最新刊期
卷 ， 期 9 ， 2015
- 摘要：It is an essential subject for coordination polymerization to achieve highly selective polymerization of conjugated dienes.As an emerging kind of homogeneous catalyst,rare-earth metal complexes bearing metallocene or multidentate non-metallocene ligands have become gradually attractive over the past ten years and more.The major emphasis of this review will be these rare-earth metal complexes and the effect of various conditions on the selectivity and activity of polymerization,including the Lewis acidity and ionic radii of central metal,the geometry of ligand,the temperature of polymerization,the species of co-catalyst and solvent.Moreover,the study of active species which initiate the polymerization is particularly concerned.By generalizing the relationship between the factor and the mechanism of polymerization,it is hoped to give an inspiration to catalyst designer and the researchers of coordinate polymerization.关键词：Organometallic complexes;Butadiene;Isoprene;Selective polymerization
- 76
- |
- 58
- |
- 2
发布时间：2021-03-19 - 摘要：Various fertilizers have been widely used in agricultures and horticultures.More than 400 million tons fertilizers are used in the world every year.However,fertilizer cannot be resealed in dry soil,and could be flashed out with heaven rain or irrigation without controlling into river,which results in polluting water resources.Actually,fertilizers have already caused serious pollution for rivers and degeneration of land.Therefore,various controlled release fertilizers have been developed.This paper reviewed development of controlled release fertilizer based on both fundamental issues such as system designing and mechanisms,and materials used for coating as well as their fabrication.So far most of the materials used for coating are synthetic polymeric materials,such as PS,PE etc.,which are not biodegradable.Environmentally friendly biodegradable coatings have attracted increasingly attention,but still in development stage in laboratory.On the other hand,dry and desertification are big challenges for agriculture in China.Using superabsorbent polymers as coating materials could add the function of keeping moisture for the fertilizer,which is particularly important for dry area.It is expected that the superabsorbent polymer coatings could be favorable for crops through helping seed sprout; increasing sprouting ratio,reducing irrigation and enhancing fertilizer efficiency etc.
- 35
- |
- 21
- |
- 6
发布时间：2021-03-19
Reviews
- 摘要：Phenylboronic acid grafted chitosan hydrochloride (HCSPBA) was synthesized by introducing phenylboronic groups to the polymer chain of chitosan hydrochloride through simple molecule modification by the reaction between the amine group of chitosan hydrochloride and the carboxyl group of 3-carboxyphenylboronic acid.The structure of the amphipathic compound was confirmed by FTIR and 1H-NMR,and the graft ratio of phenylboronic can be tuned by changing the feed ratio.The cytotoxicity of the HCSPBA was assessed using CCK-8 assay,and the result showed good cytocompatibility.Hydrophobic drugs can be encapsulated to the assembled polymeric micelles of HCSPBA,and showed sustained and controllable release.Herein,doxorubicin was selected as model drug,and the drug release behavior has good glucose responsibility.Without glucose,the cumulative release rate was very low at physiological pH=7.4 and weak acidity (pH=6.5) condition of solid tumor,while the rate was accelerated when glucose was present in the medium,due to the swelling/disruption of the HCSPBA micelles as a result of the better hydrophilicity of the compound after the combination of phenylboronic group and glucose.Since the high glucose concentration physiological microenvironment of diabetes and solid tumor tissue,the HCSPBA has potential application in developing glucose responsive drug delivery systems,such as smart insulin and anti-tumor drug delivery systems.关键词：Phenylboronic;Chitosan hydrochloride;Glucose responsive;Drug release
- 36
- |
- 14
- |
- 0
发布时间：2021-03-19 - 摘要：The well-defined poly(styrene-b-isoprene-b-styrene) triblock copolymers (SIpS) with different microstructures were synthesized by living anionic polymerization and used as macromonomers in cationic polymerization.The branched butyl rubber (IIR) with bimodal distribution was successfully synthesized by cationic polymeriazation of isobutylene,isoprene and SIpS in 2-chloro-2,4,4-trimethylpentane (TMPCl) ethylaluminum sesquichloride (Al2Et3Cl3)/2,6-di-tert-butylpyridine (DtBP) initiating system in hexane/methyl chloride solvents 50/50(V/V) at -80 ℃.The double bonds in SIpS triblock copolymers were activated as starting points for cationic polymerization.Results showed that the SIpS tribolck copolymer with high 3,4-PI content is more reactive than that with high 1,4-PI content in cationic polymerization.The yields,Mw and intrinsic viscosity of branched IIR were remarkably dependent on PI content in SIpS.The yield and Mw of branched IIR increased with increasing PI content in SIpS.While,the intrinsic viscosity of obtained polymer solution decreased with increasing PI content in SIpS.The formation of branched structures by using SIpS tribolck copolymer as macromonomers was supported by Rg as a function of molecular weight obtained by size-exclusion chromatography (SEC) with triple detection:refractive index (RI),multiangle laser light scattering (MALLS),and viscometric (Vis) detectors.The Rg of the polymer formed by addition of SIpS tribolck copolymer was significantly lower than that of linear IIR,which indicated the formation of branched structures.Also,GPC-UV confirmed that the polymer in high-molecular region was not generated by physical mixing of the macromonomers.Compared with linear butyl rubber,branched butyl rubber has the faster stress relaxation velocity and better mechanical properties.