最新刊期
卷 ， 期 5 ， 2000
- 摘要：The Lagrangian-Eulerian algorithm was used for simulating flow past a confined cylinder with 1∶2 diameter/wall ratio.The one-mode Phan-Thien and Tanner(PTT) constitutive model was used in the present calculation.Profiles of both velocity and stresses are obtained at different sections of the steady flow,and compared with laser Doppler velocimetry and flow-induced birefringence data given by Baaijens et al. for a polyisobutylene/tetradecane(PIB/C14) contraction flow at Deborah number De =0.93.Overall,the simulation has reproduced the experimental results is fairly well. In addition,the dimensionless drag on the cylinder is reported to be a monotonically decreasing function of the Deborah numer,and agrees well with the numerical results of Dou and Phan-Thien.
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发布时间：2021-03-19 - 摘要：A statistical mechanical treatment concerning the helix-helix transition of polypeptide chains was attempted based on a model which specifies the state of each peptide residue by either right-handed screw sense or left-handed screw sense.Two principal parameters were introduced. γ is the statistical weight of a right-handed helical residue that follows one or more other right-handed helical residues ρ represents the difficulty for the initiation of a right-handed sequence after a run of left-handed segments,To account for the newly discovered multiple helix-helix transitions,the acid effect was further incorporated into the theory.The proposed theory was compared with experimental results and some published data,and the agreement is encouraging.
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发布时间：2021-03-19 - 摘要：The ring-opening polymerization of ε-caprolactone (CL) in the presence of water, alcohol and carboxyl acid at moderate temperature (80℃) has been investigated, indicating that carboxyl group does not initiate the polymerization of CL, but can accelerate the hydroxyl-initiated polymerization of CL, and the catalytic-ability of the carboxyl acid depends upon its acidity. Thus, a series of α -hydroxyl-ω-carboxyl (1,2,3) functional telechelic oligocaprolactones were synthesized by the polymerizations of CL initiated with hydroxy-acids glycollic acid,DL-malic acid,or citric acid at a moderate temperature (80℃).The products were characterized by the acid-base titration,hydroxyl value titration,UV,FTIR and 1H-NMR analysis,respectively.The mechanism of carboxyl-catalyzed hydroxy-initiated CL polymerization was also described.
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发布时间：2021-03-19 - 摘要：Ethylenediamine(EDA) and water were used respectively as the chain extender in the preparation of polyurethaneurea-polymethylmethacrylate(PUA) hybrid aqueous dispersions.The relationship between the structures and physical properties for dried films of these water-borne PUAs was studied by means of DSC,DMA and FTIR.The testing results of DSC and DMA show that there is only one broad glass transition peak in the PUA prepared with water as extender exhibiting a compatible system while there are two glass transition temperatures in the film made with EDA as extender giving rise to phase separated morpholygy,Furthermore,as consistent with the DSC scan results and DMA measurements,the experimental results of FTIR indicate that there are stronger hydrogen bonding effect and much higher urea bond density in the EDA system than in the water system.In this case,the different morphologies for these two multo-component systems should be expected.Ayield phenomenon appeared in the stress-strain curve of PUA prepared with water as extender while it was not observed in the EDA counterpart.The PUA synthesized with EDA as extender is superior to the water counterpart in solvent and water resistance as well as tensile strength,which could be related with the morphologies for such two extender systems studied in this paper.
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发布时间：2021-03-19 - 摘要：Hydrophobically associating polyacrylamide (HAPAM) was prepared for the first time by inverse microemulsion polymerization.Its rheological properties were determined by using a Brookfield viscometer and compared with those of HAPAM prepared traditionally by micelle polymerization.Results showed that the apparent viscosity of the former kind of HAPAM increased with increasing co-polymer concentration and co-monomer content,even if when the co-polymer concentration was low.As for the latter kind of HAPAM,when the content of co-monomer increased to 1%,the apparent viscosity decreased os as to be lower than that of the copolymer of which the co-monomer content was 0.5%.In comparison,the former HAPAM won an advantage over the latter on salt resistance and shear stability.These results were interpreted in terms of hydrophobical associations in aqueous solutions which played an important role in rheological properties:in the macromolecular chain of the former HAPAM,hydrophobical co-monomers distributed randomly,but not in block.As a result,it was the intermoleculat association instead of the intramolecular association predominated,which made the apparent viscosity increase remarkably and improved the salt resistance and shear stability.
