最新刊期
卷 ， 期 7 ， 2012
- 摘要：The effects of replacing water solvent of nanocomposite gels with alcoholic solvents are investigated on structure stability,swelling and mechanical properties of nanocomposite hydrogels (D-NC hydrogel).D-NC gels was prepared by in situ free radical polymerization of monomer (N,N-dimethylacrylamide) in the presence of exfoliated clay.Clay acts as the multifunctional plane crosslinking agent.NC hydrogels maintained the three-dimensional structure without collapsing after exchanging solvents with alcoholic solvents.It was found that NC gels that originally containing water exhibit different exchange and swelling behaviors depending on the type of alcohol in which the gels are immersed.In methanol,the swelling ratio of a D-NC gel increases monotonously as in the case of water.However,D-NC gels first shrink and then swell during immersing in other alcohols such as ethanol,propanol and butanol.Furthermore,D-NC alcoholic solvent gels with ultrahigh mechanical properties are obtained by solvent exchanging process of first swelling in a target solvent and then drying.For example,compared to those of D-NC5 hydrogels,the tensile strength of D-NC5 methanol gel increases by 67% (from 155 kPa to 259 kPa) and modulus increases by 49% (from 7.5 kPa to 11.2 kPa).Based on the reversibility of the structure during the solvent water/methanol alternative exchanging,the modification mechanism was discussed primarily.关键词：Nanocomposite hydrogel;Clay;Alcoholic solvent;Swelling;Mechanical property;Network reversibility
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发布时间：2021-03-19 - 摘要：The poly(lactic acid)/poly(butylene succinate) (PLA/PBS) blends with and without dicumyl peroxide (DCP) were prepared by melt mixing and the crystallization behaviors of the blends were investigated using a differential scanning calorimeter (DSC).The results showed that the crystallization ability of PLA was not improved when it was blended with PBS because of the higher molecular weight of PBS than that of PLA in this research,which was not in accord with results of some other researchers.However,the crystallization ability of PLA in the reactive blends (PLA/PBS/DCP) was promoted after the addition of different amount of DCP,because some crosslinked (or grafted) structures were generated in this matrix,and the crosslinked (or grafted) structures acted as nucleating points.It is found that when the content of DCP was from 0.1 phr to 0.3 phr,the crystallization was mostly caused by PBS,and this crystallization reduced with increasing the DCP content.When the content of DCP was above 0.3 phr,that is to say,PLA began to crystallize when the DCP content was 0.4 phr.The crystallization of PLA was enhanced with further increasing the content of DCP,while the crystallization of PBS was weakened in the same situation.In other words,the crystallization behavior of PLA and PBS in the PLA/PBS/DCP reactive blends was mostly depended on the DCP content.关键词：PLA;Reactive blend;Crystallization behavior
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发布时间：2021-03-19
Rapid Communications
- 摘要：Combination of biomacromolecules with biological activity and conventional synthetic polymers with good mechanical and processing properties to prepare hybrid materials is a new branch in Material Science.This paper summarizes the investigations of two light-driven proton pumps,bacteriorhodopsin(BR) and archaerhodopsin 4 (AR4),with emphasis of the work by the authors group and their cooperators in the latest decade.While BR was found forty years ago,AR4 is relatively new and was found by Chinese researchers one decade ago.In this first review about AR4,the authors made comparison between AR4 and BR,introduced their work of preparation of composite films composed of these retinal proteins and polymers.The review summarizes a series of the achievements by the authors and their cooperators,for instance:(1) revealing the mechanism of the light-driven proton pump in AR4 and putting forward a weak-coupling model; (2) finding that gellable amphiphilic polymers could enhance the relaxation time of AR4 and BR very significantly; (3) developing techniques of encapsulating BR and AR4 into polymeric hydrogels; (4) finding that a purple membrane containing retinal proteins can resist adhesion of mammalian cells; (5) a successful information recording based upon protein-polymer composite films.Finally,the future research and potential applications of the retinal proteins and corresponding functional materials are prospected.关键词：Bacteriorhodopsin (BR);Archaerhodopsin (AR);Purple membrane;Proton pump;Photoelectric response;Photochromic response;Block copolymer;Functional polymeric material;Composite material;Information material
