最新刊期
卷 ， 期 4 ， 2008
- 摘要：Synthesis and supramolecular self-assembly of hyperbranched polymers (HBPs) have received more and more attention in recent year,and many delicate supramolecuar structures at all scales and dimensions were generated up to now.However,most of the work reported the one-step self-assembly process from HBPs to supramolecular aggregates.Herein,we report a hierarchical self-assembly of HBPs: the polymer first self-assembled into giant polymer vesicles,and then the vesicles further aggregated into macroscopic surpramolecular network.Two kinds of amphiphilic multiarm copolymers with a same hydrophobic hyperbranched poly［3-ethyl-3-(hydroxymethyl)oxetane］ (HBPO) core and different hydrophilic poly(ethylene oxide) (PEO) and poly(2-(dimethylamino)ethyl methacryate) (DMAEMA) arms were synthesized by a “graft from" method.The obtained HBPO-star-PEO can self-assemble in water into giant vesicles,and the HBPO-star-PDMAEMA is pH-responsive and can self-assemble in water into large multimolecular micelles.However,when the two polymers were mixed together,they would co-assemble into pH-responsive giant vesicles around 1～10 μm in water.The self-assembly behavior of the complex vesicle was studied by zeta potential analyzer,laser scanning confocal microscope (LSCM) and optical microscope.The results show that the complex vesicles were electriferous in the solution,and the iso-electric point (IEP) was 8.6,which indicated that PDMAEMA chains were located in the shells of the complex vesicles.At the pH below IEP,the complex vesicles were stable and could be suspended randomly in the solution because of the protonization of PDMAEMA chains.When the solution pH was higher than IEP,the vesicles gradually aggregated together to form the supramolecular structures like pearl necklace and the grape bunch with the increase of pH due to the deprotonation of the vesicles.At an even higher pH,the vesicles aggregated to a threedimensional macroscopic network like a spider web.It is a novel supramolecular structure and belongs to macroscopic molecular self-assembly.The strong cohesion of the individual vesicles is responsible for the formation of such a macroscopic and highly branched vesicle network.It is expected that the present work will give a new light on controlling the hierarchical self-assembly of vesicles and on the preparation of branched and network supramolecular systems.In addition,the supramolecular network can be used as a complex template to direct the self-assembly of some inorganic precursors.
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发布时间：2021-03-19
Rapid Communications
- 摘要：Based on molecular dsign,a series of amphiphilic compolymers with different molecular structures and morphologies were synthesized via various methods such as free radical polymerization,etherification,esterification,atomic transfer radical polymerization(ATRP) and reversible addition fragmentation chain transfer(RAFT) polymerization, etc. The synthesis process,reaction conditions,and mechanisms were studied in detail.The structures of the resultant copolymers (including graft,block,alternate and super-branched etc.) were characterized by spectroscopy,and their properties were examined.These amphiphilic copolymers have various morphologies,such as linear,comb-like,dumbbell-like,and chain-sphere-like etc.On basis of the structure characters of the amphiphilic copolymers and polymer membrane materials,the synthesized copolymers were selected and used as additives to prepare blend membranes.The effects of amphiphilic copolymers on membrane structure and properties were investigated detailedly.The hydrophobic chains in amphiphilic copolymers are generally miscible with special membrane materials,while hydrophilic chains provide the blend membranes with enhanced hydrophilicity and fouling resistance.The studied membrane materials in this work include poly(vinylidene fluoride) (PVDF),polyvinyl chloride (PVC),polysulfone (PSF),polyethersulfone (PES),poly(phthalazinone ether sulfone ketone) (PPESK) etc.The structures and properties of the blend membranes were controlled via tuning the thermodynamics and kinetics of membraneforming systems.It was found that,during the course of membrane formation,amphiphilic copolymer additives accumulated spontaneously and self-organized on membrane surface.The coatings of amphiphilic copolymers on membrane surface promoted notably the hydrophilicity and anti-fouling ability of porous polymeric membranes.Based on these results,a new methodology for membrane modification that “surface modification is achieved by simple blending” was put forward.In addition,the functional groups in amphiphilic copolymers could endow the blend membranes with some special functions,such as biocompatibility,environmental responsivity,enzyme immobilization, etc.
