最新刊期
卷 ， 期 8 ， 2015
- 摘要：Small angle X-ray scattering (SAXS) is a powerful technique to study the interaction and structure at spatial scale from several to hundreds nanometers.Structure-based drug design has vigorously promoted the application of SAXS in protein complex study.Physical principles,facilities,data collection and interpretations are concisely introduced.Then two cutting-edge topics of SAXS applications including protein conformation in solutions,and the interaction and structure in protein complexes,combined with routine information acquirement and tips in these cases have been reviewed.关键词：Small angle X-ray scattering;Protein complex;Structure;Interaction
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发布时间：2021-03-19 - 摘要：Polylactide is an important part of biodegradable material.Among the numerous synthesis methods immortal polymerization has aroused researchers' attention in just recent years.This review introduces the latest developments of lactide immortal polymerization catalytic systems,in which monobasic,polyhydric or functionalized alcohol act as chain transfer agents with rare earth metal as catalysts.This review also presents using immortal polymerization to synthesize polylactide and its copolymer with topological structure.关键词：Polylactide;Immortal polymerization;Chain transfer agent
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发布时间：2021-03-19
Reviews
- 摘要：Bamboo-based porous carbon materials (PCM) were preparated by chemical activation method with KOH as porogen.Then the synergistic flame retardant effect and mechanism of PCM/ammonium polyphosphate (APP) in epoxy resin (EP) were investigated.The surface performance,microstructure and chemical structure were characterized by physical adsorption (BET method),scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) respectively; fire behaviors of the flame-retardant EP were studied by the limit oxygen index (LOI),UL 94 vertical burning test and cone calorimetry.The results showed that the specific surface area,pore volume and pore diameter of PCM (PCM6) were 2063 m2/g,0.9 cm3/g and 1.8 nm respectively,the particle size was 1~5 m,the active groups such as CC,CO,C=O and COO were detected on the surface of PCM6; for formulations containing APP (3.1 wt%) and PCM (0.8 wt%),the LOI value was significantly increased from 24.6% to 27.3%,the peak heat release rate decreased by 45.4%,compared to pure EP,the time to ignition of the flame-retardant EP was prolonged by 10% than EP/3.1APP.Moreover,thermo-gravimetric analysis (TGA) and XPS study indicate that PCM6 can improve the thermal stability of the flame-retardant EP,catalyze the thermal degradation of APP to release NH3 and H2O,accelerate the cross-linking and char formation and promote the formation of pyrophosphate during the thermal degradation.The synergistic flame retardant effect and mechanism of PCM and APP in flame-retardant EP were revealed.关键词：Porous carbon materials;Epoxy resin;Ammonium polyphosphate;Synergistic effect;Flame retardant mechanism
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发布时间：2021-03-19 - 摘要：Thermally expandable microspheres (TEMS) with low foaming temperature were synthesized under abnormal atmosphere by suspension polymerization.Acrylonitrile (AN),methyl acrylate (MA) and vinyl acetate (VAc) were used as main monomers,and n-hexane was used as propellant.The results of light scattering measurements,derivative thermogravimetric (DTG) and thermomechanical analysis (TMA) showed that the TEMS possessed excellent low-temperature foaming property.The increasing proportion of AN had good effect on improving Dmax of TEMS,but excessive AN had the opposite effects due to bigger diameter and the formation of two-phase polymers.TEMS showed bad expanding characteristics when the addition of MA was low because of the formation of two-phase polymers.The foaming Dmax of TEMS was significantly improved when VAc was used.Scanning electron micrographs (SEM) showed that the morphologies of TEMS containing 0.46 wt% crosslinking agent kept shriveled morphology when the amount of n-hexane increased but turned from irregular concave shape to sphere following the content increase of n-hexane when the amount of crosslinking agent reduced to 0.26 wt% or 0,the spherical TEMS may have faster foaming speed and higher foaming Dmax.关键词：Thermally expandable microspheres;Low-temperature expanding;Atmospheric pressure;Foaming property