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发布时间：2021-03-19
Feature Articles
- 摘要：Polylactide containing phosphorylcholine (PLA-PC) and polylactide (PLA) were synthesized with lactide (LA) as monomer,glycerophosphorylcholine and 1,4-butanediol as ring-opening initiators respectively.The comparison investigation of inducing mineralization on PLA-PC and PLA films was conducted.The result demonstrated that mineralized products could form on the film of PLA-PC as well as on the film of PLA in the simulated body fluid (SBF) of pH 6.8. Moreover,formation of the mineralized products was easier on the film of PLA-PC than on the film of PLA.The reason for that is phosphorylcholines can migrate to the surfaces of polymers when PLA-PC contacts with water,and PLA-PC can combine with more Ca2+ than PLA because phosphoryl in PLA-PC can combine with Ca2+ owing to the interaction between negative charge and positive charge.Fourier-transform infrared (FTIR),X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the mineralized products formed on the surface of PLA-PC films.The results showed that the mineral crystal was hydroxylapatite (HAP) and the crystal had a laminated structure.PLA-PC films are good for nucleation and development of crystals.The crystalline grains and crystalline thickness grew with increasing mineralization time.Therefore,PLA-PC is a promising biodegradable scaffolds material for bone tissue engineering.关键词：Polylactide;Phosphorylcholine;Inducing mineralization;Hydroxylapatite
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发布时间：2021-03-19 - 摘要：The transport and conformation of macromolecules in micro-channels were studied by using the dissipative particle dynamics(DPD) and finite extensible non-linear elastic(FENE) bead spring chains model.The dynamic behavior of macromolecules with different numbers of beads and different chain lengths in three kinds of micro-channels,straight,quadrate contraction and sloping contraction micro-channels are comparatively analyzed.It is found that macromolecules are mainly concentrated in the middle of channels.Macromolecules located near solid walls are stretched better than those in the middle of channels,which are usually coiled.The shape of micro-channel can influence the conformation and transportation of macromolecules.Straight channels can well stretch the macromolecules.Quadrate contraction channels can have negative effects in stretching the macromolecules with possible circulation flow at the corner areas.While the behavior of sloping contraction channels is between that of the straight channels and quadrate contraction channels.It is also found that macromolecule chains do not influence the temperature distribution and evolution.Instead macromolecular chains have remarkable influences on the density and velocity distribution,while the distribution and conformation of the macromolecules are closely related to the shape and geometry of the micro channels.The macromolecules tend to drag the simple DPD particles,reducing their velocity,and leading to density fluctuations.The dragging effect is more important as the number of macromolecules or the length of the macromolecular chain increases.关键词：Dissipative particle dynamics;Macromolecule suspension;Micro channel flow
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发布时间：2021-03-19 - 摘要：A series of electric-sensitive hydrogels were prepared by in-site gel polymerization with 2-acrylamido-2-methyl propyl sulfonic acid (AMPS) as organic monomer and ethyl orthosilicate (TEOS) as inorganic material,using N,N'-methylene bisacrylamide as crosslinking agent and potassium peroxydisulfate as initiator,respectively.The structure of the hydrogels was characterizated by scanning electrical microscopy (SEM).The swelling and deswelling properties of hydrogels in deionized water and in NaCl solution were studied in detail,showing that the equilibrium swelling ratio of the hydrogels ranged from 224.9 to 325.6. And the swelling rate of the composite hydrogels decreased with the increasing content of TEOS,in addition,the deswelling speed of the hydrogel decreased with the increasing concentration of polyion in interior of the hydrogels,except for the ideal hybrid hydrogels.Moreover,the electric sensitivity of the hydrogels was considered.The result revealed that the hydrogels swelled at high concentration of NaCl in solution (higher than that of polyion in interior hydrogels),but deswelled at low concentration.As for ideal hybrid gel,the reswelling ratios decreased,and the deswelling property was more obvious.Furthermore,the ideal hybrid hydrogels had more ideal mechanical properties than organic gels,and the maximum compressive strength of the hydrogels was about 23.4 MPa.关键词：Hydrogels;Electrical sensitivity;2-Acrylamido-2-methyl propyl sulfonic acid;Silica