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发布时间：2021-03-19
Feature Articles
- 摘要：Each size-exclusion chromatography (SEC) curve generally exhibits two peaks when a solvent mixture is employed as the eluent.The first peak is the solvated-polymer peak and the second is the freesolvent peak.The area of the solvated-polymer peak A eff3 can be regarded as the sum of contributions from the naked-polymer A3 and from the extra polymer-bound solvent A1.The free-solvent peak,however,is caused by deficiency of the same solvent that enriches itself around polymer chains.Theoretical analysis shows that the size of free-solvent peak A2 and that of the extra polymer-bound solvent A1 are equal in magnitude but opposite in sign.This relationship suggests that the preferential adsorption coefficient λV can also be determined from the nalysis of the polymer peak. Polystyrene(3)-benzene(1)-methanol(2) is the system taken to test the correctness of the theoretical analysis. The polystyrene (PS) sample was purchased from Krauer Company,with Mw=9.26×104,and Mw/Mn=1.1. Solvents (analytical grade purity) were purified before use.Benzene was purified by repeatedly shaking with concentrated sulphuric acid (15 vol% benzene) in a separating funnel until the acid phase remained colorless.The benzene phase was then washed with water,aqueous sodium hydroxide (10 wt%),again with water,dried with anhydrous calcium chloride,and finally distilled. Methanol was fractionally distilled,and the middle cut was used.The eluents were benzene-methanol mixtures of different compositions at a flow rate of 0.4 cm3/min.The mixtures were made by volume and equilibrated in the reservoir of the GPC system.The injected sample solutions were prepared using solvent mixtures from the solvent reservoir.The range of volume fraction of benzene in the eluent U10 was from 1.00 to 0.80.All measurements were conducted at room temperature with a Waters Associates model 244DS liquid chromatograph,equipped with a model R401 differential refractometer and a model 730 microcomputer.A single column packed with Styragel (nominal porosity 50 nm,length 30 cm) was employed. When a solvent mixture is used as eluent,two measurements can be carried out,with and without column in place.When there is a column in place,the polymer-bound solvent will get separate from the free solvent.The selective binding of solvent to the polymer causes polymer-bound solvent signal and the polymer signal to merge.The measured peak area is Aeff3.In the experiment without column in place,there is a direct connection between the outlet of the injector and the detector. In this situation,the chromatographic system cannot separate the components.The free solvent,polymer-bound solvent,and the solute will elute at the same time.The composition deviations of polymer-bound solvent and free solvent to the original solvent mixture caused by preferential solvation can generate signals,but,since they elute at the same time,the contributions from them to the refractive index will cancel because of their opposite response signals.In this case the measured peak area is A3.When Aeff3 and A3 are available,the preferential adsorption coefficient λV can be obtained. For the system consisting polystyrene (3) plus benzene (1)-methanol (2) solvent mixtures,the values of λV from the present work are plotted against （1-u10），together with the results for the same system reported by Hert from measurements of dialysis equilibrium and light scattering technique.The agreement of the present results with those from previous work shows that the proposed method is valid.The advantages of studying the solvated polymer peak are discussed. This method provides an alternate way to determine specific refractive index increment at constant potential (dn/dc)μ for polymer/mixed solvent systems.
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发布时间：2021-03-19 - 摘要：A modified nano-calcium carbonate (R-CCR) was prepared by coating a layer of unsaturated hydroxyl-fatty acid on the surface of CCR powders using a solid state method,the latter were commercial nano CaCO3 modified with stearic acid. FTIR studies indicate that the modifier is combined on the surface of CaCO3. PP/EPDM/nano CaCO3 ternary composites are prepared by a melt-mixing method. SEM and TEM are utilized to examine the morphology of the composites.The tensile fractured surface of PP/EPDM/R-CCR shows a fibroid morphology and large-scale yield deformation.The impact fractured surface shows that the amount of cavities in PP/EPDM/R-CCR systems is increased and their size diminishes obviously.R-CCR particles were dispersed uniformly in PP matrix,and their compatibility was distinctly improved as compared with CCR as the amount of R-CCR was 15 phr.The tensile strength remains nearly constant (reduces from 27.6 MPa to 27.5 MPa) while the impact strength increases from 9.6 kJ/m2 to 15.6 kJ/m2 as CCR is replaced by R-CCR.Meanwhile the flexural strength and flexural modulus are also increased correspondingly.Furthermore,the impact strength of PP/EPDM/R-CCR keeps on a high level (15.6 kJ/m2) which is more than the sum of that of PP/EPDM and PP/R-CCR (6.63 kJ/m2 and 6.04 kJ/m2 respectively).It indicates the R-CCR and EPDM has significant synergistic toughening effect on PP,keeping the strength,modulus of virgin PP as well.Both the storage modulus G′ and loss modulus G″ of PP/EPDM and PP/EPDM/R-CCR composites increase with increasing frequency,but the values of G′ and G″ of the tertiary composite are relatively in a higher level than that of the binary system.The loss factor and viscosity decrease with increasing frequency but there has little difference between tertiary and binary composites.The apparent viscosity η of the tertiary system containing R-CCR is lower than that of tertiary system containing CCR and virgin PP. The viscosity of composite significantly decreases with increasing shear rate. The measured mechanical properties of the composites indicate that replacing of CCR by R-CCR for binary composites could simultaneously enhance the toughness and strength of PP.
