最新刊期
卷 ， 期 6 ， 2004
- 摘要：The effects of self-seeding nucleation on the crystallization behavior and properties of poly(trimethylene terephthalate) were studied．Differential scanning calorimetry (DSC) results indicated that the crystallization temperature of poly(trimethylene terephthalate) increased obviously(increased about 20℃) after the process of self-seeding nucleation．The results of polarized light microscopy (PLM) showed that the spherulite size decreased markedly from 40 μm to 8 μm．
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发布时间：2021-03-19
Rapid Communications
- 摘要：Poly(vinylidene fluoride-co-hexafluoro propylene)(F26)-based asymmetry micro-porous membrane has been fabricated by a phase inversion process and applied in membrane distillation．Acetone (sweller),N-methyl pyrrolidone (solvent) and polyethylene glycol 400 (additive) were used in casting solutions．Different effect of acetone and N-methyl pyrrolidone／acetone on membrane structure parameters was investigated and demonstrated by SEM．F26 microporous membrane with fingerlike and sponge structure was prepared in N-methyl pyrrolidone／acetone．F26 membrane prepared without any additives is superior to PVDF membrane by making a comparison of their contact angle to distilled water．The membrane distillation coeffcient of the experimental F26 membrane is higher than that of the experimental PVDF membrane,which can be ascribed to the special membrane structure of F26. Membrane distillation flux of F26 membranes was a little higber than that of the PVDF ones under the same operational conditions．
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发布时间：2021-03-19 - 摘要：Computer simulation is employed to study the structure of a thin PP film in vacuum．A initial random parent chain is obtained from the simulation of bulk amorphous polypropylene and collapsed under two-dimension boundary conditions．Films with a thickness of ～3.5 nm are obtained for parent chain with 100 repetitive units．In the interior of PP films bulk density is obtained,while density drops off sigmoidally over a distance of ～0.8 nm near the free surfaces．The backbone bonds ale randomly oriented in the interior and markedly oriented along the film plane near the free surfaces：the onset of order corresponds roughly with the drop in the mass density from its bulk value. Because of the thin film more effectively relaxing along with the plane of the thin film,the trans state and the gauche state of the CH2—CH are also enriched compared to the bulk．The difference in the energy of a chain in the amorphous bulk (3D periodic) and in the film (2D periodic) allows us to calculate the internal energy contribution to the surface energy．
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发布时间：2021-03-19 - 摘要：Monte Carlo method has been firstly applied to the bulk ring-opening copolymerization kinetics of octamethylcyclotetrasiloxane (D4) with N-β-aminoethyl-γ-aminopropylmethyldimethyoxysilane (APAEDMS)．A new computational model was established to simulate the copolymerization kinetics based on the free volume theory,which is used to indicate diffusion influence,and chemical reaction kinetic theory．The reaction rate constants are obtained by simulating the main elemental reactions of the copolymerization．Based on the optimal rate constants,Monte Carlo simulation indicates that the copolymerization mechanism of D4 with APAEDMS is an anionic chain-reaction mechanism with the characteristic of step polymerization．
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发布时间：2021-03-19 - 摘要：Two kinds of chemical modified β-cyclodextrin(β-CD) with different acylation degree were synthesized relying on the content of chloroacetyl chloride agent used．The structures of β-CD with different degree of acylation were characterized using infrared spectroscopy．13C-NMR,1H-NMR and titration analysis．Infrared spectroscopy and 13C-NMR indicated that acylations occurred at C-2 and C-6 position in β-CD,1H-NMR and titration analysis suggested that the acylation degrees of β-CD are 3.2 and 4.5,respectively．A series of star polymers having different average length of poly (N,N-dimethylaminoethyl methacrylate) were synthesized by atom transfer radical polymerization (ATRP) using anterior acylated β-CD as the initiator．The branch chain structure and their compositions were characterized using infrared spectroscopy,1H-NMR,element analysis and DSC．The star polymers prepared here had a hard 1CD core with the potential to form inclusion complexes with certain small organic compounds,and also their aqueous solutions were studied by UV spectroscopy in order to explore their thermo- and pH sensitivities．The results showed that the novel star polymers exhibited clearly thermo- and pH respondings in accordance with the change of the environment．
