最新刊期
卷 ， 期 8 ， 2009
- 摘要：Biocompatible multihydroxyl hyperbranched polyglycidol (HPG) was covalently grafted from surfaces of multiwalled carbon nanotubes (MWNTs) by “grafting from" method based on in situ anionic ringopening polymerization,affording multifunctional MWNTsupported molecular amplifier with HPG content of 52 wt% (MWNTHPG).Subsequently,fluorescent molecules of rhodamine 6B and succinic anhydride were conjugated to the surfaces of MWNT-HPG by N,N′-dicyclohexylcarbodiimide (DCC) coupling and esterification,respectively,giving rise to fluorescent multicarboxylic nanotubes (MNWT-R6B-COOH).The functionalized MWNTs were characterized by the combination of TGA,FTIR,1H-NMR,SEM and TEM measurements.The asprepared MNWT-R6B-COOH was further modified with the specific peptide of D4 composed with amino acid sequence of leucine-alamine-arginine-leucine?leucine-threonine (Leu-Ala-Arg-Leu-Leu-Thr) which was previously designed against epidermal growth factor receptor (EGFR) by our pharmacy lab.We also used D4* that contains the same kind of amino acids as D4 but with different sequence to modify the MWNT-R6B-COOH as control.Through fluorescent microscope，MWNT-R6B-D4 was found to bind strongly and extensively to the EGFR high-expressing SPCAI cell,comparing with the MNWT-R6B-D4* and MWNT-R6B-COOH.The result suggests that such EGFR ligand-directed functionalized CNTs may be prospective and promising to become an efficient tumor cell targeted carrier for the cancer therapeutics.
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发布时间：2021-03-19
Rapid Communications
- 摘要：The micellization behavior of a series of multiblock copolymers ［poly(4-vinylpyridine)-b-polystyrene-b-poly(4-vinylpyridine)］n (P4VP-b-PS-b-P4VP)n in selective solvents,namely toluene and acidic water with pH3,was investigated by using transmission electron microscopy (TEM) and atomic force microscopy (AFM).Three multiblock copolymers (P4VP-b-PS-b-P4VP)n were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization with a cyclictri-thiocarbonate as chain transfer agent. The multiblock copolymers were relatively polydisperse with polydispersity indexes of ca. 1.74～2.19.The effects of block length,polymer concentration and selective solvent on the morphology of the multiblock copolymer micelle were discussed. Because P4VP blocks have longer length than that of PS blocks and can not dissolved in toluene,the (P4VP-b-PS-b-P4VP)n multiblock copolymers showed rich micellar morphologies in toluene.The experimental results indicated that the morphology of multiblock copolymer micelle in toluene changed from worm-like shape to shortrod and finally to spherical micelle as the length of P4VP block increased. The polymer concentration was found to have strong effects on the micelle morphology due to the special sequence structure of the multiblock copolymer.At low concentration,the multiblock copolymer tended to form spherical micelle in toluene. The polydispersity of molecular weight also affected the micelle morphology of the multiblock copolymer. For acidic water with pH3,a selective solvent for the P4VP blocks,all of the multiblock copolymers studied here formed spherical micelles in it due to the longer block length of P4VP blocks.
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发布时间：2021-03-19 - 摘要：Dynamic rheological behaviors of silica white (SiO2) filled solutionpolymerized styrene-butadiene rubber (SSBR) compounds were investigated,and application of the time-concentration superposition (TCS) principle to this system was verified.Master curves were obtained by shifting the frequency sweep rheological data of the filled compounds with respect to the unfilled SSBR.The master curves disclosed the existence of modulus plateaus in the low frequency region while the complex viscosity exhibited marked shearthinning.The master tanδ curves displayed maximum at a characteristic frequency that decreased with increasing filler volume fraction φ .The modulus and the frequency shift factors,AG and Aω,were introduced into the TCS principle on the basis of strain amplification effect due to the presence of rigid undeformable SiO2 particles as well as the constrained molecular motion of SSBR among the particles.Scaling relations were revealed to AG and Aω as a function of φ.However,the AG-φ relation did not follow the cluster-cluster aggregation (CCA) model that was usually suggested for particle suspensions or particle filled polymers.Influence of 3-octanoylthio-1-propyltriethoxysilane (NXT) as coupling agent to the dynamic rheological behaviors was also discussed.NXT did not influence the modulus plateaus and the shear-thinning index whereas it caused a reduction in characteristic relaxation time and marked increments in consistency and AG in comparison with the NXT-free compounds.
