海参多肽的护肤功效及应用

综述了海参多肽尤其是海参胶原多肽的结构特点,比较了不同分子量的胶原肽在抗氧化、美白和保湿方面的功效差别,总结了海参多肽的制备以及分离纯化方法,讨论了目前我国海参多肽产业所面临的问题与研究方向。     

苦瓜多肽的分离纯化研究

以苦瓜为原料分离纯化制备多肽,通过正交试验确定了酶解的最佳工艺条件:加酶量为4%,温度45 ℃,酶解时间为1 h,料液比为2,多肽得率提高19.7%.采用葡聚糖凝胶G-50纯化得到2组洗脱液.此分离纯化工艺简单可行,成本低,可适用于工业化生产.     

一种神经毒素多肽的分离纯化

目的　分离纯化一种神经毒素生物大分子 ,制备单体以供研究。方法　对已经过初步提纯的神经毒素采用RP HPLC等色谱方法进一步纯化。结果　用二极管阵列检测及质谱检测表明 ,最终所得的多肽组分为单体。结论　本法对制备少量神经毒素多肽单体具有参考价值。     

超高分子量聚乙烯分子量及分子量分布的测定

超高分子量聚乙烯UHMWPE的分子量和分子量分布直接影响其加工性能和机械性能,然而传统的凝胶色谱法(GPC)存在一定的局限性,粘均分子量难以全面反映UHMWPE的结构特点。为了开发出一种精度高、重复性好的UHMWPE分子量和分子量分布测试方法,本研究在常规高温GPC设备的基础上,基于溶液流动分级机理,选取了合适凝胶孔径的凝胶色谱柱,改善了普通GPC测试结果分子量分布偏宽的问题。并通过对UHMWPE/三氯苯溶解方法的深入研究,解决了普通GPC测试结果重复性差的问题。对UHMWPE新产品的研发和后期的加工有着重要的实际意义。     

茯苓多糖的纯化及分子量测定

通过水提醇沉的方法得到茯苓粗多糖,精制后采用离子交换柱层析对多糖进行分离纯化,用高效凝胶过滤色谱法(HPGFC)测定多糖分子量.结果表明,茯苓粗多糖用Sevag法脱蛋白效果较好,获得了精制茯苓多糖(TAP);经DEAE-650C层析柱纯化,得到中性多糖(TAP1)和酸性多糖(TAP2),高效凝胶过滤色谱法测定其分子量分...     

膜分离技术在低分子量生物产品分离纯化中的应用

介绍了膜分离技术在低分子量生产产品分离纯化中的应用。以压力差为推动力的膜分离技术包括微滤、超滤、纳滤、反渗透等，其分离性能通常由透过通量和截留率表征，而操作模式则分为浓缩和渗滤两种。本文将低分子量生物产品划分为氨基酸和多肽、抗生素、乳酸及低聚糖等，综述了膜分离技术在上述产品的回收、分离、纯化和浓缩过程中的研究与应用进展。     

凝胶色谱法测定高聚物的平均分子量及分子量分布

介绍了用凝胶色谱法测定高聚物的平均分子量及分子量分布。     

凝胶色谱法在聚丙烯分子量及分子量分布测定中的应用

根据聚丙烯在凝胶色谱柱上的淋洗特点,确定了测定其分子量及分子量分布试验条件;采用示差和黏度双检测凝胶色谱系统,利用普适校正方法,不需要Mark常数K、α值,可直接测定聚丙烯分子量分布并给出分子量分布曲线;采用统计方法计算数均分子量、重均分子量、黏均分子量,可以为课题研究提供一定的依据和指导。     

凝胶色谱法测试聚苯醚平均分子量及分子量分布

建立凝胶色谱法测试聚苯醚平均分子量及分子量分布。采用凝胶色谱仪,色谱柱为Waters HR1、HR2、HR4E,检测器为示差折光检测器,流动相为甲苯,流速为1 mL/min,柱温为40℃。此方法快速、准确、操作方便,测试数据有良好的重复性和再现性。并对影响测试结果的各因素进行分析。     

