双亲水嵌段共聚物存在下特殊形貌的BaC2O4晶体合成

近年来 ,无机新型材料已经广泛应用于各个技术领域 ,而对于所合成材料的大小和形貌的调控已经成为该材料能够应用于催化、药物、电子、陶瓷、染料和化妆品等领域的一个关键因素[1 ] .利用水溶性有机添加剂作为晶体生长的诱导剂来控制无机晶体的形貌和晶型已有很多报道 .例如 :多种生物分子[2～ 5] 和普通合成的大分子添加剂[6] 对 Ca CO3 晶体在成核、晶化和生长过程中的晶型和形貌有着明显的控制作用 .近年来 ,双亲水嵌段共聚物的功能型高分子 (DHBC) [7]已经发展成为能够有效控制无机晶化过程的新型晶体生长的调控剂 .这类高分子通常是…     

丙烯酸聚乙二醇酯-甲基丙烯酸共聚物对CaCO_3微粒形貌的调控

研究了两种聚合物丙烯酸聚乙二醇酯 (PEGA)和丙烯酸聚乙二醇酯 -甲基丙烯酸共聚物 (PEGA PMAA)对CaCO3粒子生长的调控 .发现PEGA调控下得到CaCO3 片层状粒子的粒径比在纯水中的小 ,而PEGA PMAA调控下的粒子粒径较大 ,并且长成了奇特的花状形貌 .这说明PEGA在CaCO3 粒子生长过程中起了阻碍作用 ,而双亲水的PEGA PMAA则促进了CaCO3 粒子的生长 .     

无规共聚物自组装球形胶束表面亲水性的耗散粒子动力学模拟

建立了含不同亲疏水粒子比的双亲性无规共聚物粗粒化模型. 采用耗散粒子动力学方法模拟了两亲性无规共聚物选择性溶剂自组装球形胶束表面的亲水性能. 模拟结果表明, 无规共聚物在选择性溶剂中自组装得到实心球形胶束, 球形胶束表面的亲水性与聚合物链亲水粒子含量、溶剂的选择性有关. 随着聚合物链所含亲水粒子增加, 球形胶束表面的亲水性增强. 球形胶束表面的亲水性随着疏水粒子与溶剂粒子间的排斥参数增大而增强, 模拟结果与实验结论一致. 该模拟方法给出的胶束微结构信息可以为双亲无规共聚物分子设计及自组装双亲胶束制备提供一定的理论指导.     

硫醇类配体修饰金纳米粒子在嵌段共聚物中自组装的研究进展

本文综述了不同类型硫醇配体修饰金纳米粒子的合成方法以及功能性金纳米粒子在嵌段共聚物薄膜中的自组装研究进展,重点介绍了硫醇类配体修饰金纳米粒子的合成方法,包括Brust合成法、原位合成法、grafting from合成法、配体置换法、单晶模板法等。总结了硫醇基小分子或聚合物配体修饰的金纳米粒子与嵌段共聚物之间自组装的调控方法,如利用配体与嵌段共聚物组分的隔离作用、配体与嵌段共聚物组分形成的氢键作用、溶剂蒸气退火或热退火等诱导嵌段共聚物/纳米粒子复合薄膜自组装。展望了功能性金纳米粒子以及嵌段共聚物/金纳米复合材料的发展方向。     

利用室温固态反应制备球霰石型CaCO3粒子

合成形态、大小及结构可人为调控的无机材料是现代材料科学的重要研究方向[1]. 借助于各类有机添加剂及模板剂的调控作用, 可利用溶液合成方法制备出形貌与结构受到有效调控的无机粒子[2,3]. 室温固态化学反应已被成功地应用于多种无机纳米粒子[4]及纳米线[5]的合成, 并显示出高效、节能、无污染和操作简便等优点, 因而在材料合成领域具有应用前景[6].     

手性模板合成CdS纳米棒

由于纳米材料具有量子尺寸效应及大的比表面积等性质而使其在电子学[1]、光学[2]、催化[3]和陶瓷[4]等领域显示出诱人的应用前景. 近年来纳米材料的制备及纳米技术发展迅速, 特别是具有特殊光电活性的新型无机纳米材料的制备已引起人们的普遍关注. 现在合成纳米材料的方法主要包括反相胶束法[5]、 LB膜法[6]、嵌段共聚物法[7]和模板合成法[8]. 其中模板合成技术不仅可以通过设计新型的模板分子, 还可通过模板分子的不同自组装行为来调控纳米材料的尺寸和形貌. Stupp等[9]曾利用溶致液晶的六方中间相作为模板, 在其纳米孔隙中成功地合成了具有六方排列超晶格纳米结构的材料. 本文以双亲性丙氨酸衍生物为模板, 在不同的化学微环境下合成了结构不同的CdS纳米棒.     