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发布时间：2021-03-19 - 摘要：A new type of A3B3 six-arm azobenzene-containing star-shaped copolymers based on cyclotriphosphazene was prepared by stepwise nucleophilic substitution of hexachlorocyclotriphosphazene,using the sodium salt of methoxy poly(ethylene glycol) (MPEGNa) and the sodium salt of 4methoxy4′-(6-hydroxyhexyloxy)azobenzene (AZO-Na) in sequence.Structures of the resultant copolymers ［NP(MPEG550)(AZO)］3 and ［NP(MPEG1100)(AZO)］3 were characterized by Fourier transform infrared spectroscopy (FTIR),proton nuclear magnetic resonance spectroscopy (1H-NMR) and gel permeation chromatography (GPC).Thermal properties of both sixarm azobenzene containing copolymers were investigated by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM).DSC result showed that ［NP(MPEG550)(AZO)］3 showed reversible thermotropic liquid crystalline (LC) behavior (TS-N=60.5℃; TN-I=104.7℃,by the second heating DSC curve) and was an enantiotropic LC polymer.Nematic droplets texture was observed by POM,but smectictonematic translation was not clear.This might be related to the complex LC phase transition process with the unique molecular structure of ［NP(MPEG550)(AZO)］3.It was not observed the thermotropic LC transition of ［NP(MPEG1100)(AZO)］3 by DSC and POM.This might be the result of the difficulty of crystallization of azobenzene segment linked to the long and flexible PEG chains with big volume fraction in the ［NP(MPEG1100)(AZO)］3.Thermotropic liquid crystalline behavior of such A3B3 polymers was mainly relevant to the chemical property and volume fraction of different arms.
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发布时间：2021-03-19 - 摘要：Two commercial crosslinkable polyethylene insulation cable granules,used for 35 kV and 110 kV voltage insulation respectively,with the similar melting point and crosslinking temperature,were chosen as experimental samples for examining their linear dynamic responses during cross-linking.In order to detect the structure evolution of the two samples during crosslinking,dynamic time sweep test was carried out at 140℃,145℃ and 150℃ using parallel plates model with an Advanced Rheometric Expansion System.It can be found that the pre-crosslinking time decreased with the increase of crosslinking temperature for both samples during the dynamic time sweep test,but the rising rates of the dynamic viscosity (η′) and dynamic rigidity (η″) for both samples were independent of temperature.Compared with 110 kV insulation cable granules，35 kV insulation cable granules showed higher rising rate of η″,similar rising rate of η′and longer pre-crosslinking time at the same temperature during crosslinking.As a criteria of crosslinking density,the number-average molecular weight between the junction of the networks for crosslinked samples,Mc,was calculated on the basis of the rubber elasticity theory,using the data of dynamic modulus G′ obtained from plotting dynamic storage modulus (G′) versus frequency (ω) at terminal zone where ω approaches 0.The value of Mc of 35 kV insulation cable granules calculated through rheological method was lower than that of 110 kV insulation cable granules.Moreover,the Mc dependence on crosslinking time was probed through the equilibrium swelling method.The values of Mc of totally crosslinked insulation cable getting from rheological method were similar to those from equilibrium swelling method although they crosslinked at different conditions.
