含氢聚硅氧烷／丙烯酸丁酯／丙烯酰胺聚合物乳液粒子的形成,大小与流变性研

采用一次加料法和半连续滴加法制备了含氮聚硅氧烷（ＰＨＭＳ）／丙烯酸丁酯（ＢＡ）／丙烯酰胺（ＡＭ）复合聚合物乳液,探讨了乳液成核机理,考察了ＰＨＭＳ、ＡＭ用量、加料主试对乳液粒大小及其流变形的影响,发现该聚合机理以胶束成核为主,ＰＨＭＳ用量增加,乳液粘度,乳液粒子尺寸增大,ＡＭ用量对其影响较小。     

苯乙烯－丙烯酸丁酯－甲基丙烯酸乳液聚合加料方法对粒子形态的影响

用３种不同的加料方法和２种不同的加料顺序，制备了苯乙烯（Ｓｔ）－丙烯酸丁酯（ＢＡ）－甲基丙烯酸（ＭＡＡ）复合聚合物乳液．测定了聚合物乳胶粒子的大小和分布，观测了粒子的形态，测定了羧酸基团在乳胶粒子中的分布及乳液的碱增稠性，还测定了胶膜的溶胀性．探讨了在复合乳化剂下聚合方法－成核机理－粒子微观结构－乳胶性质之间的关系     

苯乙烯—甲基丙烯酸酯—丙烯醋三元无皂乳液共聚合动力学研究

以苯乙烯（Ｓｔ）、甲基丙烯酸甲酯（ＭＭＡ）为主单体,丙烯酸（ＡＬ）为功能单体进行了无皂乳批量共聚合、考察了功能单体浓度、引发剂过硫酸铵ＡＰＳ浓度及聚合温度及其动力学行为的影响,胜Ｇａｍｍａ积分函数拟合了转化率－时间曲线,获得了聚合过程的重要特征参数中：平均成核速率（ＮＶ）,聚合最小速率（ＭＶ）和平稳期平均聚速率（ＡＶ）及成核结束和聚合进入完成期对应的转化率,同时对聚合速率与以上各聚合参数数据进行了     

VAc／MMA半连续无种子乳液共聚合数值模拟

建立了ＶＡｃ／ＭＭＡ半连续无各子乳液共聚合数学模型。通过数值模拟计算表明：ＶＡｃ／ＭＭＡ的成核以均相成核为主，与种子法比较，ＶＡｃ／ＭＭＡ无种子乳液共聚体系可选择相对较大的加料速率进行反应，而不致于导致反应末期的爆聚产生，另外，通过数值模拟考察了组分和操作参数对过程成核和反应动力学的影响。     

聚甲基丙烯酸甲酯表面改性TiO2的研究

本文采用无皂乳液聚合法，使甲基丙烯酸甲酯（ＭＭＡ）在ＴｉＯ２粒子表面进行聚合，得到了以ＴｉＯ２粒子为核，聚甲基丙烯酸甲酯（ＰＭＭＡ）为壳的复合粒子，ＴｉＯ２粒子表面由此得到改性研究了ＴｉＯ２表面聚合物成膜的条件，用ＴＥＭ证实了表面聚合物膜的存在，运用ＩＲ和ＤＴＡ对复合粒子进行了表征，并利用Ｚｅｔａ电位，接触角的测定及分散性试验对改性前后ＴｉＯ２的表面性质进行了研究。     

乳化剂对半连续乳液聚合动力学及成核机理的影响

采用半连续乳液聚合工艺制备丙烯酸酯乳液,研究乳化剂浓度([E])对聚合动力学和成核机理的影响,并分析不同[E]时整个聚合过程中粒子尺寸分布的演变规律.实验结果表明:当[E]>0.01mol/L时,聚合速率Rp∝[E]1.28,体系遵循胶束成核机理及聚合规律;而当[E]<0.01mol/L时,Rp∝[E]0.17,体系以均相成核为主要成核方式.此外,根据整个聚合过程中的粒子尺寸分布规律可进一步验证体系在不同[E]时具有不同的成核机理.     

偶氮二异丁腈引发甲基丙烯酸甲酯微乳液聚合

以一种新的Ｙ型乳化剂１２－丁酰氧基－９－十八烯酸（ＢＯＡ）,制备了甲基丙烯酸甲酯（ＭＭＡ）含量高达２０％的微乳液,并以油溶性引发剂偶氧二异丁腈（ＡＩＢＮ）引发其聚合。实验表明,与单体含量较低的微乳液聚合相比,ＭＭＡ在其含量较高的微乳液中聚合时表现出一些明显不同的特征,如在聚合初期,聚合主要在大粒子内进行。ＭＭＡ的 聚合与非极性单体的微乳液聚合相比也比较特殊,其聚合速度和聚合物分子量与引发剂浓度、单     

