最新刊期
卷 ， 期 11 ， 2012
- 摘要：Living organisms possess the ability of self-healing for nonfatal harm,like regeneration of the cut skin and broken bone,guided by instinct.As a result,their injury tolerance is substantially enhanced,which ensures healthy growth and breeding from generation to generation.Inspired by the functionality of naturally occurring species,self-healing polymers have been prepared as a member of intelligent materials family.They are coupled with built-in capability of rehabilitating tiny damages produced during manufacturing and/or usage.In recent years,the authors lab systematically studied strength recovery of self-healing polymeric materials for structural application.By using knowledge of polymer chemistry,polymer physics,materials mechanics,etc.,a series of extrinsic and intrinsic self-healing polymers and polymer composites were developed and characterized.The proposed strategies turn out to be feasible for typical thermosetting and thermoplastics polymers.Accordingly,topics including synthesis techniques,formulation optimization,processing,structure and properties relationship,healing mechanisms,stability and durability were carefully investigated.The present article briefly reviews the works carried out by the authors team.Innovative routes that correlate materials chemistry to full capacity restoration are discussed for further development from bioinspired toward biomimetic repair.关键词：Self-healing;Microcapsules;Thermal reversibility;Photoreversibility
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发布时间：2021-03-19 - 摘要：Polypropylene (PP) is one of the most widely used and the fastest growing resin in the world.Compared to other thermoplastic resins,PP presents some advantages in performances,such as a low density,high melting point,excellent mechanical properties and chemical stability etc.However,commercial PP is linear structure and non-polar,which greatly limit the application of PP in extrusion coating,foaming and the blend with Inorganic materials.The chain of PP can be easily attacked by peroxide radicals and forms PP macroradicals.The melt radical grafting is a convenient and economic approach to the modification of PP.We demonstrate herein that the chain structure and phase structure of PP can be adjusted by controlled radical melt reaction:(1) introducing long chain branches into PP backbone to prepare high melt strength PP; (2) enhancing the interfacial interactions between PP and nanomaterials during preparing PP/C60 and PP/CNTs nanocomposites,and improving the dispersion of nanomaterials in PP matrix.关键词：Radical;Melt reaction;Chain structure;Phase structure
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发布时间：2021-03-19 - 摘要：The effects of photoinitiators,light intensity,average functionality of mixed monomers,liquid crystal content,temperature and additives on the photopolymerization kinetics and photo-rheological behaviors of vinyl-monomer/liquid crystal mixtures are reviewed.The rate of polymerization Rp and monomer conversion greatly increase when an appropriate third component is added into the binary dye/amine type Ⅱ (H-abstraction type) photoinitiator system,and also largely increase when light intensity or temperature rises.Rp and first ascend and then descend with increasing the average functionality of mixed monomers.With an increase of liquid crystal content,Rp diminishes while there is no evident variation of for the type Ⅰ (cleavage type) photoinitiator; on the contrary,both Rp and significantly increase for the type Ⅱ photoinitiator in that condition.Additives that can lower the viscosity of monomer/liquid crystal mixtures also increase Rp and .Generally,higher Rp causes shorter gelation time for an identical system at a given temperature,and gelation takes place earlier when temperature increases for an identical system or the average functionality of mixed monomers rises at a fixed temperature.关键词：Holographic polymer dispersed liquid crystals;Photopolymerization kinetics;Photo-rheology;Phase separation;Gelation
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发布时间：2021-03-19
Feature Articles
