最新刊期
卷 ， 期 7 ， 2008
- 摘要：A novel peptide-grafted polymer P-GS5 was synthesized by modification of poly(D,L-lactide-co-β-malic acid) (P-COOH) with pentapeptides Gly-Arg-Gly-Asp-Ser (GRGDS),and its biocompatibility was investigated.Infrared spectroscopy (IR),element analysis (EA) and X-ray photoelectron spectroscopy (XPS) were used to characterize the synthesized materials (poly(D,L-lactide) (PDLLA),P-COOH,P-GS5).Hydrophilic properties of these polymers were investigated by contact angle measurements (CA).Subsequently,biocompatibility experiments were conducted by testing human umbilical cord vein endothelial cell (HUVEC) (24 h) and platelet (30 min) adhesion on polymer surfaces.The number of endothelial cell and platelet adhesion was counted by cytometer and automatic hematological analyzer,respectively.It has been shown that the hydrophilicity of P-GS5 was greatly improved.Water contact angle was 84° for PDLLA,78° for P-COOH and 58° for P-GS5.Cell adhesion data indicated that P-GS5 could promote endothelial cell attachments.The adhesion ratio of PDLLA,P-COOH and P-GS5 was 45%,62% and 109%,respectively.According to the platelet adhesion results,GRGDS on P-GS5 did not induce platelet aggregation.The platelet adhesion capacity of P-GS5 was much lower than that of the other two polymers,while the adhesion ratio of PDLLA,P-COOH and P-GS5 was 47%,37% and 18%,respectively.In conclusion,P-GS5 displayed improved hydrophilicity,higher affinity to endothelial cell and better ability of anti-platelet adhesion compared with PDLLA and P-COOH.It could be a potential biomedical polymer.
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发布时间：2021-03-19
Rapid Communications
- 摘要：Researches on the preparation of several polytetrafluroethylene(PTFE) functional fibers and N-isopropylacrylamide (NIPA) grafted chitosan via the radiation grafting have been described which were developed in the authors’laboratory in recent years .It is found that the radiation grafted functional materials have special properties.（1） The acrylic acid grafted PTFE fiber showed stronger acidity than the carboxylic acid grafted one, of which the carboxylic content was 3.07 mmol/g determined by the titration experiments.It showed excellent adsorption,desorption and separation properties for Cu2+,Pb2+ and La3+.The highest adsorption capacity for Cu2+,Pb2+and La3+was 107.48,246.41, 150.20 mg/g respectively,when pH was 5.（2） Hammett superacid indicators were used to estimate the superacidity of PTFE-g-ST-SO3H fibers with different degree of grafting.The results showed that the acidity of PTFE-g-St-SO3H fiber was stronger than 100% H2SO4 when the grafting degree was 21.7%.The relative catalytic activity of PTFE-St-SO3H fiber as a polymer superacid catalyst was higher than that of macroporous sulphonated resin in esterification,and it can be used repeatedly.（3） The NIPA grafted chitosan showed good thermo and pH activity,it had the potential use in drug releasing and other areas.
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发布时间：2021-03-19 - 摘要：The layer-by-layer (LbL) assembly technique,which was developed by Decher and co-workers in the early 1990s,has been proven to be an effective method to fabricate multilayer films with tailored chemical composition and architecture in micro and nanoscales.In the last decade,LbL assembly technique has made a rapid progress in film preparative methodologies and functional film materials.However,there are remaining challenges to scientists such as the general methods for fabrication of patterned films and multilayer films with noncentrosymmetric film structures,and so forth.In this paper,the recent progress in the fabrication and functionalization of the layer-by-LbL assembled polymeric multilayer film in our group is presented.Multilayer films with noncentrosymmetrically orientated azobenzene chromophores were fabricated by using the combination of surface sol-gel process and electrostatic LbL assembly technique,which can be used as second-order nonlinear optical film materials.A facile,cost-effective and generally applicable method for patterning LbL assembled polymeric multilayer films was developed by the combination of LbL assembly technique with room-temperature nanoimprinting technique.LbL assembled multilayer films with high loading capacity were fabricated by alternate deposition of slightly cross-linked polymeric microgels.Ion-triggered exfoliation method was developed to obtain large area free-standing LbL assembled polymeric multilayer film.Broad-band superhydrophobic antireflective(AR) coatings in near infrared(NIR) region with superhydrophobic surface were readily fabricated by the LbL assembly technique.