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发布时间：2021-03-19 - 摘要：This work attempts to prepare ethylene-α-olefin copolymer with relatively narrow composition distribution by modification of TiCl4/MgCl2 type supported Ziegler-Natta catalyst.A TiCl4/ID/MgCl2 type catalyst,where ID is a diester,was treated at room temperature with 2,6-iPr2C6H3-OH at phenol∶Ti molar ratio of 1∶1,and the modified catalyst was analyzed for contents of titanium and aryloxy group.It was found that about one third of the titanium atoms in the modified catalyst (M-cat) was connected with an aryloxy group,but its Ti content was decreased to 1.44 wt% from 2.36 wt% of the original catalyst (O-cat).Ethylene-1-hexene copolymerization was conducted in n-heptane with M-cat or O-cat as catalyst and triisobutyl aluminium or methylaluminoxane as cocatalyst.The M-cat showed similar activity as the O-cat in catalyzing the copolymerization,but presented a weaker comonomer activation effect than the latter.The 1-hexene content of copolymer synthesized by M-cat was lower than that of the product of O-cat at the same conditions,but had a markedly narrower composition distribution.Each copolymer sample was fractionated into two fractions by extraction with boiling n-heptane,and the soluble part contains much more 1-hexene units than the insoluble part.The ratio of 1-hexene content in the soluble fraction to that of the insoluble fraction was higher than 18 in copolymer prepared with O-cat,but this ratio was reduced to 3.7 when M-cat was used as the catalyst.On the other hand,the soluble part of copolymer prepared with M-cat showed a more random sequence distribution than that of the O-cat.The distributions of active centers in both the M-cat and O-cat were studied by deconvolution of the polymer’s molecular weight distribution curves with multiple Flory most-probable distribution function.Both catalysts showed a broad molecular weight distribution that can be ascribed to 5～6 types of active centers,but the introduction of aryloxy group in the catalyst caused marked changes in the active center distribution.Possible mechanism of the catalyst modification was proposed.
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发布时间：2021-03-19 - 摘要：The linear viscoelastic behavior and electrical conductivity of highdensity polyethylene (HDPE) filled with stainless steel fibers (SSF) were investigated and compared with those of carbon black (CB) filled HDPE composites system.It is found that CB/HDPE composites show two electrical conductivity percolation values (φc1 and φc2) and a wide percolation range.However,SSF/HDPE composites present an extremely low threshold of the electrical conductivity percolation (only 0.3 vol%) and a narrow percolation range.Only one conductivity percolation value (φc) was observed.The speciality of conductivity percolation behavior of SSF/HDPE composites owes to the formation of conducting channels of SSF/HDPE composites.It is well recognized that the rheological percolation threshold is identical to the percolation threshold of electrical conductivity for CB/HDPE composites.Whereas,for SSF/HDPE composites,dynamics storage modulus (G′) becomes almost independent of frequency in the low frequency region as the SSF loading increases up to 4.8 vol%,suggesting an onset of solidlike behavior in SSF/HDPE composites.By plotting G′ versus SSF loading,the rheological threshold is determined as 4.8 vol%,which is much lower than the percolation threshold of electrical conductivity,i.e. 0.3 vol%.Additionally,the positive temperature coefficient (PTC) effect was measured for SSF/HDPE and CB/HDPE composites.It reveals that the conductivity channels formed by SSF show a higher stability than those formed by CB particles in HDPE matrix.The difference in the percolation threshold and the stability of conductivity channels are understood in terms of the larger L/D of SSF and the particular conductive mechanism of SSF/HDPE composites.
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发布时间：2021-03-19 - 摘要：in situ Compatibilization by Friedel-Crafts alkylation reaction has the commercial potential in the recycling of commingled post-consumed polymers containing polystyrene (PS) and polyolefin.The most important problem in the approach of in situ compatibilization of PS/POE (polyolefin elastomer) blends is to increase the efficiency of grafting and limit the degradation of the blending components.In order to increase the efficiency of grafting,the styrene (St) monomers were added into the in situ compatibilized PS/polyolefin elastomer (POE) blends.The graft degree of PS/POE/St/AlCl3 (80/20/n/0.8,wt%) increased from 8.6% to 14.0% with the St content increased from 0 to 0.6%,indicating that the addition of St could accelerate the Friedel-Crafts alkylation reaction.The St/AlCl3 catalyst system initiated more PS-graft-POE copolymers than the single AlCl3 catalyst.Because those PS-graft-POE copolymers acted as the compatibilizers between the interface of PS and POE,the mechanical properties of PS/POE blends were greatly improved.For example,the Charpy impact strength increased from 8.5 kJ/m2 to 9.9 kJ/m2 and the elongation at break increased from 22% to 29% when 0.6% St was added to PS/POE/AlCl3 (80/20/0.8,wt%) blend.Besides,the two-step extrusion procedure gave better mechanical properties of PS/POE blends,which were the results of a limitation of degradation of blending components when the master batch product and virgin polymers were extruded in the second extrusion step.
