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薛 奇, Qing Sun, Dongshan Zhou, Xiaoliang Wang, and Gi Xue*
Macromolecules 2002, 35, 7089-7092,-0001,():
-1年11月30日
Poly(vinyl chloride) (PVC) samples for the conformation and structural relaxation studies were prepared by freeze-extracting the solutions in various solvents and with varying concentrations. The partially disentangled PVC samples could be obtained by freeze-extracting very dilute PVC/tetrahydrofuran (THF) and PVC/dimethyl phthalate (DMP) solution (0.05 wt %), while the PVC sample remains in an entangled state after freeze-extracting the concentrated solutions in THF and in DMP. Surprisingly, the extent of interpenetration of PVC chain decreases, even in concentrated solution in dioctyl phthalate (DOP) (5 wt %), which is contrary to accepted theories. DSC and infrared spectroscopic studies showed that a higher ordered conformation could be achieved for the disentangled specimens recovered from concentrated solution in DOP than for the entangled samples prepared from THF and DMP. DSC heating curves showed strong and sharp endothermal peaks for the disentangled polymer after sub-Tg annealing. The structural relaxation behavior of the disentangled PVC freeze-extracted from DOP solutions is more predominant, which is in good agreement with the modeling predictions.
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薛 奇, Jinglu Chen, Gi Xue, * and Yanhong Li, Lei Wang and Guohua Tian
Macromoloculos 2001, 34, 1297-1301,-0001,():
-1年11月30日
The partially disentangled poly(vinyl chloride) (PVC) samples were prepared by freezeextracting from dilute PVC/THF solutions. The conformation of these samples was investigated by infrared and Raman spectroscopy. The structural relaxation behaviors were studied by differential scanning calorimeter (DSC). The results showed that the PVC samples prepared from dilute solutions with concentrations lower than 0.25% were in the expanded state with fewer entanglements. The conformation and structural relaxation of PVC depended strongly on the entanglements in polymers, and the structural relaxation rate increased with decreasing chain entanglements, which is in good agreement with the modeling predictions.
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【期刊论文】Surface Reactions on Polymer Thin Films Studied by Surface-Enhanced Raman Scattering
薛 奇, Dong-Shan Zhou, Ning Xu, Liang Li, Gendin Ji, and Gi Xue*
J. Phys. Chem. B 2003, 107, 2748-2751,-0001,():
-1年11月30日
The laser-induced chemical reactions on the surface of a polymer film were investigated by surface-enhanced Raman scattering (SERS) using chemically deposited silver as the SERS activating layer on the surface of the film. The silver-catalyzed pyrolysis at the outermost surface of the polyacrylonitrile film under laser radiations with different wavelengths was investigated by this SERS technique. The extremely low carbonization temperature at room temperature under laser implies several responsible mechanisms.
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【期刊论文】Depletion Effect on Supermolecular Assembly: A Control of Geometry of Adsorbed Molecules
薛 奇, Liang Li, Dongshan Zhou, Junfeng Zhang, and Gi Xue*
,-0001,():
-1年11月30日
Depletion interaction of added additional polymer latex was reported to drive self-aggregation of particles in suspension or on a hard wall (Yodh, A. G.; Lin, K. H.; Crocker, J. C.; Dinsmore, A. D.; Verma, R.; Kaplan, P. D. Philos. Trans. R. Soc. London A 2001, 359, 921). We describe an experimental investigation of controlling the optimal geometrical arrangement for the adsorbed molecules by depletion interaction between the adsorbent and the metal wall. Bipyridine and a polymer of amino acid were found to form ordered structures that covered silver after adding a depletant of low molecular weight poly(ethylene glycol) (PEG) into their solutions in ethanol. The adsorbed molecules were investigated by surface enhanced Raman scattering (SERS) spectroscopy, which provided information about morphology at the molecular level. The PEG-mediated depletion interaction with the wall contributed to the entropic force for supramolecular assembling of these adsorbents on substrate.
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【期刊论文】Control of the Geometry of the Adsorbed Thin Layer by the Depletion Interaction
薛 奇, Dongshan Zhou, Junfeng Zhang, Liang Li, and Gi Xue*
J. AM. CHEM. SOC. 2003, 125, 11774-11775,-0001,():
-1年11月30日
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