PROCESS STABILITY OF THE EMULSION POLYMERIZATION OF THE GHD LATEX

采用半连续种子乳液聚合技术合成了含甲基丙烯酸缩水甘油酯（ＧＭＡ）、甲基丙烯酸羟乙酯（ＨＥＭＡ）和甲基丙烯酸二甲氨基乙酯（ＤＭＡＥＭＡ）的室温自交联乳液（ＧＨＤ）,研究了聚合工艺和配方对ＭＭＡ＿ＢＡ＿ＨＥＭＡ＿ＤＭＡＥＭＡ体系的聚合过程稳定性的影响．除了聚合过程中形成的水溶性聚合物的架桥凝聚作用之外,反应性官能团间的交联凝聚作用对ＧＨＤ乳液聚合稳定性有重要影响．增加ＨＥＭＡ和ＤＭＡＥＭＡ用量对该聚合过程的稳定性没有明显影响．     

St—BA—MAA无皂乳液聚合机理的研究

考察了Ｓｔ－ＢＡ－ＭＡＡ无皂乳液聚合反应不同时间转化率、聚合物的分子量、乳胶粒形态和粒径的变化。结果表明：当转化率达１％,Ｍ－ｎ达４．０９×１０４,初始乳胶粒子形成,主要为均相沉淀成核机理。羧基单体是影响乳胶粒形态重要因素之一。     

GHD乳液的聚合稳定性

采用半加续种子乳液聚合技术合成了含甲基丙烯酸缩水甘油酯（ＧＭＡ）、甲基丙烯酸羟乙酯（ＨＥＭＡ）和甲基丙烯酸二甲氨基乙酯（ＤＭＡＥＭＡ）的室温自交联乳液（ＧＨＤ）,研究了聚合工艺和配方对ＭＭＡ－ＢＡ－ＨＥＭＡ－ＤＭＡＥＭＡ体系的聚合过程稳定性的影响,除了聚合过程中形成的水溶性聚合物的架桥凝聚作用之外,反应性官能团间的交联凝聚作用对ＧＨＤ乳液聚合稳定性有重要影响。增加ＨＥＭＡ和ＤＭＡＥ－ＭＡ用量对该聚     

微波连续合成无皂均分散高分子微球

报道了制备均分散高分子微球的一种简捷快速,低能耗且无环境污染的聚合方法－无皂微波连续合成法,使工业化生产的均分散高分子微球成为可能。本实验中分别制备了聚苯乙 聚甲基丙烯酸甲酯两种均分散高分子微球,用动态光散射和电子显微镜等仪器对粒子进行了表征,对影响高分子微球体积的因素进行了分析,还对成核机理进行了初步的讨论。     

Ga-In liquid metal nanoparticles prepared by physical vapor deposition

Controlled synthesis and appropriate characterization of nanoscale particles of gallium-based liquid metals are critical to fulfilling their broad range of applications in the field of flexible, stretchable, and printable micro-/nanoelectronics. Herein, we report a new way to synthesize surfactant-free gallium-indium nanoparticles with controlled particle size on a variety of substrates through a facile physical vapor deposition method. It was found that with prolonged deposition time the liquid metal nanoparticles gradually grew from near-monodispersed small particles with a diameter of ～25 nm to bimodal distributed particles. A nucleation, growth, ripening and merging process was proposed to explain the observed evolution of particle size. Atomic force microscopy measurement indicates that the fabricated liquid metal nanoparticles demonstrate elastic deformation with a certain range of loads and the scanned particle size is dependent on the applied loads. We further investigated the gradual breaking process of the core-shell structured liquid metal nanoparticles, which was evidenced by multiple kinks on the force-separation curve. This work presents a new bottom-up approach to prepare nanoscale liquid metal particles and demonstrates that atomic force microscopy is a suitable technique to characterize the synthesized liquid metal nanoparticles.     

Stable sulphate clusters as a source of new atmospheric particles

The formation of new atmospheric particles with diameters of 3-10 nm has been observed at a variety of altitudes and locations. Such aerosol particles have the potential to grow into cloud condensation nuclei, thus affecting cloud formation as well as the global radiation budget. In some cases, the observed formation rates of new particles have been adequately explained by binary nucleation, involving water and sulphuric acid, but in certain locations--particularly those within the marine boundary layer and at continental sites--observed ambient nucleation rates exceed those predicted by the binary scheme. In these locations, ambient sulphuric acid (H2SO4) levels are typically lower than required for binary nucleation, but are sufficient for ternary nucleation (sulphuric acid-ammonia-water). Here we present results from an aerosol dynamics model with a ternary nucleation scheme which indicate that nucleation in the troposphere should be ubiquitous, and yield a reservoir of thermodynamically stable clusters 1-3 nm in size. We suggest that the growth of these clusters to a detectable size (> 3 nm particle diameter) is restricted by the availability of condensable vapour. Observations of atmospheric particle formation and growth from a continental and a coastal site support this hypothesis, indicating that a growth process including ternary nucleation is likely to be responsible for the formation of cloud condensation nuclei.     