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发布时间：2021-03-19 - 摘要：The hyperbranched methacrylated poly(amine-ester) oligomers synthesized from N,N-diethylol-3-amine methylpropionate and 1,1,1-trimethylolpropane as an “initiator core”,building hyperbranched arms,end-capped glycidyl methacrylate and methacrylic anhydride, respectively,are very reactive compounds which undergo fast polymerization by a radical mechanism at the presence of a photofragmenting initiator under UV irradiation.The unsaturation conversion reaches to 70% in 2 s irradiation and then to 85% in 8s irradiation with 1kW UV lamp HPM 15 from Philips at the distance of 100mm from the sample measured by FT-IR.However,65% of the unsaturation conversion is obtained in 20 s irradiation with 250W UV medium pressure lamp measured by Photo-DSC.A inetic study of the UV-induced curing of the hyperbranched poly(amine-ester)s by evaluating the reaction rate and unsaturation conversion with Photo-DSC has shown that methacrylic anhydried-modified oligomer without monomer added has much higher photocuring speed and lower unsaturation conversion than that modified by glycidyl methacrylate.The higher thermal properties of UV cured oligomer films with higher unsaturatio conversion have been obtained measured by TGA.The hyperbranched methacrylated poly(amine-ester)prepolymers are very competitive with traditional linear linear ones used in radiation curable coatings inks and adhesives.
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发布时间：2021-03-19 - 摘要：With DMF as solvent,the kinetics of copolymerization systems of four N-p-substituted phenyl maleimides with styrene in solution was systematically studied by means of dilatometry.The polymerization rate equation of N-phenyl maleimide with styrene is Rp=k[I]1/2[M].The polymerization rate of other N-p-substituted phenyl maleimides with styrene were also a linear function of monomer concentration.The overall apparent copolymerization rate constants and apparent copolymerization activity energy of the four N-p-substituted phenyl maleimides with styrene were determined,which confirmed that the polymerization activity of the four N-p-substituted phenyl maleimides with styrene decreases in an order as follows:N-p-chlorophenyl maleimide,N-phenyl maleimide,N-p-tolylphenyl maleimide and N-p-tolyloxyphenyl maleimide.The apparent copolymerization activity energy of N-p-chlorophenyl maleimide with styrene was the smallest because the polarization difference between N-p-chlorophenyl maleimide and styrene was the biggest.The result was in accordence with the theory of CTC complex,which provided the evidence of the existence of CTC complex.
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发布时间：2021-03-19 - 摘要：In recent years,the hybrids based on organic polymers and inorganic clay minerals consisting of layered silicates have attracted great interest from both scientific and industry fields,since they exhibit dramatic increases in their mechanical and thermal properties synergistically derived from the two components.In this paper the in-situ graft-intercalation method has been introduced successfully in preparing polypropylene/montmorillonite nanocomposites (PPMNC).The spaces of silicate layers of montmorillonite in the composites were investigated by using X-ray diffractometer.It was found that the space of the layers increased form1.9nm up to about 4nm.The dynamic mechanical properties of PPMNCs were also studied The results showed that the ynamic storage modulus of PPMNCs was higher than that of PP,as high as 2 times,especially at temperatures above 80℃.
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发布时间：2021-03-19 - 摘要：Kinetic studies of tetrahydrofuran polymerization intiated by heteropolyacid showed that the concentration of propagating species maintained unchanged in the main period of the polymerization,indicating the absence of chain termination.The concentration of propagating species was measured by using a modified sodium phenoxide method and hydroxyl end-group analysis method,and it showed that each of the three protons in heteropolyacid initiated one chain.The same result was also verified for the acetic anhydride promoted system by the hydroxy end-group analysis method.The values of the chain propagation rate constant of THF polymerization at 0℃ and 20℃ were found to be 3.78×10-3and 1.98×10-2 L·mol·s1,respectively,which are in correspondence with the chain propagation rate constant of THF on ionic active species.