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发布时间：2021-03-19 - 摘要：The microstructure in cured resins decides their mechanical properties. An important characteristics in cured vinyl-ester resin is micro-gels and bi-phase structure．The morphological structure of cured vinyl-ester resin and the formation of two-phase structures in vinyl-ester resin has been studied by using SEM and differential scanning calorimetry (DSC)．The results demonstrated the existence of clusters of gel-particles with a size of about 20 μm,each cluster of gel-particles containing many gel-particles with coral-like structures．The formation of gel-particles resulted in two-phase structure characterized by the two peaks in the rescanned DSC thermographs of the resin. The cure conditions (temperatures,post-cure) affected microstructure in the cured resins．The results of mechanical properties showed that the cure conditions affected the mechanical properties．The post-cure for the sample isothermally cured at 80℃ increased the tensile strengths and flexural strengths．On the contrary,the post-cure for samples isothermally cured at 120℃ decreased the tensile strengths and flexural strengths．
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发布时间：2021-03-19 - 摘要：The viscoelastic for a LDPE (PE-FSB-23D022-Q200) melt was investigated experimentally and characterized by KBKZ equation with Wagner-type damping function. The predicted non-linear time-dependent viscoelastics of the LDPE melt by KBKZ equation were compared with the experimental data and the calculation results obtained by the transformed Huang equation. At the maximum shear rate of 5 s-1,the prediction of KBKZ equation shows good agreement with the experimental result for the short-time shear of the thixotropy-loop test．However,the predictions of KBKZ equation are higher than the experiments for the long-time shear tests．The KBKZ equation can well describe the stress growth and the stress relaxation characteristic of the LDPE,i．e．the progress of stress spurt and stress relaxation,while the transformed Huang equation cannot．The parameters in the transformed Huang equation only reflect the isolate and partial theological property of the LDPE at particular test condition,while the parameters in the KBKZ equation can characterize the basic viscoelastic of the melt．Thus,the capability of describing and predicting the time-dependent viscoelastic of the KBKZ equation is superior to that of the transformed Huang equation．The results in the paper also show that the KBKZ equation cannot describe the time-dependent viscoelastic of the LDPE(Q200) completely and precisely．
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发布时间：2021-03-19 - 摘要：Functiona poly(lactic acid) microspheres with cole-shell structures have been prepared by using the PEO-PPO-PEO(Pluronics F68) or the ligand-tethered PEO-PPO-PEO derivatives as the surface stabilizer and poly-(lactic acid) as the core material．Confocal Laser Scanning Microscopy (CLSM) investigation indicated that the amphiphillic triblock copolymer PEO-PPO-PEO or its ligand-tethered derivatives existed on the shell of microspheres. The ligand-tethered microspheres were then embedded in cell-resistant PEO-PPO-PEO films to create cell-interactive surfaces with discrete clustered-ligand domains．The osteoblast compatibility test showed that the amino acid or peptide RGD existed on the surface of microspheres promoted osteoblast attachment and growth．This simple surface treatment method may have potentials for tissue engineering and other biomedical applications．
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发布时间：2021-03-19 - 摘要：Dendrimers and dendritic polymers have applications in a diverse range of many fields including medical,electronics,nanotechnolody,biology and catalysis．Dendrimers are known for their well-defined,highly branched architectures that are built in a stepwise manner．Using dendrimer PAMAM (generation 4.5) as seed,the monodisperse and nano-sized polystyrene emulsions containing dendrimer PAMAM have been obtained by seed emulsion polymerization．The size and size distribution of particles were characterized by Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS)．It has been found that when PAMAM is used,the diameters of emulsion particles are much smaller than 100 nm,and the particles are nearly monodisperse,which are not easily obtained from other emulsion polymerization systems．The FT-IR spectrums showed obviously that,when PAMAM is used,there are absorption peak at ca．1670 cm-1 and stretching peak at ca．3300 cm-1 which mean that the dendrimer is included in the obtained polymer．
