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101.
Su Jin Han Hyung-Il Lee Byung Kyu Kim Anjanapura V. Raghu Kakarla Raghava Reddy 《Journal of Macromolecular Science: Physics》2014,53(7):1193-1204
Graphene, prepared by the thermal reduction of graphite oxide (GO), was modified with stearic acid to enhance its lipophilicity. A novel method, using the intrinsic epoxy groups on the graphene, was utilized for reaction with stearic acid to minimize the negative impact of the normal functionalization method on the π-electronic system of graphene. Gravimetric analysis, thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) showed that the stearic acid was effectively attached to the graphene. In addition, Raman spectroscopy and electric conductivity of the graphene showed that this novel modification method, utilizing intrinsic defects, did not damage the π-electronic system of the sp2 bonded carbons. The dispersion of graphene in a low density polyethylene (LDPE) matrix was enhanced; consequently, the reinforcing effect in tensile testing was improved by the lipophilic modification. The crystallization behavior observed by differential scanning calorimetry (DSC) showed that the crystallization of LDPE was hindered by dispersed graphene, more evidently when dispersed uniformly. 相似文献
102.
为了减少Am-Li中子本底对高浓铀部件质量主动多重性测量的影响,对大空腔探测系统(NPLNMC)Am-Li中子本底的优化屏蔽进行了模拟研究,提出了一个基于高密度聚乙烯为中子屏蔽体的优化方案。通过对比模拟结果与屏蔽前实验测量结果,发现屏蔽使Am-Li中子本底探测效率明显降低,从原来的15.77%降为屏蔽后的1.94%,大约降低了87.7%;而屏蔽对裂变中子计数的影响却相对较小,只比屏蔽前降低约2.4%。本底中子计数的降低明显提高了系统对铀部件质量测量的灵敏度,在3000s测量时间内,其质量测量下限从原来的大约6.4kg下降到屏蔽后的2.6kg;同时,屏蔽后的NPL-NMC系统在相同测量条件下,铀部件质量测量准确性提高50%以上。 相似文献
103.
采用变温傅里叶变换衰减全反射红外光谱技术(ATR-FTIR)结合二维相关红外光谱技术,分别研究了聚对苯二甲酸乙二醇酯(PET)的羰基红外伸缩振动模式(νC=O)。研究发现:玻璃转化温度(Tg)以下时,PET的νC=O的红外吸收频率包括1700cm~(-1)、1709cm~(-1)和1718cm~(-1),而随着测定温度的升高(313~343K),其红外吸收强度变化快慢顺序为:1709cm~(-1)1700cm~(-1)1718cm~(-1);而当在Tg以上时,PET的νC=O的红外吸收频率包括1709cm~(-1)和1718cm~(-1),而随着测定温度的升高(353~393K),PET的νC=O红外吸收强度变化快慢顺序为:1718cm~(-1)1709cm~(-1)。本项研究拓展了ATR二维相关红外光谱技术在PET高分子材料热变性研究的范围。 相似文献
104.
Mustafa A. Jihad Farah T. M. Noori Majid S. Jabir Salim Albukhaty Faizah A. AlMalki Amal A. Alyamani 《Molecules (Basel, Switzerland)》2021,26(11)
Flaky graphene oxide (GO) nanoparticles (NPs) were synthesized using Hummer’s method and then capped with polyethylene glycol (PEG) by an esterification reaction, then loaded with Nigella sativa (N. sativa) seed extract. Aiming to investigate their potential use as a smart drug delivery system against Staphylococcus aureus and Escherichia coli, the spectral and structural characteristics of GO-PEG NPs were comprehensively analyzed by XRD, AFM, TEM, FTIR, and UV- Vis. XRD patterns revealed that GO-PEG had different crystalline structures and defects, as well as a higher interlayer spacing. AFM results showed GONPs with the main grain size of 24.41 nm, while GONPs–PEG revealed graphene oxide aggregation with the main grain size of 287.04 nm after loading N. sativa seed extract, which was verified by TEM examination. A strong OH bond appeared in FTIR spectra. Furthermore, UV- Vis absorbance peaks at (275, 284, 324, and 327) nm seemed to be correlated with GONPs, GO–PEG, N. sativa seed extract, and GO –PEG- N. sativa extract. The drug delivery system was observed to destroy the bacteria by permeating the bacterial nucleic acid and cytoplasmic membrane, resulting in the loss of cell wall integrity, nucleic acid damage, and increased cell-wall permeability. 相似文献
105.