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发布时间：2021-03-19 - 摘要：TWO kinds of PPO blends,PPO／SEBS(Kraton G1651)and PPO／SEBS-g-MAH(Kraton FG1901) prepared through melting extrusion,were compared in morphology and impact properies．TEM studies showed that in PPO／SEBS blends the elastomer iS dispersed in the PPO matrix in a thick cylindershape and forms the sea-island morphology until the content of SEBS is up to 500mg·g-1,In PPO／SEBS- g-MAH blends,if the concentration of elastomer is in the range from O to 100mg·g-1,SEBS-gMAH is dispersed in PPO continuous phase in a thin cylinder shape,when SEBS-g-MAH is 150mg·g-1,it forms anetwork morphology．The notched impact strength revealed that ductile-brittle transition doesn’t occur in PPo／SEBS blends．but occures for PPo／SEBS-g-MAH blends in the content range of SEBS-g-MAH from 100 to 150mg·g-1, This super-toughened level results from the network morphology in PPO／SEBS-g- MAH blend Furthermore,thermal and rheological behavior of PPO blends were measured by DSC and Instmn capillary rheometer DSC revealed that the PS segment in SEBS copolymers was miscible completely with PPO．and the PS segment in SEBS-g-MAH was miscible partly with PPO．DSC result showed that there was higher phase separation in PPO／SEBS-g-MAH blends than in PPO／SEBS blends．Rheological behavior revealed that at the same shear rate．the melt viscosity of SEBS-g-MAH was 10wet than that of PPO．and the melt viscosity of SEBS Was higher than that of PPO．Rheological result showed that SEBS-g-MAH trended to encapsulate PPO during melting extrusion and has the thin cylinder shape or network structure in PPO matrix with the increasing of SEBS-g-MAH．
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发布时间：2021-03-19 - 摘要：Acrylamide was initiated by plasma and post-polymerized in aqueous solutions.High molecular weight linera polymers up to 6×106 were obtained.According to Chinese Standard GB 120005.1-89 and GB/T 12005.10-92,the intrinsic viscosity of a series of polymers was measured and approximate molecular weights were calculated.Two plasma-initiated methods were used,and the results were almost the same.[H+] was very important for the formation of the polymer and affected the molecular weight of the polymer.The effect of plasma parameters (including discharge power and discharge time)on the molecular weight of the polymer was studied.The effect of polymerization condition (including polymerization temperature,polymerization time and initiated monomer concentration)on the molecular weight of the polymer and on the yield was obtained.The enlarged experiment made it possible to industrialize the plasma-initiated aqueous solution polymerization of acylamide.
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发布时间：2021-03-19 - 摘要：The effect of crystallinity of semi-crystaline polyethylene terephthalate(PET) on its macroscopic optical properties was studied by the spectroscopic ellipsometry.The PET films on silicon wafers were prepared by the spring method.Then the samples were irradiated by an infrared lamp and dried at 70～80℃ to remove the residual solvent.The annealing processes with different annealing temperatures and different periods of time (from 75℃ to 240℃,from 10min to 4h) were performed to obtained different crystallinity of PET films.The ellipsometric spectric spectra of these PET samples were measured by using a homemade automatic ellipsometer in the photon energy range of 4.3～6.2eV.The refractive index spectra and the extinction coefficient spectra of PET films were obtained by fitting the experimental data of ellipsometric spectra with the theoretical calculation based on a monolayer model.Some thick PET film samples with corresponding annealing treatments were characterized by the X-ray diffraction to check the crystallinity. Our results shou that the optical constants of PET thin films increase signficantly with increasing crystallinity and incline to those of crystalline state.There are peaks of the refractive nidex and the extinction coefficient in our spectra.The optical constant spectra of biaxially-stretched PET were also measured for comparison.The absorption edge is near 4.2eV for both kinds of PET,but the positions of the peak of the extinction coefficient are different.The micro-crystal dimension may also be concerned with the change of optical constants.