“双亲性”嵌段共聚物胶束形貌调控的研究*

本文综述了“双亲性”嵌段共聚物在选择性溶剂中胶束行为和胶束形貌的主要影响因素,包括溶液温度、选择性溶剂种类、嵌段长度、链段结晶、链段与溶剂间氢键作用以及共聚物浓度对胶束最终形貌产生影响的因素;系统介绍了对嵌段共聚物胶束形貌进行调控的实验方法;在此同时介绍了对环境刺激如温度和pH变化等具有响应性能的“双亲性”嵌段共聚物在选择性溶剂中胶束行为研究的最新进展;最后提出了该研究领域目前存在的问题和今后的可能发展方向。     

双亲水性嵌段共聚物对CaCO_3结晶的影响

以合成的带有磺酸基为端基的线型-超支化二嵌段共聚物PEG-b-PEI-SO3H为模板,探讨了其对CaCO3结晶的影响,并用FTIR、XRD、SEM、TEM等对产物进行了表征.结果表明,带有—SO3H端基的线型-超支化双亲水性嵌段共聚物PEG-b-PEI-SO3H对CaCO3晶体形貌和晶型表现出较强的调控能力.培养1天时得到空心环状方解石型CaCO3晶体,但当培养时间为3天和5天时,得到的CaCO3晶体形貌既有河蚌状也有类球状,同时其晶型既有方解石也有球霰石,而当培养时间达到7天后,得到的就只有球状球霰石CaCO3晶体.     

PU大分子单体水溶液性质

双亲聚合物一般由亲水和亲油 2种链段构成 ,有嵌段型[1,2 ] 和接枝型[3 ] 2种 ,其中通过大分子单体法合成双亲接枝聚合物备受关注[4] 。如以亲水性大分子单体和亲油性小分子单体共聚 ,大分子单体构成共聚物主链上支链 ,具有较大活动性 ,亲水效能高。采用对氯甲基苯乙烯[5] 或甲基丙烯酰氯[6] 与聚氧化乙烯大分子的一端相反应 ,可得到亲水性大分子单体 ,但其分子量及结构变化有限。本文采用常规条件 ,合成了嵌段式水溶性聚氨酯大分子单体 ,其分子量较大 ,共聚接枝的支链较长。利用该大分子单体具有非离子高分子表面活性剂的性质 ,采用无皂乳…     

双亲嵌段共聚物PSt-b-PAA在甲苯中的自聚集行为

以α-溴乙苯为引发剂,溴化亚铜为催化剂,2,2'-联吡啶为配体,用原子转移自由基聚合(ATRP)法合成了结构一定的嵌段共聚物聚苯乙烯-b-聚丙烯酸丁酯(PSt-b-PBA).经水解制备了双亲性嵌段共聚物聚苯乙烯-b-聚丙烯酸(PSt-b-PAA);采用单溶剂溶解法配制了PSt-b-PAA在甲苯中的反胶束溶液;以极性荧光化合物N-1-萘乙二胺盐酸盐(NEAH)为极性微区探针,用荧光光谱法并配合透射电镜观察探索了双亲嵌段共聚物PSt-b-PAA在甲苯溶液中的自聚集行为,考察了双亲性嵌段共聚物浓度、链结构及温度等因素对反胶束化行为的影响规律.结果表明,亲水链PAA短而亲油链PSt长的双亲嵌段共聚物PSt-b-PAA,用单溶剂溶解法可使其在甲苯中发生自聚集,形成以亲水段为核,疏水段为壳的星状反胶束结构;反胶束为10-20nm的球形聚集态结构;PSt-b-PAA的自聚集行为及临界胶束浓度与分子链的微结构和温度等因素相关,且随着共聚物浓度的增大,小胶束会逐渐结合形成大的纺垂状聚集体.     

