最新刊期
卷 ， 期 6 ， 2009
- 摘要：A smart biodegradable cationic polymer (CBA-PEI) based on the disulfide bond-containing cross-linker cystamine bisacrylamide (CBA) and low molecular weight branched polyethylenimine (1800-Da,PEI1800) was successfully synthesized by Michael addition reaction in our recent study.Furthermore,a series of copolymers (CBA-PEI-PEG) with different PEGylation degree were obtained by the mPEG-SPA (5000-Da) reacting with CBA-PEI at various weight ratios directly.The molecular structures of the resulting polymers CBA-PEI and CBA-PEI-PEG were evaluated by nuclear magnetic resonance spectroscopy (1H-NMR) and capillary viscosity measurements,all of which had successfully verified formation of the copolymers.The polymer/DNA complexes based on CBA-PEI and CBA-PEI-PEG were measured by dynamic light scattering and gel retardation assay.The results showed that the particle size and zeta potential of complexes were reduced with increasing amount of PEG grafting,even no particle formation.The particle size of CBA-PEI/DNA complexes was in range of 103.1 to 129.1 nm,and the zeta potential was in range of 14.2 to 24.3 mV above the 2∶1 weight ratio.In the same measure condition,the particle size of CBA-PEI-PEG complexes was reduced to a range of 32.2 to 55 nm, and the zeta potential was in range of 9.3 to 13.8 mV at the 2∶1 weight ratio.In the gel retardation assay,CBA-PEI showed a strong DNA-binding capability.Plasmid DNA was completely retarded at the 0.1∶1 weight ratio.By contrast,CBA-PEI-PEG which consists of PEG/CBA-PEI (W/W,38.9%) or PEG/CBA-PEI (W/W,95.8%) displayed a poor retardation effect even at the high weight ratio.PEG-grafted showed a shield effect in polymer/DNA complexes.However,it showed the reduced DNA binding ability if the cationic polymers were modified with too much PEGs.Moreover,the CBA-PEI and CBA-PEI-PEG were evaluated in CHO and KB cells for their cytotoxicity and transfection efficiency.MTT assay revealed that both CBA-PEI and CBA-PEI-PEG had very lower cytotoxicity in CHO cell lines compared with PEI25k.Although CBA-PEI showed 4 times higher transfection efficiencies compared with PEI25k,the transfection efficiency of CBA-PEI-PEG was reduced obviously with increasing amount of PEG grafting.
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发布时间：2021-03-19 - 摘要：A novel kind of “hairy-rod" ladder polysilsesquioxane (LPSQ) with alkyl substituted triphenylene side groups formed a stable monolayer on the air-water interface,and the effects of temperature, solvents and concentration of LPSQ solution on π-A isotherm curves were investigated.The monolayers of LPSQ can be successfully transferred onto hydrophobic surface of silicon wafer or quartz plate to develop a very stable and uniform Y-type Langmuir-Blodgett (LB) film when using toluene as the spreading solvent at proper surface pressure.High stability of LPSQ LB films is confirmed by the fact that the intensity of UV absorption does not decay within several months and AFM image shows uniform and compact films without noticeable defects.The in-plane anisotropy was monitored by the combination of polarized UV and fluorescence spectroscopy,revealing that the backbones of LPSQ adopted a preferential orientation parallel to the dipping direction with an optimum orientation parameter S of 0.42.Furthermore,the stable and uniform LB films of LPSQ with the triphenylene side groups promise to be a fine one-dimensional molecular/nano-wire material.
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发布时间：2021-03-19 - 摘要：Polypyrrole nanoparticles with a high yield (93%) were synthesized by using unstirred polymerization in the absence of any template or surfactant.The structure，elctroconductivity and morphology of the polypyrrole nanoparticles were characterized by FT-IR,wide angle X-ray diffraction,four-probe techniques,scanning electron microscopy and transmission electron microscopy (TEM).The particle size and morphology of polypyrrole nanoparticles were systematically studied by changing synthetic conditions,such as oxidant type,molar ratio of ammonium persulfate (APS) to pyrrole,polymerization temperature and reaction medium species.It was found that the particle size and morphology of the polypyrrole nanoparticles varied significantly with the above-mentioned polymerization parameters.Using different synthetic conditions,we can control the diameters of polypyrrole nanoparticles ranging from 40 nm to 260 nm.The preparation conditions of ammonium persulfate as an oxidant,APS/pyrrole molar ratio of 0.25,at a polymerization temperature of 0℃ are optimal for the unstirred polymerization synthesis of polypyrrole nanoparticles.TEM images revealed that uniform polypyrrole nanoparticles in diameters of 43 nm were prepared in 1.0 mol/L HCl aqueous medium at 0℃ (using an ice bath) with APS/pyrrole molar ratio of 0.25.The room-temperature electroconductivity of the hydrochloride doped polypyrrole disk is up to 5.5 S/cm.