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发布时间：2021-03-19 -
STUDIES ON PREPARATION AND FULLERENATION OF CROSSLINKED STYRENE AND ACRYLAMIDE COPOLYMERIC PARTICLES
摘要：St/Am crosslinked copolymeric particles were prepared by dispersion copolymerization using DVB (45% of purity) as crosslinking agent.The effects of the styrene/acrylamide ratio,ethanol/water ratio on the particle size were studied.It was found that initial solubility parameter (medium polarity) of the system was the key factor to influence the particle size and system stability.The comonomer Am also played an important role on the particle size and system stability.The Am fraction in monomer feed and the polarity of medium have dramatic effects on the particle morphology,During the polymerization,the crosslinked PS fragments and the PAm fragments in the particles were immiscible and phase separation occurred.As a result,the spherical particles turned heteromorphic and the particles became odd.Through the reaction of amide groups with fullerenes(C60),fullerenes (C60)were successfully incorporated onto polymer particles.FTIR and DSC experiments further support the above results.Photoconductivity experiment indicated that fullerenated crosslinked copolymeric particles have good photoconductivity due to the incorporation of C60onto the polymer particles.- 8
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发布时间：2021-03-19 - 摘要：The low temperature properties of polydimethylsiloxane(PDMSN) containing hexaphenylcyclotrisilazane(P3N) and the commerical PDMS were comparable according to their DSC data.The glass transition temperature of PDMSN was -120℃.After heating for 24 hours at 350℃ in a sealed N2 system,the weight loss of PDMSN was 4～10 times lower as that of the commericial PDMS,and decreased with increasing its nitrogen content,thus,its least weight loss was 1.1%.The 29Si-NMR spectra,IR spectra and the relationship between the molecular weight (by GPC) and limiting viscosity number of PDMSN,which was synthesized through the polymerization of cyclosiloxane with trilithium salt (P3NLi) of hexaphenylcyclotrisilazane as an initiator,demonstrated that PDMSN was a star polymer.Also,N,N,N-trimethylhexaphenylcyclotrisilazante,which was prepared quantitatively through the reaction of P3NLiand MeI in the polar solvent,was characterized by the elemental analysis,1H-NMR and 29Si-NMR spectra,IR spectra,The star polymer nature of PDMSNwas also proved indirectly by the characterization of N,N,N-trimethylhexaphenylcyclotrisilazane.
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发布时间：2021-03-19 - 摘要：With benzophenone as photoinitiator,a two-step vapor-phasc photografting of AA in LDPE film has been studied mechanically The diffusion of BP into LDPE film has been carried out by dipping LDPE film into BP acetone solution for various periods of time and monitoring the concentrations in the film bvmeasuring its absorption at 254nm on a 756-MC spectrophotometer．The diffusion coefficient,whichdecreased with the increasing of the concentration of BP,Was between 0．8～2．0 X 10-12m2·sec-1．This monitoring method was also used in the study of the photoreducrion of BP．The results showed that,when far UV(λG) increased quickly at first,and then leveled up．while the far UV was filtered, G became lower at the beginning of the reaction than that while it WaS radiated by UV directly．but about 5 min later,there was little difference．Raising temperature could increase the percent of graft remarkably．Furthermore．the grafting system showed some living polymerization character：The graft yield increased continually even BP has bean used up,which can be interpreted by the re-cleavage of the weak bond formed by LDPE chain and semipinacol radicals．Based on these facts,a monomer diffusion controlling principle,which Was thought the main factor affecting the graft yield was discussed．
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发布时间：2021-03-19 - 摘要：Fourier Transforrn Infrared (FTIR) Spectroscopy and Wide Angle X-ray Diffraction(WAXD) techniqueS were used to study a selective modification of montmorillonite with hydroxyl group(一OH) of toluene-2,4-di-isocyanate (TDI)．Based on the investigation results,a schematic model was presented.The selective modification product was applied to prepare an intercalated polystyrene／montmorillonite nanooomposite,and the nanocomposite was characterized by WAXD and Tmnsmiesion Electron Microscopic (TEM) techniques．The FTIR results showed that after modification of cetyltrimethylammonium bromide(CTAB) exchanged montmorillonite,TDI was successfully selectively grafted to the surface—OH group of the rnontmorillonite via two different synthetic routes．