Synthesis and phase behavior of polyurethanes end-capped with fluorinated phosphatidylcholine head groups

A series of fluorinated phosphatidylcholine polyurethane macromolecular additives were synthesized by solution polymerization using methylenebis(phylene isocyanates)(MDI) and 1,4-butanediol(BDO) as hard segments,a new phoshporycholine,2-(2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluoro-10-(2-hydroxyethoxy)decyloxy) ethyl phosphorycholine (HDFOPC) as end-capper,and four polydiols,poly(tetramethylene glycol)s(PTMG),polydimethylsiloxane(PDMS), poly(1,6-hexyl-1,5-pentylcarbonate)(PHPC) and poly(propylene glycol)(PPG) as soft segments,respectively.The chemical structures of the synthesized polyurethanes were characterized by ~1H-NMR and FTIR.DSC and DMA were employed to study the phase behavior of these novel polyurethanes due to their great influences on the surface properties,and hence their interactions with bio-systems.The results showed that phase separation of the fluorinated phosphatidylcholine end-capped polyurethanes was increased in comparison with that of normal polyurethanes.The effect of fluorinated phosphatidylcholine end-capped groups on the phase behavior was further demonstrated by analyzing the degree of hydrogen-bonding between hard and soft segments.     

The variable role of clay on the crystallization behavior of DMDBS-nucleated polypropylene

The effect of clay on the nucleating behavior of 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol(DMDBS) in cryatallization of isotactic polypropylene(iPP) was investigated by means of differential scanning calorimetry(DSC), dynamic rheology and polarized light microscopy(PLM).It is interesting to note that the incorporation of layered clay nanoparticles into DMDBS-nucleated iPP may induce a synergetic nucleation effect while the DMDBS content is below 0.1 wt%,otherwise it restricts the crystallization rate prominently as the DMDBS content increases up to 0.3 wt%,which has exceeded the content threshold to yield a nucleating agent(NA) network.As shown by dynamic rheological investigations, the clay nanoparticles demonstrate an obstructive effect of disturbing the consistency of DMDBS fibrils network.Moreover, to further demonstrate the importance of NA network formation in the crystallization of iPP,we used another NA named HPN-20e,which can not form network structure at all over the concentration studied,for comparison.In this case,the nucleated-crystallization rate is independent on the addition of clay nanoparticles,as the nucleating mechanism is an individual nuclei manner without NA network forming.     

Effects of matrix molecular weight on structure and reinforcement of high density polyethylene/mica composites

Three types of high-density polyethylene(HDPE)with different molecular weights(high,medium and low)were adopted to evaluate the influence of matrix molecular weight on the structure-property relation of injection-molded HDPE/mica composites through a combination of SEM,2d-WAXS,DSC,DMA and tensile testing.Various structural factors including orientation,filler dispersion,interfacial interaction between HDPE and mica,etc.,which can impact the macroscopic mechanics,were compared in detail among the three HDPE/mica composites.The transcrystallization of HDPE on the mica surface was observed and it exhibited strong matrix molecular weight dependence.Obvious transcrystalline structure was found in the composite with low molecular weight HDPE,whereas it was hard to be detected in the composites with increased HDPE molecular weight.The best reinforcement effect in the composite with low molecular weight HDPE can be understood as mainly due to substantially improved interfacial adhesion between matrix and mica filler,which arises from the transcrystallization mechanism.     

PREPARATION AND CHARACTERIZATION OF SOY PROTEIN ISOLATE(SPI)/MONTMORILLONITE(MMT) BIONANOCOMPOSITES

 The bionanocomposites of soy protein isolate (SPI)/montmorillonite (MMT) have been prepared successfully via simple melt mixing, in which MMT was used as nanofiller and glycerol was used as plasticizer. Their structures and properties were characterized with X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), thermogravimetric analysis and tensile testing. XRD、TEM and SEM results indicated that the MMT layers could be easily intercalated by the SPI matrix even by simple melt processing. The exfoliated MMT layers were randomly dispersed in the protein matrix as MMT content was low (less than 5 wt%), an incomplete exfoliation was evident from SEM results, and some primary particles were observed as the MMT content was high (from 5 wt% to 9 wt%). A significant improvement of the mechanical strength and thermal stability of SPI/MMT nanocomposites has been achieved. Our work suggests that simple melt processing is an efficient way to prepare SPI/MMT nanocomposites with exfoliated structure.     