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发布时间：2021-03-19 - 摘要：The upper-convected Maxwell (UCM) model was used to describe the rheological properties of polymers.A finite volume method (FVM) for the numerical solution of viscoelastic flows through an abrupt expansion channel is presented.Although there have been many successful numerical predictions of elastic fluid flows,the Weissenberg number (We) which stands for the elastic is low.With the FVM,stable solutions are found for high Weissenberg number (the elasticity levels up to We=3.2),further extending the range of previous similar simulations.The simulations reinforce the point that the FVM can be used as a viable alternative for the solution of viscoelastic problems.Through the results of numerical simulations,the contours of velocity and stream function are drawn and micro-scale sweep efficiency is calculated quantitatively.Numerical results show that the viscoelasticity of polymer solutions is the main factor influencing the sweep efficiency.With increasing elasticity,the flowing area in the dead end is enlarged significantly,thus the area with immobile zones becomes smaller,the microcosmic sweep efficiency increases.The visco-elastic nature of the displacing polymer fluids can in general improve the displacement efficiency in pores compared to using Newtonian fluids.This conclusion should be useful in selecting polymer fluids and designing polymer flooding operations.
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发布时间：2021-03-19 - 摘要：Tensile tests at various temperatures are conducted to detect the relationship of material strain and stress of the styrene-based shape memory polymers (SMP).The material elastic modulus and yielding limit stresses at the temperatures of 25℃,30℃,40℃ and 50℃ are determined according to the results of tensile tests.In order to describe the glass transition behavior of the styrene-based SMP,a new material parameter function is supposed based on the results of the tensile tests.The styrene-based SMP is assumed as an isotropic material,then a three-dimensional thermo-mechanical constitutive equation of SMP is developed based on Tobushi’s one-dimensional thermo-mechanical constitutive equation.In order to perform finite element analysis on SMP by using ABAQUS,a UMAT subroutine for ABAQUS is programmed with Fortran codes based on the three-dimensional constitutive equation and the new material parameter function.The shape memory thermo-mechanical process of styrene-based SMP is numerically simulated by ABAQUS coupled with the UMAT subroutine,which includes deformation at a high temperature upon loading,shape fixity due to cooling and shape recovery through heating.Numerical results show that the thermo-mechanical behavior of SMP can be well simulated by ABAQUS coupled with the UMAT subroutine.
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发布时间：2021-03-19 - 摘要：Monte Carlo method with annealing method was applied to study the diblock copolymer (A10B6) confined thin films with different volumes of nanoparticles.When the volume of nanoparticles increases,the morphology of diblock copolymer films changes from lamellaes to the mixture of lamellae and cylinder,and finally form the cylinders.Nanoparticles localized within one copolymer block phase.When the volume of nanoparticles are large enough, the 5-,6- and 7-fold cylinder morphologies are formed,and the percentage of 6-fold cylinder are the largest one.The average size of cylinders decreases with increasing the volume of nanoparticles.At the meantime,the average size of copolymers increases first,and then decreases when the volume of nanoparticles increases.This investigation can help us to understand the self-assemble of diblock copolymers with confinements.Some comparisons with experiments results are given.
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发布时间：2021-03-19 - 摘要：The polymer micro- or nano- fibers have been rapidly gaining popularity as a construction matrix for tissue engineering scaffolds.This paper presents a dynamic investigation of the poly(ε-caprolactone)(PCL) sub-micro fibers with diameters ranging from 100 nm to 500 nm by electrospinning method.To obtain the dynamic properties,the fiber was placed on a surface which had a groove of 100 μm width, and the experiments using a functional generator and piezo-tablet were conducted on a vibrating single-strand fiber.The amplitude and driving frequency can be observed by using the ultra-high optical microscope and functional generator respectively.Additionally,since the dynamic property is highly sensitive to the fiber diameter,and real fibers have an ellipsoidal cross-section,it is necessary to correct the experimental data.The equal diameter is defined and the value can be measured by using the AFM equipment.The elastic modulus can be obtained when the PCL fiber beam arrived at its first resonant frequency.Our measurements show that its elastic modulus exhibits an inverse size dependency with the fiber diameter.The elastic modulus of the fiber increased obviously when its diameter was reduced past a threshold size.A dynamics-based strain gradient model was presented to correlate with the experimental data,and it appeared to explain the phenomenon quite accurately.