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发布时间：2021-03-19 - 摘要：Carbon nanotubes (CNTs) have outstanding characteristics including high mechanical properties,namely tensile strength and elastic modulus,and still remarkable flexibility,excellent thermal and electric conductivities,low percolation thresholds (loading weight at which a sharp drop in resistivity occurs) and high aspect ratios (length to diameter ratio,L/D),while the latter provides the nanotubes with additional advantage over spherical fillers to obtain high property composites.Therefore,CNTs have the potential to act as a reinforcing filler of polymer matrices.The tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) cured with 4,4′-diaminodiphenylsulphone (DDS) and filled with graphite or carbon fibers are commonly used as a polymeric matrix in high performance composites employed in the aircraft and spacecraft industries.In present paper,multi-walled carbon nanotubes (MWNTs) as a nanofiller were incorporated in the TGDDM/DDS epoxy.The thermal properties of the composites were studied by differential scanning calorimetry (DSC),dynamic thermal analysis (DMTA) and thermalgravitimetric analysis (TGA).In addition,the dispersion of MWNTs in the epoxy was also investigated by scanning electron microscopy (SEM).In DSC studies,Kissinger and Flynn-Wall-Ozawa (FWO) methods were used to study the nonisothermal cure kinetics of the MWNTs filled TGDDM/DDS composites at different heating rates.The activation energy (Ea) of cure reactions of the MWNTs filled epoxy composites was obtained by Kissinger and FWO methods.For all composites,the Ea obtained by Kissinger method was slightly less than that of FWO method.With the addition of MWNTs,the Ea of the epoxy composites decreased first and then increased with the increase of the MWNTs contents.These results showed that the incorporation of carbon nanotubes accelerated the cure reaction of the TGDDM/DDS epoxy at lower MWNTs content due to the interaction between the hydroxyl groups on the surface of nanotubes and the epoxy.However,due to the high surface energy of carbon nanotubes,the viscosity of MWNTs/epoxy composites increased at higher MWNTs content.Hence,the mobility of hydroxyl groups was hindered,and the reaction energy of composites increased with increasing MWNTs contents.The influence of carbon nanotubes on the thermal stability of the epoxy was studied by TGA.It is shown that MWNTs had little influence on the thermal stability of the cured epoxy.The storage modulus and glass transition temperature of MWNTs filled TGDDM/DDS were investigated by DMTA.It is seen that the storage modulus of TGDDM/DDS system was enhanced with the increasing of MWNTs content,that is,the modulus increased 6.3% and 7.8% at 1 wt% and 5% MWNTs content,respectively.The glass transition temperature of the epoxy slightly decreased.Furthermore,the DMTA results of MWNTs/TGDDM/DDS composites were compared with that of carbon nanofibers (CNFs)/TGDDM/DDS composites.It was shown that the interactions between CNFs and epoxy were better those between that MWNTs and epoxy.The dispersion of carbon nanotubes in the epoxy was studied by SEM.The SEM results suggest that of MWNTs had poor dispersion in the cured epoxy.However,the radii of carbon nanotubes in the epoxy were greater than those of pure nanotubes.These results show the existence of interaction between carbon nanotubes and epoxy.