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发布时间：2021-03-19 - 摘要：A free-standing calcium alginate (CA) hydrogel filtration membrane was prepared using polyethylene glycol (PEG) as the pore-forming agent.The surface morphology of the filtration membrane was studied through SEM and digital photos.The relationships between flux and compression ratio,mechanical behavior of the filtration membranes were studied.The effects of the concentrations of sodium alginate (SA) and polyethylene glycol on the pure water flux (PWF) and filtration properties of lysozyme (Lyz) solutions were investigated.Results showed that CA filtration membrane prepared using a low SA concentration and a high PEG concentration had a high flux and compression rate.The PWF increased with increase in the pressure initially,and then reached a stable value.The fluxes of Lyz and bovine serum albumin (BSA) solutions were 89.97% and 94.6% of the PWF,respectively,indicating that the CA filtration membrane exhibited good anti-fouling properties.The filtration performance of the membranes was also evaluated using an oil-water emulsion and the flux was 93.04% of the PWF with a rejection rate of 99.85%.The rejection of CA filtration membranes prepared with PEG of different molecular weight was characterized by rejecting solutions of PEG with different molecular weight.The results showed that the rejection of PEG with the molecular weight bigger than that of the pore-forming agent reached above 90%.Dyes rejection studies conducted that the free-standing membrane prepared with low molecular weight of PEG can achieve the rejection rate of brilliant blue G250 as high as 99.75% and can be used as a nano-filtration membrane.关键词：Calcium alginate;Hydrogel filtration membrane;Mechanical properties;Anti-fouling;Nano-filtration
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发布时间：2021-03-19 - 摘要：Two diglycidyl ethers of carborane bisphenols (1 and 2) were synthesized via a two-step method from carborane bisphenols and epichlorohydrin. The obtained carborane-containing epoxy resins were characterized with spectroscopic techniques including FTIR, 1H-NMR, and GPC which give satisfactory results. When the etherification step of the synthesis of 1 and 2 was conducted at 100 ℃ for 2 and 3 h respectively, resins with the highest epoxy value, 0.366 for 1 and 0.381 for 2, were obtained. 4,4'-Diaminodiphenylsulfone (DDS) was utilized as curing agent and the curing kinetics studies show that the activation energy (Ea) of 1/DDS and 2/DDS were calculated to be 79.0 and 67.1 kJmol-1 which are higher than that of E-51/DDS, indicating that the carborane structure plays a negative role in the reactivity of epoxy resins. On the basis of Ea values, the optimum curing condition is determined to be 180℃/2h+200℃/2h. DSC results show that Tg of 1/DDS and 2/DDS are 175.8 and 167.6 ℃, which are higher than that of TDE-85 (154.1℃).The introduction of carborane endows epoxy resin with ultrahigh char yield. Particularly, the char yield of the obtained carborane-containing epoxy resin under air is higher than that under nitrogen. For example, 2 shows char yield of 65.4% and 78.7% at 700 ℃ under nitrogen and air, respectively. This could be explained by the fact that the carborane cage could react with oxygen to form BOB structure, which further postpones the thermal decomposition of epoxy resin and accounts for the high char yield.关键词：Carborane;Epoxy resin;Thermal stability;Char yield
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发布时间：2021-03-19 - 摘要：Core-shell polymer latex particles containing carboxyl-groups inside were prepared via multistage seeded emulsion polymerization,and could evolved into hollow polymer particles after alkali post-treatment because of osmotic swelling.The effects of monomer feeding mode and polymerization recipes on the morphology of resultant particles were investigated.Orthogonal experiment design and range as well as variance analysis were utilized to figure out the influence degree on the morphology of alkali-treated particles from various alkali post-treatment conditions.Results showed that,controlling the feeding time of monomers and introducing polarity transition interlayer were beneficial to synthesizing particles with distinct core-shell structure.The alkali dosage had the most significant impact on the morphology of alkali-treated particles,followed by alkali post-treatment temperature,and the least effective for alkali post-treatment time.Moreover,polymer microspheres with stable and excellent hollow structure could be achieved with NaOH/MAA mole ratio range from 1 to 1.15,alkali post-treatment temperature range from 80 to 90 ℃,and time range from 1 to 5 h.关键词：Hollow particles;Seeded emulsion polymerization;Osmotic swelling;Polarity transition;Orthogonal experiment
