最新刊期
卷 ， 期 4 ， 2006
- 摘要：The AFM-tip-induced crystallization of poly(ethylene oxide)(PEO)melt droplets was studied．The melt droplets with the heght of 50～100 nm and the lateral size of 2～3 μm were obtained by melting the PEO ultrathin film on the mica surface．Forthe PEO samples with the number average molecular weights(Mn)ranged from 1．0×10 3 to 1．0×104g／mol,the lateral perturbation from the AFM tip with hard-tapping or nanoscratch mode could not induce the growth of the flat—on lamellae． By contrast,under AFM nanoindentation mode,the tip—induced crystallization occufred when a sufficiently high vertical tip force was applied to the melt droplets of PEO with Mn≥1．0×lO4g／mol．Moreover,the experimental results indicated that AFM-tip—induced crystallization with nanoindentation method had PEO molecular weight(viscosity)dependence．
- 42
- |
- 13
- |
- 2
发布时间：2021-03-19
Rapid Communications
- 摘要：The phase separation kinetics of polystyrene／poly(vinyl methyl ether)(PS／PVME)blends under oscillatory shear was studied on a customized Rheo-SALS tester．It was found that,under fixed frequency and strain amplitude,the phase separation exhibited anisotropy and periodicity．At a given phase angle,the early—stage kinetics of phase separation followed the classical Cabn-Hilliard theory．The average of characteristic wavenumber qm,where the maximum scattering locates,stayed unchanged during the phase separation,implying that only the composition fluctuations with specific size will be favored under a oscillatory shear with given frequency and strain amplitude．Under shear,qxm, the characteristic wavenumber along flow direction,experienced a compulsive oscillation with a frequency same as that of shear,while qzmthe characteristic wavenumher along vorticity direction,dose not．Through simultaneous rheological measurements,it was also found that stress could appropriately reflect the stage of phase separation．For example,the first normal stress difference reached maximum when the early stage of phase separation ended.
- 4
- |
- 13
- |
- 0
发布时间：2021-03-19 - 摘要：4,4'-tetraglycidyldiaminodiphenyl methane(TGDDM)epoxy resins are widely used in the fields of aviation and airspace owing to their excellent properties,but the physical properties of the cured epoxy resins depend on their structure,the extent of cure,the curing conditions,the time and temperature of care．So it is necessary to study the curing kinetics in order to obtain the optimal curing process．The Curing kinetics of TGDDM in presence of 3,3'-diaminodiphenylsylfone(DDS)as the curing agent was studies by differential scanning calorimetry(DSC) technique at different heating rates．The kinetic mechanism funetioin was determined using n order reaction and the most probability mechanism functioin method given by Malek respectively,the kinetic parameters of curing reaction were determined with the kinetic analysis of the data obtained by the thermal treatment,then the kinetic model was built．The results indicated that the n order model deduced from Kissinger and Crane equation,by which the parameters of curing reaction,the reaction order and activity energy were obtained,had great distinction with the experimental data．While the Malek analytical mechanism showed that the curing process of the curing reactions followed an autocatalytic reaction．The two—parameter(m,n)autocatalytic model can well describe the curing reaction processs of the studied epoxy resins．The DSC curves obtained using the experimental data showed a good agreement with that theoretically calculated under 5～20 K／min heating rate．The research results will provide theoretical basis for the choice of manufacturing process and the optimization of processing window．
- 4
- |
- 10
- |
- 27
发布时间：2021-03-19 - 摘要：A cationic hydrophobically modified ethylene oxide polymer(HM-EO)was used to form aqueous two- phase system with only one phase—forming composition．It was found that the phase separation could be achieved under room temperature．The phase behavior and charge properties of HM—EO aqueous two—phase systems were studied systematically．The amphiphilic property of HM—EO molecule resulted in the micellization and aggregation of miceLLes in water．The micellar aggregates formed in the bottom phase could be charged,and the net—charge could be adjusted by the pH and conductivity of bulk solution and adding sodium dodecyl sulfate(SDS)．The increase of pH would improve the phase separation of HM-EO aqueous two-phase system．The effect of salts on the phase behavior was Observed．The influence of cations varied as K+Na+,and that of anions as SO2-4>F->Cl->Br->I-．In addition．the interaction between HM-EO polymer and anion surfactant SDS was studied．The rosults indicated that the addition of SDS caused the formation of mixed miceHar aggregates of SDS and HM-EO which changed significantly the charge property of HM-EO aqueous two-phase systems.
