Inter- and intra-molecular ionic interactions of polyampholyte: Carboxymethyl-2-diethylaminoethylcellulose

Carboxymethyl-2-diethylaminoethylcellulose (CM-DEAE cellulose) was prepared by etherification of carboxymethylcellulose with diethylaminoethyl chloride in a NaOH solution. The behaviour of CM-DEAE cellulose in aqueous solution was studied by viscosity and GPC measurements. The degree of substitution (DS) and existing states of DEAE substituents were examined by the use of proton NMR, and those of the CM substituents were observed with FT-IR. The results reveal that the reduced viscosity and apparent molecular size of CM-DEAE cellulose vary with the concentration of sodium chloride and changes in pH and DS. These phenomena can be explained in terms of inter- and intra-molecular ionic interactions.     

Monte Carlo Simulation of the Neurofilament Brush

Grand canonical Monte Carlo (MC) simulations are performed to analyse conformations of projection domains in a neurofilament (NF) brush composed of three types of tails (L, M, and H) at different concentrations of added salt. The NF is modelled as a rigid, uniformly charged cylinder (backbone), surrounded by tethered, flexible polyampholytic chains with charge distributions and stoichiometry similar to those in natural NFs. We calculate the equilibrium trajectory for each projection; that is, the average distance of the amino acid residue from the surface of the backbone as a function of its ranking number. These trajectories demonstrate the tendency for projections to fold back and adopt loop-like conformations at moderate solution salinities. We also perform extended analysis of MC data to identify metastable states of the system, and demonstrate representative snapshots of tail conformations in major metastable states.     

两性聚电解质CMCTS-g-(PDMMC-co-PDDAMC)的制备及性能初探

在K2S2O8/Na2SO3氧化-还原引发体系的引发下,通过甲基丙烯酰氧乙基三甲基氯化铵(DMMC)和烯丙基十烷基二甲基氯化铵(DDAMC)在羧甲基壳聚糖(CMCTS)分子链上的接枝共聚反应,制备了新型两性聚电解质壳聚糖衍生物CMCTS-g-(PDMMC-co-PDDAMC)。对产物的两性聚电解质性能进行了初步的探索性研究,发现CMCTS-g-(PDMMC-co-PDDAMC)在pH=1和pH=11处各出现一个黏度较大值,在pH=5附近达到等电点,黏度最小。在等电点处溶液黏度η和特性粘数[η]随离子强度的增大而增大,在pH=1和pH=11处溶液黏度随离子强度的增大而减小。研究了阳离子种类对CMCTS-g-(PDMMC-co-PDDAMC)溶液黏度的影响。     

Paclitaxel‐Loaded Polymer Nanoparticles for the Reversal of Multidrug Resistance in Breast Cancer Cells

Novel paclitaxel‐loaded polymer nanoparticles were developed for circumventing multidrug resistance (MDR) of malignant cancerous diseases, which is an unsolved clinical problem in cancer chemotherapy. In many cases, MDR is due to the intrinsic or acquired expression of an efflux pump, the P‐170 glycoprotein (P‐gp). By encapsulating paclitaxel in a water‐soluble and biocompatible synthetic polyampholyte using a solid‐state reaction the highly water‐soluble paclitaxel‐loaded nanoparticles are formed. The resulting paclitaxel nanoparticles with an average diameter of 250 nm show a significant reversal of chemoresistance in the drug‐resistant variants (MCF7/ADR, MT3/ADR) by a factor of 100 or more. The novel paclitaxel nanoparticles enter MDR breast cancer cells by adsorptive endocytosis bypassing the P‐gp, preventing the efflux of paclitaxel and thus restoring the anti‐proliferative effect of paclitaxel.     

