Comparison of Loading Efficiency between Hyperbranched Polymers and Cross‐Linked Nanogels at Various Branching Densities

The effect of branching point structures and densities is studied between azido‐containing hyperbranched polymers and cross‐linked nanogels on their loading efficiency of alkynyl‐containing dendron molecules. Hyperbranched polymers that contained “T”‐shaped branching linkage from which three chains radiated out and cross‐linked nanogels that contained “X”‐shaped branching linkage with four radiating chains are synthesized in microemulsion using either atom transfer radical polymerization (ATRP) or conventional radical polymerization (RP) technique. Both polymers have similar density of azido groups in the structure and exhibit similar hydrodynamic diameter in latexes before purification. Subsequent copper‐catalyzed azide–alkyne cycloaddition reactions between these polymers and alkynyl‐containing dendrons in various sizes (G1–G3) demonstrate an order of dendron loading efficiencies (i.e., final conversion of alkynyl‐containing dendron) as hyperbranched polymers > nanogels synthesized by ATRP > nanogels synthesized by RP. Decreasing the branching density or using smaller dendron molecules increases the click efficiency of both polymers. When G2 dendrons with a molecular weight of 627 Da are used to click with the hyperbranched polymers composed of 100% inimer, a maximum loading efficiency of G2 in the loaded hyperbranched polymer is 58% of G2 by weight. These results represent the first comparison between hyperbranched polymers and cross‐linked nanogels to explore the effect of branching structures on their loading efficiencies.

     

微乳液法制备纳米二氧化硅

制备 OP-10/正辛醇/环己烷/氨水微乳液.在该微乳液中,由正硅酸乙酯在碱性条件下受控水解反应制备了 SiO2纳米粒子.通过红外光谱(FT-IR)、X射线衍射(XRD)、透射电镜(TEM)分别对样品结构及形貌尺寸进行了表征.探讨了水与表面活性剂摩尔比(R)、水与正硅酸乙酯摩尔比(H)对SiO2纳米粒子粒径的影响.结果表明制备的SiO2粒子为无定型球形颗粒,粒径为 80～105nm,SiO2纳米粒子粒径随着R和H的增大而增大.     

DPD Simulation on the Transformation and Stability of O/W and W/O Microemulsions

The dissipative particle dynamics simulation method is adopted to investigate the microemulsion systems prepared with surfactant (H1T1), oil (O) and water (W), which are expressed by coarse-grained models. Two topologies of O/W and W/O microemulsions are simulated with various oil and water ratios. Inverse W/O microemulsion transform to O/W microemulsion by decreasing the ratio of oil-water from 3:1 to 1:3. The stability of O/W and W/O microemulsion is controlled by shear rate, inorganic salt and the temperature, and the corresponding results are analyzed by the translucent three-dimensional structure, the mean interfacial tension and end-to-end distance of H1T1. The results show that W/O microemulsion is more stable than O/W microemulsion to resist higher inorganic salt concentration, shear rate and temperature. This investigation provides a powerful tool to predict the structure and the stability of various microemulsion systems, which is of great importance to developing new multifunctional microemulsions for multiple applications.     

农村初中化学新课程实施的影响因素分析

课程实施是课程改革的关键环节,而中国的13亿人口,8亿在农村,所以关注农村中学新课程的实施情况,关系到课程改革的成败。本研究主要运用质性研究方法,辅以问卷调查,对影响农村初中化学新课程实施的影响因素进行了分析。     

AOT/异辛烷/水微乳液中结晶紫与AOT相互作用的热力学研究

用紫外-可见分光光度法在不同温度下测定了结晶紫(CV)在双-2-乙基己基硫代琥珀酸钠(气溶胶OT或AOT)为表面活性剂的W/O微乳液中的吸光度. 根据结晶紫和AOT在微乳液水滴界面缔合的模型对实验数据进行处理, 结果表明, 随着微乳液中水与AOT的摩尔比w的减小和温度的升高, 结晶紫缔合度增大, 根据不同温度下的缔合平衡常数计算了反应的热力学函数, Δ_rG_m, Δ_rH_m和Δ_rS_m     

十二烷基苯磺酸/异辛烷微乳液中脂肪酶催化合成异丁酸异戊酯

在十二烷基苯磺酸(DBSA)/异辛烷微乳液中进行了脂肪酶催化合成异丁酸异戊酯的反应, 考察了微乳体系的含水量w₀、溶解酶缓冲溶液的pH值、反应温度等因素对酯合成反应转化率的影响; 与前期研究的CTAB微乳体系进行比较发现, DBSA微乳体系中的酯合成反应速率明显增加, 短时间内的转化率显著提高, 在温和条件下反应9 h后, 转化率达90%以上; 通过DBSA体系中有酶与无酶条件下反应进程的比较得知, DBSA作为一种质子酸对酯合成反应具有一定的催化能力; 提出了该体系中微乳催化、酶催化和质子酸催化的三重催化机理.     

苯乙烯-丙烯酸酯微乳液的合成研究

目前国内外许多专家学者积极研发低污染、低能耗、高性能的胶粘剂,以代替传统的毒性大、成本高、稳定性差的溶剂型胶粘剂[1]。苯乙烯-丙烯酸酯微乳液(苯-丙微乳液)是重要的胶粘剂之一。与常规乳液胶粘剂相比,它具有以下几个特点[2]:(1)是热力学稳定体系,可以自发形成;(2)分子粒     

表面活性剂的协同作用在甲维盐微乳剂中的应用

通过测定不同类型的单一及复配型表面活性剂水溶液的临界胶束浓度和表面张力,研究了它对W(甲维盐)=1%微乳剂的性能影响。膦酸酯类阴离子表面活性剂A的临界胶束浓度为1.79×10-4mol/L,表面张力为28.90mN/m;苯乙烯基酚聚氧乙烯聚氧丙烯醚嵌段型非离子表面活性剂B(EPE型)的临界胶束浓度为1.91×10-4mol/L,表面张力为20.70mN/m;按m(A)∶m(B)=2∶3形成的复配型表面活性剂2#的水溶液的临界胶束浓度为9.30×10-5mol/L,表面张力为25.66mN/m。当W(2#)=10%时,配制W(甲维盐)=1%的微乳剂物理稳定性最佳,各项指标均合格。对甘蓝小菜蛾幼虫的田间药效的试验,结果表明该药剂具有较强的杀虫作用和较长的持效期,具有较好的推广应用前景。     

微乳液毛细管电动色谱法快速测定消炎利胆片中的穿心莲内酯和脱水穿心莲内酯

建立了微乳液毛细管电动色谱同时分析消炎利胆片中穿心莲内酯和脱水穿心莲内酯的方法。考察了缓冲溶液的浓度、pH值、十二烷基硫酸钠(SDS)以及助表面活性剂的含量对分离测定的影响。在由乙酸乙酯-SDS-正丁醇-30 mmol/L硼砂缓冲液(pH 9.5)（质量比为0.5∶0.6∶6.0∶92.9）组成的微乳液体系中,两种内酯在6 min内完成分离。该法简便、快速、选择性好,用于实际样品中穿心莲内酯和脱水穿心莲内酯的分析,获得了满意的结果。     

不同形状的钨酸钡纳米粒子的合成

不同形状的钨酸钡纳米粒子的合成;微乳液;钨酸钡;纳米粒子;十二胺;十一烯酸