反相“核壳结构”乳胶粒子的合成及其形态

以甲基丙烯酸甲酯（MMA）、丙烯酸丁酯（BA）和苯乙烯（St）为单体,采用半连续种子乳液法,合成了PS/P(MMA BA)聚合物乳液。通过粒径分布、DSC和透射电镜（TEM）表征了乳胶粒结构,并利用原子力显微镜(AFM)对不同温度处理下的乳胶粒子结构及形态变化进行了研究。结果表明,合成的聚合物乳液为反相核壳结构;随着热处理温度的升高,乳胶粒子的结构和形态发生明显的变化,出现粒子的变形、融合并发生正反核壳的翻转。     

聚丙烯酸丁酯核壳乳胶粒子增韧聚氯乙烯的核壳粒子结构与材料性能的关系

通过共混方法研究核壳、结构聚丙烯酸酯增韧改性聚氯乙烯(PVC),用冲击实验来评价核壳粒子结构参数对共混体材料性能的影响。其中包括橡胶核的组成及交联度、壳层的厚度及组成、粒子尺寸等．结果表明,适当的交联度、较薄的橡胶核壳层有利于改善PVC的韧性。     

可再分散核壳结构乳胶粉的制备

采用种子乳液聚合法制备了核壳结构聚合物乳液,研究了乳化剂用量、核壳比例对乳胶粒形态及聚合物成膜性能的影响;将上述乳液经过喷雾干燥制得可再分散胶粉,对乳胶粉微观形貌进行了表征。实验结果发现,当乳化剂占单体质量分数大于0.5%,核/壳单体质量比在7:3以上,制得的乳液稳定性较好,TEM照片显示存在清晰的核壳结构,测得乳液成膜温度在30℃以下,制得可再分散胶粉直径小于40μm。     

核壳结构聚合物乳胶粒的制备与表征

选用苯乙烯和丙烯酸丁酯为聚合单体,改变乳化剂和引发剂用量,制备粒径分布较窄的苯丙乳液.以此为种子胶乳,选用甲基丙烯酸甲酯(MMA)、丙烯酸乙酯(EA)和甲基丙烯酸(MAA)为第2步聚合单体,分别采用批量法和半连续滴加法,制备出具有核壳结构且性能稳定的乳胶粒乳液.通过粒径分析和透射电镜,测试和比较分析两种乳胶粒粒径和形貌...     

SiO_2-含氟丙烯酸酯核壳纳米复合乳胶粒子的制备和表征

以纳米SiO2水溶胶为种子,通过种子乳液聚合法合成了壳中含氟的SiO2-含氟丙烯酸酯核壳纳米复合乳胶粒子.通过透射电镜及动态光散射法证实了该乳胶粒子的微观核壳结构,并且该乳液的粒径分布窄,乳胶粒子大小均匀.另外,利用红外光谱及表面光电子能谱分析了乳胶粒子的化学结构,结果证明含氟丙烯酸酯单体能够通过种子乳液聚合方法引入到核壳结构乳胶粒子中.     

改性环氧 PBA/PMMA 核壳乳胶粒子的制备与应用

采用半连续种子乳液聚合工艺制备核壳结构的聚丙烯酸丁酯/(聚甲基丙烯酸甲酯—衣康酸—双酚A环氧树脂)(PBA/P(MMA-ITA-DGEBA))乳胶粒子.并通过红外光谱仪(IR)对乳胶粒子进行了表征,证明乳胶粒子具有核壳粒子结构.将壳层带有环氧基的核壳乳胶粒子对环氧树脂进行增韧,通过扫描电子显微镜(SEM)对固化物冲击断面进行观测,改性核壳乳胶粒子对环氧树脂起到明显增韧效果,并提升了与环氧树脂的相容性     

前驱物种类对氧化铁/氧化硅核壳结构制备的影响

分别以Fe3O4、β-FeOOH、和α-Fe2O3作为前驱物,采用Stober水解法制备了氧化铁/氧化硅核壳结构,研究了前驱物种类和原料用量对二氧化硅包覆过程的影响.随着氨水和TEOS用量的增加,包覆层厚度增加,包覆更加均匀.对样品进行了扫描电镜(SEM)、透射电镜(TEM)和红外光谱(IR)表征.实验结果表明,在三种类型的前驱物中,二氧化硅在β-FeOOH表面包覆最均匀,包覆效果最好.     

核壳粒子对PBT增韧改性研究

采用甲基丙烯酸甲酯(MMA)和丙烯酸丁酯(BA)合成了软核硬壳的核壳粒子,再用该核壳粒子改性聚对苯二甲酸二丁酯（PBT）。研究了核壳粒子合成工艺及添加量对PBT力学性能的影响,并研究了核壳粒子与马来酸酐接枝POE共同改性PBT的力学性能。结果表明,单体MMA和BA质量比为2/3时核壳粒子对PBT有较好的增强增韧效果;引发剂增加有利于减小核壳粒子粒径,有利于提高PBT的强度;核壳粒子与POE-g-MAH有共增韧效果,在基本不影响PBT强度下显著提高冲击性能。     

