最新刊期
卷 ， 期 9 ， 2008
- 摘要：The preparation of aluminumcontaining silicon carbide,SiC(Al),fibers by using polyaluminocarbosilane (PACS) and polycarbosilane (PCS) blends as precursors was investigated.The solubility parameter of PACS was determined to be 18 MPa1/2by dissolving PACS in solvents with different solubility parameters.It was very close to the solubility parameter of PCS (18.4 MPa1/2),indicating the possible compatibility of PACS and PCS.After PACS and PCS both were dissolved in xylene,a translucent yellow blend of PACS and PCS,B-PACS,was obtained by distillation.The composition and structure of BPACS,PACS and PCS were characterized by chemical analysis,GPC and FTIR.It was found that B-PACS with desirable Al contents could be obtained by adjusting the ratio of PACS (Al content 1.25 wt%) and PCS.The Si—H bond content can be indicated by A2100 cm-1/A1250 cm-1,where A2100 cm-1,A1250 cm-1 are the absorbance of Si—H bonds at 2100 cm-1 and CH3 bonds at 1250 cm-1,respectively.The FTIR results showed that the Si—H bond content of B-PACS was higher than that of PACS,while their Al contents were the same.PCS with a higher Si—H content might be responsible for the higher Si—H content of B-PACS.GPC results showed that B-PACS had a high molecular weight fraction as compared with PACS of the same Al content.The apparent activation energy of flow for B-PACS and PACS (Al content 0.6 wt%) was determined by the relationship between temperature and melt viscosity.They were 200 kJ/mol and 255 kJ/mol,respectively.The better spinnability of B-PACS was approved by spinning experiments,and finer BPACS green fibers were obtained.The tensile strength of Si-Al-C-O fibers from PACS and B-PACS were 2.0 GPa and 2.4 GPa,respectively.The higher strength of Si-Al-C-O fibers from B-PACS might be related with the finer diameter of the green fibers and the high molecular weight fraction in B-PACS.The SiC(Al) fibers derived by curing PACS and B-PACS green fibers at 1800℃ in Ar were compact and smooth,while the SiC fibers derived from PCS had pores and defects.The introduction of Al into SiC fibers may reduce the growth of SiC crystallites in fibers.The average sizes of SiC crystallites in fibers derived B-PACS,PACS and PCS were 8.5 nm,9.6 nm and 14 nm,respectively.
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发布时间：2021-03-19 - 摘要：Fuctionalized polystyrene containing salicycylic acid end groups was prepared through atom transfer radical polymerization (ATRP) of styrene using 5-（chlorosulfonyl）salicycylic acid as initiator,which was obtained by chlorosulfonation of salicyic acid,CuCl as catalyst and Bpy as ligand,then coordinated with Tb(Ⅲ).The polymerization displayed living characters as evidenced by a liner increase of molecular weight with conversation and a relatively narrow distribution (Mw/Mn less than 1.40).PSt with an ω-chlorine atom in the chain end could be used as a macroinitiator to initiate MMA to form block copolymer (PSt-b-PMMA).With ［MMA］/［macroinitiator］/［CuCl］/［Bpy］=100∶1∶1∶1,the polymerization was carried out in solution (cyclohexanone) at 90℃.After 7 h,the molecular weight measured by GPC increased from 3590 to 11240,and the polydispersity index ranged from 1.23 to 1.50 with the conversion up to 78.1%;The end structure of PSt was analyzed by 1H-NMR,and PSt can be used as a macroinitiator for block copolymerization,which also proved that the polymerization could be controlled.At the same time,because of the existence of phenolic hydroxyl and carboxylic groups,the subsequent functionalization led to novel functional materials.The polystyrene ligand was applied to prepare Tb(Ⅲ) complex.The polystyrene ligand and its complex were characterized through IR,UV-Vis and fluorescent spectra.The IR spectra of polystyrene ligand and its Tb(Ⅲ) complex showed that the band at 1683.4 cm-1 (ν(COOH)) disappeared,and the absorption band at 1210.8 cm-1 (ν(Ar—OH)) also disappeared.These results indicate that the —COOH and Ar—OH are coordinated with the Tb(Ⅲ) ion.From the UV-Vis spectrum when polystyrene ligand coordinated with Tb(Ⅲ) the absorption band at 300 nm became small,which was assigned to the charge transfers between central terbium atom and coordinated atoms.According to the fluorescent emission spectra when excited at 305 nm,the complex emitted characteristic fluorescence of Tb(Ⅲ).The effects of monomer to initiator mole ratio on the living polymerization characters and the effects of different molecular weights and reaction methods on fluorescent intensity were discussed here.Choosing small molecular weight of PSt could augment the fluorescent intensity,and microwave irradiation could accelerate the reaction rate.Compared with analogous Tb(Ⅲ) complexs by doping,coordinating of Tb(Ⅲ) ion and the polymer end group and copolymerization of Tb(Ⅲ) metalorganic complexes and other monomers,the complex was soluble in common solvents,easy to form film and show intensive fluorescence.