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发布时间：2021-03-19 - 摘要：Stable dispersions of silica were coated with polystyrene by emulsifier-free polymerization,and the monodisperse composite spheres were obtained,whose thickness is about 100 nm．Silica ranging from 150 to 250 nm was core particles．To achieve a high coating efficiency,silica was first modified with 3-(trimethoxysilyl)propylmeth-acrylate (MPS) coupling agent at three different degrees of coupling．The presence of the bound MPS agent and of the polymer at the silica surface was determined by the infrared spectroscopy,and the bound amount of MPS was calculated from mass losses of thermogravimetric analysis (TGA)．Coating efficiency and the monodispersion of the composite particles were enhanced by the degree of MPS coupling and by initial concentration of the monomer．The morphology of the composite particles were determined by transmission electron microscopy (TEM),and their monodispersities was measured by dynamic light scattering (DLS)．
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发布时间：2021-03-19 -
MECHANICAL PROPERTY AND MORPHOLOGY CONTROL OF INJECTION-MOLDED HDPE IN LOW FREQUENCY VIBRATION FIELD
摘要：The self-made low frequency vibration injection-molding device was adopted to explore relationship between mechanical property and morphology for HDPE injected moldings,and the mechanical properties are bettered and the morphology can be controlled in the low frequency vibration force field．In the research the morphology and mechanical properties produced by conventional injection molding(CIM) were used to compare with which obtained via vibration injection molding(VIM)．As for the vibration injection molding is concerned,the main vibration processing variables are vibration frequency and vibration pressure amplitude and the effect of tensile strength and morphology influenced by different vibration processing conditions．SE micrographs show the transformation of crystal from spherulite to lamellar is noticed,and the shish-kebab stucture and cylindrite structure were obtained in the shear layer via different vibration injection molding conditions．The changes of frequency (0＜f＜2.33 Hz) are beneficial to refine,orientate crystals and enhance the crystallinity in the shear layer from 59.77％ to 64.10％ produced by conventional injection molding and vibration injection molding,respectively,with shish-kebab structure in the shear layer．As a result the over-all mechanical properties are as a function of vibration frequency in vibration injection molding．The increase of vibration pressure amplitude(0＜PA＜59.4 MPa)is favor in promotion of tensile strength of vibration injection molded specimens because of the obviously preferred orientation of crystals with about 2％ increase of crystallinity in both core and shear layers,and the cylindrite crystal structure occurs in the shear layer of vibration injection moldings．On the other hand,the elongation at break becomes small because of growing of the lamella scale in the core of vibration injection-molded specimens．- 6
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发布时间：2021-03-19 - 摘要：The friction and wear behaviors of potassium titanate whiskers inodified bismaleimide resin under different coupling agent and whisker content were investigated．The results show that wear resistance can be improved and the wearing ratio of the composites decrease markedly by adding potassium titanate whiskers．The friction coefficients of the composites are corresponding wit the resin matrix．Coupling agents have no notable influence on the friction coefficient. However,appropriate coupling agent can improve wear resistance remarkably．At a relatively lower whisker content,the wear of the composites is characteristic of adhesion．While at higher whisker content,it is dominated by fatigue．
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发布时间：2021-03-19 - 摘要：A novel class of three-dimensional polycondensates were prepared with PAMAM dendrimers having terminal multi-functional groups and other compounds,on the basis of polycondensation mechanism．The X-ray electron spectrometer (XPS) was resorted to analyze the polycondensates,and the fit data of carbon element value in Electron Spectroscopy for Chemical Analysis (ESCA) was utilized to estimate the extent of polycondensation. The fit peaks of carbon of ester groups (—COO—) were almost disappeared and they might reacted with amido and formed acylamide (—CON),therefore the polycondensation reactions were almost completely．The swelling tests of polycondensates were carried out in the hexane,toluene,chloroform,isopropanal,acetic acid,ethanol,formic acid and water．It Was found that the max swelling value reached in the formic acid．Hence the solubility parameter of polycondensates (δ2) was about 27.6 (MJ／m3)1/2 (as the same as formic acid) according to the meaning of δ2．The DSC analysis of the raw PAMAM dendrimer and the polycondensates demonstrated that the glass-transition temperature (Tg) of polycondensates had been great improved,which from subzero temperature of raw materials to 48℃.