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发布时间：2021-03-19 - 摘要：New thermal stable mono-substituted polyacetylenes (PAT5 and PAT10) containing phosphaphenanthrene as side groups and endchains of different lengths were studied.4-Ethynylbenzoyl and 4-alkoxylbenzoyl were first introduced into the 2(6-oxide-6H-dibenz1,2oxaphos-phorin-6-yl) dihydroxyphenylene (ODOPB) through a two-step esterification,respectively,which synthesized the phosphaphenanthrenecontaining acetylenic monomers.The polymerization of novel monomers was carried out by using ［Rh(nbd)Cl］2NEt3 as the catalyst at room temperature in high yield (90%).The structure and optical properties of the polyphenylacetylenes were characterized by means of 1H-NMR,FT-IR,UV-Vis and photoluminescence spectroscopy,respectively,which showed that the polyacetylenes were synthesized successfully.During the introduction of phosphaphenanthrene as side-groups,PAT5 and PAT10 are yellow-brown and soluble in common solvents.However,The model polyacetylene PA5 in the absence of phosphaphenanthrene is red and insoluble.GPC reveals two peaks for the novel polacetylenes. The first peak is attributed to the aggregation state between polymeric chains (107)， and the second one is to the real molecular weight (104).The experimental results indicate that the regular supramolecular structures between phosphaphenanthrenecontaining pendent groups are fabricated based on the strong π-π stacking and polar interactions and then induce production of the polyphenylacetylene with high trans-content configuration,which may result in the high degree of extend conjugation of the main chain and enhence the interaction between adjacent pendent groups.Comparing with the model polyphenylacetylene in the absence of phosphaphenanthrene side-groups,TGA analysis reveals the excellent thermal stability of the mono-substituted polyphenylacetylenes containing phosphaphenanthrene as side-groups because the 5% weight loss temperatures are close to 400℃.
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发布时间：2021-03-19 - 摘要：Enantiopure methacrylamide derivative,N-［o-(4-methyl-4,5-dihydro-1,3-oxazol-2-yl)phenyl］ methacrylamide ((S) MeOPMAM) was synthesized and radically polymerized in the presence of rare earth metal trifluoromethanesulfonates (Ln(OTf)3,Ln = La,Nd,Sm,and Y) to yield corresponding optically active polymers.Among these Lewisacids,Y(OTf)3 was found to be most effective for increasing the isotactic specificity during the radical polymerizations when using n-butanol as a solvent.The effect of the Lewis acids was significantly influenced by the ratio of Ln(OTf)3 to monomer and the nature of solvents.The tacticity of polymers was estimated by13C-NMR spectroscopy on the basis of the peak splitting of the quaternary carbon of the main chain (δ=46.5～48.5).The conventional polymerization without Y(OTf)3 produced syndiotacticrich polymer with rr = 67%,while the polymer with a relatively high isotacticity (mm = 47%) was obtained in the case of an equimolar amount of Y(OTf)3 to the monomer.Also,the addition of the rareearth salt increased both the polymer yield and molecular weights.The relationship between the stereoregularity and the chiroptical property as well as the chiral recognition was then examined for the resulting polymers with various tacticities by spectroscopic techniques such as circular dichroism (CD) and NMR.The syndiotacticrich polymer showed a specific rotation of +118.6°; however,the absolute value of ［α］25D decreased with an increase in the isotactic triad content and a negative value (-2.1°) was observed for the polymer having mm = 47%.Correspondingly,the CD intensities at 240 nm and 220 nm were depressed evidently.On the other hand, 1H-NMR measurements of the mixture of poly［(S)MeOPMAM］s and racemic 1,1′-bi-2-naphthol (BINOL) were conducted in chloroform-d.The characteristic hydroxyl proton signal of BINOL was split into two peaks ascribed respectively to the levo- and dextro isomer; furthermore,the splitting magnitude appears to be positively correlated with the mm value of the polymers.These results indicate that the polymers containing a higher isotacticity may possess favorable enantioselective discrimination ability toward the target compound.
