Direct measurement of weak depletion force between two surfaces

In a mixture of colloidal particles and polymer molecules,the particles may experience an attractive"depletion force"if the size of the polymer molecule is larger than the interparticle separation.This is because individual polymer molecules experience less conformational entropy if they stay between the particles than they escape the inter-particle space, which results in an osmotic pressure imbalance inside and outside the gap and leads to interparticle attraction.This depletion force has been the subject of several studies since the 1980s,but the direct measurement of this force is still experimentally challenging as it requires the detection of energy variations of the order of k_BT and beyond.We present here our results for applying total internal reflection microscopy(TIRM) to directly measure the interaction between a free-moving particle and a flat surface in solutions consisting of small water-soluble organic molecules or polymeric surfactants.Our results indicate that stable nanobubbles(ca.150 nm) exist free in the above aqueous solutions.More importantly,the existence of such nanobubbles induces an attraction between the spherical particle and flat surface.Using TIRM,we are able to directly measure such weak interaction with a range up to 100 nm.Furthermore,we demonstrate that by employing thermo-sensitive microgel particles as a depleting agent,we are able to quantitatively measure and reversibly control k_BYT-scale depletion attraction as function of solution pH.     

无皂乳液聚合法制备非球形聚苯乙烯粒子研究

采用苯乙烯(St)、二乙烯基苯(DVB)、甲基丙烯酰氧乙基三甲基氯化铵(DMC)为单体,在乙醇和水混合介质中通过无皂乳液聚合法制备了非球形聚苯乙烯(PS)粒子。通过FT-IR、TEM和激光粒度及电位分析仪对粒子的结构、形貌、粒径以及Zeta电位进行了表征。结果表明,所合成PS粒子均含三种单体结构单元,且形貌上均为非球形;随着DVB用量的增加,PS粒子形貌更趋于球形,粒径和单分散系数均逐渐增加;随DMC用量增加,PS粒子粒径随之增加,单分散系数逐渐减小,表面Zeta电位也逐渐增加;KHCO3用量的增加能使PS粒子粒径和单分散系数均增加;随着醇水比的减小,PS粒子粒径逐渐减小,而单分散系数则逐渐增加。     

Poly(vinyl alcohol)/GO-MMT nanocomposites: Preparation,structure and properties

A facile, efficient and environment friendly method is established to prepare poly(vinyl alcohol)(PVA) based graphene oxide-montmorillonite(GO-MMT) nanocomposites in aqueous media. GO-MMT nanohybrid is obtained by the combination of GO and MMT in water without any reducing or stabilizing agents. The formation of GO-MMT nanohybrid is due to the hydrogen bonding and crosslinking effects. The sodium ions within MMT sheets act as crosslinkers between GO sheets and MMT platelets. The resultant nanocomposites are characterized by means of X-ray diffraction(XRD), scanning electron microscopy(SEM), differential scanning calorimetry(DSC), thermogravimetric analysis(TGA) and mechanical testing. Compared to that of pure PVA, PVA nanocomposites show enhanced thermal stabilities and mechanical properties, which results from strong interfacial adhesion of the nanoadditives in PVA matrix. The further increase in the tensile strength and modulus results from strong interaction between PVA chains and layered GO-MMT as well as good mechanical properties of GO-MMT hybrid, compared to PVA/GO and PVA/MMT nanocompsoites.     

性能优异的Rh改性的Pd/Al2O3密偶催化剂

采用等体积浸渍法制备了Pd/Al2O3和Rh-Pd/Al2O3密偶催化剂,运用H2程序升温还原、CO化学吸附和X射线光电子能谱等手段对催化剂进行了表征,并考察了催化剂对丙烷总包反应和单反应的转化活性.总包反应结果表明, Rh的添加使起燃温度和完全转化温度分别降低了23和18oC.单反应结果证明,添加Rh能提高各单反应丙烷的转化活性,尤其是有NO参与的反应.表征结果证明,掺杂Rh不仅可以抑制活性组分PdOx的烧结,提高PdOx的分散度,而且可以改变其电子状态.     