- 摘要：Tetrabutyl titanate has been selected as transesterification catalyst of poly(lactic acid) (PLA) and polycarbonate (PC) to investigate transesterification mechanism between poly(lactic acid) (PLA) and polycarbonate (PC) and the influence of transesterification reaction on the morphology of blends with different compositions.It is found that the transesterification reaction time,the fraction of reacted PC,the composition of polycarbonate in copolymer,the weight and mole number of PC-co-PLA copolymer increase substantially with the increasing of the composition of poly(lactic acid) in the blends no matter the catalyst is added or not.The difference in the amount of the reacted PC between 70/30 and 30/70 blends increases further with the addition of catalyst due to the easier alignment of PLA segments in copolymers along the interface when poly(lactic acid) is the continuous phase as compared with polycarbonate to be the continuous phase.Moreover,the interfacial reaction mechanism in PLA/PC 30/70 blend is found to be changed with the addition of catalyst since the dominated factor that influences the ester exchange reaction has changed.Furthermore,the domain size of dispersed phase decreases due to the promotion of transesterification by tetrabutyl titanate.Especially,larger mole number of copolymer in blends with PLA as continuous phase is produced when catalyst is added,which causes a more evident decrease in domain size in blends with PLA as continuous phase as compared to that in blends with PC as continuous phase.关键词：Transesterification;Morphology;Flow field;PLA/PC
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发布时间：2021-03-19 - 摘要：An acrylic rubber(ACM) with epoxide groups has been used to improve the toughness of epoxy resins(EP) for the first time.The crosslink condition effects on the morphology and properties of the EP/ACM blends have been investigated systematically.It is found that the EP/ACM blends are miscible before the crosslinking over the whole composition ranges.In contrast,the reaction induced phase separation(RIPS) takes place for the EP/ACM=80/20 and 50/50 systems,while other blend systems maintain the homogeneous structure during the crosslink process.It was further found that the phase separation by the crosslinking led to the EP-rich and ACM-rich phases for the blend,indicating the each other inclusion structures for the RIPS systems.The co-crosslink of EP and ACM was also confirmed by the solvent etching experiments.Moreover,the phase structures and physical properties of the EP/ACM blends are much dependent upon the crosslink condition,which provides feasible access for manipulating the structure and properties of the EP/ACM blends.关键词：Epoxy resins;Acrylic rubber;Toughening;Phase behaviors;Mechanical properties
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发布时间：2021-03-19 - 摘要：Produced via reversible addition-fragmentation chain-transfer (RAFT) polymerization,the monodispersed and narrow molecular weight distribution polymers,poly(tert-butyl methylacrylat) (PtBMA),were prepared by hydrolysis to poly(methylacrylic acid) (PMAA) with thiol ending groups.The PMAA monolayer protected gold nanoparticles (PMAA-@ -GNPs) were then formed through binding the thiol groups to gold surface while chloroauric acid was reduced to GNPs.Characterized by high-resolution transmission electron microscopy (HRTEM) and UV-Vis spectroscopy,the PMAA-@ -GNPs showed the formation of monodisperse spherical particles with the long-term stability in aqueous solution.The optical properties and the assembly state of the PMMA-@ -GNPs are sensitive to pH.Under acidic conditions (pH 1.5),because of the protonated form of PMAA undergoing a hydrophobicity change,the polymer chains shrink and wrap around the GNPs surface,which leads to the GNPs assembly and an absorption red shift of the surface plasmon resonance (SPR).However,after adjusting the pH value of the solution to an alkaline environment (pH 9.2),PMAA-@ -GNPs can be redispersed,resulting in an absorption blue shift of the SPR.And the optical signal of PMAA-@ -GNPs changes little after more cycles of the reversible assembly/dispersion processes.关键词：Poly(methylacrylic acid);Gold nanoparticles;Assembly;pH-responsive
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发布时间：2021-03-19 - 摘要：Dimethylaminochalcone-terminated PNIPAM (PNIPAM-DMAC) with intelligent fluorescence was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAM) with dimethylaminochalcone-containing trithiocarbonate chain transfer agent (CTA) in THF solution using AIBN as initiator,and the structure was confirmed by FTIR,1H-NMR and UV-Vis spectroscopy.The thermosensitivity of PNIPAM-DMAC and the fluorescence responsive to solvent polarity,temperature and molecular recognition were investigated.The results show that PNIPAM-DMAC has a lower critical solution temperature (LCST) poly(N-isopropylacrylamide) (PNIPAM),and the LCST of PNIPAM-DMAC decreases with the increase of polymer molecular weight and aqueous solution concentration,increases with the addition