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发布时间：2021-03-19 - 摘要：To investigate the enhancement mechanism of the oligo-chitosan (oligo-CS) on the transdermal delivery of drugs,the interactions of oligo-CS and D-glucosamine (DG) with the stratum corneum (SC) keratin were investigated in vitro with the lipid-extracted mouse SC and extracted keratin as models by EIS,SEM,DSC and FTIR methods.It was found that the DG solutions had no influence on the EIS value of the lipid-extracted mouse SCs.But oligo-CS solutions could reduce the EIS value of the lipid-extracted mouse SCs from the original 3.79×106 Ω . cm2 to 8.379×105 Ω . cm2.Moreover,SEM pictures showed that both oligo-CS solutions and DG solutions could destroy the keratin membranes.Furthermore,DSC determination revealed that the melting point of the α-helix micro-crystals in the keratin membranes was lowered from 201℃ to 190℃,189℃ and 165℃ after compositing with 1 wt% oligo-CS,5 wt% oligo-CS and 5 wt% DG,respectively.FTIR spectra exhibited that the amide II absorption peak of keratin shifted from 1523 cm-1 to 1520 and 1521 cm-1 after the treatment with 1 wt% oligoCS solution and 1 wt% DG solution, respectively.These results indicated that the interactions between the oligoCS and the SC keratin could destroy the tight junctions of the keratin cells and vary the keratin conformation from α-helix to β-sheet or random coil,resulting in a decreased skin barrier and an improved drug percutaneous permeation property.
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发布时间：2021-03-19 - 摘要：The radius of gyration is a good parameter for characterizing the dimensional distribution of a given polymer chain at perturbation conditions.But it is hard to give information about stack structures of polymer chains both in bulk and solution.It is highly desirable to establish the relationship between the micro structure parameter and macroscopical properties of polymers in bulk or in solution.The degree of chain overlap is a good parameter for that,which has been defined and applied very well in bulk state.Based on Flory theory of intrinsic viscosity of polymers and the model of concentration dependence of polymer chain dimension in solution,a quantitative expression of the degree of chain overlap ξc,ξc≡c/ρc=4πNA/3Φ′×［η］c/{1+［η］-［η］θ/［η］θ［1-exp(-c /c*)］},in terms of the concentration of the polymer solution from diluted solution to concentrated solution was deduced.A master curve of the relative viscosity ηr of polychloroprene solutions in literature for different molecular weights,various solvents and temperatures can be obtained as the ξc was used as a variable for replacing the concentration.It suggests that the microstructure parameter of ξc and its quantitative expression proposed in solution state could correlate the macroscopical properties of polymer solutions，ηr，very well even at high concentration range.Also，ξc could be expected to be a promising micro-structure parameter for associating other properties of polymer in solutions.
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发布时间：2021-03-19 - 摘要：Poly［2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta［2,1-b；3,4-b］dithiophene)-alt-4,7-(2,1,3- benzothiadiazole)］ (PCPDTBT) is a new kind of low band-gap polymers for applications in organic photovoltaic devices.However,PCPDTBT was studied as the donor to form the photoactive composites only with organic acceptors (fullerene derivatives) so far.In this article,PCPDTBT was synthesized,and its chemical structure,thermal stability and energy levels were identified and characterized by NMR,GPC,TGA,and CV,respectively.Furthermore,the composites of PCPDTBT with two electron acceptors of 1-(3-methoxycarbonylpropyl)-1-phenyl［6,6］C61 (PCBM) and ZnO nanoparticles were prepared by solutionblending.Both composites showed fluorescence quenching,indicating that the photo-induced charge transfer occurred due to the energy level offset between the donor PCPDTBT and the acceptor.Nevertheless,from the SEM images of the two composites,it was disclosed that PCBM molecules were well dispersed all over the PCPDTBT- PCBM composite whereas ZnO nanoparticles aggregated to some extent in the PCPDTBT-ZnO composite,leading to a more effective photo-induced charge transfer between PCPDTBT and PCBM.
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发布时间：2021-03-19 - 摘要：Thiol end-functionalized polycaprolactone(HS-PCL) and amphiphilic -poly (ethylene glycol)-b- polycaprolactone (PEG-b-PCL) were synthesized via ring-opening polymerization of ε-caprolactone (ε-CL) using Novozym 435 (immobilized form of lipase B from Candida antarctica) as biocatalyst,and 2-mercaptoethanol and methoxy poly(ethylene glycol) (MPEG) as initiators,respectively.The structure of the obtained polymers was characterized by means of IR, 1H-NMR and GPC.The effects of the feed ratio of initiator to CL,polymerization temperature and time on the monomer conversions and molecular weights of polymers were investigated.Oxidation of the thiol end groups of HSPCL to form disulfide bonds was studied in a series of solvents including DMSO,THF and acetone.The structure and sizes of the copolymer PEG-b-PCL micelles were analyzed by means of DLS and 1H-NMR.The results showed that the obtained polymers had the expected structure; Novozym 435 had high catalytic activity,for the bulk polymerizaion with 10 wt% Novozym 435,the monomer conversion achieved ca. 80% within 2 h at 70℃; 2-mercaptoethanol and MPEG could effectively initiate the ringopening polymerization of CL; HS-PCL samples were placed in DMSO (or THF or acetone) under ambient atmosphere at a certain temperature,such as 37℃ or 70℃,the molecular weights of the oxidized products increased,but less than 2 times that of HS-PCL,indicating that some HS-PCL molecules were oxidized to form PCL-S-S-PCL.The PEG-b-PCL copolymers could self-assemble into nanosized micelles composed of hydrophobic PCL core and hydrophilic PEG shell in aqueous solution.The hydrodynamic diameters of micelles varied from 64 nm to 122 nm as the increase of ［CL］/［EO］ of copolymer from 0.23 to 1.70.