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发布时间：2021-03-19 - 摘要：Studies of authors on the adsorption and adsorption mechanisms of various organic compounds onto three types of polymeric adsorbents in aqueous solutions are reviewed.The investigations showed that the high adsorption capacity of the adsorbents to many organic compounds was ascribed not only to their high specific surface area but also their intensive micropore structure.The double-peak pore distribution mode,two-stage dynamic character and the formation mechanism of oxygen-containing groups on their surfaces are systematically studied.To bifunctional resin,the point of our study is on its industrial application.Macroporous resins and hypercrosslinked resins were modified with many different functional groups such as amidocyanogen,carboxyl,sulfonate etc., to elevate their adsorption capacities.Some proposed applications of these bifunctional resins in industrial wastewater are presented.The observation on the acrylic ester resin is still on a preliminary stage in terms of its adsorption mechanism and application to organic industrial wastewater.The investigations showed that the matrix of acrylic ester resin and functional groups on its surface played an important role on its adsorption mechanism.
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发布时间：2021-03-19 - 摘要：According to Mo et al.research on non-isothermal crystallization process of polymers,an equation for describing the non-isothermal crystallization kinetics of polymer was obtained by combining the Avrami equation and Ozawa equation.The Avrami equation modified by Jeziorny could describe only the primary stage of non-isothermal crystallization kinetics of polymers.The apparent Avrami exponent obtained by the Jeziorny method can not predict the mechanism of non-isothermal crystallization of polymers.The Ozawa equation is also limited for the non-isothermal crystallization process of many polymers,in obtaining the reliable kinetic parameters because of the substantial curvatures in the Ozawa plots.The changing slopes indicate that Ozawa exponent m is not constant with temperature during the primary crystallization process.The substantial curvature makes it impossible to determine the cooling or heating function (K(T)) over the entire crystallization process.However,the analysis based on the new method could give a series of straight lines.According to the relationship among the new parameter a,the apparent Avrami exponent n, and the Ozawa exponent m in the new method,the mechanism of crystallization of the polymer can be predicated and the result is comparable with that obtained by the isothermal crystallization.The new method is an effective method for dealing with the kinetics of non-isothermal crystallization of many polymer systems such as PAEKs,polyamides,poly(ethylene oxide),polyolefines,poly(3-alkylthiophenes),poly(β-hydroxybutyrate) and many blending systems.
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发布时间：2021-03-19 - 摘要：Ion exchange and porous materials are high effective adsorbents.These novel adsorbents have high specific surface areas or abundant functional groups,which make them have greater adsorption/desorption rate and larger adsorption capacity than other adsorbents.Besides granules or fibers,they can also be prepared as bundle,paper,cloth and felt to meet various technical requirements.In this paper the latest progress in the studies of author,s group on the preparation and adsorption properties of these novel adsorbents such as ion exchange fibers,chelating fibers,activated carbon fibers,and carbon aerogels is reviewed.The applications of these materials in drinking water purification,environmental control,resource recovery,chemical industry,medicine and health care and in preparation of catalyst are also presented.