of -cyclodextrin (-CD).With the increase of the solvent polarity,the fluorescence emitting wavelength of PNIPAM-DMAC redshifts basically and the intensity of fluorescence possesses maximum and minimum values,which exhibits solvent polarity sensitive fluorescence properties.Compared with the fluorescence of PNIPAM-DMAC aqueous solutions in the low and high temperatures,it is found that the fluorescence intensity of PNIPAM-DMAC has been obviously enhanced and the wavelength blueshifts in the high temperatures and the fluorescence spectroscopy changes reversibly with respect to the temperature fluctuation,which endows PNIPAM-DMAC with the reversible temperature on/off fluorescence properties.After the addition of -CD to PNIPAM-DMAC aqueous solutions,the fluorescence intensity is enhanced and the wavelength shifts blue slightly,which shows molecular recognition sensitive fluorescence properties.关键词：Poly(N-isopropylacrylamide);Thermosensitivity;Temperature switch;Polarity sensitive fluorescence;Molecular recognition
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发布时间：2021-03-19 - 摘要：A series of silica/poly(methyl methacrylate) grafting composites (SiO2/PMMA) with different grafting and crosslinking structures were used to prepare poly(methyl methacrylate)/silica (PMMA/SiO2) composite fiber via solution blending and electrospinning processes.The dispersion of silica in PMMA/DMF solution and in PMMA/SiO2 composite fiber,the distribution of silica in electrospun products and the morphological characteristics of electrospun fiber were measured by dynamic light scattering (DLS),scanning and transmission electron microscopy (SEM TEM),as well as ultrasonic washing and HF etching experiments.It was found that only the simple-grafted silica with grafting percentage of 484.4% is suitable for preparing electrospun fiber.More than 90% of simple-grafted silica particles can be effectively encapsulated in PMMA/SiO2 electrospun composite fiber,and thus the entire cross section of PMMA/SiO2 electrospun fiber was filled by simple-grafted silica at a primary-particles size level.The above results are favorable for achieving the primary-particles-size-level-dispersion of functional inorganic particles in sub-micron level fiber,and thus can be used to guide the production of functional composite fiber.关键词：Nanosilica;Grafting;Electrospinning;Dispersibility
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发布时间：2021-03-19 - 摘要：Sucrose stearate (SS) is an environmentally sound surfactant with a polar head compatible with starch.Different proportions of SS was blended with corn starch or plasticized corn starch with 20% urea.The mixture was pasted with hot water and cast into films.The crystal structure of the films was characterized by using X-ray diffraction,and the moisture adsorption and the tensile performance were tested.The results indicated that SS interacted with amylose to form a V-type inclusion complex and had influences on the B-type crystallization of starch.Therefore the moisture adsorption and the tensile performance of starch films changed with their SS content.The moisture adsorption of the starch film increased upon adding a small amount of SS (say,0.5%),and then decreased with further increase of the content of SS.After adding SS into the plasticized starch with urea 20 wt%,the crystallinity,crystal size,moisture adsorption and tensile property of the starch films changed with the SS content in a complicated manner.SS and urea showed a synergistic effect of modification on starch materials.The starch film plasticized with 20 wt% urea and combined with 0.5 wt% sucrose stearate showed an amorphous feature of X-ray diffraction and higher elongation at break.关键词：Starch;Sucrose stearate;Urea;Plasticization;Inclusion complex
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发布时间：2021-03-19 - 摘要：Polymerization of norbornene (NBE) was carried out using scandium phosphonate (Sc(P204)3) combined with alkyl aluminium as catalysts.13C-NMR,1H-NMR and FTIR analyses indicate that the PNBE are mainly prepared by the ring-opened type polymerization,and also show ring-retention to varying degrees in this type of catalytic system.It was found that alkyl aluminium cocatalyst plays an important role in the polymerization.Catalyzed by Sc(P204)3/Al-iBu3 system under the optimal polymerization conditions:n(Al)/n(Sc)=5 aging at 50℃ for 2 h,n(NBE)/n(Sc)=50,polymerization at 80℃ for 4 h producing a insoluble and crosslink polymer with 39% yield was obtained.While AlEt3 was used as cocatalyst,the PNBE obtained are partly soluble in organic solvents with 98% yield under the optimal polymerization conditions:n(Al)/n(Sc)=30 aging at 40℃ for 5 min,n(NBE)/n(Sc)=50,polymerization at 60℃ for 7 h.Measured by GPC,the soluble fraction of PNBE exhibits low molecular weight Mn =2.4103~3.0103 with moderate molecular weight distributions (MWD=1.9~2.2).The soluble fraction of PNBE consists of 81%~88% ring-opened type polymer with 48%~58% cis- double carbon bond content.关键词：Scandium phosphonate;Norbornene;ROMP;Vinyl addition
