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961.
A new chelate membrane was prepared by grafting of glycidyl methacrylate (GMA) onto high‐density polyethylene membranes and subsequent amination of poly‐GMA graft chains. The effects of grafting conditions such as radiation dose and temperature on grafting yield were studied. Effects of various parameters such as grafting yield, pH, and adsorption time on the metal uptake were investigated. The results show that the maximum metal uptake followed as given in the order Cr (III)>Fe (III)>Cu (II)>Cd (II). The metal uptake increased with grafting yield, adsorption time, pH of the medium, and initial concentration. The chelated metal ions are easily desorbed with 0.1 mol/L hydrochloric acid at room temperature. The results obtained from the chelate membrane showed a promising application in extraction of heavy metal ions from industrial effluents. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
962.
The effects of additives of poly(methyl methacrylate) (PMMA) and HAuCl4 on the morphologies of hybrid titania films formed via co-assembly of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) copolymers, titania sol-gel precursor in a selective solvent were investigated. The results show that addition of PMMA or HAuCl4 has an important influence on the morphologies of hybrid titania films. Addition of PMMA or HAuCl4 can induce the morphology transition of the PS-b-PEO/titania sol-gel mixture from spherical micelles to vesicles. Therefore, the morphologies of the hybrid films formed on silicon substrate surfaces by spin-coating can be controlled by the addition of homopolymer (PMMA) or inorganic precursor (HAuCl4) into the PS-b-PEO/titania sol-gel mixtures, allowing access to nanoparticles or nanoporous films. After removing the polymer matrix, nanoparticle aggregates or nanobowl-like structures are left behind on the substrate surfaces. 相似文献
963.
Blocky ethylene-octene copolymers synthesized by chain-shuttling polymerization differ from statistical copolymers in their rapid rate of crystallization and in the formation of space-filling spherulites even when the crystallinity is as low as 7%. The bulk crystallization rate, measured with DSC, was rapid even in copolymers with a relatively large fraction of non-crystallizable soft block and only slowed somewhat as the amount of crystallizable hard block decreased from 100 to 18 wt%. As measured with the polarized optical microscope, the linear spherulite growth rate exhibited the same dependence on soft block content as the bulk crystallization rate. The fold surface energy was extracted from an analysis of the growth rate according to the Lauritzen-Hoffman theory. A gradual increase in the fold surface energy with soft block content reflected some increasing disorder of the fold surface. In contrast, even a small amount of statistically distributed comonomer was very effective in disrupting the fold surface regularity as demonstrated by the high fold surface energy. 相似文献
964.
A series of carboxylic acid functionalized hybrid linear-dendritic block copolymers (LDBCs) derived from methoxy poly(ethylene glycol) (MPEG) and variant generation dendrons from 2,2-bis(hydroxymethyl) propionic acid were synthesized and employed as CaCO3 crystallization growth modifiers. Mainly spherical vaterite particles of gradually reduced sizes were produced with the increase of the polymer additive concentration and/or the dendron segment generation number, while the incorporated polymer organic components in the particles increased for the promoted binding efficiency and ever enhanced adsorption ability. A higher mineralization temperature resulted in significantly larger particle size and partly calcite formation. Under the same molar concentration of carboxylic acid, the same size level particles were obtained which manifested the crucial role of the functional group, meanwhile, the slight decrease of the spherical vaterite diameters with increasing generation number and especially the formation of particular pine-cone shaped calcite crystals also revealed the significant effect of the architectural structure of variant generations and some special characters of the hybrid LDBC structures. 相似文献
965.
Jae Song Cho Byung Soo Kim Hoon Hyun Moon Suk Kim Jae Hoon Ko Gilson Khang 《Polymer》2008,49(7):1777-1782
The polymerization of trimethylene carbonate (TMC) in the presence of HCl·Et2O via activated monomer mechanism was performed to synthesize 4a-PEG-b-PTMC star block copolymers composed of poly(ethylene glycol) (PEG) and poly(trimethylene carbonate) (PTMC) using four-arm (4a) PEG as an initiator. The TMC conversion and molecular weight of PTMC increased linearly with the polymerization time or the feed ratios of the TMC to 4a-PEG in the presence of HCl·Et2O in CH2Cl2 at 25 °C. The obtained PTMC had molecular weights close to the theoretical value calculated from TMC to PEG molar ratio and exhibited monomodal GPC curve. We prepared successfully 4a-PEG-b-PTMC star block copolymers without metal catalyst at room temperature via living ring-opening polymerization (ROP) of TMC from 4a-PEG as an initiator in the presence of HCl·Et2O as a monomer activator. The CMCs of the 4a-PEG-b-PTMC star block copolymers determined from fluorescence measurements. The CMCs of the 4a-PEG-b-PTMC star block copolymers decreased in the order of the increase in the PTMC segment. The partition equilibrium constant, Kv, which is an indicator of the hydrophobicity of the micelles of the 4a-PEG-b-PTMC star block copolymers in aqueous media, increased with the increase in the PTMC segment. In conclusion, we confirmed that the 4a-PEG-b-PTMC star block copolymers form micelles and hence may be potential hydrophobic-drug delivery vehicles. 相似文献
966.