负载型磺酸化席夫碱二-邻苯甲醛乙二胺(Salen)-Mn(Ⅲ)配合物催化不对称环氧化反应

设计了负载型催化剂/离子液体体系：磺酸化席夫碱二-邻苯甲醛乙二胺(Salen)-Mn(Ⅲ)配合物中5, 5′-磺酸根通过氢键作用分别负载于硅胶和硅藻土,再分散于亲水性离子液体1-正丁基-3-甲基咪唑四氟硼酸盐(BMImBF₄)或憎水性离子液体1-正丁基-3-甲基咪唑六氟磷酸盐(BMImPF₆)中。研究了此催化体系对苯乙烯和α-甲基苯乙烯的不对称环氧化反应,结果表明此体系减少了催化剂的流失,催化体系可循环五次;扩大了手性诱导能力,对映体过量值(ee)可达100%;     

化学反应的内禀反应坐标法(Ⅷ)——甲基叠氮热解反应的反应路径解析

采用内禀反应坐标法完成了对甲基叠氮热解反应途径的微观动力学解析.结果表明甲基叠氮的热解是以伴随N₂消除后发生1,2-H迁移的协同方式完成的,属协同的非同步反应,此机制可解释(H₃C)nH_3-nC-N₃(n=0～2)烷基叠氮系列热解温度的光电子能谱结果.     

用子波方法研究Rayleigh-Bénard对流温度信号的标度律

采用子波分析方法 ,对实验中测得的Rayleigh_B啨ｎａｒｄ对流温度信号 (被动标量 )的标度律 ,从以下两个方面进行了研究 :第一方面 ,直接采用扩展的结构函数 (ESS)的公式对温度信号进行了分析 ,研究结果表明 ,采用该方法后的标度区域明显比不采用扩展结构函数的标度区域要宽 ,得到的标度指数与其它实验中得到的温度信号标度指数 ξ(q)一致 ;第二个方面 ,将 A .Arneodo等人对湍流中速度信号提出的基于子波分析的扩展标度公式 ,推广应用于温度信号 ,给出了一个描述温度信号的、基于子波分析的扩展标度公式 ,研究结果表明 ,提出的建立在子波系数极大模求和基础上的扩展标度公式 ,也能够比较准确地提取温度信号的标度指数 ξ(q) ·     

聚合物功能梯度材料的研究现状与展望

功能梯度材料(FGM)是一种全新的非均质复合材料.聚合物梯度材料(PGM)是基体材料为高分子材料的一类功能梯度材料,因其独特的形态结构、奇特的功能和潜在的应用价值,已逐渐引起了人们的高度重视.本文综述了国内外聚合物功能梯度材料的研究现状,介绍了PGM的概念、分类、制备方法、表征方法及应用等,并对PGM未来的研究进行了展望.     

士的宁分子印迹整体柱的制备

以士的宁为模板分子，甲基丙烯酸为功能单体，乙二醇二甲基丙烯酸酯作为交联剂，甲苯和十二醇混合溶液为致孔剂，用原位分子印迹技术，合成了士的宁分子印迹整体柱。通过优化合成条件，结果显示：模板分子、功能单体与交联剂之间的比例以1：4：16最佳，致孔剂中甲苯的最佳含量为18％（V/V)；对士的宁整体柱的色谱条件包括流动相组成、流速、柱温等进行了考察，并用于士的宁和马钱子碱的分离，其分离因子为3．5。