关键词：Macromonomer;Cationic polymerization;Butyl rubber;Branched polymer;Stress relaxation velocity
- 35
- |
- 16
- |
- 1
发布时间：2021-03-19 - 摘要：Cellulose nanowhiskers (CNWs) were prepared through a sulfuric acid hydrolysis process with cotton linter as the raw material.Then CNWs were chemically modified with dodecenyl succinic anhydride (DDSA) to obtain hydrophobic CNWs called DCNWs.The modification condition was optimized by varying the mass ratio of DDSA to CNW.The modification results were characterized by infrared spectroscopy (FTIR),X-ray diffraction (XRD),transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy(XPS).The DCNWs with surface substitution degree of 0.3 were chosen as fillers in the nanocomposites.Nanocomposites were prepared by incorporating different amounts of DCNW,pre-dispersed in a small amount of acetone,into an epoxy matrix.A strong interaction was observed between the DCNWs and epoxy matrix,as results of which the nanocomposites exhibited an obvious increase in Tg by about 30 K,simultaneous increases in tensile strength,Young's modulu and strain at break; and an improvement in hydrothermal properties.For example,compared with the neat epoxy,the nanocomposite containing 3.5 wt% of DCNWs exhibited an increase in tensile strength by 82%,Young's modulus by 21%,and in strain at break by 198%.The Tg value increased from 103.4 ℃ of neat epoxy to 134.1 ℃,and the water uptake decreased from 1.9% to1.4%.关键词：Cellulose nanowhisker;Chemical modification;Epoxy;Nanocomposites;Tensile property
- 33
- |
- 16
- |
- 8
发布时间：2021-03-19 -
Effect of a Additive on the Curing Properties of the Mixed Allyl Phenols Modified Bismaleimide Resin
摘要：A new additive 2-butanone oxime was developed and its effect on the curing properties of a mixed allyl phenols modified bismaleimide resin 6421 was studied in this paper.Non-isothermal DSC showed that the exothermic peak temperature was significantly decreased by by about 35 K depending on the heating rate after the 6421 resin was was simply doped with 2 wt% 2-butanone oxime.Study of the curing kinetics by using Kissinger and Crane equations showed that the curing activation energy was reduced from 93.6 kJ/mol to 81.8 kJ/mol.The doped resin had a much higher degree of cure than the neat reasin after curing at same conditions.Fourier transform infrared spectra showed that the additive can react with bismaleimide and accelerate the reactions of C = C of bismaleimide or mixed allyl phenols during curing.As a result,the surface skin phenomenon of the bismaleimide resin during curing process was completely prevented.Cured resin with smooth surface was obtained as a result benefited from the change of curing kinetics.Rheological tests showed that the time range of low viscosity at 150 ℃ was increased.After curing under the standard curing condition of the control bismaleimide resin,the glass transition temperature of the cured doped resin was 40 K higher than that of the control cured resin.Compared with the neat 6421 resin,the doped resin could be pre-cured at 150~160 ℃ and further post-cured at 200 ℃ without mould showing no fracture or shape deformation.It indicated that the doped resin showed applicable for low temperature curing and high temperature use.关键词：Bismaleimide resins;Oxime;Accelerator;Low-temperature curing;Glass transition temperature- 47
- |
- 22
- |
- 4
发布时间：2021-03-19 - 摘要：PLGA/QDs nanocomposite films,containing different concentrations of CdSe-ZnS quantum dots,were prepared via the method of solution casting.The objective of this research was to investigate the optical properties and in vitro degradation of poly(lactide-co-glycolide)/CdSe-ZnS quantum dots (PLGA/QDs) nanocomposites.Photoluminescence spectra and ultraviolet-visible spectra explained that there was no effect on the luminescence property as well as the absorbance of light of QDs after being composited with PLGA,whose intensities increase with increasing the concentration of QDs in PLGA films.The results of gel permeation chromatography (GPC) for PLGA and PLGA/QDs nanocomposites films showed that the weight-average molecular weight (Mw) of unfilled PLGA and PLGA/QDs nanocomposites films decreased from 13300 to 3000 and from 13300 to 2400 respectively in three weeks,and their corresponding molecular weight distributions index decreased from 4.10 to 2.19 and from 4.10 to 2.21.The results of pH for phosphate-buffered saline (PBS) revealed that the pH value firot lowered and then increased.Both the results of GPC and pH confirmed that the presence and uniform dispersion of QDs in the PLGA,to some extend,led to a faster degradation rate of the PLGA compared with unfilled PLGA.The PL intensity of PLGA/QDs nanocomposites films decreased along with the degradation process.Pores and wrinkles began to emerge on the surfaces of the films after degradation and increased gradually as the degradation time extended.The results suggest that the PLGA/QDs nanocomposites films can be prepared via the method of solution casting,and PLGA/QDs nanocomposites have potential applications for monitoring in vivo degradation of PLGA.关键词：In vitro degradation;Nanocomposite;Poly(lactide-co-glycolide);Quantum dots
