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本工作用振簧仪,在-150—80℃范围内,测试了四氟乙烯-全氟4-甲基-3,6-二氧杂△~7辛基磺酰氟共聚物的动态力学性能。样品是含有不同侧基数目的部分结晶共聚物。观察到四个松弛过程,按温度下降次序记为α、γ_1-、γ_2-、γ_3-。α峰(室温附近)系玻璃化转变。γ_1峰(-50℃,~215Hz)为主链有阻碍的短链段分子运动。γ_2-峰(-60℃,~230Hz)为侧基的分子运动。γ_3-峰(-77℃,~260Hz)为的链段运动,并且γ_3-峰的强度随结晶度增加而增强。 相似文献
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α、β、γ、δ-四苯基卟啉和稀土乙酰丙酮-α、β、γ、δ-四苯基卟啉的共振喇曼光谱研究 总被引:1,自引:0,他引:1
本文用4579A、5145A等激发线激发,测得α、β、γ、δ、-四苯基卟啉(TP_1)和12个稀土乙酰丙酮-α、β、γ、δ、-四苯基卟啉(MTPP acac)的共振喇曼光谱,对其共振特性和结构对称性进行了讨论.指认370cm~(-1)附近谱带为MTPPacac的M—O键对称拉伸振动谱带. 相似文献
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CexZr1—xO2复合氧化物负载PdO催化剂的CO和CH4氧化性能研究 总被引:9,自引:0,他引:9
以CexZr1-xO2复合氧化物为载体, 采用浸渍法配制了负载PdO催化剂,考察了催化剂对CO和CH4的氧化活性, 并对该催化剂的还原性能进行了表征. 结果表明,Ce/Zr比对催化剂的活性影响很大. 对于CO氧化, 当x=0.8时, 催化活性最高;而对于CH4氧化, x=0.5时,活性最高. 出现3个催化剂还原峰(α、β、γ), α峰归属于PdO还原,而β和γ峰归属于载体的还原. 我们认为α峰与CO氧化有关. 相似文献
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本文首次合成出镧系乙酰丙酮-α,β,γ,δ-四邻硝基苯基卟啉配合物Ho(o-NO_2)TPPacac(Ⅰ),并简单地讨论了它的性质。 反应中间物三水乙酰丙酮配合物Ho(acac)_3·3H_2O用文献方法[1]合成和纯制。α,β,γ,δ-四邻硝基苯基卟啉(o-NO_2)TPP用改进的Kim,J.B.法[2] 相似文献
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〕用反相高效液相色谱分离某些对称取代的卟啉及其金属卟啉。根据卟啉和金属卟啉在可见区的光谱特征,通过对流出色谱峰的快速扫描就可简便地鉴定它们。考察了几个不对称取代的芳基卟啉和金属卟啉的分离和定性,如中位含不同数目的对羟基苯基和对甲氧基苯基的卟啉混合物(样A)和中位含不同数目的对氯苯基和苯基的卟啉锌混合物(样B)。选用装填YWG-C18(3~5微米)的φ5×150毫米色谱柱,用含水5%的甲醇为流动相,样A和样B都得到良好分离,用两个已知样鉴定出样A中的α-对羟基苯基β,γ,δ-三对甲氧基苯基卟啉,α,β-二对羟基苯基γ,δ-,二对甲氧基苯基卟啉和α,γ-二对羟基苯基β,δ-二对甲氧基苯基卟啉对样B中的三个色谱主峰,在同一柱上用按比例放大方法,收集、浓缩得毫克级结晶,经质谱、核磁共振波谱、紫外—可见光谱综合定性,确定出α-对氯苯基β,γ,δ-三苯基卟啉锌和中位四对氯苯基卟啉锌。上述方法也适用于其他类似的卟啉和金属卟啉的分离和鉴定。 相似文献
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本文叙述了一种综合多烯酸的方法:将α-丁烯酸酯或α,γ-己间二烯酸酯与适当的醛缩合,再进行水解。这样,仅用一个步骤便可引进四个或六个碳原子的共轭双键的侧链。丁烯酸甲酯与苯甲醛或糠醛在去醇的甲氧基钠影响下缩合,得到顺-δ-苯基-戊间二烯酸(熔点137.5—138°)或顺-δ-2-呋喃-α,γ-戊间二烯酸(熔点109—111°);同样情形,α-丁烯酸甲酯与对-甲氧基苯甲醛缩合时得出顺-δ-对-甲氧基苯-α,γ-戊间二烯酸(熔点115—118°)及其反式的几何异构体(熔点:180°熔为液晶,220—221°熔为透明液体)。所有上述的顺式酸用汞弧光灯照射后,可全部转变为其相应的反式酸。α,γ-己间二烯酸甲酯与苯甲醛在去醇的甲氧基钾影响下缩合,水解后得到7-苯基-庚间三烯酸(熔点:189—190°熔为液晶,199°熔为透明液体)。 相似文献
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用声频共振法在-150°—170℃范围内测定了晶区构象为α、γ、γ+α型以及经不同拉体程度的聚酰胺-6单纤维的动态力学性质的温度谱。除三个已知的内耗峯—— -110℃(β_a),-40℃(β’_a),50℃(α_a)以外,对晶区为γ构象且含有单体及低聚体的聚酰胶-6观察到一个新的内耗峯,130℃(α’_a)。具有α构象的试样,其α_a内耗峯出现的温度较具有γ构象的试样为高。 经碘处理而未脱碘的聚酰胺-6,(β’_a)内耗峯高度显著增加,进一步证实β’_a内耗峯与自由酰胺基的运动有关。β’_a内耗峯的高度亦随拉伸比的增加而增高,说明在拉伸过程中,酰胺基之间的氢键有破坏的可能性。 出现在130℃处的α’_c内耗峯随拉伸比的增加其高度显著地下降,当拉伸到3.8倍时不再出现α’_c内耗峯。结合晶区分子链构象及碘处理对α’_c内耗峯的影响,我们认力α’_c内耗峯应为γ构象部分的松弛运动。 相似文献
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Bryan B. Sauer Peter Avakian Howard W. Starkweather 《Journal of Polymer Science.Polymer Physics》1996,34(3):517-526
Semicrystalline fluoropolymers including poly(tetrafluoroethylene) (PTFE), a 8 mol % hexafluoropropylene (HFP)/92% TFE random copolymer (FEP), and poly(vinyl fluoride) (PVF) were studied using thermally stimulated current depolarization (TSC), ac dielectric, and other thermal analysis techniques. The TSC thermal sampling (TS) technique is emphasized here for the detection of broad and weak “cooperative” relaxations with all three of the polymers studied exhibiting two cooperative (i.e., relatively high apparent activation energy) transitions. The well-studied low-temperature γ relaxation in PTFE at ca. −100°C is characterized by this method as well as the γ relaxation in the less crystalline FEP sample. Higher temperature cooperative glass transitions, associated with constrained noncrystalline regions, are