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发布时间：2021-03-19 - 摘要：Using electrochromic polymer-polyaniline,taking flexible conductive fabric as electrodes and based on the reflective electrochromic device structure model,a kind of controllable chromic fabric is assembled,which shows distinct color change between yellow and green in the low-voltage range of -1.0~+1.0 V,and provides the foundation for the preparation of the man-made controllable electrochromic fabric.The L*a*b* values,E* and the reflectivity curve of the electrochromic fabric are studied systematically at different voltages,with different relaxation time and with different color of working electrode.The difference between transmission-type electrochromic devices and the electrochromic fabric is also discussed.As the positive voltage increases,the corresponding a*b* values of the electrochromic fabric decrease and blue-green color deepens.With the growth of the negative voltage,the a*b* values of the electrochromic fabric increase and yellow color deepens.When the voltage of the electrochromic fabric is removed,the discharge relaxation phenomenon appears,and the fabric returns to the eigenstate.The background color of the electrode has significant effect on the electrochromic fabric.The relaxation time of the electrochromic fabric after removing the voltage is shorter than that of the transmission-type electrochromic devices.关键词：Chromic fabric;Polyaniline;Electrochromic;Fabric electrode
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发布时间：2021-03-19 - 摘要：A novel synthesis strategy combining of living ring-opening polymerization of -caprolactone and intramolecular cyclization by high efficient ring-closing metathesis reaction (RCMR) to synthesize cyclic macromolecules has been studied.First,homotelechelic PCL with hydroxyl end groups (PCLOH) was generated via living ring-opening polymerization of -caprolactone by using 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP) as initiator.Second,homotelechelic PCLOH was reacted with vinylacetic acid,1,3-dicyclohexylcarbodiimide (DCC) and 4-(dimethylamino)pyridine (DMAP) by utilizing p-toluenesulfonic acid monohydrate (PTSA) as catalyst and then converted to homotelechelic PCL with allyl end groups (allylPCL).Finally,cyclic ploy(caprolactone) was synthesized by ring-closing metathesis reaction of allylPCL by using bis(tricyclohexylphosphine) benzylidine ruthenium (IV) dichloride(Cl2(Cy3)2Ru CHPh)as catalyst under high dilution.The structures and thermodynamic properties of polymers were characterized by SEC,NMR,TGA and DSC technologies.The characterization by SEC and viscosity showed that the hydrodynamic volume of cyclic poly(-caprolactone) was smaller than that of its linear precursor.DSC study showed that the Tm and Hm of cyclic poly(-caprolactone) was lower than those of its linear precursor.TGA test showed that the Tmax of cyclic poly(-caprolactone) was 13 K higher than that of its linear precursor.The results indicated that the intra-molecular cyclization of homotelechelic allylPCL by RCMR was high efficient under the high dilution (2.510-5 mol/L) because the resulted cyclic PCL was pure and no need for further purification.关键词：Cyclic poly(-caprolactone);Living ring-opening polymerization;Ring-closing metathesis reaction
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发布时间：2021-03-19 - 摘要：The branched polystyrenes have been prepared via atom transfer radical polymerization (ATRP) using divinylbenzene (DVB),triethylene glycol dimethacrylate (tri-EGDMA) or 1,6-bismaleimidohexane (BMIH) as the branching agent.The four-arm star-shaped polystyrene as the reference was prepared through the way of core-first using pentaerythritol tetrakis(-bromoisobutyrate) (4BrBu) as the initiator,in which,the conversion of styrene was studied using gas chromatography (GC).The consumption of the pendent vinyl group of branched polystyrene was analyzed using proton nuclear magnetic resonance (1H-NMR).The molecular weight,polydispersity index,intrinsic viscosity and mean-square radius of gyration of the branched polymers were measured by triple detection size exclusion chromatography (TD-SEC).The results showed that the pendent vinyl groups of the polymer chains were consumed gradually,and the core formation process was not observed in these polymerization systems of DVB, tri-EGDMA or BMIH.During the early stages of polymerizations,the primary chains with pendent vinyl groups and the slightly branched chains were formed,and the molecular weight of the branched polymer increased gradually with the conversion of styrene.In the later stages,owing to further reaction of the reactive species with the pendent vinyl groups of polymeric chains,the coupling reaction between polymeric chains was more obvious,resulting in sharp increase in the molecular weight of branched polymers.The obtained branched polymers prepared using DVB, tri-EGDMA or BMIH as the branching agents were all randomly branched polystyrene.