聚烯烃分子量及分子量分布对其物理机械性能的影响

综述了分子量及分子量分布与聚烯烃物理机械性能的关系,其中包括应力-应变、冲击、蠕变、应力松驰、疲劳、结晶和流变学性质。通常,聚合物的机械性能随分子量增大而提高,而当分子量高于某一定值时保持恒定。本文对聚烯烃的生产和加工都具有实际意义。     

Effects of molecular weight and molecular weight distribution on creep properties of polypropylene homopolymer

The molecular weights of the industrial-grade isotactic polypropylene (i-PP) homopolymers samples were determined by the melt-state rheological method and effects of molecular weight and molecular weight distribution on solid and melt state creep properties were investigated in detail. The melt-state creep test results showed that the creep resistance of the samples increased by M_w due to the increased chain entanglements, while variations in the polydispersity index (PDI) values did not cause a considerable change in the creep strain values. Moreover, the solid-state creep test results showed that creep strain values increased by M_w and PDI due to the decreasing amount of crystalline structure in the polymer. The results also showed that the amount of crystalline segment was more effective than chain entanglements that were caused by long polymer chains on the creep resistance of the polymers. Modeling the solid-state viscoelastic structure of the samples by the Burger model revealed that the weight of the viscous strain in the total creep strain increased with M_w and PDI, which meant that the differences in the creep strain values of the samples would be more pronounced at extended periods of time.     

聚丙烯熔体流动指数与分子量及其分布的关系

研究了聚丙烯(PP)的熔体流动指数(MI)与聚合物不同分子量之间的关联性,对于分子量分布较窄的PP,数均分子量(Mn)、重均分子量(Mw)和粘均分子量(Mv)均能较好的关联;反之,MI与Mn关联性下降,而MI与Mn和Mv的关联性仍很好,尤其是MI与Mv的关联性受分子量分布的影响很小;MI与Z均分子量的关联性很差。同时．确定了MI与各种分子量之间的关联式,该式用于本体PP工艺反应器内氢气浓度的计算和MI的预测,与实验测量结果吻合良好。     

Determining molecular weight scale and molecular weight distribution of ethylene-tetrafluoroethylene alternating copolymer via a rheological technique

A self-scaling rheology-based technique was developed to determine the molecular weight (MW) and molecular weight distribution (MWD) of ethylene-tetrafluoroethylene alternating copolymer (ETFE). The self-scaling technique makes determining MW and MWD with isolated completely rheological method possible. Moreover, the two key parameters (the plateau modulus and zero-shear viscosity) were obtained by more robust numerical technique, which let determining MW and MWD via rheological method initiated by Tuminello [Macromolecules 1993, 26, 499] being building on more robust and rigid basis. Our case overcomes the shortage of Tuminello's method and gives more practical and simply mean to analyze the MW scale and MWD in the production and application of ETFE. It is found that the peak MW of a ETFE (commercial grade: EP541) is 1.73 × 10⁵ g/mol, the MWD curve is a pattern with a slightly raised “shoulder” at high-molecular mass end, and a high peak on the median and the polydispersity is broad (the polydispersity index is near to 10.3). The wide polydispersity indicates the commercial ETFE combining good processability of relative lower MW molecules with physical properties of high MW ones. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The molecular weight distribution of oligomers

It is shown that the relation $\text{P}{}_{\mathrm{w}}\text{P}{}_{\mathrm{n}}\text{= 2}$ or the nonuniformity U = 1 is only a limiting case for high degrees of polymerization, is no more valid for oligomers. Two new relations are derived, one including and one excluding monomers. For the oligomer part of cationically produced polystyrenes the second relation is in good agreement with experiments.     

