is more significant than that of the DL-LA／GA feed mole ratio.
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发布时间：2021-03-19 - 摘要：A series of casting films of starch and tannin-based polyurethane were prepared and the effect of tannin and starch amounts on the properties of polyurethane was investigated．It was found that when tannin was added,the thermal behavior and mechanical properties of films were improved,especially when the content of tannin reached 60％ (weight percent in biomass),tannin and the network of starch-based polyurethane interpenetrated and showed good miscibility．Its integral procedural decomposition temperature (IPDT) was 375℃,its tensile strength and Young’s modulus were 51.9 MPa and 308.4 MPa,respectively．The results indicated that tannin had great effect on the density of crosslinking,miscibility of components and the morphology of starch polyurethane．The degradation test in phosphate buffer solutions showed that tannin could adjust the speed of starch polyurethane degradation,to some extent．
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发布时间：2021-03-19 - 摘要：The critical crosslinking concentration of linked polymer solutions(LPS) formed by low concentration and high molecular weight partially hydrolyzed polyacrylamide (HPAM) and aluminum citrate(AlCit) was investigated by using dynamic viscosimetry,nuclear pore membrane,dynamic light scattering and 27Al-NMR measurements．The experimental results show that the viscosity and spin-lattice relaxation time (T13) of HPAM／AlCit crosslinking systems decrease with reaction time in low concentrations(the concentration of HPAM is between 100 mg／L and 200 mg／L) and increase with reaction time in a high concentration (300 mg／L)．The results measured by dynamic light scattering show that the mean hydrodynamic radius of linked polymer coils(LPC) is about 238 nm and 246 nm with HPAM concentrations of 100 mg／L and 200 mg/L in the solution．respectively．The filtration velocity of the LPS with HPAM concentrations of 100 mg/L and 200 mg／L in the solution is almost the same．The mean hydrodynamic radius of LPC is about 379 nm in the LPS with HPAM concentrations of 300 mg／L,and the filtration velocity of the LPS is lowered obviously．These results indicate that the linked polymer solution is formed by intra-molecular crosslinking of HPAM and AlCit forming linked polymer coils in the system of lower concentration. When the polymer concentration of HPAM／AlCit system is increased to a critical concentration,the weak gel is formed by crosslinking of LPC．The critical crosslinking concentration of LPS is between 200 mg／L and 300 mg／L for the system made up of HPAM molecular weight 1.4 × 107 and NaCl concentration 2000 mg／L. The critical crosslinking concentrations of the linked polymer solution measured by different methods are consistent with each other．
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发布时间：2021-03-19 - 摘要：Several aliphatic waterborne polyurethanes were prepared from isophorone diisocyanate (IPDI),dimethylolpropanic acid (DMPA),poly (ethylene adipate) (PEA) and polypropylene glycol (PPG)．Dynamic mechanical analysis(DMA) was adopted to study the relationships between morphology and properties of aliphatic waterborne polyurethanes．The results indicated that the interaction between soft and hard segments depended heavily on the structure of soft segments．The carbonyl of polyester-type diols can form hydrogen bonds with hard segments,which lead to a semi-compatible structure,whereas the hydrogen bonding in the polyether-based polyurethanes is formed mainly between the hard segments,which results in higher level microphase separation．The ionic groups incorporated in the hard segments improve the phase separation．As a result,the increase of DMPA amount is related with a lower glass transition temperature (Tgs) and a higher i>Tgh．At the meantime,the level of microphase separation increases with the increasing of soft segments length．