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发布时间：2021-03-19 - 摘要：Thermosetting phenylethynyl terminated polyimides are well known for their super thermo-oxidative stability and excellent toughness,and have been widely used in aerospace area.PETI-5 (PhenylEthynyl Terminated Imide-5) developed by NASA is the-state-of-art of this type polyimides,while it is a semi-crystalline polyimide with melting temperature of 353℃ near the crosslinking temperature of phenylethynyl groups,which made it difficult for PETI-5 to fabricate complex shape parts.In the pursuit of novel phenylethynyl terminated polyimides with high melt processability,researchers have developed several polyimides by introduction of fluorine groups and twisty structures.In this paper,a series of oligoimides (PIO) with calculated molecular weight of 5000 were prepared using flexible dianhydride of 4,4′-oxydiphthalic anhydride (ODPA),and mixtures of two diamines of 1,3-bis(4-aminophenoxy)benzene (1,3,4-APB) and 3,4′-oxydianiline (3,4′-ODA) in the presence of 4-phenylethynylphthalic anhydride (4-PEPA) as endcapping agent in order to enhance the processability.In addition,oligoimides (PIB) using 3,3′,4, 4′-biphenyltetracarboxylic-dianhydride (s-BPDA) were also prepared for comparison.Effects of the kind of dianhydride and diamine on their properties and melt processabilities were systematically investigated.Experimental results indicated that PIO was amorphous in nature,and exhibited low melt viscosity and high melt viscosity stability at elevated temperatures,and with the increase of the content of 1,3,4-APB the melt viscosity decreased correspondingly.The PIB is semi-crystalline in nature and exhibited high melt viscosity at elevated temperatures,meanwhile,the melt temperature of PI-B was close to the cure temperature of phenylethynyl groups,which reduced the processability.The molecular weight-controlled oligoimides could be thermally cured at 371℃ to yield thermosetting polyimides by polymer chain extension and crosslinking of phenylethynyl groups.All cured resins showed good thermal stability with 5% weight loss temperature of500℃,and high glass transition temperatures of243℃.In addition,with the increase of the content of 1,3,4-APB,the glass transition temperatures of PIO cured resin decreased from 281 to 243℃.PIO-2 cured resin also exhibited good mechanical properties with tensile strength of 102 MPa,tensile modulus of 1.8 GPa,high break elongation of 10%,flexural strength of 142 MPa and flexural modulus of 3.1 GPa.
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发布时间：2021-03-19 - 摘要：Ring-opening metathesis polymerization (ROMP) is a widespread tool for synthesizing well-defined and highly functionalized polymers.The catalyst is an important factor which affects the ROMP of monomers.It is well-known that the ruthenium-based Grubbs’catalysts have good solubility in non-polar solvents such as CH2Cl2,benzene and toluene,but their solubility in polar solvents such as alcohol,acetone and ionic liquid was very poor,which limited their applications for ROMP in polar solvents.In this paper,an imidazolium saltsupported ruthenium catalyst was synthesized,and its catalytic performance for ROMP of polar or nonpolar cycloolefinic monomers in ionic liquid ［BMIm］BF4 was investigated.A novel pyridyl ligand 2,3-dimethyl-1-2-(4-pyridyloxy)ethyl］ imidazolium hexafluorophosphate (4) was initially designed and synthesized,and its single crystal was obtained.The crystal is monoclinic with the parameters as follow: P21/c,a=1.2469(5) nm,b = 1.6470(7) nm,c=0.7943(3) nm,β=106.691(5)°, V=1.5625(11) nm3.The pyridyl ligand was then used to coordinate with the second generation Grubbs’catalyst to get the first example of the ruthenium catalyst supported by imidazolium saltcontained pyridyl ligand (IL-cat 5).The characterization of the synthesized ligand and the catalyst was carried out by NMR,ICP and elemental analysis.In 1H-NMR spectroscopy,the signal of the benzylidene proton shifts from δH=19.2 in the second generation Grubbs’catalyst to δH=16.3 in the novel catalyst IL-cat 5.In 31P-NMR spectroscopy,the signal of PF-6 in pyridyl ligand was observed at δP=-143.3,while δP=36.6 for PCy3 group was disappeared,which demonstrated the group of PCy3 was replaced by the pyridyl ligand completely.The content of IL-cat 5 in the mixture of prepared catalyst contained excess 4 was 14 wt% tested by ICP method.As expected,the novel catalyst IL-cat 5 is soluable in polar solvents including methanol acetone,and ionic liquid,thus ROMP in pure ionic liquid could be carried out conveniently.The ROMP of three different cycloolefins, i.e.nonpolar cyclooctene (monomer 1),medium polar 5-hydroxy-1-cyclooctene (monomer 2),and especially the strong polar monomer 5-norbornene-2-carbonitrile (monomer 3),was explored in ionic liquid ［BMIm］BF4.The polymerizations of the three monomers catalyzed by catalyst IL-cat 5 processed successfully,and the conversion reached up to 96.0%,73.0%,and 51.7% for monomer 1,monomer 2,and monomer 3 under conventional conditions,respectively.It was worth noting that the value of 51.7% for cyano group (—CN) contained monomer 3 was reasonably high,which is surprisingly much larger than that using the pyridine coordinated second generation Grubbs’catalyst for the same monomer in ［BDMIm］PF6 as reported in published literature.The results strongly confirmed that ROMP could be undertaken readily for all functionalized monomers using ruthenium catalyst coordinated with imidazolium saltcontained pyridyl ligand in ［BMIm］BF4,and fortunately Grubbs’catalyst was actually not poisoned in this imidazolium ionic liquid medium without —CH3 group in 2-position of imidazolyl ring.The molecular weights of polymers were measured by GPC,which were nearly in according with the calculated ones.