A systematic examination of the morphogenesis of calcium carbonate in the presence of a double-hydrophilic block copolymer

In this paper, a systematic study of the influence of various experimental parameters on the morphology and size of CaCO3 crystals after room-temperature crystallization from water in the presence of poly(ethylene glycol)-block-poly(methacrylic acid) (PEG-b-PMAA) is presented. The pH of the solution, the block copolymer concentration, and the ratio [polymer]/[CaCO3] turned out to be important parameters for the morphogenesis of CaCO3, whereas a moderate increase of the ionic strength (0.016 M) had no influence. Depending on the experimental conditions, the crystal morphologies can be tuned from calcite rhombohedra via rods, ellipsoids or dumbbells to spheres. A morphology map is presented which allows the prediction of the crystal morphology from a combination of pH, and CaCO3 and polymer concentration. Morphologies reported in literature for the same system but under different crystallization conditions agree well with the predictions from the morphology map. A closer examination of the growth of polycrystalline macroscopic CaCO3 spheres by TEM and time-resolved dynamic light scattering showed that CaCO3 macrocrystals are formed from strings of aggregated amorphous nanoparticles and then recrystallize as dumbbell-shaped or spherical calcite macrocrystal.     

Determination of the coefficients of selective sorption in the system polymer–ternary solvent by the density and refractive index increments method

The method of density and refractive index increments was used for the determination of the coefficients of selective sorption of acetophenone and bromoform on polymer in the system poly(methyl methacrylate)–isopropanol–acetophenone–bromoform as a function of the composition of the ternary solvent. In systems containing more than 80% by volume of bromoform the precipitant—isopropanol—is selectively sorbed. The conditions under which the method gives satisfactory results and some methodological problems of densitometry have been discussed.     

Rosette‐Shaped Calcite Structures at Surfaces: Mechanistic Implications for CaCO3 Crystallization

Biomineralization is believed to be achieved by the intimate cooperation of soluble macromolecules and an insoluble matrix at the specific inorganic–organic interface. It has been reported that positively charged matrices play an important role in controlling the structure of CaCO₃ at surfaces, although detailed mechanisms remain unclear. In this work, we studied the transformation from amorphous CaCO₃ to calcite crystals on surfaces by using thin films of poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA) and its quaternized form. The positively charged PDMAEMA film was found to possess unique properties for CaCO₃ crystallization: individually separated, single calcite crystals were formed on the PDMAEMA film in the absence of poly(acrylic acid) (PAA), while circularly fused calcite crystals were formed in the presence of PAA. The circularly fused (rosette‐shaped) calcite crystals could be changed from a completely packed rosette to a ring‐shaped, hollow structure by tuning the crystallization conditions. A number of factors, such as reaction time, amount of (NH₄)₂CO₃, concentration of PAA, and charge of matrix‐films, were varied systematically, and we now propose a mechanism based on these observations.     

固载蛋白A交联聚甲基丙烯酸缩水甘油酯连续床亲合色谱柱的制备及性能考察

采用沉淀聚法“原位”（in-situ)聚合合成了交联聚甲基丙烯酸缩水甘油酯连续床色谱柱,对其进行化学改性后,分别得到含有11个碳原子间隔臂以及不含间隔臂键合了蛋白A的高效亲合色谱柱。考察了这两种色谱介质的性能,结果表明含有间隔臂的介质有一定的疏水性;对传统制备蛋白配基的亲合色谱介质的合成路线进行了改进;采用不含间隔臂的亲合柱测定了人血浆中人免疫球蛋白G（HIgG)的含量,所测得的定量标准曲线线性相关系数达到0．999;考察了流速对合成的连续床色谱柱柱压的影响,当流速高达9．0mL/min时,柱压也仅为6．5MPa;采用pH梯度对HIgG的不同亚基进行了分离。     

Fibrous and helical calcite crystals induced by synthetic polypeptides containing o-phospho-L-serine and o-phospho-L-threonine