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发布时间：2021-03-19 - 摘要：Dopamine-containing polyurethane was prepared by isocyanate chemistry and carbodiimide chemistry.In this polymer,polyurethane backbone was used to take the place of the protein polyamide chain and dopamine was appended to the polyurethane to mimic the strong adhesion of mussel adhesive proteins.It is possible to combine the unique adhesion of marine adhesive proteins with the designability,easy synthesis,and low cost of simple polymers.First,NCO terminated urethane prepolymer was synthesized from a polyether polyols and isophorone diisocyanate.Then the desired urethane-based prepolymer,together with dimethylol propionic acid was employed to synthesize carboxyl-containing polyurethane.Finally,mussel mimetic polyurethane was prepared using dopamine-HCl and carboxyl-containing polyurethane.The successful incorporation of dopamine with polyurethane was characterized by FTIR, 1H-NMR and UV-Vis.FTIR showed the appearance of a shoulder peak 1656 cm-1 associated with the newly forming chemical bond amideⅠbetween —COOH in carboxylcontaining polyurethane and —NH2 in dopamine-HCl. 1H-NMR spectrum was also consistent with the structure of dopaminecontaining polyurethane.Chemical shifts in δ=7.4～8.0,6.3～6.7 and 8.5～9.0 are corresponding to hydrogens of newly forming chemical bond amide,aromatic hydrogens and phenolic hydrogens in catechol,respectively.The absorbance peak in UV-vis also implies the absence of catechol groups in the polymer.In the characterization of shear adhesive strength,we found that grafting dopamine to polyurethane by amide linkage greatly enhanced the adhesive strength.For the substrate of Fe,the adhesive strength has been improved by 30%,at about 5.2 MPa,which can be compared with mussel adhesive proteins.
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发布时间：2021-03-19 - 摘要：A novel kind of metalloporphyrin-based molecularly imprinted polymers was prepared to epoxiconzole,a triazole fungicide template,using 5-(4-methacryloxyphenyl)-10,15,20-triphenylporphinatozinc(Ⅱ) as the functional monomer and ethylene glycol dimethacrylate as the cross-linker.The interaction between the functional monomer and the triazole fungicide template as well as four other triazole analogs was quantitatively investigated with UVvisible titration spectroscopy,which reveals the formation of 1∶1 complex in the system.The interaction was attributed to the coordination between the central zinc ion of the porphyrin and triazole ring in the fungicide.Selective rebinding and solid phase extraction measurements were used to characterize the recognition properties of the obtained polymer.It was found that the metalloporphyrinbased molecularly imprinted polymer exhibited specific affinity to the template molecule in comparison with other triazole fungicide analogs.The effect of polymer cross-linking degree on the molecular recognition properties was investigated,showing the specific affinity was enhanced with a certain extent of cross-linking.It was noted that the rebinding properties of the molecularly imprinted polymer was greatly influenced by the polarity of the binding solvent.The rebinding amount of the triazole fungicide in dichloromethane was determined to be about ten times of that in methanol.