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发布时间：2021-03-19 - 摘要：Polyvinylsilazane (PVSZ) is a well known ceramic precursor for the fabrication of high performance ceramic structures which are involved in harsh environments.The shaping process for ceramic structures usually involves thermal or photo curing techniques with the aids of polydimethylsiloxan (PDMS) molds to transform liquid preceramic polymer into well-shaped solid structures.Thermal curing of PVSZ needs more than 60～120 min at about 100℃,and photo curing needs about 20 min at room temperature.Both these two curing methods are very hard to get fine microstructures because of the absorption or adhesion between the surface of preceramic polymer and PDMS molds.In order to develop a preceramic photoresist based on PVSZ for the fabrication of non-oxide SiCN ceramic microstructures by a mold-free fast photocuring shaping process,UV sensitive acrylate functional groups were successfully grafted onto the backbone of PVSZ by its reaction with ethyl-4-bromocrotonate(EBC) via a high efficiency allyl bromide electrophilic substitution process.In a typical reaction,3 g of EBC was added drop-wisely into 4 g of PVSZ dissolved 20 mL of toluene.The mixture was heated in an oil bath at 90℃ for 72 h with continuously magnetic bar stirring.Finally,the white HBr precipitate was removed by high speed centrifugal treatment and a filtration process; the solvent and unreacted precursor was subsequently removed by vacuum pump.All of the processes were carried out in an inert gas atmosphere to avoid exposure to moisture,utilizing standard Schlenk techniques.The asmodified polymer was characterized by 1H nuclear magnetic resonance (1H-NMR) and 2D-1H-1H-NMR (COSY) spectroscopy,and its UV sensitivity was investigated by differential photocalorimetry (DPC) and Fourier transform infrared (FT-IR) spectroscopy.The samples for photosensitive checking were prepared by an addition of 5 wt% of photoinitiator IRGACURE369.The results of 1H-NMR pointed out that the hydrogens on the NH groups of PVSZ at δ=0.65 were obviously consumed after chemical modification,and there was a new peak at δ=2.23 on the 1H-NMR spectra of m-PVSZ which was assigned to the hydrogen of (CH2—N).The results of 2D-1H-1H-NMR gave out further evidence of the newly appeared chemical bond (CH2—N).The peak at δ=2.23 (CH2—N) was correlated to the peak at δ=7.01 (—CHCH—),which had confirmed that there was a group like (N—CH2—CHCH) on m-PVSZ.The new chemical bond of (CH2—N) strongly supported the chemical modification of grafting UV sensitive acrylate functional groups onto the backbone of PVSZ.The results of DPC pointed out that 90% UV curing of m-PVSZ could be finished within 60 s with a peak heatflow of 1.18 w/g; however,it would take about 20 min for PVSZ for curing at the same conditions as m-PVSZ.The results of TGA pointed out that the chemical modification had some negative effects on its ceramic yield,the final ceramic yield of mPVSZ at 1000℃ was 55.34%,and that was 63.13% for PVSZ.All the above results showed that m-PVSZ is a promising candidate of negative photoresist for the fabrication of micro ceramic structures by photolithography.The dramatically increased UV curing speed would be good for the fabrication of fine ceramic microstructures,which is still under progress in our group.