found at ca. 100°C in PTFE and ca. 80°C in FEP at TSC frequencies. Comparisons with relaxation studies of linear polyethylene are made, and the effects of crystallinity on the various transitions are discussed. The unique characterization by the TSC-TS technique in the detection of multiple “cooperative” relaxations, even in the case of overlapping transitions, is emphasized here. An example is the low-temperature relaxation in FEP. Two cooperative transitions were detected in PVF. The higher temperature one at ca. 45°C is the glass transition, as is well known in the literature. More information is needed to confirm the molecular origin and the effects of crystallinity and chemical structure on the low-temperature cooperative transition in PVF. © 1996 John Wiley & Sons, Inc. 相似文献
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The nature of the transition in molten FEP copolymer was examined in relation to the enthalpy change, mechanical damping and melt viscosity. For a pre-heat-treated FEP copolymer sample a small endothermic peak appeared at 309—312 ℃in DSC trace with enthalpy change 0.03—0.05 cal/g. A peak was also detected in damping versus temperature curve at the same temperature range. The theological property of FEP copolymer melt was similar to that of liquid crystal, but no birefrigence was viewed in the melt. Therefore the transition was explained as the melting of small crystallites which persist in typical copolymer beyond its melting temperature. These crystallites can act as nuclei for crystallization upon cooling. 相似文献
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Howard W. Starkweather 《Journal of Polymer Science.Polymer Physics》1973,11(3):587-593
Internal motions in an alternating copolymer of ethylene and tetrafluoroethylene were investigated by dynamic mechanical and dielectric measurements and by nuclear magnetic resonance. At 1 Hz the α, β, and γ relaxations were observed at 110, ?25, and ?120°C in a quenched sample. The activation energy was 76 kcal/mole for the α relaxation and 10.6 kcal/mole for the γ relaxation. These relaxations are attributed to the motion of long and short segments in the amorphous regions, respectively. The β relaxation, which was observed only in the dynamic mechanical experiments, appears to occur in the crystalline regions. The copolymer is isomeric with poly(vinylidene fluoride), but it has a higher melting point and a much lower dielectric loss. 相似文献
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Through improvements on a fully commercial and automatic system measuring frequency andtemperature spectra of the complex elastic, dielectric, and piezoelectric constants of polymerfilms, the precision for measuring complex dielectric constants achieved 2‰ from original 1%.The complex dielectric constants of PVDF, VDF (95 )/VF (5), VDF (52)/TrFE (48) and VDF(47. 5)/TrFE(47. 5)/HeFP (5) over a range of-120-140℃, 10-2-10~4Hz were measured bythe described system. The diminution of chain regularity due to 5mol% vinyl fluoride in the chainof PVDF led to disappearing of α-relaxation and increase in T_g (3℃) of VDF (95)/VF (5).Because of the spatial impediment of 5mol% HeFP in copolymer chain, the Curie point of VDF(52)/TrFE(48) decreased by 30℃ and T_g by 3℃. The behavior of dielectric relaxation indicatedthat 5mol% vinyl fluoride and HeFP made the relaxation strength of noncrystalline regionreduced, the activation energy of local relaxation increased and the relaxation time prolonged respectively. 相似文献