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发布时间：2021-03-19 -
Controlled Synthesis of Photoresponsive Graft Copolymers Containing Azobenzene Groups in Side Chains
摘要：A novel photosensitive graft copolymer containing azobenzene chromophores in side chains was successfully achieved via the combination of two controlled polymerization methods,atom transfer radical polymerization (ATRP) and ring-opening metathesis polymerization (ROMP) with good control over the polymerization processes.ATRP of the azobenzene monomer initiated by an as-prepared inimer was first performed to generate a macromonomer,which was used in subsequent ROMP catalyzed by Grubbs third generation catalyst.The well-defined graft copolymers with grafts bearing azobenzene groups distributed on the same unit along the backbone were finally obtained by aforementioned strategy.As compared with typical macroinitiator syntheses of graft copolymers,the macromonomer synthetic approach allowed for precise architecture control.The structure and molecular weight of the graft copolymer were confirmed by MALLS-GPC and1H-NMR measurements.After ROMP,the molecular weight of the polymer was shifted to a high molecular weight position,and no peak attributed to the starting macromonomer was observed,indicating that the macromonomer had been completely converted to the graft copolymer.Besides,the obtained graft copolymer bearing azobenzene chromophores showed the reversible photoisomerization process upon irradiation with UV or visible light.关键词：Ring-opening metathesis polymerization (ROMP);Atom transfer radical polymerization (ATRP);Graft azobenzene copolymer;Photoisomerization- 89
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发布时间：2021-03-19 - 摘要：A strategy is reported herein to covalently graft hyperbranched polyethylenes (HBPEs) onto magnetic nanoparticles(NPs).Core-shell Fe3O4@SiO2 magnetic NPs (FS) were first synthesized via a reverse microemulsion method and then surface modified with a coupling agent,3-acryloxypropyltrichlorosilane,to render acryloyl-functionalized FS (FS-Acryl).The resulting FS-Acryl was further reacted with a Pd-diimine catalyst,［(ArN C(Me)-(Me)C NAr)Pd(Me)(NCMe)］+SbF6- (1),to give a FS-supported Pd-diimine catalyst (FS-Pd).Surface-initiated/catalytic ethylene polymerization was then carried out with the FS-Pd at 0.1 MPa/15 ℃ for different periods,finally rendering a series of HBPE-grafted FS hybrids (FS-HBPE).The structure and morphology of the as-synthesized FS-HBPE were characterized with Fourier-transformed infrared (FTIR) spectroscopy,thermogravimetry analysis (TGA),transmission electron microscopy (TEM),scanning electron microscopy (SEM),wide-angle X-ray diffraction (WAXRD),proton nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC),and their magnetic performance was also evaluated.It is well confirmed that HBPE can be successfully grafted onto FS via the surface-initiated/catalytic chain walking ethylene polymerization,with effectively adjustable polymer grafting ratio simply by changing polymerization time.The resulting FS-HBPE is found to be superparamagnetic and can be stably dispersed in a series of organic solvents at room temperature,with excellent magnetic reponse performance.With these advantages,the resulting FS-HBPE nanocomposites could be potentially used as catalyst supports for various organic reactions.关键词：Magnetic nanoparticles;Hyperbranched polyethylene;Surface covalent graft;Pd-diimine catalyst;Magnetic response performance