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发布时间：2021-03-19 - 摘要：Graft polymerization of acrylamide (AM) on the surface of crosslinked polyvinyl alcohol (CPVA) microspheres was realized by using ammonium cerium (Ⅳ) sulfate as initiator in an acidic aqueous solution (sulfuric acid),resulting in the grafted microspheres CPVA-g-PAM.The effects of various factors on the graft polymerization reaction and the mechanism were emphatically studied.The experimental results show that by the oxidation action of Ce(Ⅳ) ion,free radicals can be produced on the surface of CPVA microspheres,on which there are a great deal of hydroxyl groups,and the radical graft polymerization of acrylamide (AM) can be favorably carried out.The grafting degree of PAM on CPVA-g-PAM microspheres is first decided by the acid concentration.The grafting degree initially increases with increasing the acid concentration,and then gradually decreases with the further increase of the acid concentration.As the concentration of H+ ion is 0.36 mol/L,the grafting degree has a maximum.The dependence of the grafting degree on the acid concentration reflects the special mechanism of the graft polymerization initiated by cerium salt.As the concentration of the initiator,ammonium cerium sulfate,is too great,the grafting degree will be decreased owing to the accelerating of the oxidation termination step,leading to the decrease of the grafting degree.The optimal concentration of cerium ammonium sulfate is 598×10-3 mol/L.During the graft polymerization process,the concentration of the monomer AM and the reaction temperature also affect the graft polymerization reaction to a certain extent.
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发布时间：2021-03-19 - 摘要：A novel alicyclic polythiocarbonate with a complex structure sequence has been synthesized by a convenient one-pot polymerization of carbon disulfide (CS2) and cyclohexene oxide (CHO) with Zn-CoⅢ double-metal cyanide complex (DMCC) as the catalyst.The catalytic activity of the Zn-CoⅢ DMCC could reach to 445 g polymer/g catalyst when the reaction temperature was 100℃ and molar ratio of CHO/CS2 was 2Further increasing or decreasing the temperature resulted in a decrease in the catalytic activity.The weight-average molecular weight (Mw) of the obtained copolymer was in the range of 1.1×103～1.3×103 with a molecular weight distribution (MWD) of 1.57～1.71The copolymer has terminated —OH and —SH groups from the results of FTIR spectrum and Raman spectrum.Furthermore,one carbonate unit —O(O)CO—,and four thiocarbonate units —S(O)-CO—,—S(O)CS—,—S(S)CO—, and —S(S)CS— in the copolymer were found from 1H and 13C-NMR spectra,and the monothiocarbonate unit (—S(O)CO—) was the main unit in the copolymer,which was consistent with the results from FTIR spectrum.Cyclohexene sulfide,which was a direct evidence for O—S atom-exchange reaction, was detected by GC-MS technique from the products.Only hexahydro-benzo［1,3］oxathiol-2-one,hexahydro-benzo ［1,3］ dithiol-2-one,and hexahydro-benzo ［1,3］ dithiole-2-thione(theoretically six five-membered cyclic products) were detected due to the monomer structural factors and thermodynamical factors.The copolymer chain structure and variety of cyclic products indicates that an O—S atom-exchange reaction existed in the copolymerization.Further efforts and experiments are on going in order to further explore the mechanism of the atom-exchange copolymerization and with a view to synthesizing a sulfur-containing polymer with high molecular weights,controllable stereochemical structures,as well as high catalytic activity.
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发布时间：2021-03-19 - 摘要：Rheology,solvent extraction and scanning electron microscopy (SEM) were employed to investigate the influence of hydrophilic nano-SiO2 on the co-continuity interval of immiscible poly(methyl methacrylate) (PMMA)/polystyrene (PS) blends.For unfilled systems,the co-continuity intervals of PMMA/PS blends measured by the three methods were nearly consistent.However for filled blends,SEM and solvent extraction means showed that increasing the filler content will broaden the co-continuity interval.The preferential distribution of hydrophilic SiO2 particles in more affinitive PMMA phase led to a strong increase both in melt viscosity and elasticity of PMMA and further slowed down all relaxation processes associated with the destruction of the co-continuous structure such as breakup or retraction.However,the co-continuity interval obtained by rheology was found to be narrower than that by SEM and solvent extraction,which was contrary to unfilled system.It was proposed that the enhancement in the melt viscosity and elasticity of PMMA/PS blends due to the incorporation of hydrophilic nano-SiO2 particles could significantly prolong the relaxation time of sample loaded before beginning the rheological tests.When the sample was subjected to high temperature for a long time before test,its co-continuous structure would be easily coarsened and disintegrated under the driving of interfacial tension.Furthermore,the higher filler content the more time consumed,which might seriously destroy the co-continuous structure.It was proposed that SEM and solvent extraction might be more suitable in detecting the co-continuity interval of filled PMMA/PS blends than rheological test.Finally,the advantages,disadvantages and applicable range of three methods were compared and summarized.
