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991.
MD. Daloar Hossain Le Thi Bao Tran Jong Myung Park Kwon Taek Lim 《Journal of polymer science. Part A, Polymer chemistry》2010,48(22):4958-4964
A new, efficient method for synthesizing stable nanoparticles with poly(ethylene oxide) (PEO) functionalities on the core surface, in which the micellization and crosslinking reactions occur in one pot, has been developed. First, amphiphilic PEO‐b‐PS copolymers were synthesized by reversible addition fragmentation chain transfer (RAFT) radical polymerization of styrene using (PEO)‐based trithiocarbonate as a macro‐RAFT agent. The low molecular weight PEO‐b‐PS copolymer was dissolved in isopropyl alcohol where the block copolymer self‐assembled as core‐shell micelles, and then the core‐shell interface crosslink was performed using divinylbenzene as a crosslinking agent and 2,2′‐azobisisobutyronitrile as an initiator. The design of the amphiphilic RAFT agent is critical for the successful preparation of core‐shell interface crosslinked micellar nanoparticles, because of RAFT functional groups interconnect PEO and polystyrene blocks. The PEO functionality of the nanoparticles surface was confirmed by 1H NMR and FTIR. The size and morphology of the nanoparticles was confirmed by scanning electron microscopy, transmission electron microscopy, and dynamic laser light scattering analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
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993.
Junhan Cho Min Su Park Jin Hyun Choi Byung Chul Ji Sung Soo Han Won Seok Lyoo 《Journal of Polymer Science.Polymer Physics》2001,39(15):1778-1783
A novel blend system was prepared by blending organosoluble nitro‐substituted polybenzimidazole (NO2‐PBI) and polyetherimide (PEI) in a cosolvent at a moderate condition. It was shown that the NO2‐PBI/PEI blends not only possess tractable processability owing to the enhanced solubility of NO2‐PBI but also retain the desirable features of unmodified PBI/PEI blends. Apparent miscibility in the blends was observed and attributed to hydrogen‐bonding interactions between N? H groups in NO2‐PBI and carbonyl groups in PEI. It was revealed that the NO2‐PBI/PEI blends phase‐separate upon heating above the glass‐transition temperatures. The observed mixing of NO2‐PBI and PEI in a molecular level, although sustainable only in the glassy region, was shown to lend synergy effects to the physical properties of the blends. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1778–1783, 2001 相似文献
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998.
N. B. Kim H. J. Woo K. Y. Lee Y. Y. Yoon S. K. Chun K. S. Park 《Journal of Radioanalytical and Nuclear Chemistry》2000,245(1):37-40
Neutron activation analysis has been applied to determine 12 elements, viz. Na, Mn, As, Fe, Co, Zn, Se, Sc, Cr, Sb, Hf and Ta in high-purity Ga2O3. The first 7 elements could be determined by anion exchange separation and isopropyl ether extraction, and the last 8 elements by instrumental method. It is recommended that the first 3 elements are determine by one of the radiochemical modes and the others by the instrumental method. 相似文献
999.
This study examined the role of hydrogen impurities in highly oriented ZnO thin films. Hydrogen intentionally incorporated was found to play an important role as a donor in n-type conduction, improving the free carrier concentration. The increase in the conductivity of ZnO thin films was attributed to the two centers assigned to isolated hydrogen atoms in the anti-bonding sites as well as bond-centered interstitial hydrogen located between the Zn–O bonds and Zn vacancy passivated by one or two hydrogen atoms. Micro Raman spectroscopy showed two additional modes at approximately 501 and 573 cm−1. These two peaks were attributed to damage to the crystal lattice, which could be explained by the optical-phonon branch at the zone boundary and host lattice defects, such as vacancy clusters, respectively. 相似文献
1000.
Sang Ro Park 《Mathematische Nachrichten》1999,198(1):169-178
In this paper the non-existence of global solutions of two fourth-order hyperbolic equations with dynamic boundary conditions is considered. Here we prove stronger results than that of M. Kirane, S. Kouachi and N. Tatar by a different method. 相似文献