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发布时间：2021-03-19 - 摘要：A novel β-cyclodextrin (β-CD) graft copolymer was synthesized by immobilizing β-CD onto the linear chain of PVA through acetalization reaction．The optimum reaction condition was tested as that the feed weight ratio of β-CD-6-CHO with PVA is 4:1 at 70℃ for 2 h．The structures of PVA-β-CD were characterized by Infrared Spectroscopy (IR) and Nuclear Magnetic Resonance (NMR)．The molecular inclusion complex of PVA-β-CD with camptothecin (CPT),an anticancer drug,was studied．The results indicated that due to the inclusion of PVA-β-CD with the drug,the solubility of the CPT increased gready．And the cumulative release rate and extent of drug released from PVA-β-CD matrix can be effectively improved with the increase in β-CD content．
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发布时间：2021-03-19 - 摘要：The reversible oxygen-binding properties of the polyethyleneimine-cobalt (PEI-Co) complex and the effect of the PEI-Co complex on the reduction current of oxygen were studied. The color of the PEI-Co complex in the electrolyte solution changed on exposure to oxygen atmosphere,which was monitored by UV-visible absorption spectrometry．The UV-visible absorption spectra of the PEI-Co complex displayed a new adsorption band at 310 nm,with an isosbestic point at 280 nm．The spectral change was attributed to the reversible oxygen-adduct formation of the PEI-Co complex even in the electrolyte solution．The oxygen-binding equilibrium curve of the PEI-Co complex obeyed a Langmuir isotherm,to give the high oxygen-binding affinity (p50=0.667 kPa)．And the apparent dissociation rate constant of oxygen from the PEI-Co complex (kd=1.1×105 s-1) was also high．The aqueous solution of the PEI-Co complex that had rapid and reversible oxygen-binding properties functioned as an oxygen-enriching medium for oxygen electrode to enhance the diffusion-controlled current for the oxygen reduction．Based on the rapid release of oxygen from the PEI-Co complex,a high current was obtained for the reduction of oxygen in the presence of the PEI-Co complex,and the current increased with the increase of the concentration of the PEI-Co complex and the oxygen concentration in the atmosphere．The reduction current reached a saturated value near [ethyleneimine unit]／[Co]=5,which suggested the structure of a six-coordinate μ-dioxo dinuclear complex [N5CoⅢ-O2-CoⅢN5]．A new type of oxygen-diffusion electrode for metal／air batteries and fuel cells is proposed using the oxygen-enriching material immobilized at the electrode surface．
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发布时间：2021-03-19 - 摘要：The photograft polymerization on porous substrate,poly(ethylene terephthalate) (PET) nucleopore membranes,was investigated by directly observing the configuration under SEM．The result of photografting strongly depends on the grafting methods and the nature of substrate membranes,such as pore size and pore shape,and different membrane configurations were obtained,for instance,decreasing pore size,pore-covering and pore-filling．To topside method,a standard straight pore shape is adverse to grafting inside pores,especially to small pore size membranes (0.4 μm),and it tends to give a pore-covering effect i．e．graft mainly occurs on the membrane surface rather than inside the membrane pores. The cone-shaped pores have much effective grafting area and are mole easily filled than straight pores．To large pore size membrane (5 μm),crosslink agent is necessary to form a thick graft layer on the pore wall．A new backside adsorption method was applied in which the reaction solution was adsorbed into pores from the membrane backside owing to the capillarity and grafting polymerization was restricted inside pores. It is suitable for the synthesis of small pore diameter pore-filling membrane without changing the membrane surface characters,such as the photograft pore-filling modification of ultrafiltration membrane．Membrane pore size could be adjusted via selecting correct photografting technique and grafting degree (Dg)．With the increase of grafting degree,the pore size and water flux of grafted membranes are decreased．The results of photograft polymerization on nucleopore membranes,a model of ideal membrane,provide valuable information for the photografting modification of other membranes.