And the WAXD results revealed that the interlayer distance of the montmorillonite was increased dramatically．Combining with the previous nvestigations, it mav be deduced that the orientation of the CTAB might be changed from a bilayer structtire parallel to adiacent silicate layers in CTAB-exchanged montmorillonite to a double layer inclined。tructure in the interlayer space of the TDI grafted montmorillonite product．The TDI modified montmorillomte product could be successfully applied to obtain an intercalated polystyrene／montmorillonite nanocomposite During the intercalative polymerization process,the interlayer distance of the TDI modified montmofillonite was increasedfurther．Five sharp diffraction peaks,d001=4 24,4．60,5.07,6.59,7.48nm,appeared for the polvstyrene／TDI modified montmorillonite nanocomposite The TEM investigation indicated tat the thickneSs of the montmorillonite primary particles was reduced to 20～50nm in the polystyrene matrix.The WAXD and TEM results suggested that an intercalated polystyrene／TDI modified montmorillonite nanocomposite was suceessfully achieved．
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发布时间：2021-03-19 - 摘要：The monomer reactivity ratio (mrr) of emulsion copolymerization of tetrafluoroethene (TFE) with vinylidene fluoride (VDF) was examined and studied at relatively low pressure.In this study with the general pressure less than 1.53MPa,Henry's law was applied well to relate the monomer concentration in the liquid phase and the mole fraction in the gas phase.In this case,the copolymer composition equation could be kept in the same way as Mayo-Lewis equation after replacing the monomer concentration with gaseous mole fraction and the mrr with apparent mrr.The initial and the end monomer mole fractions were determined with gas chromatograph (GC) and the copolymer compositions were calculated from GC experimental data as well as from the data measured by using 19F-NMR.The apparent monmer reactivity ratio estimated from reactivity ratio error-in variables model (RREVM) are 0.35 (γVDF)and 0.63(γVDF)for TFE and VDF respectively.95% probability contour shows the experiment results of apparent mrr is accurate and the compositions of such copolymers (FTFE)calculated from the copolymer composition equation produced are in good agreement with those measured by means of 19F-NMR.
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发布时间：2021-03-19 - 摘要：A maleic anhydride grafted polyethylene-octene rubber/semi-crystalline polymer blend(TPEg)was adopted as a compatibilizer to compatibilize amorphous copolyester (PETG)/polyethylene-octene rubber (TPE) blends.The presence of maleic anhydride group on the TPEg increases the compatibility between PETG and TPE and decreases the dispersed phase size.At a fixed PETG content of 85wt%,a sharp brittle-tough transition occurs when the TPEg content in the dispersed phase increases from 20 to 30 wt%,namely that the TPEg content in the blend increases from 3 to 4.5 wt%.
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发布时间：2021-03-19 - 摘要：Benzoxazine-based phenolic resin has recently attracted a great desl of attention due to its versatile properties．One of its unique properties is volumetric expansion or near-zero shrinkage uponpolymerization．However,the cause for the expansion or near-zero shrinkage is not well understood．In this paper．systematic investigation on the cure shrinkage of three benzoxazines based on bisphenol A,p-cresol and 2．4-diehlorophenol respectively has been made This research has laid particular emphasis on the effect of the Dhenlic portion of the benzoxazine molecule on volumetric expansionl,wich is different from that of Ishida’s work,namely,the effect of the amine moiety of the benzoxazine molecule on volumetric expansion The cufe reactions of these benzoxazines are carried OUt without the aid of catalysts above 140℃．By means of gravimetric and dilatometric methods etc,the studies on volumetric shrinkage,density versus cure time plots,isothermal cure shrinkage and density versus temperature plots have been performed．The cure shrinkage of benzoxazine is demonstrated from the point of view of polymerization for the first time．The volumetric changes of benzoxazines during core reaction process as well as their effects on volumetric expansion are discussed．The results of apparent volumetric shrinkage show that both mono-benzoxazine and bis-benzoxazine precursors exhibit apparent volumetric expansion after polymerization,that is,the densities of monomer are larger than those of polymers at room temperature Moreover,the apparent volumetric expansion of crystalline monomer after polymerization is larger than that of amorphous monomer．