- 32
- |
- 8
- |
- 1
发布时间：2021-03-19 - 摘要：Dentritic polymers which combine the temperature—and pH—sensitivities wel'e synthesized．At first, polyamidoamine(PAMAM)dendrimers with generations 1 to 3 wele synthesized by reaction of ethylenediamine with methyl acrylate,then polymers synthesized were acylated by chloroacetyl chloride to obtain PAMAM-C1,which can act as a maeminitiator for further synthesizing functional polymers having both pH—and thermo—sensitives．For fulfiUing this goal,polymers with dentritic PAMAM as the core and different average length of poly(N,N-dimethylaminoethyl methacrylate)(PDMAEMA)were synthesized by atom transfer radical polymerization(ATRP)． Their maeromoleeular structures were characterized by FTIR．1H—NMR and particle size analyses．Their aqueous solutions were studied by UV spectroscopy for understanding their thermo—and pH-sensitivities．The results showed that these dentritic polymers exhibit clearly thermo—-and pH··respondings in accordance with the change of the environment．Using ehlorambucil(CLB)as a model drug,the controlled drug release behavior of the polymers having different average length of PDMAEMA was studied．The results indicated that the rate of the drug release can be effectively controlled by pH values．
- 9
- |
- 10
- |
- 6
发布时间：2021-03-19 - 摘要：The macromer of PLA—PEG-PIA terminated with methacryloyl moieties was prepared by one—pot procedure in high yield,both the ring-opening polymerization of L—lactide and end—capped reaction with methacrylie anhydride were carried out in toluene under nitrogen atmosphere at 120℃．Then the polypseudorotaxanes were obtained through supramolecular self-assemblies between α—CDs and the macromer．Afterwards,the resultant polypseudomtaxanes were suspended in aqueous solution of N—isopropylacryamide(NIPA)in the presence of a photo—initiator．While exposed to UV irradiation,the suspension mixtures could be photopolymerized rapidly to give rise to the thermosensitive and supramolecular structured hydrogels．Their thermosensitivity was confirmed by the swelling ratio changes under different temperatures．The polypseudorotaxanes and hydrogels were characterized by FTIR,XRD and TG techniques．The studies on their potential use as biomedical materials are ongoing.
- 34
- |
- 8
- |
- 2
发布时间：2021-03-19 - 摘要：surface modification of carbon nanotubes by multi monomer(glycidyl methacrylate and styrene)grafting polystyrene(PS-g-(GMA—co-St))sheathing was carried out．First,Multi—wall carbon nanotubes(MWNTs)was functionalized by a mixture of concentrated sulfuric and nitric acids(3：1,by volume)．As a result,many carboxylic actd groups were created in MWNTs．Carboxylic MWNTs were then mixed with PS-g-(GMA-co—St)／THF solution,and the esterification reaction occurred between carboxylic acid groups of the MWNTs and epoxy groups of PS—g-(GMA-co-St),leading PSg-(GMA-co-St)grafting onto MWNTs．SEM observation shows that the average diameter of the grafted MWNTs from polymer solution is about 100 nm,larger than the average diameter of about 40 nm for the neat carboxyiic or grafted MWNTs,implying that the MWNTs Can be sheathed with polymer after modification.After solvent etching throush THF,the average diameter of the grafted MWNTs decreased to about 40 nm again,indicating the polymer sheathing can be washed up．Otherwise,after washing-up,FT-IR measurements confirmed that a little polymer still remained on the carboxylic nanotubes．
- 2
- |
- 8
- |
- 12
发布时间：2021-03-19 - 摘要：The simulated annealing method was applied to study the self-assembling morphologies of amphiphilic, semi—flexible diblock copolymem in solution with a series of interactions between the core-forming blocks and the solvents．The simulation results illustrated that the core—corona aggregates were formed in all cases．The spherical micelles with thorns on the surface ale formed when the interaction parameter is small．And the spherical micelles increase in size with the increase of the interactions．Rod-like mieelles with thorns on the surface are formed when the interaction parameter increases．And the thorns on the surface gradually tailed off with the further increase of the interactions．The bigger spherical micelles without thorns on the surface are formed when the interaction parameter increases further.
