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41.
乙二胺改性聚乳酸溶液的性质 总被引:1,自引:0,他引:1
乙二胺改性聚乳酸(EMPLA)是一种具有支化结构的新型生物材料。文中采用GPC-MALLS技术对其在四氢呋喃(THF)中的分子量、分子量分布、半径、支化及其这些量之间的相互关系进行了分析与研究,结果表明:乙二胺改性聚乳酸在四氢呋喃中的折光指数增量dn/dc值为0.052 mL/g,第二维利系数A2为3.905e-3 mol mL/g2,重均分子量-Mw为5.753e 4,重均均方根旋转半径Rw为4.5 nm,-Mw与Rw的关系式为:Rw=0.608×-Mw0.316,通过与线性聚乳酸(PDLLA)的比较,能够得到具有与PDLLA相同分子量的EMPLA有较小的均方根旋转半径的结论,并能够推出EMPLA在四氢呋喃溶液中的分子构象为球形。 相似文献
42.
Pesticides and polychlorinated biphenyls (PCBs) are found in various parts of the environment in quite small concentrations, but they accumulate and thus become a threat to human health and life. A review is focused on the application of some popular techniques for sample preparation in analysis of these compounds in food. Even with the emergence of advanced techniques of final analysis, complex matrices, such as food, require extensive sample extraction and purification. Traditional sample preparation techniques are time consuming and require large amount of solvents, which are expensive, generate considerable waste, contaminate the sample and can enrich it for analytes. There have been many sample preparation techniques proposed to meet the requirements connected with the multiplicity of food. Optimal sample preparation can reduce analysis time, sources of error, enhance sensitivity and enable unequivocal identification and quantification. Sample extraction and purification techniques are discussed and their most recent applications in food analysis are provided. This review pointed out that sample preparation is the critical step. 相似文献
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44.
旧报纸漆酶/介体脱墨过程中木素结构的研究 总被引:2,自引:0,他引:2
利用元素分析、功能基分析和傅里叶变换红外光谱(FTIR)对旧报纸漆酶/介体脱墨过程中木素结构的变化进行分析,并利用凝胶渗透色谱(GPC)测定木素的分子质量及其分布。元素分析及功能基分析结果表明,漆酶/介体处理后,木素C9单元分子质量降低,木素的酚羟基和甲氧基含量降低,羰基和羧基含量升高。红外光谱分析结果显示,漆酶/介体处理过程中存在木素结构的部分破坏与溶出。GPC测定结果表明,漆酶/介体处理后浆料中木素的数均分子质量、重均分子质量及多分散性均下降,说明木素受到了一定程度的降解。 相似文献
45.
Jianmin Man Fengling Qin Lijia Zhu Yong-Cheng Shi Minghong Gu Qiaoquan Liu Cunxu Wei 《Food chemistry》2012
High-amylose cereal starch has a great benefit on human health. Acid modification is very helpful for application of high-amylose starch in food and non-food industries. In this study, the ordered structure of acid-modified high-amylose rice starch was investigated by GPC, HPAEC, 13C CP/MAS NMR and XRD. Acid preferentially degraded the amylose, then A chain and short B chain of amylopectin. Relative double helix content and crystallinity both initially increased sharply and then progressively with acid hydrolysis. The relative crystallinity of starches obtained from 13C CP/MAS NMR was higher than that from XRD. The onset gelatinisation temperature decreased, while the peak and conclusion temperatures increased with increasing hydrolysis time. The endothermic value initially increased and then decreased with acid hydrolysis. The swelling power decreased while solubility increased after acid hydrolysis. These results add to our understanding of the effect of acid hydrolysis on the high-amylose rice starch. 相似文献
46.
The activated‐monomer cationic ring‐opening polymerization of ethylene oxide, initiated with ethylene glycol and using an acid‐exchanged montmorillonite clay called Maghnite‐H+ as an effective catalyst, was carried out to obtain the corresponding homopolymers with narrow polydispersity ratios. The molecular weights of the obtained polymers were controlled with the feed ratio of the monomer to the initiator. The effects of the amount of the catalyst and time on the polymerization yield and viscosity of the polymers were studied. The structure was confirmed with proton nuclear magnetic resonance and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
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48.
Suyeon Kim Carla Silva Andrea Zille Carmen Lopez Dmitry V Evtuguin Artur Cavaco‐Paulo 《Polymer International》2009,58(8):863-868
BACKGROUND: The ‘double function’ of laccase, from the ascomycete Myceliophthora, to depolymerise/polymerise lignin was studied in this work. A lignosulfonate (LS) compound was oxidised by enzymatic action and several techniques were applied to measure the polymeric changes obtained. This study was focused on the attachment level of the oxidised LS at the flax surface. RESULTS: Modified solutions were studied in terms of surface charge. Zeta potential values obtained showed an increase of polymerisation after several days of incubation. The change in molecular weight after LS polymerisation was detected using gel permeation chromatography. An increase of 1700 Da was achieved. Fourier transform infrared and UV‐visible spectroscopy techniques were applied and the results showed an increase of the degree of polymerisation. The colour strength of flax fabrics incubated with oxidised LS solutions was also measured and an increase of K/S (K, absorption coefficient; S, scattering coefficient) after enzymatic oxidation was observed. CONCLUSION: The oxidised lignin products obtained show good potential for use in natural surface modification of textile materials containing flavonoids. These findings have important practical implications for lignocellulosic fibre coloration, where new polymers can replace harsh chemicals in the textile industry. Copyright © 2009 Society of Chemical Industry 相似文献
49.
联用宽分布VDC-MA悬浮共聚物试样的[η]和GPC谱图数据,确定了此共聚物在四氢呋喃溶剂中、30℃下的Mark-Houwink常数:K=2.54×10-2,α=0.6757。进一步研究了单体配比、转化率、引发剂浓度以及聚合温度等因素对于分子量及其分布的影响,并建立了分子量模型。 相似文献
50.