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The relaxation behavior of four amorphous poly(aryl ether ketone)s was investigated using dielectric relaxation spectroscopy and dynamic mechanical analysis. The temperature dependence of the relaxation times of the glass transition process and the cooperative nature of this process were unaffected by changes in polymer structure. The temperature location of the loss peaks for all polymers progressed smoothly between the low frequency of the mechanical measurements and the higher frequencies of the dielectric probe. Differences were observed in mechanical activation energy and dielectric relaxation strength for one polymer which contained a significant concentration of meta linkages, compared with the para-linked polymers, while relaxation broadness was generally greater in the dynamic mechanical mode. Changes in chemical structure had little effect on the shape, intensity, and location of the β-relaxation peak, the main observation being that the Arrhenius activation energy measured by dynamic mechanical analysis was significantly higher than that calculated from the dielectric data. The dielectric β-relaxation was sensitive to absorbed moisture. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 851–859, 1998 相似文献
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本文首先研究了成型方法和热处理对聚对苯二甲酸乙二酯与聚氧四亚甲基嵌段共聚物动态力学温度谱的影响,结合应力-应变曲线讨论了微相分离与力学性能的关系。其次,比较了三种不同链结构的聚酯-聚醚嵌段共聚物在不同温控程序下的动态力学温度谱,讨论了链结构对软链段结晶的影响。最后观察了聚氨酯-聚醚嵌段共聚物双重玻璃化转变现象并作了解释。 相似文献
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M. Shen V. A. Kaniskin K. Biliyar R. H. Boyd 《Journal of Polymer Science.Polymer Physics》1973,11(11):2261-2272
A styrene–butadiene–styrene block copolymer (SBS) and a plasticized SBS were studied as a function of temperature by an ultrasonic wave propagation technique at 9 MHz. Two absorption maxima were found for each of these polymers, one being attributable to the primary glass transition of the polybutadiene blocks and the other to that of the polystyrene blocks. The SBS was cast from two different solvents, namely benzene and tetrahydrofuran–methyl ethyl ketone. Parallel dielectric loss measurements were also made of the SBS in the frequency range of 50–105 Hz. Relaxation temperatures determined from the ultrasonic and dielectric loss maxima over a range of measurement frequencies can be correlated by an Arrhenius-type equation. The polystyrene loss peak in the ultrasonic data was found to be much weaker than the polybutadiene loss peak. However, these two peaks were of comparable magnitude in dielectric data. This observation was interpreted as being due to the onset of structured–unstructured (heterophase to homogeneous) transitions at sufficiently high temperatures. Ultrasonic data were also compared with low-frequency dynamic mechanical data (11 Hz) and stress relaxation data (102–105 sec) through the use of simple time–temperature superposition principle. Considerable discrepancies were found by using this principle, indicating that the heterophase SBS block copolymer was thermorheologically complex. 相似文献
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主链玻璃化转变区在室温附近的梳形聚合物电解质 总被引:1,自引:0,他引:1
主链玻璃化转变区在室温附近的梳形聚合物电解质*齐力林云青夏永姚王佛松(中国科学院长春应用化学研究所长春130022)关键词梳状高分子,固体电解质,离子导电性,玻璃化转变,分子运动*1994-10-30收稿;1995-12-10修稿732高分子固体电解... 相似文献