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发布时间：2021-03-19
Feature Articles
- 摘要：A new organic guanidine compound, i.e. creatinine-guanidinium lactate (CGLA),was synthesized for the first time by the direct reaction of creatinine with lactic acid under selected conditions (50℃,3 h,water solution).Evaporating off water in vacuo the solid was recrystallized in water for three times,and a snow-white product was obtained. 1H-NMR characterization indicated that the synthesized CGLA was of high purity (99%).Using CGLA as a mono-component organic initiator the ringopening polymerization (ROP) of L-lactide (LLA) was conducted for the first time.Bulk ROP of LLA was carried out at 100℃ under vacuum producing a poly(L-lactide) (PLLA) with narrower molecular weight distribution (［LLA］0/［CGLA］0=100， t=87 h， Mn＝1.20×104～1.3×10 4，PDI=1.29).Investigation on the kinetics of the polymerization in toluene showed that plots of ln［M］0/［M］t versus time and Mn versus conversion were linear which were the typical features of living polymerization.To know the nature of the propagation species,an experiment on additiveadding effect of the polymerization was carried out as follows.2,2,6,6-Tetramethyl-1-prperidinyloxy (TEMPO; a freeradical capturer),H2O and CH3COOH (terminators for cation and anion) were added to the three started polymerization systems after the polymerization was conducted for 24 h (polymerization in toluene at 100℃,［M］0/［I］0=50,24 h,Conv.=30.2％，Mn=4.3×103).Maintaining the original polymerization conditions for another 24 h,then the contents in the three reactors were checked simultaneously.The experimental results revealed that the polymerizations were not stopped,but continued synchronously in the three reactors.The molecular structure characterization of the propagating polymer species by 1H-NMR indicated that the growing polymer bore a creatinineguanidinium-alkoxy bond as its active end.Based on the experimental investigations,the mechanism of the CGLA-initiated ROP of LLA was postulated as follow:initiation occurred through a monomer-activated mode.The association of the creatinineguanidinium (CG+) with the acyl-oxygen atom in the LLA molecule greatly increased the nucleophilic activity of the lactate anion (LA-) in the CGLA molecule.Initiatin occurred when a lactate anion attacked at the carbonyl carbon causing the cleavage of the RCO-O bond in LLA molecule.Owning to that the reaction of CG+ with the cleavaged LLA residue RO- formed a molecule with polar covalent bond CGOR,but not an ionic bond,the propagation was postulated to follow the coordination insertion mode through the repeatedly insertion of the monomer in the CG-O bond in the propagating polymer molecule.Homonuclear decoupled 1H-NMR characterization of the methine in the product indicated that the synthesized PLLA possessed higher isotacticity (76%).
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发布时间：2021-03-19 - 摘要：Monodisperse,highly charged polystyrene colloidal particles with an average diameter of 170 nm were prepared by emulsifier-free emulsion polymerization.These particles spontaneously self-assemble into crystalline colloidal arrays (CCAs) in low ionic strength aqueous solutions due to long-range electrostatic repulsions among the particles.These CCAs diffract light,meeting the Bragg condition in the ultraviolet,visible and near-infrared spectral regions.CCAs were embedded into a polyacrylamide hydrogel to form polymerized crystalline colloidal arrays (PCCA) by adding acrylamide, N,N-methylenebisacrylamide and 2,2-diethoxyacetophene into the liquid CCAs,and then photopolymerizing the mixture of monomers to make a thin PCCA film.Modified PCCAs containing —NH2 groups were prepared via Mannich reaction with ethylenediamine.Hydrogel modified with ethyleneamide underwent a volume phase transition in response to the change in ionic strength of the solution.The biotinylation of the PCCA was achieved by chemical conjugation of the polymer gel with biotin after appropriate chemical modification of the gel.The interaction of the biotinylated PCCA with avidin led to a shrinkage in volume of the system caused by increased cross-linking in the hydrogels due to the binding between biotin and avidin.This volume change of the hydrogels altered the periodicity of the CCAs,resulting in a blue shift in the diffraction spectra.When excess biotin hydrazide was added,it was able to displace avidin bound to the biotinylated PCCA by the formation of a stronger complex with avidin.The disassociation of avidin from the PCCA led to the re-swelling of the hydrogels,corresponding to an increase in the interparticle distance in the PCCA and thus a red shift in the diffraction spectra.Our results demonstrated the response of a model sensor system made of biotinylated PCCA to the binding of an interacting protein,avidin.This may provide a basis for the sensing of protein molecules by functionalized PCCA systems.