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发布时间：2021-03-19 - 摘要：Organic or polymeric ferromagnet is a new kind of magnetic material．Compared with inorganic ferromagnet,the organic ferromagnet exhibits the characteristics of structural diversities,low density,and readily processing．The magnetic properties of organic magnets can be tuned by changing their molecule structure. So the synthesis of novel organic magnets is significant in the field of magnetic materials．In this article we report three poly(Schiff base)s (PBTAP,PBTMP,PBTPP) synthesized by condensation from 2,2′-diamino-4,4′-bithiazole (DABT) with 2,6-diacetypyridine(DAP),m-phthaldialdehyde and p-phthaldialdehyde,respectively and a new series of complexes prepared from Fe2+ with the three polymers．The polymers and their Fe2+ complexes were characterized with FTIR instruments. The magnetic properties of complexes were measured by using PPMS-9 (Physical Property Measurement System)．It was found that these Fe2+ complexes were soft magnets and had relatively high saturation magnetizations．The saturation magnetization of PBTAP-Fe2+ is 6.2 emu／g,its paramagnetic Curie temperature is 88 K,and there is a magnetic hysteresis loop at 2 K．The results show that PBTAP-Fe2+ is a soft ferromagnet at low temperatures．The magnetic properties of PBTMP-Fe2+ is similar with those of PBTPP-Fe2+．The saturation magnetization of PBTMP-Fe2+ is 4.8 emu／g,and that of PBTPP-Fe2+ is 3.4 emu／g．Both of them have a negative Curie-Weiss temperature and an “S” shape magnetic hysteresis loop．These results mean that PBTPP-Fe2+ as well as PBTMP-Fe2+ exhibits ferromagnetism at low temperatures and antiferromagnetism at relatively high temperatures．
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发布时间：2021-03-19 - 摘要：Polypropylene (PP)／maleic anhydride grafted polypropylene (gPP)／expanded graphite (EG) (gPP／EG =3／2 wt) electrically conductive nanocomposites were prepared via solution intercalation (SI) and its combination with melt mixing named as masterbatch melt mixing (MMM)．Room temperature electrical conductivity (σ) measurements revealed that thc percolation thresholds (φc) of the nanocomposites prepared via SI and MMM were 6 wt％ and 8 wt％ respectively,much lower than those of the composite and the PP／EG control prepared via direct melt mixing(φc=11 wt％ and 12 wt％)．The increment of gPP content (Cg) can elevate the σ of the composites,ex. when its composition became PP／gPP=1／1 wt,the φc of the composites prepared in MMM and DMM decreased to 7 wt％ and 10 wt％,respectively；while for the nanocomposite prepared via MMM,in the case of fixing the EG content of 9 wt％,its σ might jump up more than 7 degress of magnitude as the Cg exceeded 30 wt％．The reasons causing the above differences and phenomena mentioned above were analyzed and elucidated by means of TEM,SEM and OM observations and according to the differences among the preparation methods．
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发布时间：2021-03-19 - 摘要：The linear relationship between UV-absorbance of poly(styrene sulfonate)(PSS)／poly(diallyldimethyl ammonium choloride)(PDDA) and the number of MD films confirms that PSS／PDDA monolayers are alternately deposited. The contact angle of water on polyelectrolyte MD films indicates that the surface wettability varies with the number of deposited layers exhibiting a regular odd-even effect,when the number is low．This regularity becomes not obvious when more layers are deposited. This phenomenon shows that the structural defect of polyelectrolyte MD films aggravates with the increment of the number of layers．Through analyzing Atomic Force Microscopy (AFM) images of PSS／PDDA MD films,granular protrusion of about 1.5 nm height can be detected．It indicates that the surface of MD films is rough．This means that molecules of adjoining layers can penetrate into each other and form unclear interface. The results of AFM further verify the uneven surface properties and structural defect of the 20th layer of a PSS/PDDA MD film.
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发布时间：2021-03-19 - 摘要：The magnetic and configurational properties of Ising polymer chains on simple cubic lattice are simulated using annealing Monte Carlo technique．Spontaneous magnetization at low temperature is found for magnetic polymers,and the critical temperature is estimated as Tc=1.77±O.05(J／kB) for long chains．At Tc,the chain also undergoes a collapse transition from a random coil at high temperature to a compacted globule at low temperature. For all simulated chain lengths,it is found that the configurational properties change very little above Tc but obviously below Tc. The analysis of chain dimension,shape,nearest neighbor number as well as energy shows that the phase transition of Ising polymer chains results from the cooperation of segment movement and Ising interaction.