水汽在细微颗粒表面异质核化数值分析

建立蒸汽在同时含有不溶物质与可溶成分的粗糙颗粒表面核化特性数值实验平台,对水汽异质核化晶核形成自由能、成核速率、成核几率、成核临界饱和度、平衡水汽饱和度进行数值分析.结果表明:可溶性盐含量对成核自由能势垒、成核临界饱和度无影响,但对晶核越过自由能势垒进一步长大过程自由能及平衡水汽饱和度影响显著.用自仿射分形理论描述粗糙颗粒表面,将表面粗糙程度与接触角联系起来,研究发现:颗粒表面粗糙度降低了成核自由能势垒,引起成核速率与成核几率迅速增大,成核临界饱和度降低,而对晶核进一步长大过程中水汽的平衡无明显影响.较高的可溶性盐含量有利于核化液滴的长大;颗粒表面越粗糙,越易于核化.     

柴油轿车燃用生物柴油的模态颗粒排放特性

以帕萨特柴油轿车为试验样车,使用排气颗粒数量及粒径分析仪(EEPS),对分别燃用沪Ⅳ柴油、生物柴油混合体积分数分别为5%,10%,20%和50%的沪Ⅳ柴油-生物柴油混合燃料、纯生物柴油的模态颗粒排放特性进行了试验研究.结果表明:GB18352.3—2005Ⅰ型试验循环中,该车燃用生物柴油的聚集态颗粒数量浓度下降,核模态颗粒数量浓度上升,总颗粒数量浓度变化不大;随着生物柴油混合比例的增加,该车燃用沪Ⅳ柴油-生物柴油混合燃料排气颗粒的平均粒径降低,颗粒数量浓度峰值向小粒径方向偏移.     

梯度核壳乳液的合成研究

采用多步乳液聚合法合成具有核/中间层/壳梯度结构的纯丙乳液,并对影响聚合物粒子核壳结构的主要因素进行了探讨。实验发现硬单体和软单体在选用多步乳液聚合技术时,可形成具有梯度的硬核软壳结构型乳液,降低了乳液的最低成膜温度;采用壳预乳化法添加乳化剂可使其在不同的反应阶段得到合理分配,有利于维持反应体系稳定,并避免在反应后期生成新粒子;当乳化剂用量为3%时,凝聚率仅有1%,所得乳液粒径在100nm左右且粒径分布均匀。同时,通过粒度仪和透射电镜（TEM）对粒子结构进行分析并验证了其梯度核壳结构形态。     

氧化催化转化器对柴油机颗粒物排放特性的影响

以某高压共轨重型柴油机为样机,研究氧化催化转化器(Diesel Oxidation Catalyst,DOC)对柴油机颗粒排放规律的影响.研究结果表明,各工况下,DOC后测点颗粒物质量浓度相对于前测点均有所下降,降幅随转速升高而减小,随着负荷的增大变化不大;外特性下,DOC对总颗粒、核态颗粒和聚集态颗粒的转化率均随着转速增加而波动下降,其平均转化率分别为21.5%,26.2%和15.4%;最大转矩转速1 400r·min-1负荷特性下,DOC对总颗粒、核态颗粒、聚集态颗粒的转化率均随着负荷的增大先下降再上升,其平均转化率为34.6%,38.8%和27.3%;DOC对核态颗粒物的转化率高于聚集态颗粒物,在粒径为9~12nm的范围内转化率达到最高,其他粒径范围内转化率大多介于20%~40%之间.     

Suppression of crystal nucleation in polydisperse colloids due to increase of the surface free energy

The formation of small crystallites is governed by two competing factors: the free energy gained upon transferring constituent atoms, molecules or colloidal particles from the metastable liquid to the more stable solid, and the free energy needed to create the surface area of the crystallite. Because the ratio of surface area to bulk is large for small particles, small crystallites dissolve spontaneously under conditions where larger crystallites are stable and macroscopic crystal growth occurs only if spontaneously formed crystallites exceed a critical minimum size. On theoretical grounds, the probability of forming such critical crystal nuclei is expected to increase rapidly with supersaturation. However, experiments show that the rate of crystal nucleation in many systems goes through a maximum as the supersaturation is increased. It is commonly assumed that the nucleation rate peaks because, even though the probability of forming critical nuclei increases with increasing concentration, the rate of growth of such nuclei decreases. Here we report simulations of crystal nucleation in suspensions of colloidal spheres with varying size distributions that show that the probability that critical nuclei will form itself goes through a maximum as the supersaturation is increased. We find that this effect, which is strongest for systems with the broadest particle size distribution, results from an increase with supersaturation of the solid-liquid interfacial free energy. The magnitude of this effect suggests that vitrification at high supersaturations should yield colloidal glasses that are truly amorphous, rather than nano-crystalline.     

纳米尺寸聚合物胶乳及其粒径分布

用半连续乳液聚合法合成了粒径为５０ｕｍ～１００ｕｍ的苯乙烯－丙烯酸了酯－丙烯酸共聚物胶乳，讨论了搅拌速度等其它因素对胶乳粒度及分布的影响．实验表明，增加乳化剂量有利于胶乳粒度减小，但超过一个阔值将使粒径分布变宽．