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发布时间：2021-03-19 - 摘要：The Zn2+/chitosan blending system was investigated by tuning the Zn2+/chitosan ratios.First,the Zn2+/chitosan composite films were prepared by adding Zn(Ac)2#8226;2H2O into chitosan solutions.Then the structure,surface morphology,crystallization and thermal stability of the films were characterized with FTIR,XRD,DSC,DMA and AFM measurements.The FTIR results showed that coordination reaction occurred among the groups of —NH2,—OH,—NHCO—in chitosan and Zn2+,and this coordination reaction would play a crucial role in the subsequent characterizations.The coordination reaction occurred among the Zn2+,—NH2 and —OH groups was corroborated strongly by the FTIR measurements.The action between Zn2+ and —NH2 was evidenced by the disappearance of the 1630 cm-1 band(assigned to —NHCO—) and meanwhile the shift of the 1332 cm-1band (assigned to ν(C—N)); and the action between Zn2+ and —OH was reflected by the shift of 1066 and 1025 cm-1 bands (all are assigned to νas(C—OH)).The subsequent XRD and DSC results indicate further that the coordination would lead not only to the decrease in CS crystallization degree but also to the varia tion in the orientation of zinc acetic (ZnO) crystals.In addition,with more zinc acetic added,phase separation in solutions may take place also influence the CS crystallization.As the DMA revealed,that the tremendous phase separation would result in the significant decrease in the storage modulus.The size of chitosan crystal particles and the surface roughness of Zn2+/chitosan composite films increased with the content of Zn2+.Phase separation occurred between the chitosan and zinc acetate when the content of Zn2+reached a certain level,which led to obvious reduction of storage modulus of the composite film.
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发布时间：2021-03-19 - 摘要：Relationships between solution parameters including concentration of polyeletrolyte and potassium bromide (KBr),pH value of solution and the aggregation behavior for the micelles formed by the amphiphilic diblock polyeletrolyte,poly(styrene-b-acrylate acid) (PS-b-PAA) were studied.The effect of the micellar aggregation behavior on the rheological properties of the micellar latex was examined.Results revealed that increasing the copolymer concentration and salt concentration led to formation of greater irregular structure in polyelectrolyte micelles due to the aggregation of them,while the effect of pH value can be negligible due to the higher composition of PS block in the copolymer composed of a long hydrophobic block (PS) and a comparable short amphiphilic block (PAA).The aggregation structures were characterized through dynamic light scattering (DLS),transmission electron microscopy (TEM),and rheological properties of the micellar latex were tested using the stress-control rheometer AR-G2.All of the micellar latex exhibit shear thinning behavior,while the apparent viscosity increases with increasing copolymer concentration at lower shear rates,and approaches a constant value (0.01 Pa#8226;s) of ten times of magnitude greater than that of water.Furthermore,the presence of potassium bromide remarkably increases the latex viscosity,comparable with that without added salt,and newtonian plateaus at lower shear rates appeared when the salt concentration reached 4.31 g/L.It is suggested this phenomenon is resulted from the effect of corona expansion involving in the chargesshielding by the added ions.The obvious effect of pH value on the latex viscosity could hardly be observed due to the comparable short amhpihpilic block.
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发布时间：2021-03-19 - 摘要：To improve the dispersion stability of carbon black in water,the grafting of watersoluble polymer poly-(sodium 4-styrenesulfonate) (PSS) onto carbon black (CB) was achieved by the radical polymerization of the corresponding monomers in the presence of CB under ultrasonic irradiation.This technique could generate efficient polymerization of sodium 4-styrenesulfonate (NaSS) in the presence of CB in a rapid reaction at relatively low temperature.The grafted amount of polymer on CB was assessed by thermogravimetric analysis (TGA).In addition, molecular weight and molecular weight distribution of the ungrafted polymer was tracked by gel permeation chromatography (GPC).The influences of ultrasonic time and power output on grafting ratio were also investigated.Fourier transform infrared spectroscopy (FT_IR) was used to determine the chemical structure of the resulting products.Particle analysis indicated that the diameters of the obtained grafted carbon black (GCB) particles were smaller than those of original CB particles.TEM photographs showed that PSS were attached on the surface of carbon black, and the conglomeration degree of GCB decreased apparently.The results of zeta potential measurements revealed that the GCB surface had more negative charges than the original CB.Accordingly,UV transmission measurements conformed that the dispersion stability of GCB in water was improved apparently than that of initial CB.Because of the attachment of polyelectrolyte to the CB surface the grafted CB could be well dispersed in water.