助剂对Cu/Cr催化剂上甲醇部分氧化制氢的活性影响

曾研究了Cu/Cr二元催化剂上甲醇部分氧化制氢的反应,发现当Cu/Cr比为6：4时,催化剂的Cu^0比表面积最大,呈现出较好的活性。在Cu/Cr（6：4）催化剂中添加Fe,Zn,Al等8种助剂,考察其对甲醇部分氧化制氢催化性能的影响,并着重研究了Zn助剂的作用。实验结果表明,Zn的引入,有利于催化剂活性的提高。当Zn含量为10％时,催化剂活性最好。XRD表征结果表明,Cu/Cr催化剂的失活与其表面上的Cu物种烧结有关,Zn的引入可明显增强Cu/Cr（6：4）催化剂的热稳定性,提高其寿命。     

端羧基芳脂型超支化聚酯自组装性能的研究

利用聚电解质逐层浸渍 ( layer- by- layer dipping)法制备自组装膜是最近发展起来的进行表面改性的新方法[1～ 3] .一方面 ,从理论上来说 ,只要是带电荷的聚合物都可以利用该技术制备具有优异性能的自组装膜 ;另一方面 ,还可以通过调节溶液的 p H值和离子强度等控制阴阳离子的组装过程 ,从而控制自组装膜的内部结构和表面形态 ,为在纳米级范围内设计和控制聚合物聚集态内部结构提供了可能性 .近年来 ,具有高度支化结构的超支化分子由于具有独特的物理和化学性能而受到了广泛的关注 [4 ,5] ,但以聚电解质逐层浸渍法制备超支化分子自组装膜…     

Preparation and characterization of pentaerythritol/butane tetracarboxylic acid/polyethylene glycol crosslinking copolymers as solid-solid phase change materials

Pentaerythritol/butane tetracarboxylic acid/polyethylene glycol (PBPEG) crosslinking copolymers as a novel solid-solid phase change material (SSPCM) were successfully synthesized through the reaction mechanism and conditions of hydroxyl-carboxyl condensation reaction. The composition and chemical structure, crystalline properties, phase change behaviors, thermal reliability and chemical stability of PBPEG crosslinking copolymers were investigated by Fourier transform infrared spectroscopy (FT-IR), wide-angle X-ray diffraction (WAXD), polarization optical microscopy (POM), differential scanning calorimetry (DSC), and thermogravimetry (TGA), respectively. The results show that PBPEG crosslinking copolymers have typical solid-solid phase transition temperatures in the range of 10.31～53.27°C and high latent heat enthalpy in the range of 89.6～102.8 J/g, the synthesized SSPCMs have good thermal reliability and chemical stability after 300 thermal cycles, and PBPEG crosslinking copolymers have good thermal stability before 364°C. In summary, the synthesized PBPEG crosslinking copolymers could be potentially used for thermal energy storage.     

聚苯乙烯磺酸掺杂聚苯胺的合成

以苯胺（An）为单体,过硫酸铵（APS）为氧化剂,在聚苯乙烯磺酸（PSSA）的水溶液中,合成了可完全溶于水的PSSA掺杂PAn。研究了An浓度,PSSA浓度,APS浓度,APS的滴加时间,反应时间及温度对An聚合反应及其产物的水溶性,导电性及特性粘度[η]的影响。结果表明：在比较宽的实验条件下,都可以合成出具有良好导电性的可溶于水的PSSA掺杂PAn;其中当An：PSSA:APS的摩尔比为1．7：2．5：1,APS溶液的滴加时间为3h,反应时间为1h,反应温度为14℃时,得到的掺杂PAn导电率最高达0．156S／cm。     

Synthesis and Properties of Polyetherketones Containing Sulfide and Phthalazinone

High molecular weight copoly(ether ketone)s (PEK) based on 4-(4-hydroxyphenyl)-1-phthalazinone (DHPZ)/4,4′-thiobisphenol (TBP)/4,4′-diflourodiphenylketone (DFK) were prepared by nucleophilic substitution polycondensation. The copolymers were characterized by FT- and ^1H-NMR. Thermal properties and solubility of copolymers were studied.