UV固化水性超支化聚酯的制备研究

以季戊四醇为核、2,2-二羟甲基丙酸为臂单体合成第一代超支化聚酯;然后以第一代超支化聚酯为核,2,2-二羟甲基丙酸为臂单体合成第二代超支化聚酯,采用丙烯酰氯、顺丁烯二酸酐对第二代超支化聚酯进行改性,合成了UV固化水性超支化聚酯,并对其进行了红外光谱和差热分析,研究了丙烯酰氯、顺丁烯二酸酐用量对涂膜性能的影响。结果表明,当超支化聚酯、丙烯酰氯、顺丁烯二酸酐三者的物质的量之比为1∶6∶8时,水性超支化聚酯的稳定性和涂膜的耐水性较好。     

芳香族超支化聚酯型环氧树脂的合成及表征

以三羟甲基丙烷为中心核,与偏苯三酸酐和环氧氯丙烷开环聚合反应合成芳香族超支化聚酯,在碳酸钾水溶液作用下对其进行了闭环反应合成了超支化聚酯型环氧树脂。分别用红外光谱、核磁氢谱、凝胶色谱仪、热重分析表征了超支化聚酯型环氧树脂的结构。结果表明,合成产物具有芳香族超支化聚酯型环氧分子结构,合成的芳香族超支化聚酯型环氧树脂具有较好的热稳定性。     

末端环氧化超支化荧光聚合物的合成

通过季戊四醇、偏苯三酸酐、环氧氯丙烷合成超支化聚酯,利用合成聚合物分子外围的羧基与二缩水甘油醚、甲萘胺反应,形成末端官能化超支化荧光聚合物,在获得荧光聚合物的同时,不仅保留了超支化聚合物的良好的相溶性,其热性能也得到了改善;通过DSC、TG、红外光谱、荧光光谱等手段研究了合成聚合物的热稳定性,及结构与荧光性能的关系。     

芳香族超支化聚酯的合成及表征

以三羟甲基丙烷为核单体,双酚酸甲酯为AB2型单体,采用熔融缩聚的方法合成了具有芳香型结构的超支化聚酯.使用IR、黏度、化学滴定、热重分析等方法进行了表征.结果表明,合成芳香族超支化聚酯为多端羟基的类球型聚酯,具有较好的流动性和热稳定性,可作为加工助剂用于改善体系加工性能.     

超支化聚酯的研究现状

综述了超支化聚酯的合成方法,主要重点介绍了最新合成的芳香族超支化聚酯和脂肪族超支化聚酯;阐述了目前超支化聚酯在共混改性、纳米材料、医药、涂料等方面的应用进展;旨在加深人们对超支化聚酯的了解,从而促进其快速发展.     

超支化糖苷聚合物的合成及生物基质共混膜性能

单糖分子为原料,Koenigs-Knorr法合成一种带羧基和多羟基的糖苷衍生物,以此糖苷衍生物为单体制备超支化聚酯。用傅里叶变换红外光谱、核磁共振波谱、凝胶渗透色谱、差示扫描量热分析和热重分析表征中间产物和超支化聚酯结构。超支化聚酯与聚乳酸共混制备复合膜,扫描电镜观测复合膜的相容性,拉力试验测试复合膜的力学性能,差示扫描量热分析复合膜的热性能,接触角测量仪测试复合膜的润湿性。结果表明,成功合成了超支化聚酯目标产物,超支化聚酯的相对分子质量随代数的增加而上升,支化度较高,热稳定性较好。超支化聚酯与聚乳酸相容性良好,共混之后聚乳酸的力学性能、热性能及润湿性均有提高。     

紫外光固化超支化聚酯丙烯酸酯/二氧化硅杂化材料的制备EI北大核心CSCD

以季戊四醇为"核",2,2-二羟甲基丙酸为支化单体,用逐步聚合的方法合成了不同代数超支化聚酯;将不同代数超支化聚酯分别与六亚甲基二异氰酸酯和丙烯酸羟乙酯半加成产物进行反应,得到一系列超支化聚酯丙烯酸酯低聚物。最后,将得到的超支化聚酯丙烯酸酯低聚物与改性纳米二氧化硅进行复合,得到可紫外光固化的超支化聚酯丙烯酸酯/二氧化硅杂化材料。对合成的超支化低聚物的结构用红外光谱、核磁共振谱和凝胶色谱进行表征。紫外光谱显示所有超支化低聚物在210 nm处有强的紫外吸收。超支化低聚物的玻璃化转变温度用差示扫描量热仪进行测量,结果显示温度范围为-68.68℃到-25.4℃。此外,对紫外光固化超支化聚酯丙烯酸酯低聚物的热性能用热重分析仪进行了表征。     