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发布时间：2021-03-19 - 摘要：This paper presented a method for the preparation of raspberry-like inorganic-organic composite particles with poly(vinyl acetate) (PVAc) as core and nanosilica particles as shell.A small amount of anionic reactive surfactant,3-allyloxy-2-hydroxy-1-propanesulfonic acid sodium salt (HAPS) was used as co-stabilizer.Composite particles were obtained via the free radical copolymerization of VAc with HAPS in the presence of aqueous nano-silica dispersions.At the same time,nanosilica particles were deposited onto the surfaces of organic particles via the formation of hydrogen bonds between nanosilica particles and PVAc particles.It turned out that only acidic silica sol could stabilize the latex.Samples prepared using basic silica sol (modified with ammonia) showed large aggregates during the polymerization.At the same time,a very small amount of various surfactants, e.g., nonionic surfactant (OP-10,OP-40),anionic surfactant (SDS,HAPS) and cationic surfactant (MTC,CTAB) were tried for the synthesis of SiO2/PVAc latex in combination with nanosilica particles as stabilizer,it was found that only HAPS could act as the co-stabilizer to ensure the polymerization stability,which maybe due to the electrostatic interaction between nanosilica particles and the surfactant.TEM showed that the obtained composite particles have typical raspberrylike morphology,indicating the hydrogen bonds between nanosilica particles and PVAc were strong enough for the formation of long-stable composite spheres.It was found that the average particle size of SiO2/PVAc composite particles ranged from 200 nm to 500 nm and tended to decrease with increasing silica content from 3 g to 21 g,which had the same behavior as traditional emulsifiers.At the same time,The latexes prepared by 3 g and 9 g of silica only exhibited slight shear-thinning behavior (very close to the Newtonian fluid).However,when 15 g or 21 g silica were employed,the latexes displayed a strong shear-thinning behavior.Based on the stabilization mechanism presented in our previous work,it was believed that some hydrogen bonds formed between hydroxyl groups of the silica particles and increased the viscosity of the latex.However,the hydrogen bonds were easily cleaved under mechanical stirring.
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发布时间：2021-03-19 - 摘要：Morphologies and viscoelastic behavior of high density polyethylene/nylon 6 (HDPE/PA6) blends compatibilized by maleic anhydride grafted high density polyethylene(HDPE-g-MAH) were studied through observation of scanning electron microscope(SEM) and dynamic rheological testing.It is found that HDPE-g-MAH can efficiently enhance the compatibility between PA6 and HDPE and improve the dispersion of PA6 and the interfacial state of phases due to in situ forming of graft copolymer (HDPE-g-PA6).Such improvement appears more obviously with the increasing of HDPE-g-MAH content when the concentration of HDPE-g-MAH is below 20 wt%.Hence,change of HDPE-g-PA6 amount also results in corresponding variations of linear viscoelastic behavior for the blends.The zero shear viscosity of blends increases with the addition of HDPE-g-MAH and approaches invariablenes with 20 wt% HDPE-g-MAH.At low frequency region the dependence of storage modulus on frequency for the blends tends to be weakened with the increase of HDPE-g-MAH concentration and begins to show “second plateau" with 10 wt% HDPE-g-MAH.These phenomena reflect macromolecularchains entanglement enhancement due to HDPE-g-PA6 forming.Both changes in morphologies and viscoelastic behavior for blends are ascribed to formation of HDPE-g-PA6.Compared with SEM observation,dynamic rheological testing gives much information about interface and interaction between macromolecular-chains.It is suggested that structure evolution with increase of HDPE-g-MAH content for HDPE/PA6 blends can be characterized preferably by using dynamic rheological measurements.