The density versus cure time plots give another point of view of the volumetric expansion of beuzoxazines atroom temperature,that is,the higher the cure temperature is,the longer the core time last,the larger the volumetric expansion of benzoxazines will be．The analysis of isothermal cure shrinkage reveals that these bensoxazines exhibit volumetric shrinkage while curing isothermally at elevated temperature．Furthermore,the isothermal cure shrinkages of bis-benzoxazine precursors are smaller than those of monobenzoxazine precursots Results of the density versus temperature plots depict the full view of these benzoxazines as they undergo thermal expansion,shrinkage by curing,and shrinkage by cooling from the cure temperature to room temperature,which is in consistent with the results of apparent volumetric shrinkage and isothermal cure shrinkage．The thermal expansion coefficient of benzoxazine polymer is much smaller than that of monomer. From the deviated point of the density versus temperature plots of bensoxazine monomers,we can predict the initial polymerization temperature of benzoxazines．To sum up,these three kinds of benzoxazinesexhibit apparent volumetric expansion after polymerization and volumetric shrinkage while curingisothermallyl The volumetric changes of different benzoxazines at different cure reaction temperatures as well as with different cure times are evidently distinctive．The larger the extent of polymerization is,the larger the volumetric expansion of benzoxazines will be Therefore,this volumetric expansion phenomenon of benzoxazines is a consequence of the molecular packing rather than the ring-opening polymerization mechanism and the dimension of benzoxazine is associated with its molecular structure,extent of polymerization and crosslinking density．
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发布时间：2021-03-19 - 摘要：Because poly(butyl a-cyanoacrylate) was less toxic than poly(isobutyl a-cyanoacrylate)and its nanocapsules could be orally absorbed via intestine wall,the polymeric nanocapsules as drug delivery system of peptides was prepared by the interracial polymerization of butyl a-cyanoacrylate other than isobutyl a-cyanoacrylate used previously．The aqueous phase contained a surfactant such as Tween 20 and polymericstabilizer such as dextrin T-70,dextrin T-40 as well as Poloxamer 188 And the organic phase composed of monomer butyl a-cyanoacrylate and a cosolvent such as glycerol trioleate or benzyl alcohol in bulky solvent ethanol or acetone．The nanocapsule sizes and their distribution were measured by laser scattering technique and transmission electron micrography．It was investigated the influence of the used surfactants,polymeric stabilizers,cosolvents,and temperature in vacuum evaporation on the nanocapsule sizes．The results show that dextrin T-70 is a better polymeric stabilizer than its low molecular weight analog dextrin T-40 and Poloxamer 188 for the monomer phase soluble in ethanol to be dispersed in aqueous phase with Tween 20 as a surfaetant The size of the polymeric nanocapsules decreased with increase of amounts of dextrin T-70 and Tween 20 dissolved in aqueous phase．Compared with glycerol trioleate,benzyl alcohol as cosolvent could made the nanocapsules larger and smoother because benzyl alcohol might make the immigration of the solvent,ethanol,in the monomer phase into aqueous phase more slowly．In addition,when the formed suspension of poly(butyl a-eyanoacrylate)nanocapsules was concentrated by evaporation in vacuum at 30℃ instead of 20℃, small nanocapsules would be aggregated into large particles．
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发布时间：2021-03-19 - 摘要：Two kinds of PCL/PEO/PLA tri-component copolymers(PCEL) with different composition were synthesized by direct copolymerization of ε caprolactone, L-lactide and PEG(6000) in the presence of stannous octoacte at 130℃ for 56h.The biodegradation behavior of these copolymers was investigated in a pH7 4 phosphate buffer solution at 37±1℃ in vitro.The changes of water sorption,loss weight,molecular weight,molecular weight distribution,thermal properties and composition of the copolymer were monitored by GPC,DSC,XRD and 1H-HMR techniques.The results showed that the hydrophilicity of the copolymer was enhanced with increasing PEO content,which lead to decrease of the PEO component and increase of the loss weight of the copolymer with degradation time. It was considered that the obtained bi-modal chromatogram of the GPC profile was attributed to the degradation of the partial crystalline polymer.Since degradation has taken in priorty in amorphous zones and at the edges of crystalline of the polymer,bi-modal molecular weight distribution of GPC spectrum was formed.This interpretation was supported by DSC and X-ray diffraction data.