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发布时间：2021-03-19 - 摘要：A copolymer P(MMA-AN-MALi) (PMAML) was synthesized by solution polymerization. It was then blended with PVDF for preparing porous membranes by solution casting,and the non-solvent or extration step was unnecessary in this process. A novel gelled polymer electrolyte based on the blend of PMAML and PVDF was obtained by soaking the polymer membrane in organic liquid electrolytes．The composition of the copolymer was determined from its 1H-NMR spectrum,and the result showed that the molar ratio of MMA:AN:MALi was about 68.6:21.5:9.9. The surface structure of the polymer film was characterized by SEM. The pores were well distributed in the surface of the membrane and the porous size was about 5 μm. The ionic conductivity of the polymer electrolyte was measured by the AC impedance method,and it was about 2.5×10-3 S·cm-1 at room temperature． The electrochemical stability window was carried out on the stainless steel electrode with lithium metal electrodes as the reference and counter electrodes by the linear sweep voltammetry method．The polymer electrolyte was electrochemically stable under 4.5 V．The diffusion coefficient of salt in the polymer electrolyte was measured using Li／GPE／Li non-blocking cell by the restricted diffusion experiment,and the value was about 8.12×10-7 cm2·s-1. The coulombic efficiency of the lithium ion battery with the polymer electrolyte in the initial charge-discharge cycle was calculated to be about 89％,and the discharge capacity of the first five cycles changed only in a small range．The test resuits display that the polymer electrolyte based on blends of PMAML and PVDF was electrochemical stable and can be used in lithium ion batteries.
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发布时间：2021-03-19 - 摘要：A conception of critical solvent concentration (CSC) at the onset of phase separation was proposed. The macrovoid-formation mechanism came up with this conception．It was considered that a higher solvent concentration at lhe onset of phase separation than that critical value is required for the development of macrovoids in phase-inversion membranes. When the solvent concentration at the onset of phase separation is smaller than the critcal value,the macrovoids development stops and a sponge-like structure is fonned．The polyvinylidene difluoride(PVDF) hollow fiber membranes by using PVDF(18％)-PEGl000(5％)-DMAc(77％)casting solutions and different inner coagulation baths．A mass transfer model was established to simulate the composition variation of nascent hollow fiber during the PVDF hollow fiber formation process under the corresponding technical condition. The solvent concentration at the onset of phase separation was calculated．The membrane morphological structures were predicted according to the conception of CSC at the onset of phase separation,the macrovoids formation mechanism and the simulation resuIts. SEM observations of the membranes prepared in various inner coagulation baths show that the predicted results coincide well with the membrane morphological struetre and verify the macrovid-formation mechanism．
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发布时间：2021-03-19 - 摘要：Nanoparticles of polyaniline have attracted increasing attention for their smaller size and large surface area which may promote more effective doping,overcome the problem of process ability and lead to special electrical,optical,opto-electrical properties．In this work,polyaniline nanoparticles doped with β-naphthalenesulfonic acid were prepared by a novel solid-state reaction synthesis method. Polyaniline was characterized by FT-IR,XRD and cyclic voltammogram on powder cavity microelectrode．The morphology of polyaniline particles was studied through SEM and TEM,and the electrical conductivity of pellets formed with polyaniline nanoparticles was measured by using a four-probe apparatus．Results showed that the average size of polyaniline particles doped with β-naphthalenesulfonic acid obtained by this method was 30～50 nm,and the polyaniline particles were spherical in shape．The measured electrical conductivity of pellets formed with polyaniline nanoparticles was 17 S／cm．XRD measurements indicated that the polyaniline nanoparticles were crystalline．The cyclic voltammogram of polyaniline naoparticles on powder microelectrode showed good electrochemical properties．