The modification of CaCO(3) crystal growth by synthetic L-Ser(PO(3)H(2)) and L-Thr(PO(3)H(2)) containing polypeptides is described. The amino acids Gly, L-Glu, L-Asp, L-Ser, L-Ala, and L-Lys induced rhombohedral calcite with a rough surface. Dipeptides, Xaa-L-Ser(PO(3)H(2)) (Xaa = Gly, L-Glu, L-Asp, L-Ser, L-Ala and L-Lys) induced vaterite crystals in the lower [Ca(2+)]. On the other hand, L-Ser(PO(3)H(2))-containing polypeptides formed spherical vaterite and fibrous calcite. The characteristic helical calcite was found in the presence of copoly[L-Ser(PO(3)H(2))(75)L-Asp(25)] or poly[L-Ser(PO(3)H(2))(3)-L-Asp]. Fibrous calcite, spherical vaterite, and helical calcite crystals were subjected to XRD and EDX analysis. XRD revealed the specific faces of these crystals. EDX spectra and surface analysis visualized the localization of the polypeptides and CaCO(3) components. Together with TEM and SAED data, we propose hypothetical growth mechanisms for the fibrous and helical calcite crystals.     

Quantitative single molecule measurements on the interaction forces of poly(L-glutamic acid) with calcite crystals

The interaction between poly(L-glutamic acid) (PLE) and calcite crystals was studied with AFM-based single molecule force spectroscopy. Block copolymers of poly(ethylene oxide) (PEO) and PLE were synthesized and covalently attached to the tip of an AFM cantilever. In desorption measurements the molecules were allowed to adsorb on the calcite crystal faces and afterward successively desorbed. The corresponding desorption forces were detected with high precision, showing for example a force transition between the two blocks. Because of its importance in the crystallization process in biominerals, the PLE-calcite interaction was investigated as a function of the pH as well as the calcium concentration of the aqueous solution. The sensitivity of the technique was underlined by resolving different interaction forces for calcite (104) and calcite (100).     

Dissipative crystallization of aqueous mixtures of potassium salts of poly(riboguanylic acid) and poly(ribocytidylic acid)

Drying patterns of aqueous solutions of potassium salts of poly(riboguanylic acid) (KPolyG), poly(ribocytidylic acid) (KPolyC), and their mixtures KPolyG + KPolyC were studied on a cover glass, a watch glass, and a glass dish at room temperature. Accumulation of the polymers forming the broad rings near the outside edge and also in the inner area of the dried film was observed. The fine multiple ring structures formed, which supports the fact that the affinity of the polymer with the substrate is strong. Typical microscopic drying patterns of KPolyG, KPolyC, and KPolyG + KPolyC were spherulites, dendritic long rods, and sword (harberd)-like rods, respectively. The patterns changed depending on the location in the dried film. The dendritic long rods and sword-like rods were assigned to the crystals of double-stranded and/or triple-stranded helices of the G:C and 2G:C complexes. Cross-like drying patterns that originated from the salt-polymer interaction are also observed. The relationship between the polymer complexation of KPolyG + KPolyC systems and the drying patterns is similar to that of KPolyA (potassium salt of poly(adenylic acid)) + KPolyU (potassium salt of poly(uridylic acid)).     

Electron beam crosslinking of poly(vinylmethyl ether)

The electron beam induced branching of poly(vinylmethyl ether) (PVME) in bulk and in isopropanol solutions has been studied by gel permeation chromatography. The branching probability of bulk PVME induced by high-energy electrons can be characterized by gel permeation chromatography and a simple probability constant obtained. In isopropanol solutions this branching probability is not constant as a function of dose and is found to decrease with decreasing concentration. These results indicate the importance of solvent effects on the crosslinking of PVME in isopropanol solution by electron beam radiation. © 1994 John Wiley & Sons, Inc.     

Investigation of Calcium Carbonates Enhanced Poly(ε-caprolactone) Materials for Biomedical Applications

In this study poly(ε-caprolactone) – calcium-carbonate composites were obtained by melt-mixing. Two crystal-modifications of calcium-carbonate were used, namely calcite and aragonite. Compressive and tensile tests were executed on samples with various compositions to analyze the effect of filler content and particle geometry. Both minerals improved the compressive modulus and strength significantly, however the influence of calcite was superior. The tensile modulus was also highly increased. The elongation at break remained high even at 50 wt% aragonite filling, but decreased with two orders in the case of calcite. Biocompatibility tests were also carried out with human osteoblast cells and the results were promising. The relative cell number increased due to calcium-carbonate. Both filler material is able to enhance the mechanical and biological properties of poly(ε-caprolactone) significantly. Aragonite samples remained more ductile compared to calcite ones, but the calcite filled scaffolds are stiffer, stronger and slightly more biocompatible than aragonite filled materials.