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发布时间：2021-03-19 - 摘要：The thermally reversible covalent crosslinking of epoxy acrylate rubber(Ep-AcM)which is a copolymer of ethyl aerylate／allyl glycidyl ether was studied by using two thermally reversible covalent crosslinking agents,i.e dicyclopentadienyl dicarboxylie acid and diammonium dicyclopentadienyl earboxylate．The effects of the eroeslinker amount,crosslinking and retro-crosslinking temperatures on the eros．slinking rate,yield of crosslinking and retro-crosslinking were investigated in detail．It has been found that both the crosalinking and the retro-crosslinking rates increase with the increasing of crosslinker amount．The highest yield of crosslinked polymer was beyond 60％and the efficiency of retro-eroeslinking was as high as 79.7％ when DCPD(COONH4)2 was used as creaalinker It could be concluded that diammonium dicyclopentadienyl carboxylate was a more efficient eroeslinking agent than its carboxylic acid． But for the effect of temperature on the yield of crosslinked polymers the best optium temperature was only around 70℃ In spite of what kind of eros,slinking agent was used．the thermal irreversible covalent erosslinkage was present(20％～25％) in the crosalinked copolymer．The possible reasons for this were：(1) the retro-crosslinking was not high enough because the reaction temperature was lower than 160～220℃ (detn.by DSC)；(2)there was thermal irreversible covalent ether bond formed in the course of the Ep-ACM crosslinking with the crosslinker；(3)free radical polymerization of CPD which formed under the retro-cros,slinking conditions could happen The analysis data by FTIR and DSC confirmed that the crosslinkage provided by crosslinking agent and the gained covalent ereaslinked copolymer exhibits thermally reversible conversion behavior
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发布时间：2021-03-19 - 摘要：Papain was immobilized on porous silica beads,chitosan and cellulose by cross linking with glutaraldehyde.Thermal activation of immobilized papain on porous silica beads has been first found and reported by us.In this article,the factors related with the activity of the immobilized papain on chitosan and cellulose,such as pH of the immobilized reaction,concentration of glutaraldehyde and amount of papain were studied.We also studied the characters of these immobilized papain,comparing with native papain and immobilized papain on porous silica beads.Thermal stability and durability on heatig were emphasized.Their optimum reaction temperature were 80℃.After incubation at 90℃ for 1h,the activity of these immobilized papain was retained above 95%.After, incubation at 70℃ for 5h or 6h,the activity of immobilized papain was also retained above 90%.These results showed that thermal stability and durability on heating of immobilized papain on chitosan and cellulose were improved considerably.
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发布时间：2021-03-19 - 摘要：This paper presents the novel monosized resins with hydrophilic surface coated polysaccharides, including synthesis of the matrix beads．modification of the particle surface and characterization of HPLC properties of the modified products．The monosized matrix beads based on poly(methyl methacrylate-co-divinylbenzene)(PMMA-DVB) were synthesized by seed swelling polymerization．The linear polystyreneparticles as seeds were swollen by an emulsifying mixture of monomer,crom-linker and initiator in the aqueous solution containing stabilizer at the room temperature,then the swelling products were polymerizedin the same solution system at 70℃．finally the polymerization products were fully washed with water．The particle parameters and apparent morphology of the matrix beads were characterized by scanning electronmicroscopy(SEM)．The results show that the polymerization method is suitable to the preparation of monosized PMMA-DVB beads with particle diameters of 5～15μm,the particle dispersion coefficient of the polymerization products with different cross-linking densities is less than 2％．After being hydmlyzed with a 30％(W／V) NaOH solution at 80℃,the PMMA-DVB beads were transformed into the hydrolyzed resins contmning carboxylic groups on the particle surface．Dextran and DEAE-Dextran were coated respectively by the impregnation method,and then were cross-linked respectively with 1,4-butanedol diglycidyl ether as cross-linker Two new modified resins with covering layer of cross-linked polysaccharides on the particle SUrface were obtained The polyasccharides content of the modified resins was aboUt 7％(W／W) of the matrix beads．In order to get a uniform covering layer,the coating and cross-linking process was generally divided into two or three times to accomplish with same operation method SEM observation showed that the physical morphology of the two modified resins still kept monodisperse particle as matrix beads．Owing to highly cross-linking network structure,the modified resins exhibit good physical and chemical stability．The particles can withstand high pressure operation,can be treated with acidic and alkaline solutions(pH=1～14)．Monodisperse particle size,good particlerigidity andthe surface coated bypolysaccharidesmakethe modified resins as HPLC packings possessing high column efficiency．high permeability and excellenthydrophilic properties．The experiments show that on chromatographic columns packed with the two modified resins,human serum albumin possesses good elution behavior in elution system of phosphate buffer(pH=3.8),the protein recovery is over 97％ and 99％respectively．
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发布时间：2021-03-19 - 摘要：A new synthetic route was designed for synthesizing the luminescent polymers of alkyl substituted poly(1,4 phenylenevinylene) derivatives (alkyl-PPV).The monomer of the polymers was synthesized by two steps:first,using Li2CuCl4 to catalyze cross-coupling of aryl grignard reagent with alkyl halides to introduce alkyl long-chained substituents to benzene ring,second,using SnCl4 to catalyze chloromethylation of the alkyl long-chained substituted benzene.The yield of the monomer synthesized by this method was much higher than that by any other methods that were ever reported.The polymerization of the monormer was carried out by using t-BuOK to remove HCl.Poly(2-dodecyl-5-methyl-1,4-phenylenevinylene) was synthesized with that synthetic route.The structure and properties of the polymers were identified and characterized by IR,UV-Vis,luminescent spectra,GPC,thermal(DSC and TGA) and elemental analysis.It was found that the glass transition temperature increases and the photoluminescent relative quantum yield decreases with the increase of the conjugation extent of the polymers,and the photoluminescent relative quantum yield of the polymers can be as high as 78%.