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发布时间：2021-03-19 - 摘要：The dye-doped SiO2 particles with diameters of 80,160 and 500 nm were prepared by using the St-ber sol-gel method.Cellular uptake of the luminescent SiO2 particles by HepG2 cells and the endocytic pathway were studied by fluorescent microscopy and flow cytometry.Influence of the SiO2 particles on HepG2 cells was tested in terms of cytotoxicity,cell adhesion and migration by MTT assay,cell adhesion assay,the wound healing and transwell assay.According to the results of flow cytometry,the uptake efficiency of the SiO2 particles was significantly decreased when the culture was performed at 4℃ as well as in the presence of sodium azide or amandatine-HCl,while only very limited reduction was observed with the addition of genestein,revealing that the clathrinmediated endocytosis was the main uptake pathway.The MTT assay found that the 80 nm SiO2 particles caused cytotoxicity in a dose-dependent manner,while the 160 nm and 500 nm particles didn’t show significant cytotoxicity in a concentration range of 0 ～ 200 μg/mL.However,the results of the wound healing assay,cell adhesion and transwell assay demonstrate that the cell adhesion and migration were greatly inhibited by uptake of the SiO2 particles regardless of their size,most possibly because the endocytic process leads to disruption of the cytoskeleton.These studies suggest that the effect of endocytosis on functions of cells should also be assessed to evaluate the biocompatibility of nanoparticles.
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发布时间：2021-03-19 - 摘要：Four α-diimine nickel complexes Ar-N=C(R1)C(R2)=N-ArNiBr2 with different alkyl substituents on backbone of ligand ［Ar=2, 6-dimethylphenyl，R1=CnH2n+1，R2=CmH2m+1; Cat 1: m=1，n=1; Cat 2:m=2, n=1; Cat 3:m=3, n=1; Cat 4: m=2,n=2］ were synthesized and used to catalyze ethylene polymerization in toluene. The influences arousing from changes in alkyl substituents on the backbone carbon of the catalyst ligand on the ethylene polymerization activities, microstructures and semi-crystalline properties of polyethylene were evaluated under varied polymerization temperatures and catalyst concentrations. It was showed that the catalysts with asymmetric alkyl substituents, i.e. R1 and R2 were different, had higher activity and produced polyethylenes having higher molecular weight as compared with those with symmetric substituents. With Cat 2 and Cat 3, the ethylene polymerization activities reached 1.86×103kg PE/(mol Ni#12539;h) and 1.92×103kg PE/(mol Ni#12539;h), and molecular weights of polymers achieved 68.2×104 and 101.9×104, respectively under the condition of 20℃, atmosphere and 5.8 mmol/L of catalyst concentration. Analysis of polyethylene chain structures indicated that the main branching chain structure in polyethylene was methyl groups, and the branching degree was dependent mainly on polymerization temperature. Meanwhile, it was also showed that the polyethylene synthesized with α-diimine nickel complexes containing diversed alkyl substituents on ligand backbone had comparatively high proportion of hexyl and longer alkyl branching chains in polymer molecules, especially for the cases when polymerization was conducted at 40℃.
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发布时间：2021-03-19
Research Article
- 摘要：A novel water soluble sulfonated hyperbranched polyether (HBPO- SO3),consisting of a hydrophobic hyperbranched poly(3-ethyl-3- oxetanemethanol) core and many sulfonate terminal groups,was designed as a promising heparin-like biomaterial.The micelle formation of the resultant HBPO-SO3 in aqueous solutions was monitored by fluorescence spectroscopy using pyrene as a hydrophobic probe, and the critical micelle concentration (CMC) was determined to be 0.017 mg/mL.The analyses of transmission electron microscopy (TEM) clearly showed that all the sulfonated hyperbranched polyether samples aggregated into spherical micelles with diameters of 25～70 nm.The mean diameter of micelles determined by the laser scattering particle size distribution analyzer is about 32.5 nm.Compared with the saline solution used as a control in the plasma recalcification time (PRT) assay,both HBPO-SO3 micelles solution and unimolecular micelles solution could reduce blood clotting.In the case of HBPO-SO3 at a concentration of 0.33 mg/mL,there were no signs of clotting even after 1 h.The toxicity of HBPO-SO3 was assessed in vitro with ECV-304 cells using MTT method and found to be nontoxic for 48 h incubation up to a 0.1 mg/mL concentration.The cell morphology was also observed by confocal laser scanning microscope (CLSM).The results of CLSM revealed that the culture media containing HBPO-SO3 up to 0.1 mg/mL had no negative effect on the attachment and proliferation of cells,compared with the control.Results from the PRT assay and cell culture declared that both HBPO-SO3 micelles and the unimolecular micelles exhibited good hemocompatibility and low cytotoxicity.These experimental results suggest that HBPO-SO3 could be a good candidate for hydrophobic drug carriers.