窄分布低分子质量端羟基聚四氢呋喃的合成与研究

以三氟化硼乙醚配合物(BF3·OEt2)为催化剂,环氧丙烷(PO)为起始剂,二氯甲烷(CH2 Cl2)作溶剂,通过四氢呋喃的阳离子开环聚合合成了窄分子质量分布(Mw/Mn＜1.3)的端羟基聚四氧呋喃(PTHF).研究了三氟化硼乙醚配合物用量、溶剂用量、起始剂用量、反应时间对PTHF分子质量(Mn)及其分布(Mw/Mn)...     

Evolution of molecular weight and molecular weight distribution in ab initio styrene emulsion polymerizations using series of rigid rodlike cationic amphiphiles as surfactants

The emulsion polymerization of styrene is carried out using a series of unconventional rigid rodlike cationic surfactants (1‐[ω‐(4′‐methoxy‐4‐biphenylyloxy)alkyl]pyridinium bromides, PCX) of different lengths. The evolution of the molecular weight (M) and molecular weight distribution of the polymers is analyzed to obtain information about the chain stopping mechanism. Our results indicate that the M is strongly dependent on the initial surfactant concentration and is not dependent on the alkyl chain length. The Clay and Gilbert model [ln P(M) versus M plots] yields a concave‐up region at low molecular weights and a linear region that extends to high values. The slope of the linear region, which is related to the rate coefficient of the chain transfer to the monomer versus the propagation rate coefficient ratio, decreases as the PCX concentration increases. This behavior indicates that as the PCX concentration increases the chain transfer to monomer becomes the dominant chain stopping mechanism. On the other hand, the ln P(M) versus M plots of polymer samples taken at low and high conversions show differences in slope, particularly at low PCX concentration. It is likely that at low conversion the chain transfer to monomer competes with other chain stopping mechanisms that could be associated with a coagulative nucleation process. The formation of a high molecular weight fraction at low conversion supports this explanation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1513–1523, 2002; DOI 10.1002/app.10489     

GPC法测定苯丙树脂相对分子质量及其分布

建立了GPC凝胶渗透色谱法测定苯丙树脂相对分子质量及其分布的方法:采用Styragel Wat 044207(500~30 000)(THF),Wat 044210(5 000~600 000)(THF)及Wat044213(5 000~4 000 000)(THF)3根凝胶色谱柱串接,柱温35℃;四氢呋喃为流动相,流速1 mL/min;采用示差折光检测器,待测样品浓度0.03 g/mL,精密度和重现性实验结果表明:该方法数据可靠、重复性好、简单易行。     

乙烯淤浆聚合动态分子量分布模拟计算

以乙烯淤浆聚合反应过程为研究对象,提出动态分子量分布的严格模型的数值计算方法。将动态分子量分布的大规模微分代数混合模型解耦为小规模微分代数方程组动态矩模型与大规模常微分方程组粒数衡算模型,然后通过变量解耦的方法进一步将大规模粒数衡算方程组转换为序贯差分方程组,实现了乙烯动态分子量分布严格模型的数值模拟计算。动态模拟乙烯聚合反应从一个稳态切换到另一个稳态,通过在切换后稳态的分子量分布计算结果与Flory分布计算方法进行比较,两者得到的分子量分布曲线吻合很好,证实了本文提出的动态模拟计算方法的精度和准确度都获得良好的保障。     

利用分子量分布探讨粉末活性炭对膜生物反应器的影响

采用空间排阻液相色谱法监测了不同粉末活性炭（PAC）投加量下膜生物反应器混合液分子量分布情况,发现当PAC投加量从1 g·L^-1增加到2 g·L^-1时,混合液中分子量大于10×10³的物质会增加;分子量小于0.5×10³及介于3×10³～10×10³的物质含量相当;分子量介于0.5×10³～3×10³的物质显著减少。膜污染速率分别为2.74、3.10 kPa·m^-1,证实了混合液中分子量大于10×10³的有机物是引起膜污染的主要物质。