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发布时间：2021-03-19 - 摘要：In order to prepare a coreshell structure latex with a narrow size distribution and without the secondary nucleation to form new latex particles,a method was given for calculating the amount of surfactant，sodium dodecyl sulfate(SDS) ,in the process of multi-step seeded semi-continuous emulsion polymerization.From the total area of soap adsorbed particles and the effective molecular surface area of the soap,the above quantities can be calculated.In this method,the number of particles was the weight of monomer divided by the average particle weight,the seed particle density and average particle size could be measured by weighing strips of particles of measured volume and TEM,and the effective molecular surface area of the soap could be determined by soap titration.The influence of the amount and dropping speed of surfactant in every polymerization stage on the particles structure was studied.The amount of surfactant needed in the second and third polymerization stage was decided by both the amount surfactant added in the seeded polymerization and the particle size of seeds.A core-hell latex was synthesized with a narrow size distribution and without secondary nucleation when the amount of monomer for the seed,core and shell was 12 g,50 g and 50 g,the amount of surfactant was 0.4 g,0.64～2.07 g and 0.04～2.12 g,respectively,and the dropping speed of pre-emulsified monomer was below 0.021 mol/min.The core-shell morphology,size distribution of the final latex were confirmed by TEM analysis.
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发布时间：2021-03-19 - 摘要：Poly(9-bromofluorene) (PBF) films and poly(9,9-dichlorofluorene) (PDCF) films were electro-synthesized successfully by direct anodic oxidation of 9-bromofluorene (BF) and 9,9-dichlorofluorene (DCF) using a middle-strong Lewis acid boron trifluoride diethyl etherate (BFEE) as the solvent and the supporting electrolyte containing 0.02 mol/L BF and 0.05 mol/L DCF,respectively.The oxidation potential onset of BF and DCF in pure BFEE was 1.45 V versus SCE and 1.67 V versus SCE,respectively,which were much lower than those determined in acetonitrile containing 0.1 mol L-1Bu4NBF4 (BF,1.95 V versus SCE and DCF,2.19 V versus SCE).For spectral analysis,polymers were dedoped with 25% ammonia for 3 days.Then,they were dried at 60℃ for 24 h.For characterization of the structure and properties of as-formed polymers,UV-Vis,fluorescence,FT-IR,and 1H-NMR spectra of the polymers were determined.In the FT-IR spectra of BF or PBF,the peak at 650 cm-1 was the characteristic absorption of the C—Br bond.Three peaks at 819,759,737 cm-1 suggested that PBF was 1,2,4trisubstituted.Similarly,the peak at 802 cm-1 was the characteristic absorption of the C—Cl bond in the IR spectra of DCF and PDCF.Additionally,the peaks at 867,731,829 cm-1 indicated that PDCF was also 1,2,4-trisubstituted.FT-IR and1H-NMR spectral investigations indicated that electrochemical polymerization of BF and DCF mainly occurred at 2,7 positions.According to the UV-Vis spectra of the monomers,the UV-Vis spectra of PBF showed red-shfited absorption at 334 nm,and the PDCF showed broader absorption at 290 nm,342 nm,indicating higher conjugation length of backbone of the polymer.In the fluorescence spectra,the emission peaks of BF and DCF monomers appeared at 334 nm and 338 nm,respectively while those of PBF and PDCF in DMSO appeared at 396 nm and 537 nm,implying the blue-light-emitting property of PBF and the green-light-emitting property of PDCF.The main reason contributing to different light-emitting properties of PBF and PDCF was the electron-withdrawing effect of Cl and Br atoms.The electrical conductivity of PBF and PDCF films was measured to be nearly 10-1 S/cm.These semi-conducting and emitting properties will be greatly helpful for the applications of PBF and PDCF films.