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发布时间：2021-03-19 - 摘要：Mechanism of adsorption for panax notoginsenoside (PNS) and pigment was studied by comparing with the static adsorption capacity and the influence of eluting agent on removal of PNS and pigment among three kinds of commercial resins,such as macroporous adsorbents AB-8，gel ion-change resins 201×2 and macroporous ion-change resins D280,respectively.The result of pilot study revealed that adsorption of PNS was based on the hydrophobic interactions, and that of pigment was based on the synergistic effect of ion exchange effect and hydrophobic interactions.Hereby a series novel polymeric adsorbents with high specific surface area and high content of quaternary ammonium groups (e.g.—N＋(CH)3) were synthesized using Davankov postcrosslinked reaction.Then adsorbents were used to purify the panax notoginsenoside (PNS) in the extract of leaves.Adsorption—desorption properties of the quaternary ammonium polymeric adsorbents were investigated .It was showed that the adsorbent with 692 m2/g specific surface area and 2.1 mmol/g content of —N＋(CH)3 groups exhibited the best purification effect.The content of PNS increased from 36.2％ in crude extract of Sanqi leaves to 90.0％and E420 down to 0.008 . And the recovery of PNS was over 95%.Since the mechanism for adsorption of PNS and pigment was different,PNS and pigments can be eluted from the adsorbent using different eluting agent,respectively.Thus,the adsorptive purification procedure of PNS in the extract of leaves by using this adsorbent is much simpler as compared with conventional purification methods,the purify processes are combined in one step.Moreover,the stability and the regeneration of the quaternary ammonium polymeric adsorbents are evaluated.The results showned that pigments on the adsorption can be removed by elution with 80% aqueous ethanol solution containing 5% of sodium hydroxide, and the adsorbent should be regenerated to remove the pigments after it had been used for five circles.The purifying performance of the adsorbent was very stable after regeneration,and it can be used repeatedly.So,the quaternary ammonium polymeric adsorbent with high specific surface area can be used to purifying PNS in the extraction of leaves with high quality.
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发布时间：2021-03-19 - 摘要：Biodegradable aliphatic polycarbonates have attracted great attentions as an important kind of biomedical materials.In this study metal-free ringopening polymerization of 14-membered dimmer,cyclobis(tetramethylene carbonate) ［(TeMC)2］ was attempted at 75℃ in toluene and in the presence of porcine pancreas lipase (PPL),candida rugosa lipase (Lipase AYS) or immobilized lipase Novozyme-435 to afford poly(tetramethylene carbonate).It was found that Novozyme 435 exhibited comparatively high catalytic activity with Sn(Oct)2 while PPL and AYS exhibited no obvious activity to the polymerization of (TeMC)2 with respect to the conversion and molecular weight.Optimal reaction conditions including monomer concentration and Novozyme435 concentration were explored in an effort to positively influence the outcome of the ring-opening polymerization.The polymerization rate was markedly increased with increasing the enzyme concentration.A region exists around toluene/(TeMC)2 (mL/g) ratio of 4∶1 where Novozyme-435-catalyzed polymerizations could result in higher molecular weight and monomer conversion.It is interesting to point out that in the absence of toluene,the solid-phase polymerization could also occur at predetermined temperature of 75℃,which was much lower than the melting point of (TeMC)2 (Tm=170～172℃).The result of kinetic studies of polymerization showed that Novozym-435-catalyzed polymerization of (TeMC)2 did not behave living characteristics reported for that of ε-caprolactone.The experimental data also indicated that the immobilized lipase Novozyme-435 could be repeatedly used with high activity.
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发布时间：2021-03-19 - 摘要：The micellization process of poly(ethylene glycol)-b-poly(4-vinylpyridine) (PEG114-b-P4VP107) and poly(N-isopropylacrylamide)-b-poly(4-vinylpyridine) (PNIPAM53-b-P4VP260) in acidic aqueous solutions with varying degree of protonation of P4VP was investigated by NMR.When the micelles began to form due to the hydrophobicity of P4VP was resulted from its deprotonated,the NMR signal of pyridyl stayed unchanged.The signal kept becoming weaker with the decrease of the degree of protonation until no NMR signal can be detected at the point that all the 4VP unites were deprotonated.At the mean time,the spin-lattice relaxation time (T1) decreased significantly when the P4VP blocks began to transfer to aggregation from their unimer state.The results indicated that micelles of PEG114-b-P4VP107were formed at the degree of protonation of 0.54,while the micelles of PNIPAM53-b-P4VP260 were achieved at the point of 0.58. The twodimensional Nuclear Overhauser Effect (2D NOE) signal was also detected when the micelle solutions made separately from PEG114-b-P4VP107 (at the degree of protonation of 0.54) and PNIPAM53-b-P4VP260(at the point of 0.58) were mixed,which indicated the exchanges of macromolecules between micelles and the diblock copolymer in solution.However,no corresponding 2D NOE signal appeared while the micelle solutions were achieved at lower degree of protonation.This fact might imply the different mobility of the P4VP blocks,which formed the micelles core,at different degree of protonation.