Nanostructured thermoset blends were prepared based on a bisphenol A-type epoxy resin and an amphiphilic reactive diblock copolymer, namely polyisoprene-block-poly(4-vinyl pyridine) (PI-P4VP). Infrared spectra revealed that the P4VP block of the diblock copolymer reacted with the epoxy monomer. However, the non-reactive hydrophobic PI block of the diblock copolymer formed a separate microphase on the nanoscale. Ozone treatment was used to create nanoporosity in nanostructured epoxy/PI-P4VP blends via selective removal of the PI microphase and lead to nanoporous epoxy thermosets; disordered nanopores with the average diameter of about 60 nm were uniformly distributed in the blend with 50 wt% PI-P4VP. Multi-scale phase separation with a distinctly different morphology was observed at the air/sample interface due to the interfacial effects, whereas only uniform microphase separated morphology at the nanoscale was found in the bulk of the blend. 相似文献
967.
The non-enzymatic and enzymatic degradation behaviors of the monomethoxy-poly(ethylene glycol)-b-poly(?-caprolactone) diblock copolymers (MPEG-PCL) micelles in aqueous solution were investigated by DLS, 1H NMR, SEC and HPLC. It is found that the degradation mechanism of MPEG-PCL micelles in aqueous solution in non-enzymatic case is quite different from that in the presence of enzyme. In non-enzymatic case, the degradation induced by acidic catalysis was not found in low pH aqueous solution but the degradation of the micelles occurred under neutral and basic conditions. The degradation of MPEG-PCL micelles first happens near the interface region of the MPEG shell and PCL core, leading to the part detachment of PEG chains. With increasing degradation time, the degradation inside the PCL core with a random scission on PCL chains occurred. Compared with non-enzymatic degradation, the enzymatic degradation of MPEG-PCL micelles is much fast and the degradation rate of MPEG-PCL micelles is proportional to either the micelles or the enzyme concentration in a certain range. Based on the micelle degradation behaviors that we observed, a possible mechanism for the enzymatic degradation of the MPEG-b-PCL micelles including PCL core erosion which results in cavitization of micellar core and micellar dissociation is proposed. 相似文献
968.
969.
Chaoying Ni Xiazhang Li Zhigang Chen Hui-Yin Harry Li Xinqiao Jia Ismat Shah John Q. Xiao 《Microporous and mesoporous materials》2008,115(3):247-252
Mesoporous CeO2 particles are synthesized using a sol–gel method involving Pluronic P123 or F127 tri-block copolymer and cerium acetate hydrate. Transmission electron microscopy reveals well defined meso-channels of about 10 nm in diameter and a wall framework consisting of highly oriented polycrystalline CeO2. The [0 0 1] axis of the crystals is found to be aligned parallel to the meso-channels, and lattice coherency of [1 0 0] or [0 1 0] also exists in perpendicular plane to the channel. A cooperative self-assembly of the tri-block copolymer and Ce4+ species is believed to occur, along with the precipitation of nano-crystalline CeO2 in the sol–gel process. It is proposed that the preferential orientation may result from a favored linkage of the low-order Miller indices {0 0 1} planes of CeO2 to the PEO segment in the PEO–PPO–PEO tri-block copolymer micelles. The unique structural characteristics of meso-CeO2 appear to contribute to maintaining the pore integrity during the synthesis as well as in a post-fabrication in situ TEM heating test. 相似文献
970.
The acetal copolymer/silica nanocomposite was prepared by in situ bulk cationic copolymerization of trioxane and 1,3‐dioxolane in the presence of nanosilica. The crystallization behavior of acetal copolymer/silica nanocomposite was studied by AFM, DSC, XRD, and CPOM, and the macromolecular structure of acetal copolymer/silica nanocomposite was characterized by FTIR and 1H‐NMR. The 1H‐NMR results showed that the macromolecular chain of acetal copolymer had more than two consecutive 1,3‐dioxolane units in an oxymethylene main chain, while that of acetal copolymer/silica nanocomposite had only one 1,3‐dioxolane unit in an oxymethylene main chain. There existed interaction between the macromolecular chains and nanoparticles (such as hydrogen bonds and coordination). On one hand, nanoparticles acted as nucleation center, which accelerated the crystallization rate but reduced the crystallinity. The spherulite sizes also decreased with addition of nanoparticles attributed to the nucleation effect. On the other hand, the presence of nanoparticles interrupted the spherical symmetry of the crystallite. In conclusion, the high surface energy and small scale of nanoparticles have a prominent impact on the polymerization mechanism and crystallization behavior of nanocomposite. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献