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发布时间：2021-03-19 - 摘要：A novel amphiphilic biodegradable polyester,poly(tetraethylene glycol suberate) (PTEGSub),was synthesized viamelt polycondensation.The resulting polymers were characterized by GPC,NMR,FTIR,DTG and DSC measurements.These amphiphilic polymers are composed of short hydrophilic segments and short hydrophobic segments alternately along their main chains.These homopolymers with the amphiphilic monomers are just like the alternative copolymers of diacids and diols.The fact shows that 40 mg PTEGSub (Mn = 18700) could be dissolved in 100 mL deionized water.While it could be dissolved in the following solvents too:THF,chloroform,acetone,N,N-dimethylformamide (DMF),dimethyl sulfoxide (DMSO),ethyl acetate,ethylene glycol monomethyl ethyl,etc.These results support the conclusion that the polymer is amphiphilic,which could be dissolved in both hydrophilic and hydrophobic solvents.The polymers could self-assemble into polymeric micelles in water.A core-shell structure could be expected.The domains of enriched hydrophilic ethylene glycol oligomers might form a shell and the domains of enriched hydrophobic hydrocarbon ethylene chains would form a core.The diameters of the polymer micelles are mostly in the range of 20～120 nm from statistic data by DLS,although their molecular weights are different in water.This related with structure of PTEGSub whose hydrophilic segments and hydrophobic segments are short.At room temperature,the critical micelle concentrations (CMC) are 6.3×10-7,3.9×10-7,and 1.3×10-7g/mL when their molecular weights (Mn) are 18700,33300 and 50800,respectively.CMC diminished in accordance with the increasing molecular weights of polymers.Moreover,the success of CMC determination indicates that micelles in water are coreshell structure.Micellar morphologies in different solvents were observed by TEM.The micellar morphology is different depending on solvent.In aqueous solution,most micelles are regular spherical globules.Micelles are compact and beautiful geometrical shapes could be observed.Microphase separation of PTEGSub was studied.Spheres were found on polymeric film by AFM.This profile was proved to form during solvent volatilized on the base of TEM photographs.The result is related with two factors.On one hand,phase separation is prone to take place because solubility parameters are different between hydrophilic segments and hydrophobic segments in the solvent (THF).On the other hand,there is a strong attractive interaction between ester groups of PTEGSub and silanol hydroxyls of hydrophilic mica.However,the interaction of other segments (groups) with the mica surface is weak.Thereby,phase separation is promoted.The process is going on until viscosity of solution is so great when the segments of polymers could not move.The study of microphase separation will be the foundation for the theoretical investigation in near future.
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发布时间：2021-03-19 - 摘要：Fluorinated organic-inorganic hybrid materials were prepared using fluorine-containing monomers,silicone-containing monomers and tetraethyl orthosilicate by free-radical random copolymerization and sol-gel process,and applied as functional coatings onto aluminium alloy substrates.The fluorine-containing monomer used was dodecafluoroheptyl methyl acrylate(FA),and silicone-containing monomer used was vinyltriethoxy silane(VTES).Tetraethyl orthosilicate(TEOS) was added to prepolymerized FA-co-VTES (PFAS) solution to co-hydrolyze and co-condense with different addition values.The influence of inorganic component content (TEOS) on the physical properties of the coating films were characterized by FTIR,TGA,GPC,SEM,and XPS.The surface free energies of fluorinated organicinorganic hybrid materials prepared were estimated from the contact angle data measured by sessiledrop method. Transparent coating films with smooth surface and uniform thickness could be obtained by the dip coating technique.FTIR and XPS results indicated that,owing to the strong electronegativity of the fluorine atoms,hydrophobic perfluoroalkyl groups were preferentially enriched to the outermost layer at the coating filmair interface,and three layers probably existed in the coating film.The upper layer oriented toward the air was composed of mainly perfluoroalkyl groups originating from FA,the intermediate layer was composed of hydrocarbon backbone chain originating from vinyl polymerization,and the bottom layer was composed of mainly —O—Si—O— network originating from TEOS.The fluorinated organicinorganic hybrid materials prepared were very hydrophobic and exhibited excellent water repellency.It was demonstrated that the water repellency properties of PFAS/SiO2 hybrid materials was governed by hydrophobic perfluoroalkyl groups of the outermost layer.The contact angles of the coating films for water and methylene iodide were extremely high,at 120.9° and 93°,respectively,for TEOS/FA mole ratios at 1∶1,and their surface free energies were about 11.48 mJ/m2.An important role of tetraethyl orthosilicate (TEOS) was to increase the density of the reaction sites of the —OH groups with the surface area and the thickness of fluorinated organicinorganic hybrid coatings.It has been confirmed by FTIR and GPC results that the increase of TEOS amounts could enhance hydrolysis and condensation of alkoxide precursors to improve the adhesion between hybrid coating and aluminum substrates by the formation of Si—O—Al bonds.It was also testified that the increase of inorganic silica content had a significant effect on the improvement of thickness of the bottom SiO2 layer,while it had a slight influence on the surface wettability of the hybrid coatings.The useful properties of fluorinated organicinorganic hybrid coatings like better thermal stability and improved corrosion resistance,could be significantly enhanced by the improvement of thickness of the bottom SiO2 layer and bonding between SiO2 layer and aluminum substrates.Morphology analysis by SEM showed that the introduction of flexible organic phase could relax the stress and reduce the microcracks caused by the volume shrinkage of silicon network during heat treatment process.The thermal stability of fluorinated organicinorganic hybrid materials studied by using TGA technique could be improved with TEOS amounts.The burning temperature should be less than 290℃ because the perfluoroalkyl groups begin to decompose from this temperature.