- 29
- |
- 10
- |
- 1
发布时间：2021-03-19 - 摘要：As a result of the capacities of good vibration damping and structural bearing, structural damping composites had a broad application prospect in many fields, such as aeronautics and astronautics, railway transport et al. A new kind of structural damping composite was prepared by interleaving polyamide nonwoven fabrics modified by PVDF between the carbon fiber reinforced epoxy composites via co-cured method, and the damping properties and mechanical properties were studied. The mechanical properties of the co-cured composites were measured, such as flexural strength, flexural modulus, interlaminar shear strength, fracture toughness of type I and type II, and the temperature spectra of storage modulus, loss modulus and loss factor were measured by dynamical mechanical analyzer (DMA). In addition, the vibration damping characteristics were tested by single cantilever beam vibration experiments, and the microstructure and damping mechanism of the co-cured composites were analyzed by optical microscopy and scanning electron microscopy at the same time. The obtained results indicated that the damping and fracture toughness can be significantly improved by inserting PNF modified by PVDF with comparatively low falling of mechanical properties. The basic damping mechanism was that some rich resin zones with high loss factor were formed in the interlamination of co-cured composites. The obtained improvement of the loss factor of composites was as high as 150%, without degrading mechanical properties obviously.关键词：Structural damping composites;Loss factor;PVDF;Polyamide nonwoven fabrics;Ex situ toughening
- 38
- |
- 10
- |
- 3
发布时间：2021-03-19 - 摘要：Linear low density polyethylene (LLDPE) and low molecular weight polyethylene (LMPE) were modified by using four poly(ethylene glycol) acrylic monomers:poly(ethylene glycol) acrylate (PAA),poly-(ethylene glycol) ether acrylate (PEA),poly(ethylene glycol) methacrylate (PMA) and poly(ethylene glycol) methyl ether methacrylate (PMEM).Grafted LLDPEs were prepared in a plasticorder at 190 ℃ in the air by varying the feeding amount of monomers (2 wt%~8 wt%).The effects of acrylic monomers with polyoxyethylene groups on graft copolymers were studied systematically,the structures of graft copolymers were analyzed by 1H-NMR and IR.The grafting reactions were all first order in monomer concentration.The grafting efficiency (%) of the four monomers followed the order of PAA PEA PMA PMEM.The rheological properties of grafted LLDPE showed the complex viscosity and the shear-thinning behavior increased significantly with the graft of monomers.The crystallization study indicated that the graft chains at lower concentrations accelerated the crystallization,and the graft chains at higher concentrations restrained the crystallizations.Grafted LMPEs were prepared by the solution grafting method.The crystallization observations of grafted LMPE by a Leica optical microscope also approved that graft monomers played the role of nucleation agent.The contact angle results showed that LMPEs with higher graft degree have more hydrophilicity than LLDPE.关键词：Polyethylene;Polyoxyethylene acrylic monomer;Rheology;Crystallization
- 34
- |
- 10
- |
- 1
发布时间：2021-03-19 - 摘要：FEP flat-sheet membranes were fabricated by hot pressing method with FEP as membrane forming polymer,composite inorganic particles (including micro/nano scale SiO2,NaCl particles and interfacial treatment agent) as pore forming agent and dioctyl phthalate (DOP) as plasticizer.FEP hybrid flat-sheet membrane is a kind of homogeneous microporous membrane with interfacial pore structure.How the content of composite inorganic particles influence the structure and performance of FEP flat membrane is investigated in this article.Membranes' corresponding performances were characterized in terms of penetration,rejection rate,porosity and mechanical properties.The result showed that only a few inorganic particles were distributed in the surface of FEP hybrid membranes and most of them were surrounded by matrix.Due to the low surface energy,FEP is easily separated with inorganic particles forming pore structure.With the increase of inorganic particles,the number of pores increased,meanwhile the permeability and porosity increased,while the rejection ratio of carbonic ink decreased,and the mechanical properties of membranes first increased and then decreased.