AMPS-DMAEMA两性聚合物溶液性能的研究

研究了自制的两性聚合物ＡＭＰＳ－ＤＭＡＥＭＡ（简写为ＡＳＤＡ）组成与等电点的关系。制得了等电点状态下的两性聚合物ＡＳＤＡ－５０（ｐＨ＝５）。推导出了等电点下的两性聚合物溶液的比浓粘度与聚合物浓度无关的表达式，并用实验证实了这一关系式。利用ｐＨ的影响制得了与ＡＳＤＡ－５０具有相同分子量、相同分子链结构的单性聚电解质ｄＡＳＤＡ－５０。二者的对比研究表明，ＡＳＤＡ－５０具有明显增大的特性粘数。     

Collapse of acrylamide‐based polyampholyte hydrogels in water

The swelling behavior of balanced acrylamide (AAm)‐based polyampholyte hydrogels in water and in aqueous salt (NaCl) solutions was investigated. Equimolar ratio of the ionic comonomers 4‐vinylpyridine (cationic monomer) and acrylic acid (anionic monomer) were used together with the nonionic monomer AAm in the hydrogel preparation. The variations of the hydrogel volume in response to changes in pH were measured. It was found that the hydrogels are in a collapsed state not only at the pH of the isoelectric point pH_IEP but also over a wide range of pH including pH_IEP. The width of the collapsed plateau increased and the hydrogels assumed a more compact state as the ionic group content is increased. The antipolyelectrolyte behavior was observed along the collapsed plateau region, where the gel occupies a larger volume in salt solution. The experimental swelling data were compared with the predictions of the Flory‐Rehner theory of swelling equilibrium including the ideal Donnan equilibria. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The Influence of an Acid-base-equilibrium on the Adsorption Behaviour of a Weak Polyampholyte

A weak diblock polyampholyte PMAA-b-PDMAEMA, poly(methacrylic acid)-block-poly((dimethylamino)ethyl methacrylate), was investigated as a model system for the influence of an acid-base-equilibrium of a phthalic acid buffer system on the polyelectrolyte adsorption behaviour. The adsorption of polyampholyte from aqueous solution onto silicon surfaces is known to be strongly influenced by the parameters of the polymer solution and the properties of the polyampholyte itself like block ratio or molecular weight. In the case of the investigated polyampholytes, the main parameter with the most significant influence on the adsorption is the pH. The big influence of pH on adsorption results from the charges of the polymer chains and the substrate, which are determined by the pH. Therefore, it should be useful to investigate the influence of a buffer system on the polyampholyte adsorption. On the one hand the buffer system enables to determine the pH of the aqueous polyampholyte solution more precisely. On the other hand the concentrations of different phthalic species like the phthalic acid, the hydrogen phthalate and the phthalate are strongly influenced by pH. These different species were observed to have a strong influence on the adsorption behaviour of the polyampholyte, so the adsorption as function of pH was observed to be also determined by the acid-base-equilibrium of the buffer system. The adsorbed amount of polyampholyte dried after the adsorption process was determined using ellipsometry, while the surface topography of these adsorbed layers were characterized by atomic force microscopy (AFM). This revised version was published online in July 2006 with corrections to the Cover Date.     

两性高分子水处理剂的研究现状与发展

本文叙述了两性高分子水处理剂在水溶液中有别于一般的阴、阳离子型水处理剂的独特性质,介绍了国内外常见的两性高分子水处理药剂,及其在水处理应用中的独特优势。预测在今后的水处理研究应用中,两性高分子水处理剂将取得突破性进展,而天然改性类两性高分子水处理剂在我国将占有较重要的地位。     

两性离子抑制剂的合成及性能

以二甲基二烯丙基氯化铵（DMDAAC）、甲基烯丙醇（MP）以及2-丙烯酰胺基-2-甲基丙磺酸（AMPS） 3种单体为原料,采用水溶液聚合法合成出了一种低分子量、线型、两性离子共聚物,并采用FTIR、SEM、乌式黏度计、凝胶色谱仪对其进行了表征。考察了引发剂的加量、单体的总浓度、单体的摩尔比、反应的温度、反应时间对其抑制性能的影响。结果表明最佳反应条件为：引发剂为4%,单体总质量分数为30%,单体间摩尔比率为AMPS∶DMDAAC∶MP=4∶3∶4,反应温度为65℃,反应时间为7h。采用线性膨胀率、滚动回收率考察了产物的抑制性,并与XY-27、SIAT、聚合醇进行了比较。结果表明共聚物的抑制性优于XY-27、SIAT和聚合醇。采用XRD、zeta电位从微观角度考察了其作用机理,结果表明：共聚物能够减小膨润土晶层间距,压缩其扩散双电层。将抑制剂加入钻井液体系,考察了体系的流变性、滤失性、抑制性,结果表明该抑制剂具有良好的配伍性和抑制性。