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发布时间：2021-03-19 - 摘要：A novel amphoteric ion exchange resin was prepared by radiation-induced grafting styrene (St) and dimethylaminoethyl methacrylate (DMAEMA) onto the poly(vinylidene fluoride) resin,followed by sulfonation and protonation processes.Micro-FTIR,XPS,TG and SEM analyses testified that the grafting and sulfonation of St and DMAEMA units in poly(St-co-DMAEMA) grafts had been carried out successfully as designed.The grafting yield (GY) was greatly influenced by the grafting conditions including the solvent,the total absorbed dose and the monomer concentration,while the composition of the graft chains only depends on the initial molar ratio of St and DMAEMA.The ion exchange capacities (IEC) increases with the increasing of GY,and eventually the maximum cation and anion exchange capacities can reach to 2.16 mmol/g and 1.06 mmol/g,respectively.This type of new ion exchange resin can be used in treatment of heavy metal waste water and as ion exchange membrane material.关键词：Amphoteric ion exchange resin;Poly(vinylidene fluoride);Radiation-induced grafting;Styrene;Dimethylaminoethyl methacrylate
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发布时间：2021-03-19 - 摘要：A series of poly(phthalazinone ether nitrile)s containing phenyl-s-triazine ring moiety in the main chain has been synthesized by the nucleophilic displacement polycondensation reaction of 2,4-bi(4-fluorophenyl)-6-phenyl-1,3,5-triazine (BFPT),a kind of heterocyclic aromatic difluoride monomer containing phenyl-s-triazine ring moiety,and 2,6-difuorobenzonitrile,as coreactants,with bisphenol-like monomer 4-(4-hydroxylphenyl)(2H)-phthalazin-1-one (DHPZ).The structures of the copolymers were detected by FTIR and 1H-NMR spectra.The obtained polymers having inherent viscosities in the range of 0.65~1.02 dL/g have no crystallinity peaks in their X-ray diffraction patterns,indicating that they are amorphous.The polymers exhibit only one Tg,suggesting that PPEP containing phenyl-s-triazine segments and PPEN containing nitrile segments in the copolymer are miscible.Their glass transition temperatures (Tg) are in the range of 301~337℃.They exhibit high thermal stability with no significant weight loss up to 500℃ in nitrogen (in N2:Td 5%510℃),and the char at 800℃ is more than 60%.The content of phenyl-s-triazine in the polymer backbone is more effective in improving the thermal properties than that of nitrile.The Tg and Td 5% of the copolymers increase with increasing the content of phenyl-s-triazine structure in the main chain.However,the copolymers containing lower than 50% phenyl-s-triazine structure could be soluble in NMP,DMAc and chloroform at room temperature.The copolymers having more than 50% phenyl-s-triazine moiety could resolve in NMP and DMAc at heating.All films of the polymers synthesized possess good mechanical properties in the room temperature.Their tensile strengths are ranging from 72 MPa to 84 MPa with 7.6%~11% of elongation at break,which decreases with incorporating more phenyl-s-triazine moiety in the polymer backbone.关键词：Poly(aryl ether nitrile);Triaryl-s-triazine;Phthalazinone;Structure and property
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发布时间：2021-03-19 - 摘要：A monomer (ErQ2(HEMA-CH2-Q)) containing 8-hydroxyquinoline erbium complex was synthesized by two-step coordination reaction.First,a methanol solution of ErCl3 was added to a methanol solution of 8-hydroxyquinoline under stirring with the molar ratio of Er3+/HQ being 1∶2 to obtain ErQ2Cl.Secondly,ErQ2Cl was coordinated with 5-(2-methacryloylethyloxymethyl)-8-quinolinol (HEMA-CH2-Q).Thereafter,novel polymeric Er-complexes were prepared by free radical copolymerization of the monomer and N-vinylcarbazole (NVK).The structure and the properties of the polymeric Er-complexes were studied by elemental analysis,nuclear magnetic resonance spectroscopy (1H-NMR),Fourier transform infrared spectroscopy (FTIR),gel permeation chromatography (GPC),differential scanning calorimetry (DSC),thermogravimetric analysis (TGA),UV-Vis absorption spectra,photoluminescence (PL) spectra and PL lifetime.The polymeric Er-complexes involve 8-hydroxyquinoline erbium complex moieties and NVK segments,exhibiting good solubility in a wide range of organic solvents and excellent thermal stability.The glass transition temperature (Tg) and the temperature of 5% weight loss (Td) for the polymeric Er-complexes were around 210℃ and 373℃,respectively.The number average molecular weight of the polymeric Er-complexes was 9000~15000.Excited with UV light of different wavelengths (300,345 and 390 nm) ,the polymeric Er-complex emitted the characteristic near-infrared (NIR)-light of ErIII ions.The result indicates that the energy absorbed by carbazole (light-harvesting group) was transferred to 8-hydroxyquinoline (coordinate group),where it is finally transferred to ErIII ion.In addition,the full width at half maximum (FWHM) in the PL emission spectra of the copolymers was above 90 nm,which enabled a wide gain bandwidth for optical amplification.关键词：Erbium;8-Hydroxyquinoline;N-vinylcarbazole;Near-infrared luminescence;Polymer
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发布时间：2021-03-19 - 摘要：Amino-terminated glass surface was prepared by coupling 3-aminopropyltriethoxysilane,and the Cu2+-amino redox system was designed to initiate the radical polymerization of the electron-deficient monomers,such as N,N-dimethylacrylamide) in aqueous solutions.The results from attenuated total reflection-Fourier transform infrared spectroscopy,contact angle measurements,atomic force microscopy and X-ray photoelectron spectroscopy confirmed the formation of the glass substrate grafted with functional polymer chains.As there was no free polymer chains formed in the reaction mixtures,our approach provided a facile strategy for the preparation of organic/inorganic hybrid materials.The amount of materials m(CuSO4)∶m(DMAAm)∶m(H2O)=5∶1000∶1000 should be selected,80℃ should be selected as the suitable temperature,and 4 h should be selected as the suitable reaction time.The weight gain ratio and specific graft yield of GlassKH-550-g-PDMAAm were 0.342% and 0.47 mg/cm2.The results showed that chemical composition and microstructure on the glass surface changed obviously,and the effect of graft polymerization was very distinct.关键词：Water-soluble monomer;Glass;CuSO4-amine redox initiation system;Graft polymerization on the glass surface;Hybrid materials
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发布时间：2021-03-19 - 摘要：The objective of this work was to develop a kind of new poly(phthalazinone ether) with high hydrophobicity,good thermal stabilities and excellent mechanical properties.The introduction of fluorine into poly(phthalazinone ether) is regarded as an effective way.A fluorinated poly(phthalazinone ether) containing tetrafluorophenyl groups was successfully synthesized by aromatic nucleophilic substituting self-polycondensation from AB type phthalazinone monomer 4-(4-hydroxyphenyl)-2-(pentafluorophenyl)phthalazin-1(2 H )-one at 100℃.The structure of the polymer was characterized by FTIR ATR,1H-NMR and 19F-NMR.Number average molecular weight characterized by GPC was 1.53 104 Da.The DSC and TGA measurements of the polymer were performed under a nitrogen atmosphere,and the results showed that the polymer exhibited good thermal stabilities with high Tg of 316℃ and 5% mass loss at 491℃.Moreover,the polymer was soluble in common organic solvents,such as DMAc,DMF,DMSO,NMP,TCE,THF,chloroform,pyridine and sulpholane,and could be readily cast into tough and smooth films from solutions.The films also showed high contact angles of water.Contact angle of the film cast by DMAc is 93.3.Contact angle of the film cast by CHCl3 is 92.5.Contact angle of the film cast by THF is 127.1,which is higher than that of polytetrafluoroethylene (112),indicating that the polymer has high hydrophobicity.Tension test results of film samples indicated the polymer demonstrated excellent mechanical properties with tensile strength over 60 MPa.The polymer exhibited good insulating properties with electrical surface resistivity of 1.81015 /m2 and volume resistivity of 5.61012 /m3.The synthesized polymer may have a promising prospect in microelectronic devices,such as the substrate for printed boards and insulating materials as interlayer dielectrics and intermetal dielectrics.关键词：Fluoropolymer;Poly(phthalazinone ether);Thermal stabilities;Contact angle;Electrical properties