关键词：Atom transfer radical polymerization;Divinyl monomer;Branched polymer;Branching structure
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发布时间：2021-03-19 - 摘要：A method for calculating the temperature distribution in the polymer sample during DSC measurements was proposed in this paper based on the one-dimensional heat conduction equation and Tools-Narayanaswamy-Moynihan (TNM) model.It was found that the temperature lag increased remarkably with increasing sample thickness and heating rate.A maximum temperature difference between the center and the surface of a PS sample with 1.0 mm thickness was calculated to be 0.882 K when it was heated at a rate of 10 K/min after cooling at 1 K/min.Meanwhile,a method for calculating the sensible heat capacity of the polymer with different thicknesses after different thermal treatments was proposed.The theoretical results were consistent with the experimental data.关键词：Differential scanning calorimetry;Enthalpy relaxation;Glass transition;Heat capacity;Polystyrene;Temperature gradient
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发布时间：2021-03-19 - 摘要：Microencapsulated ammonium polyphosphate (EMFAPP) with double shell (melamine-formaldehyde resin and epoxy resin) is prepared by in situ polymerization,which is a typical intumescent flame retardant containning an acid source ammonium polyphosphate (APP),a blowing agent melamine formaldehyde (MF) and a carbonization agent epoxy resin (EP).Its structure is characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM).The flame retardancy of EMFAPP in EP is studied by limiting oxygen index (LOI) and UL 94 tests.EP/EMFAPP samples can pass V-0 in UL 94 test when the content of EMFAPP is more than 7%,and their LOI value is higher than 27.0%.After water treatment (75℃,6 days),EP/EMFAPP maintains good flame retardancy while the flame retardancy of APP in EP decreases greatly.So after microencapsulation,the water resistance of EP/EMFAPP was improved remarkably.The thermal stability of EMFAPP and EP/EMFAPP is evaluated by thermogravimetric analysis (TGA).Residue char of EP/EMFAPP (8 wt%) is as high as 16.2% at 700℃.EMFAPP can promote EP to form residue char which will play a great role in the combustion process of polymer composites.Further more,the thermal degradation behaviors of EP/EMFAPP are investigated by thermogravimetry-Fourier transform infrared spectroscopy.Based on the above results,the flame retardant mechanism is discussed.In the process of combustion,EMFAPP releases polyphosphoric acid (PPA) and NH3 firstly.With the increase of temperature,PPA reacts rapidly with OH group of EP resin to release H2O which can reduce the flammability of EP in gaseous phase.Then,along with the degradation of main chain of EP,PPA may react with the oxidised products formed during the thermal degradation and stimulate the formation of a char.After heating beyond a critical temperature,the char begins to swell and then to expand to form an intumescent charred layer.The presence of the charred layer can retard the transfer of heat and prevent underlying materials from further thermal destruction.关键词：Microencapsulation;Melamine-formaldehyde resin;Epoxy resin;Ammonium polyphosphate;Flame retardancy
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发布时间：2021-03-19 - 摘要：A novel sulfonic acid group-containing hyperbranched polyurethane was synthesized by the reaction of N- tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid (TES) and isophorone diisocyanate (IPDI) with a one-pot method.The amino group of TES added selectively to the secondary isocyanate group of IPDI at low temperature (15℃) to afford an AB3 type monomer.The resultant AB3 monomer could be polymerized in situ at high temperature (70~90℃) to give hyperbranched polyurethanes.The degree of branching (DB),molecular weight and molecular weight distribution (MWD) of the hyperbranched polyurethane increased with increasing polymerization temperature.The number average molecular weight (Mn),MWD and DB of the polymer obtained at 90℃ were 22410,3.36 and 0.87,respectively.The polymer electrolytes based on the obtained hyperbranched polyurethane sulphonate had good heat stability and high tensile strength.The temperature for 1% weight loss was more than 220℃,and the tensile strength was up to 17 MPa.The ionic conductivity of the polymer electrolyte (lithium salt) was 3.110-5 S/cm at room temperature (ca.25℃),1.410-3 S/cm at 100℃.关键词：Hyperbranched polyurethane;Sulphonate;Polymer electrolyte