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发布时间：2021-03-19 - 摘要：Modification of polyethylene with polar groups and/or polar polymer side chains has been an issue for both academic and industry fields for a long time.Many method have been presented to prepare functional polyethylene,among which the post-functional method has find its industry applications.However,this method shows many disadvantages in controlling polymer structure.The reactive monomer method is characterized by good control of polymer chain structure.We have prepared an ethylene/p-allyltoluene copolymer by Et(Ind)2ZrCl2/MAO.This copolymer can be transferred to polyethylene graft copolymers using graftfrom technique from the site of benzyl groups.In this paper,copolymerization of ethylene with three kinds of ω-p-methylphenyl-α-olefins,p-methylphenyl-1-propylene (AC3),4-p-methylphenyl-1-butene (BC4) and 6-p-methylphenyl-1-hexene (HC6) using Et(Ind)2ZrCl2/MAO as a catalyst was performed in order to compare the copolymerization abilities of the three reactive comonomers.Three comonomers were synthesized by the coupling reactions between benzyl or aryl metal (magnesium or lithium) and alkenyl halide.The comonomers were purified to get the polymerization grade.Ethylene/reactive comonomer copolymerization was carried out under 1.01×10.5 Pa of ethylene with variations of the comonomer quality in the feed.The copolymers were characterized with 1H-NMR,13C-NMR,GPC and DSC.With the feed of comonomers the catalyst activity increased,reached a maximum value and then decreased.Under the same concentration of comonomers,the highest catalyst activity occurred in the BC4 system.The content of comonomer in copolymers increased with the comonomer in the feed.Under the same concentration of comonomers,the content of comonomer in copolymers could be used to compare the copolymerization ability of the comonomers.The examination results showed that the best copolymerization ability came from BC4 With the increase of the content of comonomer in copolymers,the melting point of copolymers decreases, and the peak in DCS curves becomes broad.This is because the incorporation of comonomers destroyed the crystal of polyethylene.The incorporation of comonomers in copolymers caused a decrease in polymer molecular weight.The possible reason was that more β-H-chain transfer reactions were induced by the comonomer.Three kinds of copolymers were characterized with 1H-and 13C-NMR,all of the H and C atoms could be found in their NMR spectra.And no evidence proved that two comonomer molecules were connected directly.The above results showed that BC4 was a favorable comonomer which had the best incorporation ability.
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发布时间：2021-03-19
Research Article
- 摘要：Nano-silver/poly(2-acrylamido-2-methylpropanesulfonic acid-co-methyl methacrylate) (P(AMPS-MMA)) composite materials were prepared with the silver nitrate solution containing AMPS and MMA without initiator or reducer,in which Ag+ ion was reduced to nano silver particles,and the monomers were polymerizated simultaneously by ultrasonic.Transmission electron microscopy (TEM) showed that nanoAg particles were homogeniously dispersed in polymer martrix,and the size of particles was in the range of 5～15 nm.The results of Fourier transfer infrared spectrometer (FT-IR) suggested that the two characteristic peaks of the stretching vibration absorption peak of carbonyl at 1732 cm-1 and the stretching vibration asymmetric absorption peak of C—O—C of esters at 1191 cm-1 in the nanoAg/P(AMPSMMA) composite were shifted 13 cm-1 and 15 cm-1compared to those of the P(AMPS-MMA) copolymer respectively; The rusults of fluorescence spectra indicated that there were two emission peaks appeared in the vicinity of 318 and 393 nm for the aqueous solution of nano-Ag/P(AMPS- MMA) composites.The testing results of UV-Vis spectrum showed that there was a characteristic absorption peak at 417 nm for nanoAg/P(AMPSMMA) copolymer solution,the absorption peak of silver nanoparticles in the nanocomposites solution was shiftted to long wavelength with the ultrasonic time; X-ray photoelectron spectroseopy (XPS) proved that the O1s binding energy (531.7 eV) of CO and the O1s binding energy (533.4 eV) of C—O—C of nanocomposite copolymer reduced 0.4 eV and 0.5 eV respectively than the standards O1s binding energy (532.1 eV) of CO and 533.9 eV of C—O—C.The specific interaction between carbonyl. group in the composite copolymer and nano-Ag can be confirmed by the shift of the carbonyl C1s peak to lower binding energy.The interaction between nano silver and the functional group attached to polymer is considered to be of coordination.It is concluded that there is a kind of interaction phenomena of nanometal silver with effective polymer matrix in the nanocomposite materials.