- 32
- |
- 14
- |
- 6
发布时间：2021-03-19 - 摘要：An intiator,dimethyl 4,6-bis(bwmomethyl) isophthalate,was synthesized by bromomethylation, oxidation．esterification and bromination reaction of 1,3-dimethylbenzene．The initiator was used to initiate the atom transfer radical polymerization of styrene successfully．The results showed that the process had good characteristics of controlled／living free radical polymerization．The molecular weight of the obtained polymer increases linearly with monorner conversion,molecular weight distribution is very narrow,and a linear relationship between In([M]o／[M]) and pelymerization time exists．A well-defined novel structural polystyrene containing two esters groups in the mid-main chain was propared with controlled molecular weight and narrow polydispersity．The structure of the polymer was confirmed by 1H—NMR spectra．After being hydrolyzed,a dicarboyx polystyrene was obtained and used to form ionic—bonded supramolecules with 1-dodecamine as a model of star-shaped supramolecules．The supramolecules formed was characterized by FTIR spectrum．
- 2
- |
- 8
- |
- 6
发布时间：2021-03-19 - 摘要：Poly(p-xylylene)(PPX)prepared by chemical vapor deposition(CVD)polymerization shows promising features like absolute conformation to substrate topology,pinhole—free coverage even in ultrathin films,the ability to penetrate and cover complex geometries,and extraordinarily high chemical inertness and purity compared to common polymer coatings．However,the exploitation of[2．2]paracyelophanes for generating functionalized surfaces is interesting．The funetional groups may be useful for further modifications．Poly(carboxyl—P—xylylene—co-p—xylylene) (PPX-carb) was prepared by CVD polymerization in present work．The chemical structure of the resulted polymer was confirmed by FTIR and elemental analysis．It is indicated that PPX—carb membrane has good solvent resistant and high chemical oxidation resistant．Thermogravimetrie analysis(TGA),differential scanning calorimetry(DSC),and dynamic mechanical analysis(DMA)were used to study the thermal properties of PPX—carb membranes．It is found that the initial degradation temperature and Tg of PPX-carb membranes are reduced with the introduction of carboxyl group as side groups,while the degradation temperature of the main chain of PPX-carb is higher than that of PPX．With the introduction of carboxyl,the polymer becomes amorphous,and the softness as well as the dynamic mechanical damping pmporties of PPX—carb are improved．The hydrophilieity and vapor permeability of PPX-carb membranes are also improved．
- 3
- |
- 10
- |
- 0
发布时间：2021-03-19 - 摘要：A series of aromatic copolyimides was successfully synthesized from the commercial pyromellitic dianhydride(PMDA)with the commercial diamine P-phenyldiamine(PDA)and the diamine 4,4’-methylenebis-(2-tert-butylaniline)(MBTBA)specially designed by ourselves．The copolyimides were characterized by IR,NMR,GPC．UV-Vis．TGA and DMA．The copolyimide was precipitated in m—cresol in the polymerization process when the molar ratio of MBTBA and PDA was lower than 6／4．The number-average molecular weight of the soluble copolyimides measured by GPC was larger than 4．0×104 and the polydispersity index was higher than 1．5．Only one glass transition temperature of these copolyimdies was detected around 360℃ by DMA．The copolyimides did not show appreciable decomposition up to 500℃ under N2,and the thermal stability of the conyimide increased a little with the intreduction of the PDA into the polymer chains．
- 7
- |
- 11
- |
- 10
发布时间：2021-03-19 - 摘要：Equilibrium swelling in a non—solvent is a simple experimental method to reveal the cohesional entanglement network structure present in an amorphous polymer in its glassy state．In the present work results of visual observation of the swelling behavior of two PS granules in a series of dioxane／water mixed solvents are presented．On decreasing the water content in the mixed solvent a change of physical state of the PS granules from glassy state(water in dioxane≥40 Vol％)to swollen glassy state(water in dioxane 35 Vol％～30 Vol％)．to swollen rubbery state(water in dioxane 25 Vol％～20 Vol％)and to fluid state(water in dioxane 10 Vol％-5 Vol％)was observed．It corresponds to the change from glassy state to rubbery state and to fluid state on raising temperature of the granules．