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发布时间：2021-03-19 - 摘要：The stereospecifie block copolymer of styrene and 1-butene i．e．sPS-b-PB was synthesized with η5-pentamethylcyclopentedienyltribenzyloxidetitanium(Cp*Ti (OBz)3)／modified methylaluminoxane(mMAO) catalyst．The effects of externaltriisobutylaluminium(TIBA),prepolymerizationtime of 1-butene and concentration of styrene on catalytic activity and molecular weight were investigated．The catalyticactivity of copolymerization increases and then decreases with successive increasing concentration of external TIBA．and exhibited the highest value of 12．2kgP／gTih at[TIBA]=26 mmol／L．As increasing concentration of styrene,the catalytic activity increases at first and then level off．But it decayed with prolonging prepolymerization time．Molecular weight of the polymers obtained decreases with increasing concentration of external TIBA,but it is weak relative to prepolymerization time．Those copolymerization products obtained were extracted successively with various solvents to separate the existed homo-and co-polymers The block copolymer of sPS-b-PB are soluble either in boiling tetrahydrofuran or boiling chloroform．It accountedfor 21.0％--41.3％ of the total weight of copolymerization products．The weight percent of 1-butene segments of the block copolymer was in the range of 18.7mol％～41.7mol％.The block copolymer was characterized and confirmed by 13C-NMR,FTIR,DSC,WAXD and GPC methods.
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发布时间：2021-03-19 -
INVESTIGATING MECHANICAL RESPONSE OF SINGLE CHAIN POLYSTYRENE PARTICLES BY SCANNING PROBE TECHNIQUES
摘要：Single chain polystyrene particles were obtained by dilute solution casting method.The sample with both single chain polystyrene particles and multi-chain (more than 1000 molecular chains) polystyrene particles was obtained by a little more concentrate solution.Force modulation technique showed that single chain polystyrene particles were softer than multichain polystyrene particles.On the other hand,nanoindentation experiments on multi-chain particles and bulk polystyrene manifested that the elastic modulus of multi-chain polystyrene particles was very close to that of bulk polystyrene.Therefore,it was concluded that single chain polystyrene particles were softer than bulk polystyrene,which indicated that the desity of intrachain entanglement points in the single chain polystyrene particles was not as large as that of the interchain entang lement points in the bulk sate.- 29
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发布时间：2021-03-19
Research Article
- 摘要：A Raman spectroscopic study on the hydrogen-bond defect of water in 2-hydroxyethyl (meth)acrylate hydrogels crosslinked by ethylene glycol dimethacrylate (EGDMA) and polyethylene glycol dimethacrylates were undertaken.It was found that PEGDMA-16 possessed a different behavior on the hydrogen-bond defect from EGDMA and PEGDMA-9.That is,the extents of hydrogen-bond defect for EGDMA and PEGDMA-9 decreased with the increase of crosslinking density,whereas for PEGDMA-16,as the crosslinking density is bigger than a certain value,the hydrogenbond defect is increased with the increase of crosslinking density.This in caused by the weaker effect of —CH2OCH2— in the PEGDMA-16 to the hydronen-bond defect of water than that of —OH in HEA and HEMA.
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发布时间：2021-03-19
Research Bulletin
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