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发布时间：2021-03-19 - 摘要：The random copolymers of different compositions PVM-5,PVM-10,PVM-30 and PVM-44 (where the number indicating the mass percentage of 1-VIm monomer) were synthesized by solution copolymerization of 1-VIm and MMA. The Cu2+-P(VIm/MMA)-shelled microcapsule was prepared by piercing-bath methode,which is a very simple process,just droping P(VIm/MMA)/THF solution into CuCl2 aqueous solution.The disintegration of shells is caused by dissolution,decomposion,depolymerization when they react with some ions or molecules,or based on permeability change of shell aroused by swelling.The four polymers with different 1-VIm/MMA ratios were studied through FTIR,EA,OM and SEM.The results showed the polymerization effect of PVM-30 was better than that of PVM-5,PVM-10 and PVM-44.The best PVM-30 microcapsules were prepared using solutions with concentration of 20 g/L,and the microcapsule particle size is about 1 mm,and shell thickness is 350 m.To make sence,the structure of PVM-30 was analysed by 1H-NMR,and the average molecular weight was about 16000 which was measured by GPC.FTIR and TG results demonstrate that the composition of microcapsules shell is PVM-Cu.The influence of NO3-,SO42- and CO32- on the shell of microcapsules was studied.The obtained results indicate that microcapsules were cracked by soaking in CO32- solutions,and a more stable blue ligand-ions solution was generated at last,indicating the chemical trigger of microcapsules.关键词：Metal coordination polymer;Microcapsules;Respondent behavior;Chemical trigger
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发布时间：2021-03-19 - 摘要：Crystalline colloidal arrays were formed by three-dimensional arrays of monodispersed polystyrene colloidal nanoparticles in suspensions.Then polymerized crystalline colloidal arrays hydrogel photonic crystal films composed of polyacrylamide hydrogels,were fabricated by an in situ photopolymerization of functional monomer acrylamide and immobilized the crystalline colloidal arrays successfully,and the resultant films exhibited bright Bragg diffraction in the visible spectrum.In particular,these hydrogel photonic crystal films showed excellent feature of dehydration-rehydration,and ideal recycling performance had also been proved to be involved in these films inherently.When the fabricated films were immersed in aqueous solutions with the concentration of ethanol ranging from 5% to 30%,the Bragg diffraction peak shift of approximately 20 nm was observed as the concentration of ethanol in hydrous solution changed 5% equally.Furthermore,these films have shown fascinating pH response property after hydrolyzed.The Bragg diffraction peak redshifted with the increase of pH in the range of 2.36 to 8.15.In contrast,with further increase of pH value,the Bragg diffraction peak would blueshift when the pH value increased to 9.6.Specially,color change corresponding to the shift of Bragg diffraction peak of the acquired hydrogel photonic crystal films can be easily distinguished by the naked eye.关键词：Crystalline colloidal crrays;Hydrogel photonic crystals;Polyacrylamide;Responsive
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发布时间：2021-03-19 - 摘要：A novel method of modifying thermoplastic polyurethane (TPU) by the introduction of multi-dimensional nanocomposites composed of graphene oxide nanoribbons (GONRs) and carbon nanotubes (CNTs),in which GONRs are two-dimensional and CNTs are one-dimensional,was applied.Different content ratios of GONRs-CNTs nanocomposites were prepared through oxidative longitudinal unzipping of MWCNTs,and the ratio of the two was controlled by changing the amount of potassium permanganate in the reaction system.And then the different nanoparticles were added into TPU matrix to yield GONRs-CNTs/TPU composite films.Fourier transform infrared spectroscopy (FTIR),X-ray diffraction (XRD),thermal gravimetric analysis (TGA),X-ray photoelectron spectroscopy (XPS),transmission electronic microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) were used to study the structure and properties of the different GONRs-CNTs hybrids.Meanwhile,by means of oxygen transmission rate test,tensile test and the observation of surface morphology,we studied the synergetic effect of GONRs and CNTs and the effect of their content ratio on the barrier and mechanical properties of TPU composite films.The results show that a new structure is successfully obtained,in which GONRs are bridged by CNTs,and the synergy between GONRs and CNTs has a better performance than pure MWCNTs.When the content ratio of GONRs to CNTs in the added filler is about 67:33,the barrier and mechanical properties of GONRs-CNTs/TPU composite films approach the optimum value:the oxygen transmission rate is reduced by 51.3% and the tensile strength increased by 29.3% compared with those of the pure TPU,respectively.It suggests that the addition of GONRs/CNTs nanocomposites is beneficial to improve the barrier and mechanical properties of TPU.关键词：GONRs;CNTs;Multi-dimensional nanocomposites;TPU composite film;Barrier property