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发布时间：2021-03-19 - 摘要：Narrow-dispersed calcium alginate microspheres were prepared by a membrane emulsification-gelation method.The microspheres were treated with NaCl solutions of different concentrations to control the amount of free carboxylate groups.The size of the microspheres increased simultaneously after salt treatment.The quantity of calcium and sodium ions in the microspheres was measured by atomic absorption spectrometer, and the change of functional groups was determined by Fourier transform infrared spectroscopy.During the treatment process calcium ions in the microspheres were replaced by sodium ions,and the carboxylate groups were converted from a chelate to a free state.As doxorubicin hydrochloride was positive in water while alginate was negative,doxorubicin was loaded into the alginate microspheres via electrostatic interaction.The loading capacity of microspheres was enhanced greatly after treatment with NaCl solution.When the microspheres were treated with 1.8% NaCl solution,the drug content increased remarkably to 1310 g/mg,which was nearly 10 times the amount of the untreated ones.In vitro release tests confirmed that relative smaller percentage of drug was released from the microspheres containing more drug.The release behavior of the drug-loaded microspheres was pH-sensitive,i.e.slower at pH 7.4 but faster at pH 5.5.After salt treatment,the drug release mechanism was transformed from diffusion alone to the combination of diffusion and matrix erosion.关键词：Membrane emulsification;Alginate microsphere;Salt treatment;Doxorubicin;Drug release
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发布时间：2021-03-19 - 摘要：A series of thermo-sensitive hydrogels were designed and synthesized via radical polymerization of N-isopropylacrylamide (NIPAAm) by using a biodegradable acryloyl-poly(-caprolactone)-2-hydroxylethyl methacrylate (AC-PCL-HEMA) as a cross-linker.The influence of temperature on the equilibrium swelling ratio and the optical transmittance of the hydrogel was studied.The in vitro release of parathyroid hormone related peptide (PTHrP) which can increase the number and viability of osteoblasts and promote bone formation, from the hydrogel was investigated.The release profiles indicated that the sustained release of PTHrP from the smart hydrogel was over 13 days,indicating that the materials have potential applications in the field of oral implantology.关键词：Parathyroid hormone related peptide;Thermo-sensitive;Hydrogel;Controlled-release
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发布时间：2021-03-19 - 摘要：Via the process of photografting surface modification by UV light,fluorenone (FL) was employed as an initiator in the grafting reaction of acrylic acid (AA), acryamide (AM), methylacrylic acid (MAA), methyl acrylate (MA) and methyl methacrylate (MMA) onto the surface of LDPE films for introducing new chemical properties to the film surface.In this study,influences of the initiator concentration,UV light irradiation time,UV light irradiation intensity as well as the types of functional monomers on the grafting yield of LDPE films were investigated respectively.Within a certain range,the results showed that raising the fluorenone concentration would lead to the increasing of the grafting yield,however,when the fluorenone concentration reached 5%,the grafting yield decreased.The grafting polymerization was fully promoted by increasing the light irradiation intensity up to 100 W/m2 and prolonging the UV light irradiation time to 4 min.Grafting ability of different types of monomers on LDPE films was concerned with parameters such as activity of monomers,compatibility of monomers with the matrix and so on.After successful grafting of functional monomers,the changes of water contact angle of the grafted LDPE film were related to the grafting yield of monomer on the film as well as the hydrophilicity of the applied monomers.关键词：Fluorenone;UV-photografting;LDPE film;Grafting yield;Contact angle
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发布时间：2021-03-19
Research Article
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