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发布时间：2021-03-19 - 摘要：In order to improve the ionic conductivity of the poly(methyl methacrylate-co-maleic anhydride)(P(MMA-co-MAh))-based gel polymer electrolytes,the poly(ethylene glycol)methyl ether chains were introduced in the side of P(MMA-co-MAh)binary copolymer to prepare comb-like poly(methyl methacrylate-co-maleic anhydride)-g-poly((ethylene glycol)methyl ether)(P(MMA-co-MAh)-g-PEGME)copolymer.The comb-like copolymer P(MMA-co-MAh)-g-PEGME was synthesized through two esterification reactions.The esterification of P(MMA-co-MAh)with PEGME at first in butanone,then injecting a definite volume of p-toluenesulfonic acid into the reaction mixture under a flow of nitrogen.The mixture was stirred continuously for 24 h at 80℃.After the reaction was complete,solvent in the mixture was then removed.An excess amount of methyl alcohol and definite volume of dimethyl sulphate were added to the residue so as to thoroughly endcap the unreacted carboxyl groups.The reaction proceeded with continuous stirring for another 24 h at 60℃.The methyl alcohol in the reaction mixture was then removed.The crude product was purified by butanone/toluene reprecipitation,and dried at room temperature.Further more,the product must be purified three times using petroleum ether and deionized waters at 80℃ to get the purified product.The purified product was dried in a vacuum oven to remove the trapped solvent at 40℃ for 24 h.The final product is white power.The structure of the comblike copolymer was characterized by Fourier transform infrared spectroscopy (FTIR),which showed that the characteristic absorption of CO in anhydride at 1851 cm-1 and 1786 cm-1 disappeared,and the absorption of a saturated cyclic five-member anhydride(OC—O—CO)also disappeared.While a strong characteristic absorption of an ether group at 1152 cm-1 is shown.This is an evidence that appreciable amount of the anhydride has been esterified and the product is an ester of poly(ethylene glycol)mono.The structure of P(MMA-co-MAh)-g-PEGME polymer was further examined by 13C-NMR,1H-NMR and H,C-COSP spectra.The FTIR and NMR spectra indicated that the comb-like P(MMA-co-MAh)-g-PEGME copolymer was successful synthesized.The thermal properties of P(MMA-co-MAh)-g-PEGME were studied by thermogravimetric analysis (TGA)and differential scanning calorimetry (DSC).The TGA indicated that the thermal stability of P(MMA-co-MAh)-g-PEGME polymer was littler lower than that of P(MMA-co-MAh)copolymer.The decomposition temperature of the comblike polymer P(MMA-co-MAh)-g-PEGME is 325.9℃.The thermal stability of comb-like P(MMA-co-MAh)-g-PEGME copolymer and the P(MMA-co-MAh)copolymer are both better than that of the pure PMMA polymer.The DSC curves showed that the comb like polymer P(MMA-co-MAh)-g-PEGME had two glass transition temperatures(Tg),the one glass transition of the main-chains,which was at around 120℃,and the other was about 32℃,which can be considered as the glass transition of the sidechains.The sidechains can move at room temperature,which will help to transfer and expand the electro active material.
