Effect of Nanoclay on the Phase Separation Behavior of Poly（methyl methacrylate）/Poly（vinyl acetate） Binary Polymer Blends

The effect of nanoclay on the phase-separation behavior of poly（methyl methacrylate）/poly（vinyl acetate）（PMMA/PVAc） blends has been mainly investigated by small-angle laser light scattering. It is found that the effect of clay on the thermodynamics and kinetics of phase-separation for PMMA/PVAc blends seems inconsistent. The kinetics phaseseparation rate decreases, while the thermodynamics parameters, cloud points Tc and delay time tD of isothermal phaseseparation also decrease, and the variation amplitude depends on the matrix composition. The affinity of clay to PMMA results in the composition difference between the border layer and the polymer matrix and further causes the concentration fluctuation at the early stage of phase separation to reduce Tc and tD. On the other hand, the decrease of phase-separation rate is caused by the mechanical barrier effect of clay on the macromolecular diffusion of blend matrix. Hence, such seemingly counterintuitive results on the thermodynamics and kinetics of phase-separation are attributed to different dominant factors.     

氯化镁-乙醇络合物中乙醇的NMR定量研究

利用核磁氢谱技术对氯化镁-乙醇络合物中的乙醇进行定量分析研究,结果表明,采样时间和延迟时间的值对定量结果有一定的影响。以四氢呋喃为内标,将采样时间和延迟时间分别设定为4s和20s,利用核磁氢谱内标法测得氯化镁-乙醇络合物中乙醇的质量分数为55.40%,与热重法测定结果相符合。该方法测定结果的相对标准偏差为0.13%(n=6)。     

Influence of clay on the morphology and phase separation behavior of poly(methyl methacrylate)/poly(styrene-co-acrylonitrile) blends

The effect of clay on the morphology and phase-separation behavior of poly(methyl methacrylate)/poly(styreneco-acrylonitrile)(PMMA/SAN) blends and the variation of clay dispersion have been investigated. With the evolution of phase separation in PMMA/SAN, most of the clays are first located at the boundaries between PMMA and SAN, and then gradually move to the PMMA-rich domain, owing to the affinity of clay to PMMA. The introduction of clay causes the increase of binodal and spinodal temperatures of PMMA/SAN and enlarges their metastable region, indicating the phase stabilizing effect of clay on the matrix. But the influence of clay on the cloud points obviously depends on the composition of PMMA/SAN. The selective adsorption of PMMA on the clay results in the difference between the composition of surface layer and that of polymer matrix. Hence, the clay plays the role of an agent changing the conditions of phase structure formation.     

SiO_2粒子对PMMA/SAN共混体系相分离行为的影响

采用小角激光光散射(SALLS)并结合动态流变学方法,考察了气相法二氧化硅(SiO2)粒子的加入对聚甲基丙烯酸甲酯/苯乙烯-丙烯腈无规共聚物(PMMA/SAN)共混体系相行为的影响,得到了添加SiO2粒子前后的相图,发现SiO2粒子对基体相行为的影响与基体的组成有关.对PMMA/SAN(60/40)体系,加入SiO2粒子后相分离温度上升,但并未改变相分离机理,仍为亚稳单相分解过程(spinodal decomposition,SD);而对于PMMA/SAN(30/70)体系,加入SiO2粒子后却降低了体系的相分离温度.该现象可能是SiO2粒子和基体组分界面间组成与PMMA/SAN共混物基体组成的差异造成的.     

高分子复杂体系的结构与流变行为

流变学测试对非均相体系的结构变化具有敏感响应,被认为是表征多相/多组分聚合物体系结构与性能极为有效的方法.本文主要依据作者及其合作者的工作,对近年来围绕非均相体系形态结构与流变响应所开展研究的最新结果进行了总结和评述,涉及LCST型高分子共混体系的相形态与黏弹松弛、嵌段共聚物的微结构与线性/非线性黏弹行为、聚烯烃剪切诱导结晶时间尺度与流变响应、填充聚合物体系的结构性能和流变行为.对多相/多组分高分子共混体系形态结构演变的特征流变响应的充分认识,将有助于优化非均相体系的形态结构与最终力学性能.     

一种新的基于粗集的增量式规则提取算法

通过引入属性值通配符,进而将规则表示为带通配体的样本－－规则样本,并对粗集的知识约简方法稍作修改,使得加入新样本后更新规则库时能够充分利用已经获得的规则,尽量减小待简的决策表的数据量,避免每次从庞大的原始决策表开始约简,从而加快更新速度,减小计算量,只作少量修改,而不必再从头约简,最后结合个实例阐明了该方法的基本思路。     

具有部分状态信息的二阶多智能体系统的一致性

研究二阶连续多智能体系统的一致性问题,其中每个智能体只能在一系列离散时刻上获得位置信息.为了关于完全状态,即位置和速度,都达到一致,设计一类协议,并建立在该协议下,一致性成立的充要条件.该条件揭示了交流拓扑、控制器增益、采样周期和保持器的更新周期之间的关系.仿真例子表明理论结果是有效的.     

ZSM-5分子筛催化剂稳定性的研究

为观察C₄烯烃转化制丙烯过程中影响催化剂稳定性的因素，对经历不同反应时间（即新鲜、反应48h、反应650h、反应650h后再生和再生后再进行反应48h）的系列ZSM-5分子筛催化剂进行了表征。结果表明，经历长期反应后，催化剂微孔体积和BJH吸附累积孔体积明显降低；再生后，孔体积可以恢复到新鲜催化剂的初始值。与此同时，NH₃-TPD酸量不仅降低，而且再生后也不能得到恢复。与高温水蒸气处理的催化剂相比较，²7Al MAS NMR表征结果说明，积炭因素对催化剂孔体积的影响可通过再生消除，而分子筛骨架铝丢失和分子筛晶胞参数的降低对催化剂酸量的持续减少起主要作用。长期在高温水蒸气条件下运行后，催化剂酸量可维持在一定水平，使催化剂长期稳定运行成为可能。     

Molecular dynamics and phase behavior of polystyrene/poly(vinyl methyl ether) blend in the presence of nanosilica

The variation of phase morphology, critical temperature of demixing, and molecular dynamics for polystyrene/poly(vinyl methyl ether)(PS/PVME) blends induced by hydrophilic nanosilica(A200) or hydrophobic nanosilica(R974) was investigated. With the phase separation of blend matrix, A200 migrated into PVME-rich phase due to strong interaction between A200 and PVME, while R974 moved into PS-rich phase. The thermodynamic miscibility and concentration fluctuation during phase separation of blend matrix were remarkably retarded by A200 nanoparticles due to the surface adsorption of PVME on A200, verified by the correlation length ξ near the critical region from rheological measurement and the weakened increment of reversing heat capacity(ΔC_p) during glass transition via modulated differential scanning calorimetry(MDSC). The restricted chain diffusion induced by nanosilica still occurred despite no influence of A200 and R974 on the segmental dynamics of homogenous blend matrix. The interactions between nanosilica and polymer components could restrict the terminal relaxation of blend matrix and further manipulate their phase behavior.