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发布时间：2021-03-19 - 摘要：Rare earth (Nd,Y,La,Dy) acetates have been synthesized and used as single component catalysts for the polycondensation of dimethyl terephthalate,adipic acid and ethylene glycol first preparing aromatic/aliphatic copolyester are poly(ethylene terephthalate-co-ethylene adipate) (PETA) with high molecular weights.The copolyesters catalyzed by different rare earth acetates were characterized by means of 1H-NMR,DSC,SEC and mechanical testing.The compositions of the coplyesters calculated by the peak integrals of 1H-NMR spectra show that the molar fractions of the copolyester are consistent with the feeding molar ratio of the raw materials.The analysis on the sequence distribution of the two segments in the copolyester chains reveals that the average sequence length of PET and PEA is in the range of 1.92～2.02 ,and the random distribution of the two segments is also validated by the degree of randomness around 1.01. The DSC analysis shows a single glass transition temperature (Tg) of PETA at -1～-4℃ without melting temperature (Tm) suggesting the random structures and thermoplastic elastomeric property.The SEC spectra showed high weightaverage molecular weight (Mw) and polydispersities of PETA in the values of 3.24～3.88×104 g/mol and 1.81～1.94,respectively,demonstrated the high effect of the catalysts,but there is no significant difference of the activity between the four rare earth acetates.The copolyesters exhibit good mechanical properties such as high tensile strength (ca.11 MPa) and large breaking elongation (＞510%) measured with the remolten films at room temperature.The tensile strength of the copolyesters has a slight increase with the increasing of molecular weight.
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发布时间：2021-03-19 - 摘要：The ringopening polymerization (ROP) of ε-caprolactone (CL) in 1-butylmethylimidazolium chloride (［bmim］［Cl］) ionic liquid (IL) and styrene oxide (SO) is reported without using any metal compounds.Both ［bmim］［Cl］ and SO were essential in the ROP of CL.No polymerizations were found without ［bmim］［Cl］ or SO or both of them under the same conditions.No poly(styrene oxide) was found by heating IL and SO indicating that the ROP of SO was absent or too slow to be detected.IL acted as both solvent and catalyst.SO was regarded as initiator since a ring-opened SO unit was found at one end of PCL chain according to the 1H-NMR analysis.The molecular weights of the obtained PCLs were between 4.22 and 6.86 kDa with the molecular weight distributions less than 1.3. The ［bmim］［Cl］ IL could be recycled and reused.The polymerization was quenched and the product was precipitated by the addition of ethanol.After PCL was isolated by suction,the filtrate was a homogeneous mixture of IL and ethanol.The latter was collected by distillation under reduced pressure and thus IL was recovered.The yield and the molecular weight of PCL obtained in the recycled IL were similar to those in the original one.
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发布时间：2021-03-19 -
PREPARATION OF CARBON NANOMATERIALS WITH COPOLYMER OF ETHYLENE AND FERROCENYLFORMYLOXYETHYL ACRYLATE
摘要：A novel copolymer,poly(ethylene-co-ferrocenylformyloxyethyl acrylate), P(E-co-FcEA), was synthesized from ethylene and ferrocenyl formyloxyethyl acrylate with an α-diimine palladium catalyst.The molecular weight and composition of the resultant copolymers were analyzed with gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR).The results suggested that the FcEA content in copolymerization system influenced not only the molecular weight,but also the composition of resultant copolymers.The molecular weight decreased dramatically with increasing FcEA contents.When the FcEA content was 0.02 mol/L in copolymerization system,the polar monomer content of the resultant copolymer was 0.03 mol% and Mn=75100,while the FcEA content was 0.4 mol/L,the polar monomer content increased to 0.23 mol% and Mn was 2200.In addition,carbon nanomaterials were successfully prepared with P(E-co-FcEA) as precursor by self-catalyzed process, and the pyrolysis products were investigated with transmission electron microscope (TEM).Amorphous carbon containing a small amount of nanosheets was obtained using the copolymers containing 0.03 mol% and 0.04 mol% FcEA when the pyrolysis temperature was 700℃.Nevertheless,carbon nanowires were efficaciously prepared when FcEA content in copolymer was 0.08%.Moreover,increasing pyrolysis temperature to 900℃ also afforded carbon nanowires.- 19
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发布时间：2021-03-19
Research Bulletin
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