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发布时间：2021-03-19 - 摘要：Star poly(lactic acid)was successfully synthesized via bulk ring opening polymerization of lactide using meso-tetra(p-aminophenyl)porphyrin (TAPP)as initiator and stannous octanoate (Sn(Oct)2)as catalyst under vacuum.Molecular structure of the four armed poly(lactic acid)was characterized via 1H-NMR and FTIR.It was confirmed that the star poly(lactic acid)was comprised with four-armed polymer chain and a tin porphyrin core.The molecular weight was also studied via GPC and 1H-NMR,and molecular weight distribution was also characterized (Mw/Mn=1.97).Both star poly(lactic acid) film and linear poly(lactic acid) film were prepared using solution-casting method.Structural analysis via X-ray diffraction indicates that the star poly(lactic acid)films display the orthorhombic -crystalline form,while linear poly(lactic acid)films display amorphous structure.The photoelectron study of the functional poly(lactic acid) via UV-Vis absorption spectra reveals that the star poly(lactic acid)displays photoelectric property of tin porphyrin.关键词：Star polymer;Porphyrin;Polylactic acid;Ring opening polymerization
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发布时间：2021-03-19 - 摘要：Composite nanofiber separators of polyvinylidene fluoride(PVDF) and titanium dioxide (TiO2) were prepared by electrospinning of PVDF solution containing in situ generated TiO2.The effects of TiO2 contents on the seperators structure and properties were investigated.The morphology of seperators was characterized by scanning electron microscopy (SEM),and the fiber diameter distribution was also calculated using scnimage software.Differential scanning calorimetry (DSC) measurements were carried out to investigate seperators thermal properties such as melting point,melting enthalpy and crystallinity.The mechanical strength was determined by tensile tests.The ionic conductivity was determined by AC impedence method,and the decomposition potential was determined by linear sweeping voltammetry (LSV).The results indicate that the seperators tensile strength and elongation at break were improved remarkably after the addition of TiO2,with the maximum increase rate of 228.6% and 244.8%,respectively.The presence of TiO2 reduced the crystallinity of the seperators,which is benificial to the transfer of lithium ions.The polymer electrolytes electrochemical performance was also enhanced,and the ionic conductivity at room temperature increased from 3.9 mS/cm to 5.1 mS/cm.关键词：Electrospinning;PVDF;Seperator;Lithium ion battery;in situ TiO2
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发布时间：2021-03-19 - 摘要：The effect of the oxygen concentration of stabilization atmosphere on the radial structure of polyacrylonitrile (PAN) stabilized fibers and the resulting carbon fibers (CFs) was investigated quantitatively by means of X-ray energy dispersive spectrometer,infrared spectrum analysis,microscopic laser Raman spectrometer and electron spin resonance.Results reveal that with the increase of the volume concentration of oxygen(Vo),radial structure of PAN stabilized fibers tends to be more homogeneous as a consequence of the stronger transferring of oxygen into fiber interior.When Vo increases from 20.38% to 21.15%,an obvious decrease in the radial skin-core structure and a rapid increase in the cyclization degree of PAN stabilized fibers are observed; meanwhile,the porosity of the resulting CFs is decreased and the tensile strength is increased.This condition is demonstrated to be beneficial to form turbostratic graphite structure in the skin region of CFs during the carbonization.In the case of Vo is greater than 21.34%,the radial shin-core structure is almost disappeared in the PAN stabilized fibers,however,the increase of the cyclization degree turns into much slower,which impedes the formation of turbostratic graphite structure in the skin region of the resulting CFs and gives rise to the increase of the porosity and decrease of the tensile strength.When Vo is dominated between 21.15% and 21.34%,the cyclization and the homogenization of radial structure of PAN stabilized fibers are both facilitated.Meanwhile,the turbostratic graphite structure is increasing in the core and is keeping at a much higher degree in the skin of CFs,enabling a 12.22% increase in tensile strength of the resulting CFs compared to the one obtained from regular air atmosphere.关键词：Polyacrylonitrile;Atmosphere;Radial structure;Oxidative stabilization;Carbon fiber