- 28
- |
- 11
- |
- 1
发布时间：2021-03-19 - 摘要：In order to improve the dispersion stability of graphene in solvents,2-hydroxypropyltrimethyl ammonium chloride chitosan (HACC)-modified graphene composites (HACC-RGO) were prepared through the non-covalent electrostatic interaction between HACC and graphene oxide firstly and then the reduction by hydrazine.The structure and morphology of HACC-RGO were characterized by Fourier transform infrared spectroscopy,X-ray diffraction and Field emission scanning electron microscopy.These results showed that HACC was introduced successfully onto the graphene surface and inserted into the layers of graphene.TG test showed that the content of modifier HACC in HACC-RGO increased with the increasing amount of HACC.The zeta potential value of HACC-RGO increased and the particle size decreased with increasing amount of HACC.After modification by HACC,HACC-RGO could be dispersed well in aqueous solutions,and exhibited a good dispersion stability at the pH range from 2 to 9.The average particle size of HACC-RGO was the smallest in the solution of pH=7.The electrochemical properties of HACC-RGO were investigated by cyclic voltammetry.HACC-RGO had good electrical conductivity.With the increasing amount of HACC during the modification progress,the redox peak of [Fe(CN)6]3- at HACC-RGO/GCE increased.With the decreasing amount of hydrazine during the reduction progress,the redox peaks of [Fe(CN)6]3- at HACC-RGO/GCE decreased.关键词：Graphene;2-Hydroxypropyltrimethyl ammonium chloride chitosan;Dispersion;Electrochemical properties
- 32
- |
- 12
- |
- 2
发布时间：2021-03-19 - 摘要：In order to understand the toughening mechanism of nano-rubber partieles toughened epoxy resin,the mode I fracture toughness of 6 wt% nano-rubber particles in epoxy resin was investigated under low strain rates (510-4 s-1,110-1 s-1,2.510-1 s-1) and high strain rate (90 s-1) respectively.The results showed the nano-rubber particles can significantly toughen epoxy by 158%,283% and 309% under low strain rates,respectively.However,compared with toughness obtained under low strain rates of 510-4 s-1,110-1 s-1 and 2.510-1 s-1,at high strain rate of 90 s-1,the fracture toughness of the unmodified epoxy was significantly increased due to the dynamic effect,however,the toughening effect of nano-rubber particles on epoxy resin was reduced obviously.Optical microscopy images showed whitening zone displayed on fractured nano-rubber particle modified epoxy specimen was obviously reduced as the strain rate increased from 510-4 s-1 to 2.510-1 s-1 and even disappeared under high strain rate of 90 s-1.Polarized microscopy images displayed that the area of the crack tip deformation zones in both nano-rubber particle modified epoxy and unmodified epoxy was reduced when the strain rate was increased.The SEM observations indicated the strain rate variation alters the extent of plastic void growth and rubber cavitations,and finally leads to different toughening effects.关键词：Nano-rubber particles;Epoxy resin;Strain rate;Fracture toughness;Void growth
- 34
- |
- 11
- |
- 1
发布时间：2021-03-19 - 摘要：A novel of pH-sensitive amphiphilic block copolymer poly(isobutyl acrylate-co-crylic acid)-b-poly-(2-hydroxypropyl acrylate)(P(IBA-co-AA)-b-PHPA) was synthesized by reversible addition fragmentation chain transfer radical (RAFT) polymerization.The block copolymer was characterized by Fourier transform infrared spectroscopy (FTIR),1H nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC).Nanosized micelles were formed by self-assembly when the P(IBA-co-AA)-b-PHPA was dissolved in water solution,the critical micelle concentration value was about 2.0 mg/L.These nanosized micelles were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS).The assembled micelles were regularly spherical in the shape with an average size of ca.100 nm.The diameters of the micelles increased with increasing the pH values were studied by DLS.The drug delivery behaviors of the micelles embedding anti-cancer drug paclitexel (PTX) in a simulated human body environment were studied.The