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发布时间：2021-03-19 - 摘要：A new monomer derived form carbazolyl triphenylethylene was synthesized through Wittig-Horner and Suzuki reactions with excellent yields,and its polymer was obtained by radical polymerization initiated with AIBN.Their thermal and photophysical properties were characterized by differential scanning calorimetry (DSC),thermal gravimetric analysis (TGA),ultra-violet (UV) spectra and photoluminescence (PL) spectra.The preliminary results show that:the monomer and polymer possess high glass transition temperatures (210℃ and 229℃,respectively) and high thermal decomposition temperatures (466℃ and 467℃,respectively);in dichloromethane solution,the emission peak of the monomer locates on 455 nm,while the peak of the polymer red shifts to 466 nm;the polymer exhibits higher quantum yield (0.16) in dichloromethane solution than that of the monomer (0.017);both the monomer and polymer emit very intense blue emission in solid form,while the monomer has the maximum emission wavelength at 472 nm and the polymer at 482 nm;the monomer exhibits obvious aggregation-induced emission (AIE) while adding water into it’s THF solution and on/off fluorescent switching which senses to organic vapor,and the polymer has aggregation-induced enhanced emission (AIEE) characteristics.The twist structures of the monomer are considered as the key structure for the AIE and AIEE phenomena of those carbazolyl triphenylethylene derivatives.It is suggested that they are potential materials for fabrication in OLED devices and fluorescence sensors.
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发布时间：2021-03-19 - 摘要：The diamine monomers 4,4′-diamino-3,3′-dimethyldiphenylmethane (DMMDA) and 4-diphenyl 3,5-diaminobenzoate (DABBE) were successfully synthesized.Polyimides containing asymmetric units in the main chain and biphenyl pendant groups were synthesized with the copolymerization of DMMDA,DABBE and aromatic dianhydride 4,4′-oxydiphthalic anhydride (ODPA) by chemical imidization.The structures and properties of the resulting co-condensation type polyimides were characterized by IR,GPC,UV-Vis and DSC etc.The polyimides as alignment layers of liquid crystal molecules in liquid crystal display (LCD) were also examined.The polyimides obtained were readily soluble in polar solvents,such as N-methylpyrrolidone (NMP) and N,N-dimethyl form a mide (DMF)etc.The number-average molecular weights of the soluble copolyimides were influenced by the mole ratio of the diamine monomers.It can be observed under POM that the liquid crystals could achieve uniform alignment and a pretilt angle of about 1.8° can be obtained when PI was used as the liquid crystal alignment layer.Moreover,the transmittances of the PIs are more than 80%，and their glass transition temperatures are above 220℃.
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发布时间：2021-03-19
Research Article
- 摘要：The oxidative polymerization of hydroquinone in acidic solutions in the presence of chitosan was studied.The reaction rate was facilely represented by the increase rate of absorption at 470 nm and measured under various conditions.The reaction does not proceed in the absence of oxygen.The presence of chitosan increases the reaction rate significantly,suggesting chitosan works as a template for the oxidative polymerization of hydroquinone.Kinetic studies reveal that the reaction is first-order for hydroquinone,while the reaction rate increases linearly with chitosan concentration when molar ratio of chitosan/hydroquinone is less than 0.8,but keeps constant beyond that point.These results suggest a pick-up mechanism for the template polymerization of hydroquinone.The energy of activation was calculated to be 71.6 kJ/mol.Preliminary results also show that the reaction mixture gelates in certain cases.Further investigation on the structure,molecular weight and its distribution of the resultant poly(hydroquinone) is still on-going.These redox-active hydrogels may find applications in electrochemical biosensor.
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发布时间：2021-03-19 - 摘要：Abstract The initiation of a novel macroinitiator is presented.The oligomers of α-methyl styrene (AMS) and glycidyl methacrylate (GMA) (designated as PAG) were used as macroinitiator in the bulk polymerization of methyl methacrylate (MMA) and styrene (St).The polymerization of MMA was carried out at 90℃ and that of St at 100℃,respectively.The resulting copolymers were characterized by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The results indicated that the copolymers can be prepared by simply heating PAG in the presence of the second monomer,without any other initiator.During the process of polymerization of MMA,the higher AMS content in PAG led to higher monomer conversion,which suggested that the polymerization reaction was initiated by PAG.Under the certain reaction time,copolymers can be obtained from the reaction system of St and PAG,but there had nothing in the system of pure St.Also,the copolymers gained by polymerization of MMA initiated with PAG have the reinitiating reactivity,and the curve of molecular weight with reaction time(Mn-t) has a well linear relation,as well as that of molecular weight with yield of copolymers (Mn-Y%).Based on the research results,the possible reaction mechanism has been put forward.This simple method is expected to be applied to some other monomers,and it might be suitable even for industrial applications.