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发布时间：2021-03-19 - 摘要：The thermoreversible gelation of κ-carrageenan (KC) was studied by small angle laser light scattering (SALLS). The mobility of random fluctuation of scattering speckles is used to detect the sol-gel transition,and the mobility disappears suddenly at a point during the cooling process of KC solutions．The temperature at that point is designed as gelation point (Tgel)．Effects of several counterions,including Na+,K+,NH4+,Ca2+,Cu2+ and Zn2+,on Tgel were determined. Although all ions are able to promote the gelation of KC,the promoting ability can be ranged to three resions：K+,NH+4 (I),Ca2+,Cu2+,Zn2+(II) and Na+(III),their promoting abilities have the following sequence：I＞II＞lII. Tgel is found to be proportional to the square root of concentrations of conterions,except Na+．The influence of KC concentration on Tgel in NaCl and KCl aqueous solutions also shows the promoting abilities of both Na+ and K+ ions．Furthermore,the phase diagram of KC-KCl aqueous solutions at 30℃ was obtained. The comparison of Tgel values for KC-NaCl solutions before and after dialysis further reveals the promoting function of Na+ ions,and some controversial results in literature concerning the function of Na+ ions ale supposed to result from the different methods used for Tgel determination．
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发布时间：2021-03-19 - 摘要：Polymer precipitation curves for the ternary systems PPES/NMP/additive were determined by a titration method. Membrane-forming additives used were H2O,MeOH,EE,EGME and BO．The position of the precipitation curve in the triangle phase diagram reflects the effect of the type of nonsolvent additive on the ternary systems．In addition,the effect can also be demonstrated by the different dropping rate of the intrinsic viscosities caused by various nonsolvent additives．These results indicate that the polymer conformation in solutions varies with the use of different additives．Besides the type of nonsolvent additive,the amount of nonsolvent additive can alter the polymer conformation in solution somewhere．Along the path leading from the initial starting point up to near the precipitation point,a stage would be reached in which the NMP／nonsolvent mixture becomes a theta-solvent for the polymer,and the macromolecules would assume an unperturbed conformation. NMP／nonsolvent theta-compositions were determined by the method of Elias using precipitation point data．A series of ultrafiltration membranes were made from poly(phthalazinone ether sulfone) with NMP as solvent. The membrane structure changes with the increase of the content of nonsolvent additive．When the content of EGME additive is close to 40 wt％ — the theta-composition of NMP／EGME mixture,the structure and properties of membranes change greatly.
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发布时间：2021-03-19 - 摘要：The kinetics of polymerization of propylene oxide(PO) catalyzed by zinc hexacyanocobaltate complex catalyst was studied by means of pressure measurements. All the reactions were carried out in 0.1 L autoclaves equipped with manometers．As soon as the pressure of the system began to decrease,the polymerization was considered to have been initiated．By evaluation of vapor-liquid equilibrium of toluene solutions of propylene oxide,the pressure was found to linearly depend on the PO volume fraction．Therefore,the rate of the reaction was known to be proportional to the rate of pressure decreasing. The influence of reaction temperature,catalyst and monomer concentrations on the reaction rate was investigated．It was found that the polymerization was a first order reaction to the concentration of catalyst C,but a second order reaction to that of monomer M as shown in the following equation．The rates also depended on reaction temperature while the apparent activation energy was 59.1 kJ／mol according to the Arrhenius equation．It was proposed that the epoxide monomer must be involved in the initiation stage of the polymerization．Based on this assumption a kinetic equation in which K was a rate constant was deduced in well accordance with the experimental results：Rp=KM2C.
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发布时间：2021-03-19 - 摘要：Soap-free Cationic Emulsion Copolymerization of vinyl-acetate (VAC) with methacryloyloxyethyl trimethylammonium chloride (DMC) has been studied．The factors influencing the reaction rate were discussed,such as the comonomer concentration,initiator concentration,temperature,etc．The result of kinetics showed that the influence of comonomer concentration and initiator concentration on the rate of coplymerization could be expressed as：Rp=k1 [M]0.63 [AIBA]1.0,the reaction order of VAC and DMC was：Rp=k2[VAC]0.16[DMC]0.89,and the apparent activation energy of polymerization was 44.01 kJ·mol-1. The mechanism of the soap free emulsion compolymerization was also discussed.