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发布时间：2021-03-19 - 摘要：Magnetic microspheres with polymer brushes containing epoxide and amino groups were prepared and used as the support for immobilization of penicillin G acylase.The introduction of the amino group would accelerate the adsorption of enzyme to the support by ionic interaction, and then the adsorbed enzyme was immobilized covalently by reacting with the epoxide group.Magnetic microspheres with atom transfer radical polymerization (ATRP) initiators were first prepared from crosslinked poly(acrylic acid) microspheres in which superparamagnetic Fe3O4 nanoparticles were dispersed.Random copolymer P(GMMA-r-DMAEMA-r-GMA) (GMMA,glycerol monomethacrylate,DMAEMA, N,N-dimethylamino)ethyl methacrylate,GMA,glycidyl methacrylate) was grafted onto the magnetic microspheres by ATRP initiated from the magnetic microsphere initiators.For comparison,magnetic microspheres with P(GMMA-r-DMAEMA) or P(GMMA-r-GMA) brushes were also prepared.The GMMA units in the brushes made the brushes to be hydrophilic; DMAEMA units introduced amine groups and GMA units introduced epoxide groups.Immobilization of penicillin G acylase on these brush-grafted magnetic microspheres showed that both of the activity and activity yield of immobilized penicillin G acylase on P(GMMA-r-DMAEMA-r-GMA) brush-grafted magnetic microspheres were the highest, and the immobilization on them was faster than that on P(GMMA-r-GMA) brushgrafted magnetic microspheres.The immobilized enzyme possessed much higher thermal stability than the free enzyme.The optimal pH value for the immobilized enzyme was slightly higher.After ten cycles of repeated use,70% of the activity still remained.
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发布时间：2021-03-19 - 摘要：The design of next-generation organic light-emitting diodes (OLEDs) is focused on polymers containing electroluminescent functionality with efficient chargetransport capability.It is desirable to investigate display materials which have excellent fluorescent properties of 8-hydroxyquinoline metal chelates and outstanding processing properties of polymers.An 8-hydroxyquinoline lithium (LiQ)-containing polymer (CPA-HQ-Li) was synthesized by chelating reaction of Li+ and HQ-pendant copolymer (CPA-HQ),in which CPA-HQ was prepared with 5-chloromethyl-8-hydroxyquinoline (CHQ) and a copolymer (CPA) which was synthesized with n-butyl acrylate (BA),2-(dimethylamino) ethyl methacrylate (DM),methyl methacrylate (MMA),2-hydroxyethyl acrylate (HEA) and styrene (ST).As a functional group,DM was added according to 9.69 wt% as original material in the process of synthesizing CPA.Moreover,this positive-charged polymer was suitable for thin film deposition from dilute polymer solutions,the quarternary amonium PDM was used as the cation first adsoption layer to abtain a flexible substrate,the sulfonated fluoropolymer (Nafion 117) was used as the anion hole electon transport,and then,multilayer thin films were obtained by electrostatic self-assembly (ESA).For the characterization of the structures and properties of these polymers and multilayer films,the technologies inclucding 1H-NMR,UVVis,FTIR,photoluminescence (PL) spectra and gel permeation chromatography analysis (GPC) etc. were used.FT-IR analysis displays that the stretching vibration peak located initially at 1638 cm-1 is blue shifted to 1593 cm-1 nearby.It is found from UV-Vis absorbance that the absorption peak corresponding to π→π* electron transition of quinoline is still present,but it is red shifted from 248 nm to 258 nm, and the n→π* electron transition at 320 nm weakens or disappears.In addition,there is a broad absorption at 371 nm corresponding to the chelating of the polymer containing 8-hydroxyquinoline ligands with metal ion Li+.It is an enantiomorphous symmetrical connection between excitation and emission spectra of CPA-HQ-Li at λexit=366 nm and λemit=482 nm.Both the UV-Vis absorptions and fluorescence spectra of the films show a red shift compared to those examinated in tetrahydrofuran solutions.The UV-Vis absorptions show that the maximum UV absorbances of the composite films increase linearly with the number of film layers,but the fluorescence spectra reveal that the fluorescence intensity decrease linearly with the number of film layers.The results of the present work implies that these kinds of materials could be used for practical applications in OLEDs.