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发布时间：2021-03-19 - 摘要：High molecular weight block copolymers with different backbone compositions were synthesized from eugenol end capped polydimethylsiloxane (PDMS)and fluorophenylterminated poly(phthalizinone ether nitrile)(PPEN)oligomers.These oligomers of PPEN were prepared via SNAr stepgrowth polymerization from 4-(4-hydroxylphenyl)(2H)-phthalazin-1-one (DHPZ)and 2,6-difluoro-benzonitrile(DFBN)using DMSO as solvent at 180℃.The oligomers with welldefined fluoroterminated and various quantitative molecular weights were obtained by using an excess of DFBN.The number-average molecular weight (Mn)values of PPEN oligomers ranged from 3100 to 10500.The eugenol terminated PDMS oligomers were prepared by reacting silane terminated PDMS with eugenol in toluene via the well-known Ptcatalysed hydrosilation reaction.The phenolgroup of eugenol was protected by trimethylchlorosilane in the hydrosilation to avoid side reactions and loss of functional group,and the aryl-trimethylsilyl ethers can be cleaved by refluxing in aqueous methanol.The Mn values of PDMS oligomers were 4550 and 7220,respectively.The block polycondensation was carried out in the presence of dimethyl sulfoxide/o-dichlorobenzene and K2CO3 as solvents and catalyst at 180℃ by the SNAr reaction.The Mn values of block copolymers ranged from 19400 to 25100.The results of GPC indicated that reaction of two oligomers occurred and then the higher molecular weight copolymers were obtained.It further suggested that the new synthesis method is an effective and convenient approach to prepare similar PDMS based block copolymers.The structure of copolymers obtained was characterized by FTIR and 1H-NMR.Differential scanning calorimetry analysis indicated that the block copolymers showed two glass-transition temperatures (Tg) at -98～-90℃ and 255～287℃,respectively.The distinct twoTg’s in the block copolymers suggested that microphase separation occurred in the block copolymer.The copolymer also showed a high thermal stability with 10% weightloss temperatures in excess of 450℃ in nitrogen according to thermogravimetric analysis.The migration of PDMS segments to the copolymer surface was observed directly by atomic force microscope (AFM) and transmission electron microscope (TEM).PDMS expanded to the continuous phase on the surface,suggesting that PDMS segments were rich on the surface.The PPEN phase as the particle cavities was dispersed in copolymer surfaces with diameters of 0.1～0.3 nm.
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发布时间：2021-03-19 - 摘要：Rubber was used as an additive instead of an inorganic filler to mediate the thermal expansion behavior of plastics.This is based on the fine control of the microstructure so that the expansion is preferentially along the thickness direction.Reactive extrusion and injection molding processes were employed for deformation of the rubber domains into microlayers.It is found that when the rubber domains are deformed into microlayers and cocontinuous with the plastic matrix,the coefficient of linear thermal expansion (CLTE)in directions parallel to the microlayers decreases to a very low value.The relationship between the content of styrene/ethylenebutylene/styrene block copolymer (SEBS),the crystallization behavior of polyamide 6 (PA6)and CLTE for injection-molded PA6/SEBS blends was investigated.It was found that when the content of SEBS phases exceeded 20 wt%,the CLTE of PA6/SEBS in flow direction decreased drastically.TEM observation showed that both the plastic and rubber phases were elongated and orientated along flow direction (FD),and PA6 crystals were mostly oriented normal to the SEBS layers.WAXD measurements demonstrated that b-axis of PA6 unit cells preferred to orientation along FD based on the calculations of the degree of orientation for PA6 crystallographic axes,and the CLTE of PA6 lattice was determined to be 7.0×10-5 K-1,-5.8×10-5 K-1,and 25.8×10-5 K-1 for a,b,and caxes,respectively,for the injectionmolded PA6/SEBS (60/40).Since the baxis has thermal retraction effect,the orientation of b.axis along FD might provide the second driving force to reduce the CLTE of injection-molded PA6/SEBS.
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发布时间：2021-03-19 - 摘要：In order to obtain homogeneous,smooth and size controllable layers of thermosensitive polymer on superfine silica particles,a novel synthetic route was developed.The thermosentive polymer,poly(N-isopro-pylacrylamide)(PNIPAM),has successfully been grafted onto the surface of superfine silica particles.The synthetic procedure includes the connection of silane coupling agent γ-glycidylpropyltrimethoxysilane (KH-560) with the superfine silica particles,reaction of diethanolamine with glycidyl group of KH-560,and reaction of 2-bromoisobutyryl bromide with resulting hydroxy groups respectively,and finally the ATRP reaction of N-isopropylacrylamide grafting on the superfine silica particle surface.The ATRP was carried out at room temperature in the present of CuCl as a catalyst,ME6TREN as a Ligand,and (50∶50,V/V) DMF/H2O as a reaction medium.The resultant composite particles afforded a coreshell structure.The composites particles were characterized by FTIR,TG,EA,SEM,DSC.The weight losses in TG analysis showed that γ-glycidylpropyltrimethoxysilane,diethanolamine,2-bromoisobutyryl bromide and PNIPAM attached to the silica particles step by step according to the designed route.The grafting ratio of PNIPAM on the surface of silica particles reached to 25.2％ based on the superfine silica.The diagram of DSC indicated the composite silica particle was thermosensitive with LCST of 34.1℃.The GPC measurements for the PNIPAM cleaved from the composite silica particles gave an average molecular weight of 8000,and the molecular weight distribution of 1.06.The SEM images revealed that the modified composite particles had smooth surface,displaying the superiority of active polymerization of ATRP.The results showed that the grafting ratio in this method was higher than that of other methods,the thermosentive polymer on the surface of superfine silica particles formed a homogeneous,smooth and flat layer film,and the modified superfine silica particles will potentially have applications in HPLC.