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发布时间：2021-03-19 - 摘要：Shell crosslinked core-shell nanoparticles (SCCSN) with modified SiO2 as core and crosslinked polystyrene (PS) as shell were prepared via miniemulsion polymerization in the presence of silane modified nanosilica.The structure characterization of SCCSN was examined by transmission electron microscopy (TEM),thermogravimetry (TG),dynamic light scattering (DLS),modulated differential scanning calorimetry (MDSC) and dynamic mechanical analysis (DMA).It was found SCCSN of about 90 nm in diameter was spherical and could uniformly disperse after surface grafting PS.In addition,the glass transition temperature of SCCSN obviously increased with increasing divinyl benzene amounts.The PS shell was crosslinked using divinyl benzene as crosslinker,which not only tightly anchors the shell on the nanoparticle surface,raises PS grafted ratio and prevents nanoparticles interaction,but also segregates the silica core from the matrix and avoids entanglement between the shell PS and the matrix macromolecules in SCCSN filled PS composites.MDSC analyses showed that both silica and SCCSN led to slight reduction in glass transition temperature of PS.Dynamic rheology showed both silica and SCCSN did not influence the mechanism responsible for the origin of rheological nonlinearity assigned to disentanglement of PS macromolecules in the matrix.The SiO2 core in SCCSN exhibited a reinforcement effect slightly stronger than that of bare SiO2 particles and the reinforcement was related to the crosslinking degree of the PS shell.关键词：Core-shell particles;Miniemulsion polymerization;Reinforcement
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发布时间：2021-03-19 - 摘要：Regular single crystals of polyethylene oxide were obtained through solution crystallization.To study their melting behavior on different iPB-1 substrates,iPB-1 thin films with different lamellar orientation have been prepared by crystallizing from melt at different temperatures.AFM observation shows that crystallizing from melt in air at room temperature the iPB-1 film exhibits an edge-on lamellar structure with molecular chains in film plane.On the other hand,crystallizing from melt at 100℃ isothermally,the iPB-1 film has a flat-on lamellar orientation with molecular chains perpendicular to the film plane.The melting of PEO single crystals on these different iPB-1 surfaces was then monitored by in situ AFM observation.It was found that the PEO single crystals on edge-on and flat-on iPB-1 crystalline film surfaces melted approximately at same temperature,which was confirmed by theoretical calculation.However,the dewetting behavior of the molten PEO single crystals depends on the lamellar orientation of the iPB-1 evidently.The PEO melt on edge-on iPB-1 film surface shows somewhat a better wetting ability than on flat-on iPB-1 crystalline film surface.关键词：AFM;Isotactic polybutene-1;Poly(ethylene oxide) single crystal;Melting
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发布时间：2021-03-19 - 摘要：The melt grafting of acrylates onto LLDPE was investigated for monomers of GMA,HPMA,HEMA,EMA,MMA and HEA by Haake mixer.It is found that,the depolymerization would occur during the melt grafting process for the grafted acrylate oligomer chains when the temperature was higher than the ceiling temperature (Tc) of the grafted acrylate polymers,which induced the decrease in the grafting ratio of the acrylates.Tc varied with different molecular structures of acrylate monomers.The influence of the steric hindrance and the special interactions between monomers was discussed.For the monomers with hydroxyl groups (GMA,HPMA,HEMA,HEA),the larger the steric hindrance is,the lower the reaction heat,which results in the lower ceiling temperature.The monomers of MMA and EMA have no hydroxyl groups,so the reaction heat is much lower,which results in the relatively low ceiling temperature than that with hydroxyl groups.The order of the ceiling temperatures was finally suggested:Tc(HEA) Tc(HEMA) Tc(HPMA)Tc(GMA) Tc(EMA,MMA).The solution polymerization in dichlorobenzene of the acrylate monomers was carried out respectively and the ceiling temperature ranges of different acrylate monomers were identified,which agreed well with the results of melt grafting.The styrene (St) was added as co-monomer to assist the grafting of acrylate monomers onto LLDPE,and the effect could be predicted by the Q-e rule.The grafting ratio of GMA,HPMA,MMA and EMA could be improved by adding St because they can copolymerize with St well and the depolymerization in melt grafting could be depressed even at high temperatures.关键词：Acrylate;Polyolefin;Melt grafting;Depolymerization;Q-e rule
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发布时间：2021-03-19
Research Article
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