极低密度聚乙烯与其它聚乙烯的共混 总被引:3,自引:0,他引:3
从结构角度,用DSC,WAXD,SAXS研究了聚乙烯(PE)家族中极低密度聚乙烯(VLDPE)与其它PE的互容性.HDPE/VLDPE是共晶互容的,以其大量无规部分“溶解”了HDPE的结晶缺陷部分,提高了HDPE的Tc,Tm,Xc,结晶峰半高宽变窄,晶胞参数随组成而有最低值.VLDPE与LLDPE结构极为相似,DSC及WAXD证明其共混物是共晶相容体系.LDPE/VLDPE的结晶度符合按组成的计算值,但晶胞参数a,b以及晶粒尺寸增大,DSC上有分别相应于两组份的两个Tm;VLDPE的Tc,Tm峰高之和高于按组份的计算值,LDPE的Tm,Tc则低于计算值.认为是正如LLDPE/LDPE,LDPE向充满整个体积的VLDPE中不断填入,以VLDPE为晶核而结晶,形成相分离的不相容体系. 相似文献
106.
107.
S. N. Kreitmeier G. L. Liang D. W. Noid B. G. Sumpter 《Journal of Thermal Analysis and Calorimetry》1996,46(3-4):853-869
Thermal analysis by classical molecular dynamics simulations is discussed on hand of heat capacity of crystals of 9600 atoms. The differences between quantum mechanical and classical mechanical calculations are shown. Anharmonicity is proven to be an important factor. Finally, it is found that defects contribute to an increase in heat capacity before melting. The energy of conformational gauche defects within the crystal is only about 10% due to internal rotation. The other energy must be generated by cooperative strain. The conclusion is that the next generation of faster computers may permit wider use of molecular dynamics simulations in support of the interpretation of thermal analysis.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthday 相似文献
108.
A. Uedono T. Kawano S. Tanigawa M. Ban M. Kyoto T. Uozumi 《Journal of Polymer Science.Polymer Physics》1996,34(13):2145-2151
Relaxation processes in polyethylene (PE) and polystyrene (PS) were studied by positron annihilation technique. For PE, above the glass transition temperature, Tg, the size of free volumes and its concentration were increased by the micro-Brownian motion of molecules. For PS, local motions of molecules in backbone chains were found to start above 260 K. However, these local motions were suppressed by an interphenyl correlation. For both PE and PS, below 250–260 K, the formation probability of positronium atoms increased with decreasing temperature. This fact was assigned to the freezing in of the local motions of molecules. For PS, an onset of the local motions of molecules was observed above 100 K. These motions were expected to be associated with liberation of phenyl groups. © 1996 John Wiley & Sons, Inc. 相似文献
109.
110.
Leonardo C. Simon Raquel S. Mauler Roberto F. De Souza 《Journal of polymer science. Part A, Polymer chemistry》1999,37(24):4656-4663
Different chlorine-free alkylaluminum compounds were active cocatalysts for ethylene polymerization in the presence of 1,4-bis(2,6-diisopropylphenyl)-acenaphthenediimine-dichloronickel (II) (1). The combination of 1 with trimethylaluminum or triisobutylaluminum produced catalytically active species that polymerized ethylene with productivities up to 469 kgpolymer/(molNi · h). The activity of the catalytic system and the properties of the polymeric materials were influenced strongly by the reaction temperature. The polymers had a high molecular weight (up to 642 × 103 g · mol−1), and the molecular weight increased with the reaction time. The polyethylenes were branched, and the branching could be modulated by the proper choice of reaction parameters. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4656–4663, 1999 相似文献