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发布时间：2021-03-19 - 摘要：A series of different methods have been used to fabricate the polyelectrolyte multilayer films through the layer-by-layered adsorption self-assembly method based on electrostatic attraction.In this presentation the multilayer building-up methods through dipping and spin-coating were used to study the influence of the multilayer buildingup methods on the multilayers’ structure and properties.Experimentally,azobenzenecontaining polyelectrolyte PNACN was fabricated into multilayers with counterpart polyelectrolyte PDAC using the layer-by-layer technique based on dipping and spin-coating,respectively.The differences in growth mechanism,structure and photo-sensitive properties of the multilayers fabricated with the two different methods were studied using UV-Vis,ellipsometer and AFM for characterization.Experimental results show that both of the dipping and spin-coating methods could fabricate uniformly layer-by-layered growth multilayer films while the multilayers fabricated by dipping grew faster than those fabricated by spin-coating.Both of the multilayers have relatively smooth surfaces with some spherical structure on them,which is believed to be due to the aggregation of hydrophobic azobenzene chromophores.Interestingly,these two kinds of multilayers have obviously different and complicated responses to the photo irradiation.Under irradiation with interference polarized laser beams,the multilayers by spin-coating could be written with surface relief gratings (SRGs) while not for those by dipping in case that both of the multilayers were less than 100 nm thick approximately.When the multilayers became thicker (for example more than 200 nm) both of the multilayers could be written with obvious SRGs,and the SRGs on the dipping multilayer surface were deeper for its thicker total multilayers.The difference of the multilayers in optical properties is believed to have close relationship with their difference in multilayer structures.Generally,the polymer chains in the multilayers fabricated through dipping are strongly interpenetrated among the ambient layers so that the combination of the interpenetration and electrostatic attraction between the opposite charged polyelectrolytes leads to a crosslinkagelike multilayer structure.On the other hand,the interpenetration of the polymer chains in the multilayers fabricated through spin-coating are much weak for the short time fabrication cycles,and consequently the polymer chains in the multilayers fabricated through spin-coating are more free and mobile.As a result,when the multilayer is relatively thin (less than about 100 nm) the SRGs structure can be formed on the spin-coating multilayer surface,but not on the dipping multilayer surface.
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发布时间：2021-03-19 - 摘要：The pasting behavior of rice starches from different varieties was investigated using both attenuated total reflectance Fourier-transform IR spectroscopy and X-ray diffraction.For IR spectroscopy analysis,absorbance spectra were recorded on a spectrometer equipped with a deuterated triglycine sulphate detector using the Digilab attenuated total reflectance accessory.Starch dispersions (6%) heated to different temperatures were loaded on the OMNI sampler.Each spectrum,obtained at a resolution of 4 cm-1,was an average of 64 scans,recorded against an empty cell as background and was subtracted from the spectrum of water.Spectra were baselinecorrected at 1200 cm-1 and 800 cm-1 by drawing a straight line.All spectra were deconvoluted.The results indicated that the crystalline areas of the granule were mainly ascribed to double helices formed by amylopectin branches.The crystallinity of the granules was disrupted during pasting.The short-range order of waxy (Calmochi101) and medium (Koshi and M202) grain rice starches decreased rapidly with the temperature increasing from 60℃ to 65℃,which indicated that the loss of crystallinity was significant as soon as the temperature reached the pasting onset temperature of each rice starch.At temperatures above 70℃ a relative small decrease of short-range order was observed.In the case of long grain rice starch (Cocodrie and L205),significant decrease of short-range order was observed when the temperature was over 70℃.This was due to the higher pasting onset temperature of long grain rice starch.The rice starches with high amylose content were found to lose the crystallinity more slowly as compared to those starches with low amylose content.It suggested that the amylose could restrain the swelling and disruption of starch granules and inhibit the loss of the crystalline areas of rice starch granules during pasting.Relative crystallinity of pasted starches at different temperatures was determined using X-ray diffraction.The results verified the loss of crystallinity of starch granules during pasting and were consistent with the results obtained by IR spectroscopy analysis.Although the definitions of “crystallinity” were different for the two methods,the results were correlative and comparable and could provide useful information for the study of starch pasting.