紫外光固化超支化聚酯丙烯酸酯/二氧化硅杂化材料的制备

以季戊四醇为"核",2,2-二羟甲基丙酸为支化单体,用逐步聚合的方法合成了不同代数超支化聚酯;将不同代数超支化聚酯分别与六亚甲基二异氰酸酯和丙烯酸羟乙酯半加成产物进行反应,得到一系列超支化聚酯丙烯酸酯低聚物。最后,将得到的超支化聚酯丙烯酸酯低聚物与改性纳米二氧化硅进行复合,得到可紫外光固化的超支化聚酯丙烯酸酯/二氧化硅杂化材料。对合成的超支化低聚物的结构用红外光谱、核磁共振谱和凝胶色谱进行表征。紫外光谱显示所有超支化低聚物在210 nm处有强的紫外吸收。超支化低聚物的玻璃化转变温度用差示扫描量热仪进行测量,结果显示温度范围为-68.68℃到-25.4℃。此外,对紫外光固化超支化聚酯丙烯酸酯低聚物的热性能用热重分析仪进行了表征。     

超支化聚合物

超支化聚合物独特的三维分子结构使其具有低粘度,高反应活性和良好的相溶性等优良性能。同时大量的末端基可以进一步功能化,这些独特的性质使得超支化聚合物成为21世纪高分子科学研究的重要方向。本文综述了超支化聚合物的发展现状及发展趋势,并介绍了它的性质,应用,种类,表征方法和合成方法。     

新型多羟基树枝化线形聚氨酯的合成

聚氨酯侧链接枝末端舍有大量羟基且具有良好生物相容性的脂肪族聚酯树枝状分子,在引入大量反应官能团的同时增加分子间空间间隔,为生物活性分子的接枝提供一种性能优异的中间材料.通过1H-NMR、DSC、接触角及表面分析等测试方法表征聚氨酯树枝化前后结构及性能的改变.结果显示,多羟基树枝化线形聚氨酯的氢键化程度大大提高,结晶性能降低,亲水性及表面粗糙度增加.细胞培养试验证明,该材料具有很好的细胞相容性,为其在生物医学上的应用奠定了良好的基础.     

氢还原制备树枝状Fe_3O_4和α-Fe及其静磁性能研究

以树枝状α-Fe2O3为前驱物,通过氢还原制备得到Fe3O4和α-Fe树枝状结构,系统研究热处理还原条件对产物形貌和成分的影响。结果表明:随着还原温度和还原时间的增加,树枝状α-Fe2O3前驱物逐渐被还原为α-Fe,还原产物的树枝状形貌保持程度依次降低。还原是一个缓慢且分级进行的过程,因此通过控制还原反应的温度和时间,可以得到形貌良好的树枝状Fe3O4和α-Fe。而当还原温度和时间增加时,产物会发生晶粒生长以及重结晶过程,从而导致树枝状形貌被破坏程度逐渐增加,精细结构逐渐消失。对其进行静磁性能表征发现:由于具有大的形貌各向异性,Fe3O4和α-Fe树枝状结构在室温下具有大的矫顽力和剩余磁化强度。     

凝固方向对单晶高温合金枝晶组织的影响

用籽晶法制备了沿不同晶体取向凝同的镍基单晶高温合金试样,研究了单晶中枝晶形貌和一次枝晶臂距随凝固取向的变化规律.结果表明:凝同方向偏离[001]取向小于15°时,枝晶排列比较规则,一次枝晶臂距随偏离角度增大而减小;偏离角度为25°时,部分二次枝晶臂阻断了相邻一次枝晶干的生长,导致一次枝晶臂距增大.沿[011]和[111...     

基于一种改进CA模型模拟双辊连续铸轧纯铝微观组织

基于枝晶生长的基本传输过程和元胞自动机(Cellular Automaton,简称CA)-有限元(Finite Element,简称FE)模型基本原理,建立了适应双辊连续铸轧纯铝薄带工艺特点的凝固过程形核和晶体生长的数学模型.模型耦合了宏观温度场和微观组织模拟计算,考虑了溶质扩散、曲率过冷和各向异性等重要因素的影响,定义了界面单元捕获规则,能够模拟凝固过程中枝晶生长的形态.应用本模型对双辊连续铸轧纯铝薄带凝固过程中等轴晶生长、等轴晶多晶粒生长及柱状晶生长、柱状晶向等轴晶演化进行模拟并与实验结果进行对比,模拟结果与实验结果吻合较好,验证了模型的正确性.     

Investigation of self-assembled dendrimer complexes

Dendrimer complexes[(G-2)₄P and (G-3)₄P]with a porphyrin core have been prepared by self-assembling of sodium tetrakis(4-sulfonatophenyl) porphyrin with dendritic quaternary bromides (G-2 and G-3), which were synthesized by reaction of Frechet type dendritic bromides (G-2 and G-3) with triethylamine. The structure of dendrimer complexes was confirmed by ¹H NMR and element analysis. The stoichiometry rate between the dendritic quaternary bromide and porphyrin core was 4:1. Solvatochromism studies of the dendritic complexes showed that the (G-3)₄P dendritic complex is more stable than the (G-2)₄P dendritic complex. It is inferred that hydrophobic interactions play an important role in stabilizing these dendrimer complexes in addition to coulombic interactions.     