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发布时间：2021-03-19 -
UNCOMMON MELT RHEOLOGICAL BEHAVIOR OF HYPERBRANCHEDPOLYMERS BEARING QUADRUPLE HYDROGEN BONDING UNITS
摘要：Abstract A series of hyperbranched polymers with different contents of ureidopyrimidone(Upy) units were prepared by reacting hydroxyl terminated hyperbranched poly(amine-ester)(HPEA) with monoisocyanato methylisocytosine at —OH/—NCO ratios of 1∶0.13，1∶0.25，1∶0.33 and 1∶0.5，respectively.The melt rheology of the modified polymers was investigated by using a Physica MCR300 rheometer.Due to the formation of self-complementary quadruple hydrogen bonding of Upy groups,the modified polymers demonstrated strong temperature and frequency dependent characters in melt rheological properties,and the dissociation temperature appeared to increase as more Upy units existed in the samples.The results indicated that at the low frequency range,the complex viscosity decreased,the storage modulus became larger as increasing the frequency.However,at the high frequency range,the samples displayed shear-thickening behavior,and the storage modulus decreased sharply to rather low values as increasing the frequency.Meanwhile,the loss modulus seemed to increase as elevating the frequency at all frequency range.Such uncommon rheological performance could be explained based on the disruption of Upy micro-domains by shearing force and the formation of quadruple hydrogen bonds between the released Upy units.This investigation is helpful for understanding the rheological behavior of Upy contained polymers and designing new dynamic functional materials.- 16
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发布时间：2021-03-19 - 摘要：The polyurethane (PU) latex interpenetrating polymer networks (LIPN) with high contents of the epoxy resin (EP) were prepared,using polytetrahydrofuran glycol (PTMG) and polybutylene adipate (PBA) as soft segments respectively.The structure and properties of the samples with different soft segments were investigated by FTIR,DMA and AFM.The results revealed that the LIPN had formed and with no chemical bond between PU and EP.PU and EP had higher interpenetrating properties in LIPN and lower degree of phase separation with the increase in the content of EP when using PBA as the soft segments because the better compatibility between EP and PBA.The PU samples generally had a higher tensile strength when using PBA as soft segments compared to the samples using PTMG as soft segments,but because PBA and EP had higher interpenetrating properties,the samples showed obviously synergistic effect of IPN,the moving of PBA soft segments were limited more by epoxy resin compared with that of PMTG soft segments,resulting in the tensile strength of LIPN samples with high contents of the epoxy resin decline faster,in the same time the glass transition temperature of the LIPN samples has also rising faster.The solvent resistance of the LIPN using PBA as soft segments is vastly superior to that of the samples using PTMG as soft segments.
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发布时间：2021-03-19 - 摘要：Atom transfer radical polymerization(ATRP) was used to synthesize narrowly distributed 4-arm-polystyrene star chains (4-PS-Br).Then the bromine end functional groups were further modified to thiol groups (4-PS-SH).Oxidization of each two thiol end groups leads to a disulfide bond (—S—S—),which enables us to slowly crosslink the PS star chains in THF solutions to form polymer clusters,then gels.Static laser light scattering (SLS) shows that in both semidilute solutions and gels the time-average scattered intensity changes little with the sample position,where the sample position is arbitrarily chosen by rotating and lifting the sample cuvette,indicating this chemical gel is homogeneous and speckle-free.Dynamic laser light scattering (DLS) shows that first there is only one fast decay mode of the time-time intensity correlation function in the original semidilute solution.Then the slow modes of the correlation function appear and the contributions of the slow modes increase at the early oxidation stage,indicating the formation of large cross-linked clusters.With oxidation time increase the contribution of the slow mode decreases,finally disappears.The correlation functions of the chemical gel are nearly the same as those of the original semidilute solution.The normalized intermediate scattering function can fully relax to zero,indicating that the gel has no frozen-in static component,and the speckles of other polymer gels originate from large voids inside,not cross-linked chains (clusters).Both SLS and DLS results indicate that this polystyrene gel is a homogeneous chemical gel.
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发布时间：2021-03-19
Research Bulletin
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