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发布时间：2021-03-19 - 摘要：A mixture of a low molecular weight poly(ethylene glycol) (PEG,Mn=600) and dichloromethane (CH2Cl2) was polycondensated to form a block polymer．The block polymer electrolytes containing lithium salt reacted with an appropriate amount of toluene 2,4-diisocyante(TDI) to form a cross-linked polymer network,with improving the film processability,mechanical and thermal stability properties．Enhancement of the ionic conductivity and electrochemical stability of cross-linked polymer electrolyte was observed by adding lithium bis(trifluoromethane sulfonylimide) (LiN(CF3SO2)2)．In the range of measured temperature,the relationship between conductivity and temperature coincided with Arrhenius formula(σ=Ae-Ea/RT)．One or two activity energy (Ea) values appeared in curves of Arrhenius plots with different salt concentrations．The cross-linked polymer electrolyte exhibited a high ionic conductivity of 1.12×10-5 S／cm at room temperature,and a decomposition voltage at about 5.0 V.
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发布时间：2021-03-19 - 摘要：A photoinitiator,cyanine dye-borate complex(CDBC),sensitive to light of 680 nm was synthesized,and the factors affecting the viscosity,the curing time and the volumetric shrinkage ratio of resins,composed of CDBC,EA612 and POTMPTA were also studied．The experimental results showed that a high weight content of EA612 and a low weight content of POTMPTA resulted in high viscosity and low volumetric shrinkage ratio of the resin,and vice versa．The curing time of the resin decreased with the increasing of the weight content of CDBC,when the weight content of CDBC was not more than 3％．However．the curing time of resin did not decrease with the increasing of the weight content of CDBC,when the weight content of CDBC is more than 3％. When the weight content of CDBC was not more than 5％,the viscosity and the volumetric shrinkage ratio of resin had no relationship with the weight content of CDBC. When the weight contents of EA612,POTMPTA and CDBC were 70％,27％ and 3％,respectively,the viscosity of the resin was 420 mPa·s,the curing time of the resin was 1.0 s,the volumetric shrinkage ratio of the resin was 4.0％ and the cured resin exhibited good properties.
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发布时间：2021-03-19 - 摘要：Emulsifier-free cationic poly (styrene-methylmethacrylate) (P(St-MMA)) copolymer nanoparticles were synthesized under microwave irradiation in the presence of cationic radical initiator 2,2′-azaobisisobutyramidine dihydrochloride(AIBA)．Several factors affecting the polymerization were discussed．The polymer conversion was followed gravimetrically at different time intervals during the reaction. The particles were characterized using TEM,LLs．The latex stability in electrolyte-resistance was determined by the critical coagulation concentration of electrolyte．The results indicated that in acetone-water medium,the average particle hydrodynamic radius of P(St- MMA) decreased from 122.21 nm to 24.68 nm with the addition of acetone／water volume proportion in the range of 0～1.26:1,and the stability of latex increased,but the polymerization rate was lowered and the particle distribution broadened．With increasing the concentration of methylmethacrylate or AIBA,the particle size dropped and the polydispersity index enlarged．
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发布时间：2021-03-19
Research Article
- 摘要：An epoxy-based precursor polymer was prepared from the diglycidyl ether of Bisphenol A and aniline．The precursor polymer was doped with a certain amount of cross-linking agent M2OS to obtain a thermal-curable polymeric system BPAN+M2OS．The thermal curing behavior of BPAN+M2OS was studied by means of in-situ infrared spectroscopy and it was found that BPAN+M2OS showed significant thermal-curability and had the similar curing dynamics at both 120℃ and 180℃．The curing degree can reach 70.7％ at 120℃ and 8l.8％ at 180℃ within 20 min,respectively．When a two-layer film was prepared with the cured polymer BPAN+M2OS as the bottom cladding and an E．O．polymer BPAN-1A-NT as the upper layer,SEM studies showed a perfect interface between the bottom and the upper layers of the two-layer film and the surface of the upper layer was quite smooth．A polymeric planar prototype waveguide,which was fabricated based on the above two-layer film and covered by another layer of UV photoresist,showed good wave-guide performance．
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发布时间：2021-03-19 - 摘要：The effect of temperature on the characteristic of Fourier Transform Infrared(FTIR),the dependence of the average molecular weight and the polydispersity on the annealing temperature and the relationship between linear expansion coefficients and temperature of poly(propylene carbonate) end-capped with maleic anhydride(MA-PPC) were investigated．The vibration peak of hydroxyl group at 1714 cm-1 in the FTIR spectra,which belongs to the carboxyl end-group in MA-PPC,decreases with increasing the temperature of the sample and it disappeared totally when the sample was heated over 70℃．The average molecular weight of MA-PPC almost doubled when the sample was annealed at 110～150℃ for 30 min,however the polydispersity was maintained roughly．A new relaxation transition at about 80℃ was detected on the curve of the linear expansion coefficient versus temperature that is the characteristic of macromolecular coupling or crosslinking reaction. These results confirmed that the macromolecular coupling reaction was carried out between the end carboxyl groups of MA-PPC when the sample was heated over 70℃.