原子力显微术对透明质酸自组装行为的研究

应用原子力显微术(AFM)对透明质酸(HA)在云母表面的自组装体系进行表征,获得了HA在云母表面自组装成的纤维状、三维网状及独特的具有分形特征的树枝状结构。纤维状及三维网状形貌对于研究其在体内发挥的生理作用具有重要意义。树枝状结构符合分形学中的DLA模型。研究HA通过自组装形成的自然界普遍存在的网状及树枝状分形结构,对于理解其结构与功能之间的关系具有重要意义。     

树枝状聚醚的合成与实验条件探讨

以3,5-二羟基苯甲醇和氯化苄为原料,经Willamson醚化反应和卤代反应合成了1-3代以CH2Br为核的树枝状聚醚,并分别用核磁和差示扫描量热仪进行了结构和熔点分析。对比了氯化亚砜、三溴化磷、四溴化碳卤代试剂的卤代效果,以及聚乙二醇-400、18-冠-6为相转移催化剂的催化效果。结果表明,采用Williamson醚化反应可以合成确定结构的1-3代树枝状聚醚,其熔点分别为80℃、107℃、122℃。以四溴化碳为卤化剂,冠醚为催化剂可以得到较高的产物收率。     

Preparation of dendritic-like Ag crystals using monocrystalline silicon as template

Symmetric dendritic silver structures with controlled morphology were successfully synthesized by a solvothermal method with the assistance of monocrystalline silicon. The morphology and structure of the dendritic silver were characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and scanning electron microscopy (SEM). It was found that the architecture of silver crystals could be controlled via simply adjusting the experiment parameters: AgNO₃ concentration, reaction time and temperature. Moreover, structural characterizations suggested that the dendritic silver structures preferentially grew along (1 1 1) and (2 0 0) directions, leading to the formation of dendritic structures with 1-2 μm in stem diameter and 10-50 μm in length. Additionally, the formation process of the dendritic silver structures was studied, and a possible formation mechanism was proposed based on the experimental results.     

3D Stochastic Modeling of Grain Structure for Aluminum Alloy Casting

A 3D stochastic modeling was carried out to simulate the dendritic grains during solidification of aluminum alloys,including time-dependent calculations for temperature field, solute redistribution in liquid, curvature of the dendritic tip, and growth anisotropy. The nucleation process was treated by continuous nucleation. A 3D simplified grain shape model was established to represent the equiaxed dendritic grain. Based on the Cellular Automaton method,a grain growth model was proposed to capture the neighbor cells of the nucleated cell. During growing, each grainc ontinues to capture the nearest neighbor cells to form the final shape. When a neighbor cell was captured by other grains, the grain growth along this direction would be stopped. Three-dimensional calculations were performed to simulate the evolution of dendritic grain. In order to verify the modeling results, the predictions were compared with the observation on samples cast in the sand mold and the metal mold.     

Visualization of solute distributions in dendritic and spheroidized Al grains characterized by both color etching method and electron probe microanalysis

Spheroidization of Al grains was realized by compressing and partially remelting the as-received A356 aluminum alloy billets with a dendritic microstructure. A color etchant named Weck’s reagent was used to characterize the microstructures of both dendritic and spheroidal Al grains. After etching, color differences were observed inside Al grains. In the spheroidal grains, both the original dendritic structure and grain growth during water quenching were revealed by this reagent. By electron probe microanalyses, it was found that such color difference was strongly related to the microsegregation of Ti. Also, both microsegregations of Si and Ti were found in dendritic Al grains, as well as the grain growth of spheroidal Al grains during water quenching. Quantitative analyses indicated that after heating and partial remelting, the concentration of Ti was increased from dendritic grain to spheroidal grain. This phenomenon was discussed and considered to be related to Ostwald ripening and the increase of Ti solubility in Al as the temperature increased.     

Solute redistribution in a duplex dendritic structure

A duplex dendritic structure consists of co-existing regions of coarse and fine dendrites. Such a structure in aluminium-4,5 wt % copper alloy was produced by rapid quenching from the partially solid-partially liquid state. The concentration of solute was found to be low and constant within the coarse structure, which contains a smaller amount of non-equilibrium secondary phase than does the fine dendritic structure. The solute distribution profiles within both the coarse and fine dendritic structures were found to be fairly accurately described by the Scheil equation for non-equilibrium solidification. Complete dissolution of the secondary phase occurred within the coarse structure after a shorter solutionizing time than it did within the fine dendritic structure. A spherical diffusion model accurately described solution kinetics within the coarse structure and a cylindrical diffusion model within the fine structure.