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发布时间：2021-03-19 - 摘要：Radiation-induced grafting of binary grafting systems of styrene (St)／maleic anhydride (MAn) or St／dimethylamino ethyl methacrylate (DMAEMA) onto polytetrafluoroethylene (PTFE) porous membranes was studied．Grafting was carried out using γ-radiation from a 60Co source at room temperature．The effects of absorbed dose,dose rate,the initial comonomer concentration,and the molar ratio of both monomers in the grafting solution on the degree of grafting were investigated．The degree of grafting was found to be strongly dependent upon the grafting conditions．The effect of the reactivity ratio of two monomers on the degree of grafting,the composition and characteristics of the grafted film were measured and discussed．There is a synergistic effect in St/MAn binary system,but a weak antagonistic effect in St/DMAEMA system．The grafted PTFE porous membranes can be used after sulfonation as proton exchange membranes for proton exchange membrane fuel cell．
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发布时间：2021-03-19 - 摘要：Multi-arm star polymers with high density of hydroxyl functional groups on the shell were synthesized via atom transfer radical polymerization (ATRP)．Reaction of hyperbranched poly(3-ethyl-3-hydroxymethyloxetane) (HP) with 2-bromo-isobutyrylbromide resulted in a multifunctional macroinitiator (HP-Br)．HP-Br was used to initiate the ATRP of 2-hydroxyethyl methacrylate (HEMA) in the presence of Cu(I)Br and N,N,N′,N′,N″- pentamethyldiethylenetriamine (PMDETA) in a mixed solvent of 2-butanone and 1-propanol,giving rise to various multi-arm star polymers with different lengths of arms(HP-g-PHEMA)．In addition,the reaction of benzoyl chloride with HP-g-PHEMA indicated that the hydroxyl groups were reactive．The structure and thermal properties of the resultant polymer brushes were characterized and confirmed with 1H-NMR,FTIR,GPC,TGA and DSC．
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发布时间：2021-03-19 - 摘要：Based on the atom transfer radical polymerization (ATRP) and the large amount of functional groups of hyperbranched polymers,core-shell multi-arm star polymer brushes with gradient polarity distribution were designed and prepared. ATRP of MMA initiated from hyperbranched macroinitiator (HP-Br) in the presence of Cu(I)Br and N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA) resulted in multi-arm star polymers (HP-g-PMMA)．Then ATRP of HEMA with HP-g-PMMA as polymeric initiator afforded another multi-arm star polymer with hydroxyl groups (HP-g-PMMA-b-PHEMA)．Accordingly,further reaction of HP-g-PMMA-b-PHEMA with 2-bromo-isobutyrylbromide produced multi-arm star polymer initiator (TL-HPB-Br)．Finally,ATRP of HEMA initiated from TL-HPB-Br gave multi-arm star polymer brusches with three-layer structures．The structure of the resultant novel objects was confirmed with 1H-NMR,FTIR and GPC．
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发布时间：2021-03-19 - 摘要：Template copolymerization of acrylamide (AM) with acylic acid(AA) was carried out in the presence of polyallylammonium chloride (PAAC) as matrix in aqueous solutions．The various influences on the rate of polymerization were studied by dilatometer and electrical conductivity measurements．The obtained results indicated that the process of copolymerization under the effect of polyallylammonium salt was according to type I (zip) template mechanism．The maximum of reaction rate was appeared at equivalence mole ratio of template unit (T) to monomer AA. T／AA=1 indicated a high interaction between the monomer AA and the template in the solution．The reactivity ratios of r1 2.68 for AA and r2 0.44 for AM were also obtained. The considerable enhancement of r1 compared with that without the template indicated that the presence of PAAC significantly increases the probability of long sequences of AA unites in copolymers．The rate of polymerization was found to be proportional to the concentration of monomers and initiator with exponents of 1.1 and 0.83,respectively,which are larger than the ordinary values due to the effect of PAAC．