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发布时间：2021-03-19
Research Article
- 摘要：The anionic polymerization of cyclosiloxane in aqueous emulsion was performed with octamethylcyclotetrasiloxane(D4) as monomer and benzyldimethyldodecylammonium hydroxide (BDAH) as catalyst and emulsifying agent.The innovation of this study includes:(1) Based on the analysis of elementary reaction,the forming mechanism of concentration of active center was proposed.(2) The changing rule of the concentration of active centers with reaction was quantitatively obtained according to the generalized kinetic model of ring_opening polymerization of cyclosiloxanes.Emulsion polymerization recipe used in this study consists of octamethylcyclotetrasiloxane,benzyldimethyldodecylammonium hydroxide and water. All materials were heated up to reaction temperature (wmonomer∶wBDAH∶wwater=33∶1∶66).The mixture was then homogenized for 1 min to obtain emulsion.The emulsion was transferred to a glass reactor,and nitrogen was bubbled through the solution.The reaction temperature was adjusted with a constant temperature water bath.The polymerization was carried out under mechanical stirring (200 r/min).A certain amout of reactant was taken out during the course of polymerization and neutralized with glacial acetic acid to a pH near 8 in order to stop the reaction,and then used for measuring the needed data.The bulk polymerization of cyclosiloxane was performed with octamethylcyclotetrasiloxane (D4) as monomer and benzyldimethyldodecylammonium hydroxide as catalyst.And the sample was periodically taken out for conversion measurements.The anionic polymerization of cyclosiloxane in aqueous emulsion was performed.The conversion and the molecular weight of synthesized polymer were examined by gel permeation chromatography (GPC).The forming mechanism of concentration of active center was proposed,and the changing rule of the concentration of active centers with reaction was quantitatively obtained.The results show that the concentration of active center gradually increases to a steady state when the temperature is relatively low,and that the concentration of active center only increases monotonously with time when the temperature is relatively high.
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发布时间：2021-03-19 - 摘要：The nonliquidphase coordination crosslinking reaction of acrylonitrilebutadiene rubber/copper sulfate(NBR/CuSO4) mixture was investigated by differential sanning calorimetry (DSC),Fourier transform infrared (FT-IR) spectrometry and X-ray photoelectron spectroscopy (XPS).The NBR/CuSO4 mixture specimens for DSC and FT-IR were prepared in an open two-roll mill at room temperature by blending NBR (100 phr) and CuSO4 powders (10,20 and 30 phr,respectively).Specimens for XPS test were prepared by molding NBR/CuSO4 mixtures at 120,170,190 and 200℃ for 20 min.DSC results showed that pure NBR was thermostable and inert between 150℃ and 270℃,while the curves of NBR/CuSO4 mixtures presented three thermo positive peaks in the temperature range from 150℃ to 330℃.FT-IR spectrometry indicated that the polymer structure of the specimens maintained without noticeable alteration at temperatures below 200℃.It means there were no oxidations or other exothermal reactions except for the probable coordination reaction between —CN and Cu2+.N1s XPS spectrum of NBR/CuSO4 mixtures only displayed a single peak with a binding energy of 399.1 eV belonging to free —CN at lower temperature(120℃),while fitting N1s spectrum gave two secondary peaks at 399.2 eV and 401.3 eV at the test temperature of 170℃,190℃ and 200℃,and the latter was attributed to coordinated —CN.It bore out that the coordination reaction of —CN and Cu2+carried out well and truly.Moreover,it was confirmed that the first thermo positive peak of DSC was attributed to the coordination crosslinking reaction of —CN and Cu2+in the non-liquid-phase mixture.The apparent activation energy and reaction order of the non-liquidphase coordination crosslinking reaction were evaluated by Kissinger method and Crane equation.With CuSO4 content of 10，20 and 30 phr the results of apparent activation energy were 86.22,85.89 and 83.98 kJ/mol，and the reaction orders were around 0.9.