Base on these observations a mixed solvent of dioxane／water(water 6．8 wt％) was chosen for equilibrium swelling and phase separation equilibrium measurements for a monodisperse PS sample of Mm =1．68×105at 30℃．In this mixed solvent PS granule can only swell but not dissolved．For the phase separation equilibrium the PS granule in the mixed solvent wilts first brought to 130℃(in a sealed tube)to become a homogeneous single phase solution,then phase separation occurred on cooling and phase separation equilibrium at 30℃ was reached in 30 days to give a volume fraction of the polymer in the concentrated phase φ”=0．304．The dilute phase is practically the pure solvent．Monodisperse PS granules quenched from being heated to 120℃ for 30 min to erase thermal history of the sample(Pp=1．0451 g／mL)reached a swelling equilibrium in the mixed solvent in 80 days to give φP”=0．308．This quenched PS granules after being subjected to a sub—Tg annealing at 80℃ for 100 days(Pp=1．0470 g／mL)reached swelling equilibrium in the mixed solvent in 70 daysto give φp”=O．312．From the curve of increasing volume of the swollen phase Vg(t),in mL/g PS,during the equilibrium swelling process it could be inferred that during sub—Tg annealing the cohesional network structure in the PS glass became more uniform,being closer to the equilibrium state at the annealing temperature,the van der Waals crosslinking density was increased,with tighter inter-chain cohesion resulting in higher density of the glass．If we take the polymer-solvent interaction parameter χ=0．63 obtained from phase separation equilibrium measurement,we obtained the molar mass between crosslinking points ofthe network,Mc=11．6×104 for the quenched sample,and Mc=6．9×104for the annealed sample from Flory theory of network swelling．The experimental results clearly indicate that swelling process and swelling equilibrium measurements in a very poor solvent can offer a rather sensitive way to obtain some idea about the structure details of the cohesional network in polymer glassy state．
- 6
- |
- 9
- |
- 2
发布时间：2021-03-19
Research Article
- 摘要：The testing specimens of all injected polypropylene sample were subjected to heat treatment for 30 min at various temperatures around its melting peak,and then the treated samples were characterized by DSC．It was found that there existed an temperature window at which the resulting melting temperature and crystallinity of the treated sample increased obviously．For heat treated specimens under static conditions the temperature window occured only below the peak melting temperature．For heat treated specimens under vibration in a dynamic mechanical analyzer with definite amplitude and frequency,this temperature window covered the whole melting range．Heat treating the PP sample under vibration in a temperature range of 5℃ above its melting peak．the resulting specimen possessed a maximum melting temperature．
- 2
- |
- 10
- |
- 1
发布时间：2021-03-19 - 摘要：Ethylene-octene copolymer(POE)samples exposed to γ—radiation under a series doses were investigated using solid state 13C-NMR．The chemical shifts of POE were assigned,and the peak evolution as a function of radiation dose was discussed．An obviously chain seission was found near the branch carbons,and the 13C—NMR spectra of the corresponding gels confirmed the result．Linewidths of irradiated POE samples of various absorbed doses were observed to which were related to the molecular mobility of the radiation-crosslinked polymer．
- 45
- |
- 11
- |
- 3
发布时间：2021-03-19 - 摘要：Three kinds of nano composite particles were synthesized by seeded emulsion polymerization．which are high crosslinking poly(methyl methacrylate)／polystyrene(PMMA(HC)／PS),high crosslinking poly(methyl meth—acrylate)／low crosslinking poly(butyl acrylate)／polystyrene PMMA(HC)／PBA(LC)／PS and high cross—linking poly (methyl methacrylate)／poly(methyl methacrylate-styrene)／polystyrene(PMMA(HC)／P(MMA-St)／PS)．Then the dry particles were molded or extruded to obtain the corresponding nanocomposites．Furthermore．the dispersion stability of nano phases in matrices was investigated during their processing．The results show that the coalescence mechanism of nano phase in these composites is different from that of binary immiscible polymer blends.