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发布时间：2021-03-19 - 摘要：The Izod notched impact strength of foamed and unfoamed high density polyethylene (HDPE) was tested systematically in a wide temperature range from -196℃ to 23℃,and the impact fracture surface morphology of samples was observed and analyzed by scanning electron microscopy (SEM).The size and size distribution of cells were analyzed by using the image_pro plus software.The samples were also characterized by dynamic mechanical measurements.The results show that the cell size is in the range of 35～40 μm having a normal distribution.The Izod notched impact strength of unfoamed HDPE is much higher than that of the foamed ones at room temperature.The impact strength of both samples decreases with the descent of test temperatures.As the decreasing rate of impact strength for unfoamed samples is high than that for the foamed samples,an inversion of impact strength values between the two samples occurs at around -35℃,below which the foamed HDPE samples exhibit higher impact strength than the unfoamed HDPE samples.For both samples a sudden drop of impact strength can be observed in the temperature range from -43℃ to -53℃ followed by a very slow decrease trend in the low temperature range,and the transition between the two regions is quite sharp.The effects of microcells on the impact properties of HDPE were analyzed.It is supposed that the existence of microcells may reduce the actual section area of samples under impact testing,on the other hand it may also favor the plastic deformation of the HDPE matrix and the inhibition of crack propagation under low temperatures.The contribution of these factors determines the different temperature dependence of the foamed and unfoamed HDPE samples under impact testing.
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发布时间：2021-03-19
Research Article
- 摘要：An organic-inorganic hybrid bent-core liquid crystal (BCLC) with eight bent-core mesogens end-attached to inorganic polyhedral oligomeric silsesquioxanes (POSS) cores was synthesized and characterized to study how the inorganic cubic core may affect the liquid crystalline phase behavior and electro-optical properties of the BCLC.POSS8BC was successfully synthesized by hydrosilylation reaction of Q8MH8 and 3′-［4-(4-dodecyloxybenzoyloxy)-benzoyloxy］-4-(10-undecen-1-yloxy) benzoyloxybiphenyl with Pt(dvs) as catalyst in high yield.Well-defined chemical structure of POSS-8BC was confirmed by NMR,IR,elemental analysis,and GPC.Liquid crystalline phase behavior of this compound was investigated by differential scanning calorimetry,1D and 2D wideangle X-ray diffractions,and small-angle X-ray scattering.Meanwhile,electro-optical characterization was carried out by applying a triangular wave electric field.Response current was measured,and texture change under the electric field was observed.Two bilayer antiferroelectric SmC phases can be confirmed for POSS-8BC.In the higher temperature LC phase,the arrangement of POSS cores in the layer is not ordered.It is a conventional SmCA2PA phase with layer thickness of 8.0 nm.In the lower temperature LC phase, layer thickness decreases to 7.7 nm.POSS cores from a two-dimensionally ordered structure between two bilayers.It is a bilayer SmCAPA phase with inorganic nano-size mesophase dispersed in it.To our best knowledge,it is the first antiferroelectric LC phase with inorganic nano-size mesophase dispersed in it.
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发布时间：2021-03-19
Research Bulletin
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