表层功能化PDMS/PMMA核壳乳胶粒子的制备与表征

分别以衣康酸(ITA)、马来酸酐(MAH)和甲基丙烯酸缩水甘油酯(GMA)为功能单体,采用预乳化半连续工艺通过种子乳液聚合方法成功合成了表层功能化的聚二甲基硅氧烷/聚甲基丙烯酸甲酯(PDMS/PMMA)核壳乳胶粒子(~320 nm)。PDMS核乳胶粒子以八甲基环四硅氧烷(D4)和四甲基四乙烯基环四硅氧烷(VD4)为单体、甲基三乙氧基硅烷(MTES)为交联剂构建而成,实验研究了反应时间、乳化剂和催化剂用量、单体D4与VD4比例对聚合体系的影响,并确定了PDMS核乳胶粒子合成最佳工艺。通过激光粒度分析仪、傅里叶变换红外光谱仪、透射电子显微镜等分析表明:当反应时间为10 h、乳化剂用量为核单体总量的5.3%、催化剂用量为核单体总量的5.3%、核单体比D4∶VD4=4∶1时,核单体转化率接近85%,PDMS核乳胶粒子尺寸在290 nm左右。     

Study on the specific interaction between angiogenin and aptamer by atomic force microscopy （AFM）

The specific interaction between angiogenin and aptamer has been investigated by using AFM. The specificity of the interaction is revealed by comparing the binding probability of aptamer to other elements in a series of control experiments. The results have shown that there is specific interaction force between angiogenin and aptamer. Moreover, the single molecular pull-off force between angiogenin and aptamer has also been determined using the Poisson statistical method to be 133.7±11.7 pN. These findings obtained are helpful to the better revelation of recognition mechanism between angiogenin and aptamer, which provided basis for further understanding the inhibition of the aptamer to angiogenic activity.     

Analysis of the Structure of Adsorbed Fibrinogen on Solid Surfaces and Its Dynamic Processes Using AFM

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Determination of hydration film thickness using atomic force microscopy

Surface forces between particles control phenomenasuch as dispersion, agglomeration, coatings, adhesion,wetting, friction, and polishing, which play a crucial rolein materials processing. The importance of surface forcesis more appreciated especially in colloidal processing,while materials in a colloidal state are frequently preferredin industrial processing operations (e.g., printing inks,toners, paints, skin creams, blood substitutes, gels used asdrug-delivery systems, etc.) because their lar…     

Atomic force microscopic view of the fine topography on the tobacco stigma surface during its response to pollination

During compatible pollination in tobacco, an extracellular matrix （ECM） is secreted from the stigma surface; however, it is unknown whether the pattern of secretion across the stigma depends on the pollen source. In fact, technical limitations have prevented clear observation of ECM secretion. Here, we report the detailed topographic changes on the stigma surface that accompanies intraspecies and interspecies pollination in tobacco using contact mode atomic force microscopy （AFM）. Our results, which show the dynamics and time course of ECM secretion after pollination, indicate that a certain pattern of secretion already exists on the stigma prior to pollination. Intraspecies induced a two-step response, characterized by topographical changes on the stigma surface several hours after pollination, which was distinct from the pattern of ECM secretion induced by interspecies pollination. This difference was confirmed by root-mean-square analysis, which assessed the roughness of the stigma surface. Our findings indicate that compatible pollination not only induces ECM secretion from the stigma, but also results in a specific distribution of the ECM. Thus, this study demonstrates the powerful potential of AFM in studying the pollen-stigma interaction.     

Micro-friction of diazoresin/polyacrylic acid self-assembly films in water with atomic force microscopy

Ultrathin films composed of diazoresin（DR）and polyacrylic acid（PAA）were fabricated.The surface morphology of the films in water was measured using an atomic force microscopy（AFM）.The self-assembly technique makes the surface rather flat and uniform.The friction force and its dependence on the velocity differ from the surface charge of the thin films.The friction force of repulsive DR/PAA film increases linearly with velocity and has lower values than that of attractive DR film over the full range of velocity.As the velocity increases,the attractive friction of DR film first decreases to a minimum at a velocity of 2 line/s and then increases all the way.When the surface is repulsive to the friction substrate,the friction of thin films that is determined by hydrated lubrication of polymer chains that is ultralubricated;when it is adhesive to the friction substrate,the friction is mainly contributed from the elastic deformation of adsorbed polymer chains in the low velocity region and from viscous sliding in the presence of hydrated-layer lubrication of the polymer chains in the higher velocity region.     

有机溶剂对纳滤膜结构及透过特性的影响

观察了两种纳滤膜(NF-SH,MPF-44)的稳定性,并利用原子力电镜技术(AFM)观察膜的活性表面结构,发现有机溶剂导致膜结构发生显变化。观测在溶剂中的传递通量以及溶质截留率发现,影响NF-SH膜的通量的主要因素是膜本身的结构;对MPF-44膜,影响膜通量的主要因素是溶剂性质。对于这两种纳滤膜影响截留率的主要因素都是溶剂与溶质的相互作用。     

MOCVD生长源流量对p型GaN薄膜特性影响的研究

利用金属有机物化学气相淀积(MOCVD)技术在蓝宝石衬底上生长p型GaN:Mg薄膜,对不同二茂镁(CP2Mg)流量和Ⅴ族和Ⅲ族摩尔(Ⅴ/Ⅲ)比生长的p型GaN:Mg薄膜特性进行研究。研究表明,增加Ⅴ/Ⅲ比,可以降低螺旋位错密度,提高p型GaN晶体质量。当Ⅴ/Ⅲ比为3 800时,Cp2Mg流量最高为170sccm,获得p型GaN(002)面峰值半高宽(FWHM)最窄为232"。同时研究发现,单纯提高Ⅴ/Ⅲ比对降低刃型位错影响较不明显。