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发布时间：2021-03-19 - 摘要：A novel hyperbranced azo polymer with terminal diazonium groups was synthesized by step-growth polymerization of 4,4′-diamino diphenyl sulphone’s diazonium salts (A2) and benzene-1,3,5tricarboxylic acid tri-2-(N-ethylanilino)ethyl ester (B3) through azo-coupling reaction.4,4′-diamino diphenyl sulphone (0.248 g,1 mmol) was dissolved in a hot homogeneous mixture of glacial acetic acid (7.5 mL) and sulfuric acid (1 mL).Aqueous solution of sodium nitrite (0.166 g,2.4 mmol) in 0.5 mL water was added dropwise into the solution at 0℃ and kept at this temperature for 5 min.The diazonium salt solution of 4,4′-diamino diphenyl sulphone was then added dropwise into the solution of benzene-1,3,5tricarboxylic acid tri-2-(Nethylanilino)ethyl ester (0.326 g,0.5 mmol) in 50 mL DMF at 0℃.After the reaction was carried out at 0℃ for 8 h,the solution containing the diazoniumhyperbranched azo polymer was directly used as the polycation solution.The purchased sodium polystrene sulfonate (PSSA) was used as polyanion.Then the multilayer films were prepared by an electrostatic layer-by-layer deposition method.The self-assembly processes and morphologies of surfaces were characterized by UV-Vis spectra,ellipsometer and AFM.A linear increase of absorbance and thickness was observed as the number of the bilayers increased.Dichroism was optically induced in the self-assembly film under the irradiation of a polarized Ar+ laser beam at 488 nm.After 15 min irradiation of the laser beam at an intensity of 80 mW/cm2,the orientation order parameter of the multilayer film obtained was about 0.02.With interfering illumination of Ar+ laser beams for 30 min,significant surface relief gratings formed on the self-assembly multilayer film were observed.The spatial period and height of the obtained SRGs were about 744 nm and 20 nm,respectively.
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发布时间：2021-03-19 - 摘要：A3-Arm PEG (Mn=16900) was first reacted with acryloyl chloride to give rise to an acryloyl endcapped macromer.Afterthen,a kind of injectable hydrogels was prepared via Michaeltype addition reaction of dithiothreitol with this macromer.The gelation time was visually determined when the mixture did not flow by inverting the vials.The hydrogel structure was characterized by using FTIR and DMA analyses as well as swelling and degradation tests.It was found that robust and transparent hydrogels were quickly formed in situ with high gel fractions.DMA measurements confirmed that the hydrogels hold intact 3D network structure.The gelation time and swelling ratio are adjustable by changing the concentration of macromer solution in PBS due to the fact that the number of reactive acrylates in unit volume is increased with the concentration of precursor solution making them more easily to be linked with DTT to form hydrogel networks.The results revealed this kind of hydrogels is injectable and degradable.Meanwhile,MTT evaluation also showed the good cell-compatibility for this kind of hydrogel material.As Michael-type addition can be smoothly carried out at physiological temperature and pH in the absence of any sensitizer or catalyst,and the reactants involved are all biocompatible,the asprepared hydrogels have the potential to be used in the area of biomedical materials.
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发布时间：2021-03-19 - 摘要：Non-linear optical (NLO) polymers have potential application in ultra-fast electro-optic modulators.Although physical doping of NLO chromophores into a matrix polymer appears to be efficient in the preparation of NLO polymers and electric poling,it suffers from low chromophore loading and poor temporal stability.In this paper,a new approach of preparation towards highly efficient NLO materials was demonstrated by doping a novel type of zwitterionic chromophore (BPIPP-DEMI) into an acid-containing matrix polyimide (API) and fabrication via alternate spin-coating of polymeric multilayer films comprising layers of the resulting NLO polymer and layers of a spacing tertiary amine-containing polyimide (BPI).The individual polymer layers had a thickness in the range of 100～200 nm,which can be readily controlled by adjusting the concentration of polymer solutions and the spin speed.Investigation of the UV-Vis absorption and the growth in the thickness of the multilayer films indicated a uniform growth of multilayer films.A five bi-layer NLO multilayer film (1.6 μm) was thus fabricated,with each API layer containing 10 wt% of the NLO chromophore BPIPPDEMI.In contrast to API films containing 10 wt% of BPIPPDEMI,which showed significant phase separation,NLO multilayer films containing the same amount of BPIPP-DEMI exhibited no obvious phase separation under optical microscope,indicating a better host for NLO chromophores.
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发布时间：2021-03-19
Research Bulletin
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