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发布时间：2021-03-19 - 摘要：In order to improve the cycle stabilities of tin based anode materials and keep their high capacities,Sn/C composites with different carbon contents were prepared by disperse polymerization and pyrolysis of poly(para-divinyl benzene)encapsulated tin dioxide nanoparticles.The morphologies of Sn/C composites were analyzed by means of transmission electron microscope (TEM) and powder X-ray diffraction (XRD).Tin-based particles(about 100 nm) can be uniformly distributed in carbon matrix when the carbon content in composite exceeded 50 wt%.With the decrease of carbon content,the aggregation of tin oxides became serious for no enough carbon as barrier,and the diameter of tin based particles increased.During the pyrolysis of poly(para-divinyl benzene),part of SnO2 was reduced into metallic tin and SnO,and as the carbon content in composite increased,the degree of reduction increased.The electrochemical performances of Sn/C composites as electrodes were compared.Electrochemical performances of the Sn/C composite depended on morphologies of tin and carbon phases.The reversible capacities of Sn/C composites increased with the decrease of carbon content because the pyrolyzed carbon showed a low reversible capacity.On the other hand,the cycle ability of Sn/C composites increased as the carbon content increased because the carbon effectively suppressed the sintering agglomeration of tin based material and maintained the electrical conductivity of composites.Further,the morphologies of electrodes were analyzed by SEM and XRD.With the increase of carbon content,the electrochemical sinter of tin based material in electrode was inhibited.The different morphologies of various electrodes were consistent with their different cycle performances.According to the analysis results of morphologies and properties of Sn/C composites,stable electrochemical performances of the Sn/C composites can only be achieved by homogeneous dispersion of the tin-based particles in carbon matrix so as to avoid aggregation of tin and its pulverization and to keep conductivity of the Sn/C composites.
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发布时间：2021-03-19 - 摘要：The oil in water (O/W) type raw lacquer emulsion (RLE) was prepared by using a mixed emulsifier of urushiolbased emulsifier (UE)/polyvinyl alcohol (PVA).The effects of concentration of urushiolbased emulsifier UE10 (cUE10),mixed emulsifier UE10/PVA concentration (cME) and the structure of UE on the rheology of RLE were investigated.The results showed that the viscosity of RLE increased with increasing cUE10,and RLE exhibited shearthinning behavior.At low concentration of mixed emulsifier UE10/PVA(cME≤8.5%),RLE belonged to pseudoplastic fluids,and shearthinning character was observed.As cME was increased to no less than 9.0%,the viscosity of RLE decreased remarkably with the increasing of shear rate,pass through a minimum,then increased slowly with increasing shear rate,and RLE exhibited swell fluids characteristics.The viscosity of RLE increased with increasing the chain length of oxyethyl groups in UE molecules,and the flow curves of RLE prepared by UE with different chain length of oxyethyl groups were well described by the Hershel-Bulkley equation.Networklike structure between RLE particles became stronger with increasing of chain length of oxyethyl groups in UE molecules.
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发布时间：2021-03-19 - 摘要：A new gelator 3-hydroxy-2-［N-(carboxypropyl carbonyl)amino］ pyridine(defined as SWG) was synthesized from 3-hydroxy2-amino pyridine and glutaric anhydride by a simple procedure.The gelator structure was confirmed by IR,1H-NMR and elemental analysis.The characteristic peaks of 2576 cm-1and 1906 cm-1 in the IR spectrum indicated the formation of hydrogen bonds between carboxylic acid and pyridyl groups.Supramolecular hydrogels were formed within 1 min via cooling the 1.5 wt% SWG aqueous solution in an ultrasonic vessel at 20℃ under different ultrasonic powers.However,only macroscopic crystals were formed in the same solution without ultrasonic treatment.The gels were analyzed by SEM,DSC and geltosol dissociation temperature(Tgel) measurements.The results indicated that SWG molecules assembled into aggregating fibers during the gelating process.With increasing the ultrasonic powers from 200 W to 500 W,the fiber width decreased from 8 μm to 2 μm,the network density increased,the freezing water content increased from 86.5% to 96.1%,and the Tgel increased from 60℃ to 70℃.Therefore the ultrasonic treatment is effective in controlling gel structures and properties.Furthermore,the gel with larger fiber,more compact fibrillar network and higher Tgel were obtained as increasing the gelator concentration from 1 wt% to 2.5 wt%.The X-ray powder diffraction (XRD) analysis of xerogel and powder samples of SWG indicated that the molecules assembled in a preferred direction during the gelating process.These results are important for understanding the gelating mechanism and designing new hydrogels.
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发布时间：2021-03-19
Research Bulletin
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