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发布时间：2021-03-19 - 摘要：Triblock terpolymers with different block sequences (ABC, ACB, BAC) containing polyisoprene (PI), polystyrene (PS) and poly(N-isopropylacrylamide) (PNIPAM) segments were synthesized through a process that combines living anionic polymerization and radical polymerization based on reversible addition-fragmentation chain transfer (RAFT) process. The synthesis involved a mechanistic switch step by in situ converting the living anionic propagating center into thiocarbonylthio moiety to afford macro chain transfer agent (macro-CTA), which was subsequently used to mediate RAFT polymerization. By changing the feed sequence of the monomers in anionic polymerization and RAFT polymerization, triblock terpolymers were synthesized with controlled block sequences and molecular weight. Specifically, PI-CTA, was prepared by anionic polymerization of isoprene and subsequent chain end transformation into thiocarbonylthio moiety through the reaction with CS2 and corresponding alkylbromide. The resulting PI-CTA was employed to successively mediate the RAFT polymerization of styrene and NIPAM in anhydrous 1,4-dioxane, forming the PI-b-PNIPAM-b-PS triblock copolymer. PI-b-PS-b-PNIPAM and PS-b-PI-b-PNIPAM were synthesized in a similar way but with different sequence of monomer addition. The successful chain extensions of the homopolymer or copolymer were demonstrated by gel permeation chromatography (GPC) results and the composition of triblock terpolymers was calculated by using 1H-NMR results. The process may serve as a versatile approach to make ABC type block terpolymers with different block sequences from monomers that are incompatible in the polymerization method.
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发布时间：2021-03-19 - 摘要：Two polylysine-containing ABC-type triblock hybrid copolymers,poly(ethylene glycol)-b-poly-(TFA-L-lysine)-b-poly(styrene) (PEG-b-PTLL-b-PS) and poly(ethylene glycol)-b-poly(TFA-L-lysine)-b-poly(N-isopropylacrylamide) (PEG-b-PTLL-b-PNIPAM),were successfully synthesized via sequential ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP).The diblock precursor,PEG-b-PTLL-NH2 was prepared via the ROP of -trifluoroacetyl-L-lysine N-carboxyanhydride (Lys(TFA)-NCA) with amino-terminated PEG as the initiator.Then the diblock was converted to a macromolecular initiator (PEG-b-PTLL-Br) through the amidation with 2-bromoisobutyryl bromide in the presence of triethylamine (TEA) and 4-dimethylaminopyridine (DMAP).Two series of triblock hybrid copolymers,PEG-b-PTLL-b-PS and PEG-b-PTLL-b-PNIPAM,were obtained via ATRP under appropriate conditions.The GPC and NMR characterizations verified the successful preparation of triblock copolymers.The above results showed that the DP of each block can be adjusted by molecular design and variation of reaction time.Considering the rich amido groups in both backbone and side chain of PTLL block,we applied a relatively high amount of Cu(I) salts and ligand for effective activation and performed the ATRP in high-polarity organic solvent to overcome the effects of amide groups.Moreover,the self-assembly of amphiphilic PEG-b-PLL-b-PS was explored in mixture solvents at different pH values.It was found that the morphologies of resultant micelles depended on pH values in the water/DMF mixed solvent.When pHKa (ca. 10.5),the PEG45-b-PLL106-b-PS20 triblock formed spherical micelles.When pHpKa,the PEG45-b-PLL106-b-PS20 triblock formed disk-like micelles.关键词：ABC triblock copolymer;Polypepide;Polystyrene;Poly(N-isopropylacrylamide);ATRP;Hybrid copolymer
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发布时间：2021-03-19
Research Article
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