- 33
- |
- 12
- |
- 0
发布时间：2021-03-19 - 摘要：Ethylene-propylene copolymers were synthesized using a TiCl4／MgCl2／SiO2／diester type supported Ziegler-Natta catalyst with or without the presence of hydrogen in a slurry polymerization process·The copolymer was inhomogeneous in composition and can be fractionated into two parts,fractions soluble and insoluble in n-octane at room temperature,respectively．The soluble part is a nearly random copolymer,while the insoluble part is a kind of segmented copolymer,as revealed by 13C—NMR and DSC analyses．Adding H2in the reaction system caused an increase of copolymer yield and a decrease of the insoluble part,but the propylene content and average length of propylene segments of the insoluble part were markedly increased,meanwhile the average length of ethylene segments of the insoluble part was markedly decreased．Copolymer sequence distribution of the soluble part was only slightly changed by H2．The segmented copolymer fraction present in this ethylene-propylene copolynmr has the similar structure as the segmented copolymer fractions found in polypropylene／poly(ethylene—-copropylene)reactor alloy. Mechanism of the hydrogen effect on copolymer structure is discussed．
- 38
- |
- 9
- |
- 1
发布时间：2021-03-19 - 摘要：An nanostructured thermoset blend of unsaturated polyester(UPR) and PEO—PPO-PEO triblock copolymer was prepared and characterized by solid-state NMR and other techniques．It is concluded that the blend is microphase separated and the determined long period is 20 nm．A distinct dynamic difference between the cured-UPR matrix and block coploymers was observed by 1D and 2D NMR experiments,the formation of PEO crystalline domains was inhibited in the blend．The PEO blocks are panially miscible with the cured—UPR matrix．Upon curing,part of the mobile PEO was locally expelled from the cured—UPR matrix and formed dispersed mierophase together with the mobile PPO,the residual immobilized PEO blocks were intimately mixed with the partially cured-UPR,and they formed an interphase region．
- 4
- |
- 12
- |
- 3
发布时间：2021-03-19 - 摘要：A series of aminated chitosan microspheres were prepared from chitosan,and then an affinity dye—ligand,Cibacron Blue F3GA,was covalently coupled．The maximum attachment of cibacron blue F3GA was 494 μmol／g．Albumin adsorption onto cibacron blue F3GA—attached chitosan microspheres was investigated．The human serum albumin(HSA)equilibrium adsorption capacity WaS 79．8 mg／s(wet beads)．The adsorption equilibrium isotherms appeared to follow a typical Langmuir isotherm．The hisheet desorption ratio(100％)was achieved by using an eluent of 1．0 mol／L NaSCN(pH 8．0)．The cibacron blue F3GA-attached chitosan microspheres could be reused without significant decreases in the adsorption capacities．
- 7
- |
- 8
- |
- 0
发布时间：2021-03-19 - 摘要：Polyurethane／montmorillonite nano-composites were synthesized,and then used for fiber spinning．The viseosity of the spinning solutions,dispersion of montmorillonite in cast films and drawn fibers,as well as the mechanical properties of polyurethane／montmorillonite fibers weie investigated．The results indicated that the viscosities of spinning solutions containing montmorillonite were lower than that of the pure polyurethane solution,and the viseosity of spinning solutions increased after standing 24 h at room temperature．TEM images showed that montmorillonite particles were dispersed at the scale from nanometer to micrometer in fiber matrix．Compared with pore PU fibers,the mechanical pmporties of polyurethane／montmorillonite composite fibers were not improved except that the elongation at break was sightly increased．
- 38
- |
- 8
- |
- 2
发布时间：2021-03-19
Research Bulletin
- Postal code：100190
- Tel：010-62588927 Email：gfzxb@iccas.ac.cn
- Technical support is provided by Beijing Founder electronics co., LTD 京ICP备05002797号-8
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0