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发布时间：2021-03-19 - 摘要：Compared with the conventional monofunctional initiators,the multifunctional initiators can increase the polymerization rate and polymer molecular weight simultaneously．As a novel initiator,the decomposition rate constant,initiator effciency and chain transfer constant to the initiator are its basic parameters．However,these basic parameters have rarely been determined,and the mechanism and the kinetics have not been studied．In the present paper,a new kind radical initiator,2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane (DMDEHPH),has been utilized to initiate styrene polymerization in the temperature range of 55～80℃ and DMDEHPH concentration range of 0.01～0.10 mol／L．The effects of initiator concentration,monomer concentration and reaction temperature on the polymerization rate were investigated in details．The increase of monomer concentration,initiator concentration and reaction temperature all can increase the polymerization rate．The relationship of polymerization rate and the corresponding concentration shows that the orders of polymerization rate to active group of initiator concentration and monomer concentration are 0.5 and 1.0,respectively,which validates the correctness of kinetic model presented from the mechanism of polymerization. The activity energy obtained from the polymerization rate constants at various temperatures is 92.0 kJ／mol．The initiator efficiency is in the range of 0.55±0.03 under the experiment conditions,and the initiator efficiency decreases with the increase of initiator concentration．Considering the decomposition degree of O—O bonds during the polymerization,the chain transfer constants to DMDEHPH and monomer are 0.037 and 0.59×10-4 at 60℃,and 0.048 and 0.75×10-4 at 70℃,respectively．
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发布时间：2021-03-19 - 摘要：An ordered reactive ladderlike polyhydrosilsesquioxane (H-T) was successfully synthesized via a modified “stepwise coupling polymerization” process,which included two improvements in synthetic method．First,dehydrochlorination polycondensation between Si—OH and Si—Cl groups during polycondensation reaction is employed instead of the dehydration between Si—OH groups used before,which improves the H-bonding template effect of the bridged-phenylene diamine．Meanwhile,trimethylchlorosilane is used to block the terminal silanol groups,avoiding the further intermolecular crosslinking of the phenylene diamine-bridged ladderlike macromolecular intermediates．Consequently,the regularity of H-T has been improved,and compared with a very low Tg(-123℃) of the single-chained polydimethylsiloxane,a significantly higher Tg(117.0℃) of H-T in DSC measurement confirms that the ordered reactive H-T macromolecule possesses comparatively stiff main chain．Above all,the peak of HSiO3/2 (-84.8) with the baseline width (Δ) of about 5 in 29Si-NMR spectrum which is much narrower than that of the polysilsesquioxane (Δ=8～10) prepared by the usual dehydration condensation method shows that the regularity of H-T is obviously improved．Furthermore,H-T is the first soluble,reactive and purely inorganic ladderlike macromolecule,which can be grafted through hydrosilylation reaction and others to generate functional LPSs with different side groups.
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发布时间：2021-03-19
Research Article
- 摘要：Lys(z)-NCA was synthesized in the presence of triphosgene,amphiphilic triblock copolymers poly(Nε-CBZ-Lysine)-PEG-poly(Nε-CBZ-Lysine) were synthesized in DMF using amino-end ended PEG as initiator with the mechanism of anion ring opening polymerization．The structures of block copolymers were characterized by IR,1H-NMR,GPC and DSC．The results showed triblock copolymers with expected structure and low polydispersity in molecular weight could be synthesized by this method．At the same time,the self-assembling behaviors of block copolymer were investigated by TEM. A novel helical aggregates were found to be formed in DMF．Because of biocompatibility of two components of block copolymers,these block copolymers have potential applications in the field of biomaterials.