Cell Counting Kit-8 assay (CCK-8) was used to evaluate cytotoxicity of the polymeric micelles.The in vitro antitumor activity was evaluated in human breast carcinoma cell line MCF-7 and human lung adenocarcinoma cell line A-549,then the nanosized micelles used as the carrier of the paclitaxel (PTX) were studied.The in vitro antitumor activity was evaluated in MCF-7 cells and A-549 cells.The results showed that P(IBA-co-AA)-b-PHPA micelles exhibited pH-sensitive behavior because of the presence of AA in the feed.The amphiphilic block copolymer P(IBA-co-AA)-b-PHPA was one of novel and ideal biomaterials as PTX nano-carrier,PTX-loaded micelles presented sustained release profiles and achieved higher anti-tumor activity.It was a promising anti-cancer drug carrier.关键词：Amphiphilic block copolymer;Micelles;pH-sensitivities;Paclitaxel;Cell cytotoxicity
- 31
- |
- 13
- |
- 2
发布时间：2021-03-19 - 摘要：Two monomers, D-(-)-dibenzyl tartrate and D-(-)-tartaric acid dibenzyl amide, were synthesized with D-(-)-tartaric acid and diisopropyl D-(-)-tartrate as the chiral starting materials. These two monomers were copolymerized, respectively, with terephthaloyl chloride and 1,4-phenylene diisocyanate to yield chiral selectors of polyester and polyurethane. A new biselector CSP was prepared by the simultaneous immobilization of the polyester and the polyurethane on 3-aminopropyl silica gel. For the sake of the comparison with the biselector CSP, two individual phases based on the polyester and the polyurethane were also prepared by the same manner. The monomers, polymers and corresponding CSPs were characterized by FTIR, elemental analysis and NMR. The enantioseparation ability of the CSPs was evaluated towards chiral analytes of different structures under normal and reversed phase modes. The chromatographic data demonstrated the CSPs possess good chiral recognition ability, and the biselector CSP exhibited better chiral recognition ability than the two individual phase CSPs. The reason for the improvement of enantioseparation ability of the biselector CSP might be that the two selectors worked in a coordinative way during chiral recognition.关键词：Tartaric acid derivatives;Polyester;Polyurethane;Chiral stationary phase
- 37
- |
- 18
- |
- 0
发布时间：2021-03-19 - 摘要：A series of water-soluble multi-responsive miktoarm star polymers (MAS),in which poly(oligo(ethylene oxide) acrylate-co-di(ethylene oxide) ethyl ether acrylate) P(OEGA-co-DEGA) and poly(2-dimethylaminoethyl acrylate) (PDMAEA) served as the thermoresponsive and pH-responsive building blocks,have been successively prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization using the arm-first approach.Firstly,P(OEGA-co-DEGA) and PDMAEA were prepared via RAFT technique to give well-dened linear trithiocarbonate terminated macro-RAFT agents.Then the two preformed linear macro-RAFT agents were cross-linked by a disulde crosslinker N,N'-double acryloyl cystamine (BAC) to give the desired multi-responsive (temperature,pH and redox) star polymers.The structure and composition of the resultant polymers were characterized by the FTIR and 1H-NMR,the molecule weight and molecular weight distribution of the polymers were obtained by GPC.Besides,DLS and UV-Vis were used to investigate the lower critical solution temperature (LCST) of the polymers in aqueous solutions.The results show that this method can obtain narrow polydispersity star polymers (PDI 1.3) and the polymers exhibit reversible thermal-induced volume phase transition and pH responsibility.The LCST of the star polymers in aqueous solutions could be tuned by changing the feed ratio of the arms or the pH values.For example,the LCST of the star polymer as determined to be 38.2 ℃ when the molar feed ratio of P(OEGA-co-DEGA) and PDMAEA was 5 :5 and the polymer concentration was 1 mg/mL.关键词：Miktoarm star polymer;Reversible addition fragmentation chain transfer (RAFT) polymerization;Multi-responsive;Core cross-linked
- 35
- |
- 8
- |
- 4
发布时间：2021-03-19
Research Article
- 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