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- 20
发布时间：2021-03-19 - 摘要：A synchronization observation was carried out to investigate the growth of PEO spherulites by using a polarizing optical microscope in order to learn the phenomenon of concentric banded stripes occurred during the growth of PEO spherulites．It was found that the concentric banded stripe didn’t come into being until at least two independent PEO-spherulites met each other,the formation of the concentric banded stripes were owing to the tortuosity of the spherulite after colliding with other spherulites.
- 3
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- 8
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- 2
发布时间：2021-03-19 - 摘要：Silk fibers were chemically modified by grafting with polyethylene glycol dimethacrylate(PEGDMA)．The structure and thermal properties of these grafted silk fibers were investigated in relation to the graft yield by using DSC,TGA and dynamic viscoelastic measurements．The DSC and TGA results showed that the decomposition peak of grafted silk fibers shifted to higher temperatures,suggesting that grafting of silk fibers with PEGDMA can improve the thermal stability．Dynamic mechanical data showed that the major loss peak became broader and its temperature shifted to lower values following the increase of the graft yield．The cross-linkage between the molecules of silk fibers and PEGDMA may limit macromolecular motion in silk fibers,so,the peak of loss modulus (E″) determined by dynamic viscoelastic measurements became lower and the initial position of this peak shifted to higher temperature,when the graft yield increased.
- 38
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- 10
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- 2
发布时间：2021-03-19 - 摘要：Block copolymerization of methyl methacrylate (MMA) ms and 2,2,3,3,4,4,5,5-octafluoropentyl acrylate(OFPA) was conducted at 25℃ in water dispersion system catalyzed and initiated by CuBr/CuBr2/1,10-phenanthroline(phen)／ethyl 2-bromoisobutyrate (EBiB) or CuCl／phen／EBiB in the presence of sodium lauryl sulfonate and sodium perfluorononenyloxyl benzene sulfonate．The results of GPC and 1H-NMR characterization demonstrated that a fluorine-containing block copolymer composed of MMA and OFPA was successfully synthesized in such a water dispersion system．The water-resistance performance of the PMMA film surface was greatly improved when only 2 wt％ (based on PMMA) of the resulted fluorine-containing block copolymer was employed as the film surface enhance agent.
- 4
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- 9
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- 5
发布时间：2021-03-19 - 摘要：The diblock copolymers of methyl acrylate and perfluoroalkyl ethyl acrylate(FAEA) were synthesized by atom transfer radical polymerization (ATRP)．GPC,1H-NMR and fluorine-elementary analysis (F-EA) were used to study the structure of the block copolymers．To combine GPC with NMR and to combine GPC with F-EA were used to calculate the block length．It was found interestingly that the results of 1H-NMR showed a “temperature-dependent” feature．It means the relative ratios of MA block to FAEA block calculated from NMR were changed with measuring temperature．It might be caused by the formation of molecular association. Temperature and solvents can affect the degree of association. Therefore,1H-NMR and GPC can’t be used in quantitative analysis of the fluorinated diblock copolymer. To combine GPC with F-EA is suitable for the characterization of fluorinated diblock copolymers.
- 2
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- 10
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- 5
发布时间：2021-03-19
Research Bulletin
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