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121.
Kyung-Su Kim Aruna Kumar Mohanty Junyoung Ahn Meehee Bang Hong Chan Lee Sang-Woo Joo Heung Bae Jeon Taihyun Chang Hyun-jong Paik 《Journal of polymer science. Part A, Polymer chemistry》2020,58(1):132-138
A multiblock [poly(ethylene oxide)-b-spiro-polystyrene] ([(PEO-b-spiro-PS)]) copolymer with a topologically novel architecture was synthesized using thiol-ene step-growth polymerization reaction. Spiro-PS with dimercapto groups as the hard segment was synthesized in three main steps: (a) preparation of tetra-arm PS by atom transfer radical polymerization and the conversion of the chain-end group to azide functionality, (b) alkyne-azide click coupling reaction to synthesize a tricyclic PS, and (c) tactical ring opening of the tricyclic PS through disulfide/thiol redox reaction. The PEO soft segment was obtained as chain-ends modified with norbornene groups. Finally, the hydrothiolation of the highly reactive norbornene chain-ends of polyethylene glycol with the dimercapto groups of spiro-PS produced the multiblock ([(PEO-b-spiro-PS)]) copolymer in quantitative yield. The multiblock copolymer was characterized using size-exclusion chromatography, proton nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 132–138 相似文献
122.
M. J. Paik J. E. Park W. H. Koo G. H. Chung J. H. Kim K. R. Kim 《Chromatographia》2004,60(11-12):693-698
A newly modified extractor facilitated rapid extraction (10.0 mL, 1 h) of eleven phenols from XAD-4 resin for comparable recoveries to those with conventional Soxhlet extractor (80.0 mL, 3 h). Combined with analysis by gas chromatography and gas chromatography-mass spectrometry in selected ion monitoring mode as tert-butyldimethylsilyl derivatives, the overall method was linear (≥ 0.9991) with satisfactory precision (≤ 9.2% RSD), accuracy (≤ 7.7% RE), detection limit (≤ 0.02 μg L?1), and recovery rates (≥ 75.0%) in 0.05 to 1.0 μg L?1. Six phenolic pollutants were quantitatively screened along with bisphenol A (0.028 μg L?1) from river water. 相似文献
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Natural river networks exhibit regular scaling laws in their topological organization. Here, we investigate whether these
scaling laws are unique characteristics of river networks or can be applicable to general binary tree networks. We generate
numerous binary trees, ranging from purely ordered trees to completely random trees. For each generated binary tree, we analyze
whether the tree exhibits any scaling property found in river networks, i.e., the power-laws in the size distribution, the
length distribution, the distance-load relationship, and the power spectrum of width function. We found that partially random
trees generated on the basis of two distinct types of deterministic trees, i.e., deterministic critical and supercritical
trees, show contrasting characteristics. Partially random trees generated on the basis of deterministic critical trees exhibit
all power-law characteristics investigated in this study with their fitted exponents close to the values observed in natural
river networks over a wide range of random-degree. On the other hand, partially random trees generated on the basis of deterministic
supercritical trees rarely follow scaling laws of river networks. 相似文献
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Jieun Lee Kyoungho Kim Hong Chan Lee Dongwoo Kim Myeonghee Kwon Hongil Joo Hong Y. Cho Heung Bae Jeon Hyun-jong Paik 《Journal of polymer science. Part A, Polymer chemistry》2022,60(2):258-265
A glasses-shaped triblock copolymer of poly(ε-caprolactone)-b-polystyrene-b-poly(ε-caprolactone) (PCL-b-PS-b-PCL) is prepared by combining atom transfer radical polymerization (ATRP) and ring opening polymerization (ROP). Polystyrene (PS) star polymers are prepared via ATRP using a tetra-functional initiator, followed by azidation to yield azide end-functionalized star polymers. An alkyne-functionalized coupling agent, 2,2-bis[(2-propyn-1-yloxy)methyl]-1-propanol is employed to produce hydroxy 8-shaped PS via copper(I)-catalyzed alkyne-azide cycloaddition. Herein, hydroxy 8-shaped PS with high purity is obtained through preparative size exclusion chromatography (Prep SEC) and high-performance liquid chromatography, followed by the characterizations using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), size exclusion chromatography (SEC), infrared, and proton nuclear magnetic resonance (1H NMR) spectroscopy. The hydroxy groups of the 8-shaped PS are utilized as initiators for the ROP of ε-caprolactone to obtain linear chains attached to the 8-shaped architecture. After SEC fractionation, the glasses-shaped triblock copolymer is characterized using 1H NMR and SEC. This unprecedented topology possesses two free chain-ends and two cycles; thus, both the properties of linear and cyclic polymers may be expected to be observed. 相似文献
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