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发布时间：2021-03-19 - 摘要：Tri-block amphiphilic copolymers with hybrid architectures were synthesized by coupling linear poly(ethylene glycol) (PEG) and dendritic second-generation Fréchet-type poly (benzyl ether) (PBE) via the Williamson reaction (Gisotv,et al．Angew Chem,Int Ed Engl,1992,31:1200～1202). Our experimental study shows that the powerful two-dimensional 1H- 13C heteronuclear multiple-quantum correlation (HMQC) and two-dimensional 1H- 13C heteronuclear multiple-bond correlation (HMBC) NMR techniques rather than the classical one-dimensional 1H and 13C-NMR methods can provide clear evidence to verify the formation of the tri-block copolymers．In our measurements HMQC and HMBC NMR techniques directly detected the signal of ether bonds bridged in-between PBE dendrons and PEG blocks,therefore,the formation of the block copolymers are evidently confirmed in molecular level．This work also provides a general method to exactly confirm the formation of block copolymers．
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发布时间：2021-03-19 - 摘要：Branched polyethylene from ethylene as single monomer was prepared by the tandem catalyst system of {2-[2-Me C6H4 =(Me)]2C5H3N}FeCl2(1) and {2,6-[1-(2,6-Me2-4-Br-C6H4N=(Me)]2C5H3N} FeCl2 (2) activated with methylaluminoxane (MAO)．The products of polymerization were characterized by DSC,GPC and 13C-NMR. The results revealed that the copolymer produced by in situ copolymerization of ethylene was a mixture of branched polyethylene and α-olefin．The content of α-olefin in the mixture was increased with increasing the molar ratio of catalysts 1／2．The MWD paramelers of polyethylene and copolymer were 28.6 and 7.9,respectirely. 13C- NMR spectra showed that there were ethyl groups,butyl groups and long chain alkyl groups in the copolymer．The average degree of branching of such branched polyethylene was less than 5C／1000C．
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发布时间：2021-03-19 - 摘要：A three-dimensional (3D) ordered structure was achieved by self-organization of monodisperse polystyrene latex about 250 nm in diameter after being ambient dried. The stacked morphology was investigated by scanning electron microscopy(SEM) observation．It is shown that the face-centered cubic(FCC) phase dominantly exists．This finding presents a potential template for preparing an inverse FCC structure as a photonic crystal of full band gap if the index contrast is higher than 2.8．
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发布时间：2021-03-19 - 摘要：A new method was proposed to prepare binary composite colloidal crystal hydrogels by interlocking the as-prepared polystyrene／sulfonated polystyrene core／shell colloidal crystal hydrogel with a second responsive gel．The shell thickness thus the core size were synchronously controlled by altering the sulfonation time and temperature．The proper monomers were radically polymerized forming the second gel within the first gel network．The composition and structure were confirmed．Nanopatterned hydrogel including porous bulk hydrogels and surface patterned hydrogels were derived by properly treating the binary composite hydrogels．Specially,some typical patterns such as arrays of “nano-bowls”,arrays of“nano-ribbons” and “nano-mask” were achieved by changing the treatment method such as by immersion in the solvent,after solvent evaporation from the sample surface during high rate rotation．This work provides a method to prepare nanopatterned hydrogels．
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发布时间：2021-03-19 - 摘要：Nanocrystalline cellulose (NCC) was prepared from microcrystalline cellulose (MCC) by acid hydrolysis．It was observed that the diameter of NCC particles mainly distributed over 30～50 nm by transmission electron microscope (TEM). The crystal form and degree of crystallinity were detected by X-Ray diffraction．The results showed that NCC and MCC have the same crystal form of cellulose Ⅰ,and that the reactions mainly occurred in the amorphous region of MCC during the acid hydrolysis process．The thermal behavior of NCC in different pH conditions was characterized by differential scanning calorimetry (DSC)．The consequences indicate that the thermal stability of NCC distinctly decreased by contrast with the thermal stability of MCC,and that the thermal stability of NCCs in alkali conditions was higher than that of NCCs in acid conditions．The specific surface area distinctly increased with sharp decreasing of the particle size of NCC．This induced the end carbons and active groups of surface of NCC to increase sharply,therefore caused the thermal stability of NCC to distinctly abate．That NCC has very strong adsorption affinity is the cause of the obvious difference of thermal behavior of NCC in different pH．In acid conditions the surface of NCC adsorbed a great lot of H+,which induced the cellulose chains of surface of NCC to decompose at low temperature catalyzed by H+．When adding sodium hydroxide solution,on one hand the H+ of surface of NCC was neutralized；on the other hand,the cellulose chains of low molecular weight were dissolved in sodium hydroxide solution and the defects of surface of NCC rearranged and stable structure formed．These factors improved the thermal stability of NCC in alkali conditions．
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发布时间：2021-03-19
Research Bulletin
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